Cutaneous & Chemical Senses

Question 1

What’s an auditory space?

Answer 1

• Perception of where sounds are located in space
• Auditory space extends around a listener’s head in all directions, existing wherever there is a sound

Question 2

What’s auditory localization?

Answer 2

The perception of the location of a sound source in auditory space

Question 3

Why is it easier to locate visual stimuli in the environment over auditory stimuli?

Answer 3

• Ex: consider a tweeting bird and a meowing cat near a tree
• Visual information for the relative locations of the bird and the cat is contained in the images of the bird and the cat on the surface of the retina
• The bird’s “tweet, tweet” and the cat’s “meow” on the other hand stimulate the cochlea based on their sound frequencies, and these frequencies cause patterns of nerve firing that result in our perception of a tone’s pitch and timbre
• Activation of nerve fibers in the cochlea is based on the tones’ frequency components and not on where the tones are coming from
• Meaning that 2 tones with the same frequency that originate in different locations will activate the same hair cells and nerve fibers in the cochlea
• The auditory system must therefore use information other than the place on the cochlea to determine location -> location cues

Question 4

What are location cues?

Answer 4

• In hearing, characteristics of the sound reaching the listener that provide information regarding the location of a sound source
• These are created by the way sound interacts with the listener’s head and ears

Question 5

What are the 2 types of location cues?

Answer 5

• Binaural cues
• Spectral cues

Question 6

What do binaural cues locations cues depend on?

Answer 6

They depend on both ears

Question 7

What do spectral cues location cues depend on?

Answer 7

They depend on both ears

Question 8

Researchers studying the different sound location cues have determined how well people can utilize these cues to locate the position of a sound in what 3 dimensions?

Answer 8

• Azimuth
• Elevation
• Distance

Question 9

What’s the azimuth dimension?

Answer 9

In hearing, specifies locations that vary from left to right relative to the listener

Question 10

What’s the elevation dimension?

Answer 10

In hearing, sound locations that are up and down relative to the listener

Question 11

What’s the distance dimension?

Answer 11

• How far a stimulus is from the observer
• In hearing, the distance coordinate specifies how far the sound source is from the listener
• Localization in distance is much less accurate than azimuth or elevation localization, working best when the sound source is familiar, or when cues are available from room reflections

Question 12

What are binaural cues?

Answer 12

• Sound localization cue that involves both ears
• They use information reaching both ears to determine the azimuth (left–right position) of sounds
• Sounds that are off to the side are more intense at one ear than the other and reach one ear before the other

Question 13

What are the primary binaural cues?

Answer 13

• Interaural time difference
• Interaural level difference
• Both are based on a comparison of the sound signals reaching the left and right ears

Question 14

What’s the interaural level difference (ILD)?

Answer 14

• It is based on the difference in the sound pressure level (or just “level”) of the sound reaching the 2 ears (left & right)
• A difference in level between the 2 ears occurs because the head is a barrier that creates an acoustic shadow, reducing the intensity of sounds that reach the far ear
• This reduction of intensity at the far ear occurs for high-frequency sounds (greater than about 3,000Hz for humans), but not for low-frequency sounds
• The ILD provides a cue for sound localization for high-frequency sounds

Question 15

Stimulating receptors on the tip of the finger, and other outer body areas, creates perceptions of what?

Answer 15

• Touch
• Pressure
• Temperature

Question 16

People with a rare condition that results in losing the ability to feel sensations through the skin often suffer with what?

Answer 16

Constant bruises, burns, and broken bones in the absence of the warnings provided by touch and pain

Question 17

What could losing the sense of touch result in?

Answer 17

• Increase the chance of injury
• Makes it difficult to interact with the environment because of the loss of feedback from the skin that accompanies many actions

Question 18

What have experiments in which participants have had their hands temporarily anesthetized shown?

Answer 18

They’ve shown that the resulting loss of feeling causes them to apply much more force than necessary when carrying out tasks with their fingers and hands

Question 19

Describe the case of Ian Waterman

Answer 19

• One of the most extreme examples of the effect of losing the ability to sense with the skin
• As a result of an autoimmune reaction that destroyed most of the neurons that transmitted signals from his skin, joints, tendons, and muscles to his brain, he lost the ability to feel skin sensations so he couldn’t feel his body when lying in bed, and he often used inappropriate force when grasping objects—sometimes gripping too tightly, and sometimes dropping objects because he hadn’t gripped tightly enough
• Destruction of the nerves from his muscles, tendons, and joints eliminated Ian’s ability to sense the position of his arms, legs, and body, so the only way he could carry out movements was by visually monitoring the positions of his limbs and body
• Ian’s problems were caused by a breakdown of his somatosensory system

Question 20

What’s the somatosensory system?

Answer 20

The system that includes the cutaneous senses (senses involving the skin), proprioception (the sense of position of the limbs), kinesthesis (sense of movement of the limbs), haptic perception, and the vestibular system

Question 21

What are the cutaneous senses?

Answer 21

The ability to perceive sensations, such as touch and pain, that are based on the stimulation of receptors in the skin

Question 22

What’s proprioception?

Answer 22

The ability to sense the position of the body and limbs

Question 23

What’s kinesthesis?

Answer 23

The ability to sense the movement of the body and limbs

Question 24

What are the cutaneous senses important for?

Answer 24

• They’re important not only for activities like grasping objects and protecting against damage to the skin, but also for motivating sexual activity
• They also create good feelings -> social touch
• They’re important both for day-to-day functioning and survival

Question 25

List the various feelings involving the cutaneous senses in the skin

Answer 25

• Touch
• Pain
• Pressure
• Vibration
• Tickle
• Temperature
• Pleasure

Question 26

What does the sense of touch enable us to perceive?

Answer 26

It enables us to perceive properties of surfaces and objects such as details, vibrations, texture, and shape

Question 27

What did M. Comèl (1953) call the skin?

Answer 27

The “monumental facade of the human body”

Question 28

What’s the heaviest organ in the human body?

Answer 28

• The skin
• It’s also the most obvious, especially in humans, whose skin isn’t obscured by fur or large amounts of hair

Question 29

What are the functions of skin?

Answer 29

• Warning function
• Prevents body fluids from escaping and at the same time protects us by keeping bacteria, chemical agents, and dirt from penetrating our bodies
• Skin maintains the integrity of what’s inside and protects us from what’s outside, but it also provides us with information about the various stimuli that contact it
• The sun’s rays heat our skin, and we feel warmth; a pinprick is painful; and when someone touches us, we experience pressure or other sensations

Question 30

What’s the epidermis?

Answer 30

The outer layers of the skin, including a layer of tough dead skin cells

Question 31

What’s the dermis?

Answer 31

The layer of skin below the epidermis

Question 32

What are the different layers of the skin?

Answer 32

• Epidermis
• Dermis

Question 33

What are mechanoreceptors?

Answer 33

• Receptors that responds to mechanical stimulation of the skin, such as pressure, stretching, or vibration
• Located in the epidermis and the dermis
• The Merkel receptor (SA1) and Meissner corpuscle (RA1) are mechanoreceptors close to the surface of the skin, near the epidermis

Question 34

What’s glabrous skin?

Answer 34

Skin without hairs or projections

Question 35

Describe the Merkel receptor (SA1)

Answer 35

• A disk-shaped receptor in the skin associated with slowly adapting fibers
• Mechanoreceptor near the surface of the skin
• Fires to continuous pressure
• Perceives fine details and texture
• Perceives shapes
• Because it’s located close to the surface, it has small receptive fields
• Because the nerve fiber associated with the slowly adapting Merkel receptor fires continuously, as long as the stimulus is on, it is called a slowly adapting (SA1) fiber

Question 36

Describe the Meissner corpuscle (RA1)

Answer 36

• A receptor in the skin, associated with RA1 mechanoreceptors
• It has been proposed that the Meissner corpuscle is important for perceiving tactile slip and for controlling the force needed to grip objects
• Mechanoreceptor near the surface of the skin
• Fires to “on” and “off”
• Perceives handgrip control
• Perceives motion across skin
• Because it’s located close to the surface, it has small receptive fields
• Because the nerve fiber associated with the rapidly adapting Meissner corpuscle fires only when the stimulus is first applied and when it is removed, it is called a rapidly adapting (RA1) fiber

Question 37

What’s a cutaneous receptive field?

Answer 37

Area of skin that, when stimulated, influences the firing of a neuron

Question 38

The rapidly adapting (RA1) fiber is associated with which skin receptor?

Answer 38

Meissner corpuscle

Question 39

The slowly adapting (SA1) fiber is associated with which skin receptor?

Answer 39

Merkel receptor

Question 40

What are the types of perception associated with the Merkel receptor/SA1 fiber?

Answer 40

• Details
• Shape
• Texture

Question 41

What are the types of perception associated with Meissner corpuscle/RA1 fiber?

Answer 41

• Controlling handgrip
• Perceiving motion across the skin

Question 42

What’s the Ruffini cylinder?

Answer 42

• A receptor structure in the skin associated with slowly adapting (SA2) fibers, which responds continuously to stimulation (fires to continuous pressure)
• It has been proposed that the Ruffini cylinder is involved in perceiving “stretching”

Question 43

What’s the Pacinian corpuscule?

Answer 43

• A receptor with a distinctive elliptical shape associated with RA2 mechanoreceptors
• It’s a rapidly adapting fiber (RA2) which responds when the stimulus is applied or removed (fires to “on” and “off”)
• It transmits pressure to the nerve fiber inside it only at the beginning or end of a pressure stimulus and is responsible for our perception of vibration and fine textures when moving the fingers over a surface

Question 44

Both the Ruffini cylinder and Pacinian corpuscle are located where?

Answer 44

Deep in the skin, so they have larger receptive fields

Question 45

The Ruffini cylinder is associated with what kind of perception?

Answer 45

Perceiving stretching of the skin

Question 46

The Pacinian corpuscle is associated with what kind of perception?

Answer 46

With sensing rapid vibrations and fine texture

Question 47

The perception of texture often involves what?

Answer 47

The coordinated activity of different types of neurons working together

Question 48

Where are cutaneous receptors in the skin located?

Answer 48

They’re distributed over the whole body

Question 49

Why do we sometimes refer to the detection of stimulation of the skin as the “journey of the long-distance nerve impulses”?

Answer 49

• Because of the wide distribution of the cutaneous receptors in the skin, plus the fact that signals must reach the brain before stimulation of the skin can be perceived
• This reference is especially true for signals that must travel from the fingertips or toes to the brain

Question 50

Signals from all over the body are conducted from the skin to the what?

Answer 50

To the spinal cord

Question 51

How many segments does the spinal cord have?

Answer 51

Consists of 31 segments, each of which receives signals through a bundle of fibers called the dorsal root

Question 52

What happens after signals from the stimulation of the cutaneous receptors enter the spinal cord?

Answer 52

Nerve fibers transmit them to the brain along 2 major pathways: the medial lemniscal pathway and the spinothalamic pathway

Question 53

What are the 2 major pathways from the spinal cord to the brain?

Answer 53

• The medial lemniscal pathway
• The spinothalamic pathway
• Fibers from both pathways cross over to the other side of the body during their upward journey and synapse in the thalamus and then send signals to the somatosensory cortex in the parietal lobe
• Most of the fibers in the cutaneous system synapse in the ventrolateral nucleus of the thalamus
• Signals originating from the left side of the body reach the thalamus in the right hemisphere of the brain, and signals from the right side of the body reach the left hemisphere
• The case of Ian Waterman illustrates the separation in function between these 2 pathways, because although he lost the ability to feel touch and to sense the positions of his limbs (lemniscal pathway), he was still able to sense pain and temperature (spinothalamic pathway)

Question 54

What’s the medial lemniscal pathway?

Answer 54

• A pathway in the spinal cord that transmits signals from the skin toward the thalamus
• It has large fibers that carry signals related to sensing the positions of the limbs (proprioception) and perceiving touch
• These large fibers transmit signals at high speed, which is important for perceiving and for reacting to touch

Question 55

What’s the spinothalamic tract/pathway?

Answer 55

• One of the nerve pathways in the spinal cord that conducts nerve impulses from the skin to the somatosensory area of the thalamus
• The spinothalamic pathway consists of smaller fibers that transmit signals related to temperature and pain

Question 56

What supports the idea that different pathways serve different sensations?

Answer 56

The idea of 2 pathways conducting cutaneous signals to the thalamus and then to the somatosensory cortex

Question 57

Name some of the brain structures associated with the cutaneous system

Answer 57

• Primary somatosensory cortex (S1)
• Secondary somatosensory cortex (S2)
• Anterior cingulate cortex (ACC)
• The insula

Question 58

What are 2 of the areas that receive signals from the thalamus?

Answer 58

• The primary somatosensory cortex (S1) in the parietal lobe
• The secondary somatosensory cortex (S2)
• Signals also travel between S1 and S2 and to a network of other areas in the brain in additional pathways

Question 59

What’s the secondary somatosensory cortex (S2)?

Answer 59

The area in the parietal lobe next to the primary somatosensory area (S1) that processes neural signals related to touch, temperature, and pain

Question 60

What is the insula important for?

Answer 60

Sensing light touch

Question 61

What is the anterior cingulate cortex (ACC) involved in?

Answer 61

Pain

Question 62

How is the somatosensory cortex organized and how was this discovered?

Answer 62

• It’s organized into maps that correspond to locations on the body
• The story behind the discovery of these maps -> when British neurologist Hughlings Jackson observed that in some cases of epilepsy, his patients’ seizures progressed over the body in an orderly way, with a seizure in one body part being followed by a seizure in a neighboring body part
• This sequence, known as “the Jacksonian march,” suggested that the seizures reflected the spread of neural activity across maps in the motor area of the brain

Question 63

Describe Wilder Penfield and Edwin Boldrey (1937) study of the somatosensory map

Answer 63

• They measured the map of the somatosensory cortex by stimulating points on the brain of awake patients who were having brain surgery to relieve symptoms of epilepsy
• When Penfield stimulated points on the primary somatosensory cortex (S1) and asked patients to report what they perceived, they reported sensations such as tingling and touch on various parts of their body
• Penfield found that stimulating the ventral part of S1 (lower on the parietal lobe) caused sensations on the lips and face, stimulating higher on S1 caused sensations in the hands and fingers, and stimulating the dorsal S1 caused sensations in the legs and feet
• The resulting body map is called the homunculus

Question 64

What’s the homunculus?

Answer 64

• Latin for “little man”
• The homunculus shows that adjacent areas of the skin project to adjacent areas in the brain, and that some areas on the skin are represented by a disproportionately large area of the brain
• Ex: the area devoted to the thumb is as large as the area devoted to the entire forearm
• This result is analogous to the cortical magnification factor in vision
• Similarly, parts of the body such as the fingers, with the highest tactile acuity are represented by larger areas on the cortex
• A similar body map also occurs in the secondary somatosensory cortex (S2)

Question 65

Where is the somatosensory cortex located?

Answer 65

In the parietal lobe

Question 66

Where does the primary somatosensory area (S1) receive inputs from?

Answer 66

From the ventrolateral nucleus of the thalamus

Question 67

Where is the secondary somatosensory area (S2) located?

Answer 67

It’s partially hidden behind the temporal lobe

Question 68

Recent research has shown that the primary somatosensory area (S1) is divided into how many interconnected areas?

Answer 68

Recent research has shown that S1 is divided into 4 interconnected areas, each with its own body map and its own functions

Question 69

The area in S1 involved in perceiving touch is connected to what other area?

Answer 69

It’s connected to another area that is involved in haptics (exploring objects with the hand)

Question 70

TRUE OR FALSE: The cutaneous system involves numerous areas of the brain which communicate with each other over many pathways

Answer 70

TRUE

Question 71

What’s one of the most impressive examples of perceiving details with the skin?

Answer 71

• Braille
• The system of raised dots that enables blind people to read with their fingertips
• A Braille character consists of a cell made up of 1-6 dots
• The Braille alphabet consists of raised dots in a 2x3 matrix
• Different arrangements of dots and blank spaces represent letters of the alphabet
• Additional characters represent numbers, punctuation marks, and common speech sounds and words
• Experienced Braille readers can read at a rate of about 100 words/min, slower than the rate for visual reading, which averages about 250-300 words/min
• A Braille reader transforms an array of raised dots into information that goes far beyond simply feeling sensations on the skin
• The ability of Braille readers to identify patterns of small raised dots based on the sense of touch depends on tactile detail perception

Question 72

What’s the first step in describing research on tactile detail perception?

Answer 72

To consider how researchers have measured tactile acuity

Question 73

What’s tactile acuity?

Answer 73

• The capacity to detect details of stimuli presented to the skin
• The smallest details that can be detected on the skin

Question 74

Describe the methods for measuring tactile acuity

Answer 74

• Just as there are a number of different kinds of eye charts for determining a person’s visual acuity, there are a number of ways to measure a person’s tactile acuity
• The classic method of measuring tactile acuity is the two-point threshold
• The two-point threshold is measured by gently touching the skin with two points, such as the points of a drawing compass, and having the person indicate whether he or she feels one point or two
• Another more recent method is the grating acuity method
• Grating acuity is measured by pressing a grooved stimulus onto the skin and asking the person to indicate the orientation of the grating
• Acuity is measured by determining the narrowest spacing for which orientation can be accurately judged
• Finally, acuity can also be measured by pushing raised patterns such as letters onto the skin and determining the smallest sized pattern or letter that can be identified

Question 75

What’s the two-point threshold?

Answer 75

• A measure of acuity on the skin
• The smallest/minimum separation between 2 points on the skin that when stimulated is perceived as 2 points
• The two-point threshold was the main measure of acuity in most of the early research on touch

Question 76

What does the firing of the Merkel receptor’s fiber signal?

Answer 76

• It signals details, and more specifically, details of patterns that are pushed onto the skin
• The firing of the fiber reflects the pattern of the stimuli pushed onto the skin
• Demonstrates tactile acuity

Question 77

What’s one of the things that determine what we experience when the skin is stimulated?

Answer 77

The properties of the receptors

Question 78

There’s a high density of what kind of receptors in the fingertips?

Answer 78

• Merkel receptors
• Explains why the fingertips are the parts of the body that are most sensitive to details

Question 79

How has the relationship between locations on the body and sensitivity to detail been studied?

Answer 79

It has been studied psychophysically by measuring the two-point threshold on different parts of the body

Question 80

What kind of receptors correspond with tactile acuity?

Answer 80

Merkel receptors

Question 81

A comparison of grating acuity on different parts of the hand shows that better acuity is associated with what?

Answer 81

It’s associated with less spacing between Merkel receptors

Question 82

Describe the correlation between density of Merkel receptors and tactile acuity

Answer 82

• As the SA1 receptor spacing (mm) increases, so does the distance needed for tactile acuity (mm)
• Fingertips have tactile acuity for the smallest amount of distance and have the smallest receptor spacing
• Then the base of the finger
• Finally, the hand has bigger SA1 receptor spacing with a larger distance needed for tactile acuity

Question 83

How are regions of high acuity, like the fingers and lips, represented in the cortex?

Answer 83

• They’re represented by larger areas on the cortex
• Ex: the homunculus -> “magnification” of the representation on the brain of parts of the body such as the fingertips
• The map of the body on the brain is enlarged to provide the extra neural processing that enables us to accurately sense fine details with our fingers and other parts of the body
• Also, cortical neurons representing parts of the body with better acuity, such as the fingers, have smaller receptive fields
• Meaning that 2 points that are close together on the fingers might fall on receptive fields that don’t overlap and so would cause neurons that are separated in the cortex to fire
• 2 points with the same separation when applied to the arm are likely to fall on receptive fields that overlap and so could cause neurons that are not separated in the cortex to fire
• The small receptive fields of neurons receiving signals from the fingers translates into more separation on the cortex, which enhances the ability to feel 2 close-together points on the skin as 2 separate points

Question 84

What are the Two-Point Thresholds (in mm) on Different Parts of the Male Body?

Answer 84

• Fingers (4 mm)
• Upper lip (8 mm)
• Big toe (9 mm)
• Back (42 mm)
• Thigh (44 mm)
• Upper arm (46 mm)

Question 85

What’s the mechanoreceptor that’s primarily responsible for sensing vibration?

Answer 85

• The Pacinian corpuscle
• One piece of evidence linking the Pacinian corpuscle to vibration is that recording from fibers associated with the corpuscle shows that these fibers respond poorly to slow or constant pushing but respond well to high rates of vibration

Question 86

Why do the Pacinian corpuscle fibers respond well to rapid vibration?

Answer 86

• The presence of the corpuscle surrounding the nerve fiber determines which pressure stimuli actually reach the fiber
• The corpuscle, which consists of a series of layers, like an onion, with fluid between each layer, transmits rapidly repeated pressure, like vibration, to the nerve fiber, but doesn’t transmit continuous pressure
• Thus, the corpuscle causes the fiber to receive rapid changes in pressure, but not to receive continuous pressure

Question 87

Because the Pacinian corpuscle doesn’t transmit continuous pressure to the fiber, what should presenting continuous pressure to the corpuscle cause?

Answer 87

It should cause no response in the fiber

Question 88

Describe Werner Lowenstein (1960) study on the Pacinian corpuscle

Answer 88

• He showed that when pressure was applied to the corpuscle, the fiber responded when the pressure was first applied and when it was removed, but it did not respond to continuous pressure
• But when Lowenstein dissected away the corpuscle and applied pressure directly to the fiber, the fiber fired to the continuous pressure
• Lowenstein concluded from this result that properties of the corpuscle cause the fiber to respond poorly to continuous stimulation, such as sustained pressure, but to respond well to changes in stimulation that occur at the beginning and end of a pressure stimulus or when stimulation is changing rapidly, as occurs in vibration

Question 89

Vibration plays a role in perceiving what?

Answer 89

Fine textures

Question 90

What’s surface texture?

Answer 90

The visual and tactile quality of a physical surface created by peaks and valleys

Question 91

Why is visual inspection a poor way of determining surface texture?

Answer 91

• Because seeing texture depends on the light–dark pattern determined by the angle of illumination
• Thus, although the visually perceived texture of the 2 sides of something could look very different, moving the fingers across the 2 surfaces could reveal that their texture is the same

Question 92

What’s the duplex theory of texture perception?

Answer 92

• The idea that texture perception is determined by both spatial and temporal cues that are detected by 2 types of receptors
• Originally proposed by David Katz and now called the “duplex theory”
• Although Katz proposed that texture perception is determined by both spatial and temporal cues, research on texture perception has, until recently, focused on spatial cues

Question 93

What are the spatial cues from the duplex theory of texture perception?

Answer 93

• In tactile perception, information about the texture of a surface that is determined by the size, shape, and distribution of surface elements such as bumps and grooves
• Spatial cues are provided by relatively large surface elements, such as bumps and grooves, that can be felt both when the skin moves across the surface elements and when it is pressed onto the elements
• These cues result in feeling different shapes, sizes, and distributions of these surface elements
• Ex: perceiving a coarse texture such as Braille dots or the texture you feel when you touch the teeth of a comb

Question 94

What are the temporal cues from the duplex theory of texture perception?

Answer 94

• In tactile perception, information about the texture of a surface that is provided by the rate of vibrations that occur as we move our fingers across the surface
• Temporal cues occur when the skin moves across a textured surface like fine sandpaper
• This type of cue provides information in the form of vibrations that occur as a result of the movement over the surface
• Temporal cues are responsible for our perception of fine texture that cannot be detected unless the fingers are moving across the surface
• Additional evidence for the role of temporal cues in perceiving texture has been provided by research that shows that vibrations are important for perceiving textures not only when people explore a surface directly with their fingers, but also when they make contact with a surface indirectly, through the use of tools

Question 95

Describe how Mark Hollins and Ryan Risner (2000) presented evidence for the role of temporal cues

Answer 95

• By showing that when participants touched surfaces without moving their fingers and judge “roughness” using the procedure of magnitude estimation, they sensed little difference between 2 fine textures (particle sizes of 10 µm and 100 µm)
• However, when participants were allowed to move their fingers across the surface, they could detect the difference between the fine textures
• Thus, movement, which generates vibration as the skin scans a surface, makes it possible to sense the roughness of fine surfaces
• These results and the results of other behavioral experiments support the duplex theory of perception—that the perception of coarse textures is determined by spatial cues and of fine textures by temporal (vibration) cues

Question 96

TRUE OR FALSE: You can detect differences in texture by running a tool over a surface

Answer 96

TRUE
- Your ability to detect differences in texture by running a pen (or some other “tool,” such as a stick) over a surface is determined by vibrations transmitted through the tool to your skin
- The most remarkable thing about perceiving texture with a tool is that what you perceive is not the vibrations but the texture of the surface, even though you are feeling the surface remotely, with the tip of the tool

Question 97

Describe how Justin Lieber and Sliman Bensmaia (2019) studied how textures are represented in the brain and their findings

Answer 97

• By training monkeys to place their fingers on a rotating drum
• Textures ranged from very fine (microsuede) to coarse (dots spaced 5 mm apart)
• They studied the responses of 5 neurons in the somatosensory cortex to 6 different textures
• These patterns showed that
  1. Different textures caused different firing patterns in an individual neuron
  2. Different neurons responded differently to the same texture
• These results showed that texture is represented in the cortex by the pattern of firing of many neurons
• Lieber and Bensmaia found that cortical neurons that fired best to coarse textures received input from SA1 neurons in the skin (Merkel receptors) and neurons that fired best to fine textures received input from PC receptors (Pacinian corpuscles)

Question 98

What’s active touch?

Answer 98

• Touch in which the observer plays an active role in touching and exploring an object, usually with his or her hands and fingers
• Involves haptic perception

Question 99

What’s passive touch?

Answer 99

A situation in which a person passively receives tactile stimulation on the skin, as when 2 points are pushed onto the skin to determine the two-point threshold

Question 100

What’s the difference between active touch and passive touch?

Answer 100

With active touch, where you move your fingers across the object, you’re much more involved in the process than with passive touch, and you have more control over what parts of the objects to which you’re exposed

Question 101

What’s haptic perception?

Answer 101

• The perception of three-dimensional objects by touch
• An example of a situation in which a number of different systems are interacting with each other
• These processes working together create an experience of active touch that is quite different from the experience of passive touch

Question 102

What 3 distinct systems are used to arrive at the goal of identifying objects?

Answer 102

1. Sensory system -> involved in detecting cutaneous sensations such as touch, temperature, and texture and the movements and positions of your fingers and hands
2. Motor system -> involved in moving your fingers and hands
3. Cognitive system -> involved in thinking about the information provided by the sensory and motor systems

Question 103

Why is haptic perception an extremely complex process?

Answer 103

• Because the sensory, motor, and cognitive systems must all work together
• Ex: the motor system’s control of finger and hand movements is guided by cutaneous feelings in the fingers and the hands, by your sense of the positions of the fingers and hands, and by thought processes that determine what information is needed about the object in order to identify it

Question 104

How did J. J. Gibson (1962) compare the experience of active and passive touch?

Answer 104

• By noting that we tend to relate passive touch to the sensation experienced in the skin, whereas we relate active touch to the object being touched
• Ex: if someone pushes a pointed object into your skin, you might say, “I feel a pricking sensation on my skin”; if, however, you push on the tip of the pointed object yourself, you might say, “I feel a pointed object”
• Thus, for passive touch you experience stimulation of the skin, and for active touch you experience the objects you are touching

Question 105

According to psychophysical research, how quickly can people accurately identify most common objects using active touch?

Answer 105

Within 1 or 2 seconds

Question 106

Describe Susan Lederman and Roberta Klatzky (1987, 1990) findings when they observed participants’ hand movements as they identified objects

Answer 106

They found that people use a number of distinctive movements, which they called exploratory procedures (EPs), and that the types of EPs used depend on the object qualities the participants are asked to judge

Question 107

What are exploratory procedures (EPs)?

Answer 107

• People’s movements of their hands and fingers while they are identifying three-dimensional objects by touch
• People tend to use just 1 or 2 EPs to determine a particular quality
• Ex: people use mainly lateral motion and contour following to judge texture, and they use enclosure and contour following to judge exact shape

Question 108

What are 4 of the EPs observed by Lederman and Klatzky?

Answer 108

• Lateral motion
• Pressure
• Enclosure
• Contour following

Question 109

Describe the process that occurs between exploring objects with our fingers to activating specialized neurons

Answer 109

Exploring objects with our fingers and hands activates mechanoreceptors that send signals toward the cortex. When these signals reach the cortex, they eventually activate specialized neurons

Question 110

What kind of receptive fields do neurons in the ventral posterior nucleus have?

Answer 110

• Center-surround receptive fields
• Similar to the center-surround receptive fields in the lateral geniculate nucleus, which is the visual area of the thalamus

Question 111

What’s the tactile area of the thalamus?

Answer 111

The ventral posterior nucleus

Question 112

What kind of neurons responding to touch do we see in the somatosensory cortex?

Answer 112

• In the cortex, we find some neurons with center-surround receptive fields and others that respond to more specialized stimulation of the skin
• There are neurons that respond to specific orientations and neurons that respond to movement across the skin in a specified direction
• There are also neurons in the monkey’s somatosensory cortex that respond when the monkey grasps a specific object -> in a monkey’s parietal cortex

Question 113

Cortical neurons involved in tactile perception are affected not only by the properties of an object but also by what?

Answer 113

By whether the perceiver is paying attention

Question 114

Describe Steven Hsiao and coworkers (1993, 1996) study on the effect of attention on cortical neuron responding to tactile information

Answer 114

• They recorded the response of neurons in areas S1 and S2 to raised letters that were scanned across a monkey’s finger
• In the tactile-attention condition, the monkey had to perform a task that required focusing its attention on the letters being presented to its fingers
• In the visual-attention condition, the monkey had to focus its attention on an unrelated visual stimulus
• The results show that even though the monkey is receiving exactly the same stimulation on its fingertips in both conditions, the response is larger for the tactile-attention condition
• Thus, stimulation of the receptors may trigger a response, but the size of the response can be affected by processes such as attention, thinking, and other actions of the perceiver

Question 115

How does a person’s active participation influence perception?

Answer 115

• It influences what stimuli stimulate the receptors
• It influences the processing that occurs once the receptors are stimulated

Question 116

What’s interpersonal touching/social touch?

Answer 116

One person touching another person

Question 117

What kind of nerve fibers are found in hairy skin?

Answer 117

CT afferents

Question 118

What are CT afferents?

Answer 118

• Unmyelinated nerve fibers found in hairy skin, which have been shown to be involved in social touch
• CT stands for C-tactile
• These fibers are unmyelinated, which means that they aren’t covered by the myelin sheath that covers the fibers associated with the receptors in glabrous skin
• The activity of these slow-conducting CT fibers was first recorded using a technique called microneurography

Question 119

What’s the difference between myelinated and unmyelinated nerve fibers?

Answer 119

Unmyelinated fibers conduct nerve impulses much more slowly than myelinated fibers, a property which is reflected in the type of stimuli they respond to

Question 120

What’s microneurography?

Answer 120

• Technique used to record neural signals that involves inserting a metal electrode with a very fine tip just under the skin
• When the skin on the forearm is stroked, the electrodes pick up signals as they are transmitted in nerve fibers conducting signals toward the brain

Question 121

Describe patient G.L.

Answer 121

• 54-year-old woman who contracted a disease that destroyed all of her myelinated fibers, which she reported had caused her to lose her sensation of touch
• Careful testing revealed that she could detect light brush strokes presented to the hairy part of her forearm, which contains CT afferents
• Her sensations of light touch were accompanied by activation of the insula, which receives signals from CT afferents
• These results led Olausson to propose that CT afferents are involved in “caress-like skin to skin contact between individuals” -> the type of stimulation that came to be called social touch

Question 122

What’s the social touch hypothesis?

Answer 122

• Research that followed the study of G.L. led to the social touch hypothesis
• Hypothesis that CT afferents and their central projections are responsible for social touch
• This was recognized as a new touch system that is different from the systems which sense the discriminative functions of touch
• The CT system, in contrast, is the basis of the affective function of touch

Question 123

What are the discriminative functions of touch?

Answer 123

Functions of the touch system such as sensing details, texture, vibration, and objects

Question 124

What are the affective functions of touch?

Answer 124

Sensing pleasure and therefore often eliciting positive emotions

Question 125

Describe Line Loken and coworkers (2009) study on the affective functions of social touch

Answer 125

• They focused on the pleasant aspect of social touch by using microneurography to record how fibers in the skin responded to stroking the skin with a soft brush
• Loken found that the stroking caused firing in CT afferents and also in the SA1 (associated with Merkel receptors) and SA2 myelinated fibers associated with the discriminative functions, but with an important difference
• Whereas the response of SA1 and SA2 fibers continued to increase as stroking velocity increased all the way to 30 cm per second, the response of the CT afferents peaked at 3–10 cm per second and then decreased
• CT afferents are therefore specialized for slow stroking
• Loken also had participants rate the pleasantness of the sensation caused by this slow stroking and found a relationship between pleasantness and CT afferent firing (higher firing rates for CT afferents are associated with higher pleasantness ratings)
• Further research showed that maximum pleasantness ratings occurred at stroking speeds associated with optimal CT firing

Question 126

What’s the main area of the brain that receives input from the CT afferents being stimulated by social touch?

Answer 126

• The insula
• Known to be involved in positive emotions

Question 127

Describe Monika Davidovic and coworkers (2019) study on the role of the insula in the detection of pleasant touch

Answer 127

• They determined the functional connectivity between different part of the insula caused by pleasant touch and found that slow stroking creates connections between the back of the insula, which receives sensory information, and the front of the insula, which is connected to emotional areas of the brain
• Apparently, this connection to emotional areas helps create the pleasurable response to social touch

Question 128

What kind of stroking of the arm (and other parts of the body) is pleasant?

Answer 128

Slow stroking

Question 129

The pleasant effects of slow stroking can be influenced by what other factors in addition to the location and rate of stroking?

Answer 129

Knowledge of who is doing the stroking can determine whether the stroking is perceived as pleasant or unpleasant

Question 130

Describe how Dan-Mikael Ellingsen and coworkers (2016) demonstrated the effect of knowledge on the perception of whether slow stroking is perceived as pleasant or unpleasant

Answer 130

• They demonstrated this effect by having heterosexual male participants rate the pleasantness on a scale of 1 (very unpleasant) to 20 (very pleasant) of a sensual caress to their arm
• They were led to believe that the caress was delivered by a female or a male
• Although the stroking was the same in both cases, the pleasantness rating was 9.2 if they thought they were being stroked by a male, and 14.2 if they thought they were being stroked by a female
• Results such as this demonstrate that although slow stroking is often pleasant, evaluation of the situation can turn a pleasant interaction into a less pleasant interaction or even a negative one

Question 131

What’s an example of how top-down processing (AKA knowledge-based processing) can influence the perception of social touch?

Answer 131

The fact that people’s thoughts about who is touching them can influence their perception of pleasantness

Question 132

What are the functions of pain?

Answer 132

Pain functions to warn us of potentially damaging situations and therefore helps us avoid or deal with cuts, burns, and broken bones

Question 133

What is pain?

Answer 133

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

Question 134

What are the 3 different types of pain determined by Joachim Scholz and Clifford Woolf (2002)?

Answer 134

• Inflammatory pain
• Neuropathic pain
• Nociceptive pain

Question 135

What’s inflammatory pain?

Answer 135

• Pain caused by damage to tissues, inflammation of joints, or tumor cells
• This damage releases chemicals that create an “inflammatory soup” that activates nociceptors

Question 136

What’s neuropathic pain?

Answer 136

• Pain caused by lesions or other damage to the nervous system
• Ex: Carpal tunnel syndrome, which is caused by repetitive tasks such as typing; spinal cord injury; and brain damage due to stroke

Question 137

What’s nociceptive pain?

Answer 137

Type of pain that serves as a warning of impending damage to the skin and is caused by activation of receptors in the skin called nociceptors

Question 138

What are nociceptors?

Answer 138

• A fiber that responds to stimuli that are damaging or potentially damaging to the skin
• A number of different kinds of nociceptors respond to different stimuli -> heat, chemical, severe pressure, and cold
• Signals from the nociceptors are transmitted to the spinal cord and then up the spinal cord in pathways that lead to the brain

Question 139

In the 1950s and early 1960s, how was pain explained?

Answer 139

Pain was explained by the direct pathway model of pain

Question 140

What’s the direct pathway model of pain?

Answer 140

• The idea that pain occurs when nociceptor receptors in the skin are stimulated and send their signals directly from the skin to the brain
• This model doesn’t account for the fact that pain can be affected by other factors in addition to stimulation of the skin
• Examples such as not perceiving the pain from serious wounds or perceiving pain when no signals are being sent to the brain couldn’t be explained by the direct pathway model

Question 141

Describe the report by Beecher (1959) on American soldiers wounded at the Anzio beachhead in World War II

Answer 141

• He reported that most American soldiers wounded at the Anzio beachhead in World War II “entirely denied pain from their extensive wounds or had so little that they didn’t want any medication to relieve it”
• One reason for this was that the soldiers’ wounds had a positive aspect: they provided escape from a hazardous battlefield to the safety of a behind-the-lines hospital

Question 142

What’s the phantom limb phenomena?

Answer 142

• A person’s continued perception of a limb, such as an arm or a leg, even though the limb has been amputated
• Example in which pain occurs without any transmission from receptor to brain
• This perception is so convincing that amputees have been known to try stepping off a bed onto phantom feet or legs, or to attempt to lift a cup with a phantom hand
• For many, the limb moves with the body, swinging while walking
• It’s not uncommon for amputees to experience pain in the phantom limb

Question 143

What causes pain in the phantom limb?

Answer 143

• One idea is that signals are sent from the part of the limb that remains after amputation
• However, researchers noted that cutting the nerves that used to transmit signals from the limb to the brain doesn’t eliminate either the phantom limb or the pain and concluded that the pain must originate not in the skin but in the brain
• This led Ronald Melzak and Patrick Wall (1965, 1983, 1988) to propose the gate control model of pain

Question 144

What’s the gate control model of pain?

Answer 144

• Melzack and Wall’s idea that perception of pain is controlled by a neural circuit that takes into account the relative amount of activity in nociceptors, mechanoreceptors, and central signals
• This model has been used to explain how pain can be influenced by factors other than stimulation of receptors in the skin
• This model begins with the idea that pain signals enter the spinal cord from the body and are then transmitted from the spinal cord to the brain
• The model proposes that there are additional pathways that influence the signals sent from the spinal cord to the brain
• The central idea behind the theory is that signals from these additional pathways can act to open or close a gate, located in the spinal cord, which determines the strength of the signal leaving the spinal cord
• The gate control system consists of cells in the dorsal horn of the spinal cord
• According to this model, the perception of pain is determined by a balance between input from nociceptors in the skin and non-nociceptive activity from the skin and the brain

Question 145

Along what 3 pathways does input to the gate control system occur?

Answer 145

• Nociceptors
• Mechanoreceptors
• Central control

Question 146

Describe how input to the gate control system occurs along the nociceptor pathway

Answer 146

• Fibers from nociceptors activate a circuit consisting entirely of excitatory synapses, and therefore send excitatory signals to the transmission cells
• Excitatory signals from the (+) neurons in the dorsal horn “open the gate” and increase the firing of the transmission cells
• Increased activity in the transmission cells results in more pain

Question 147

Describe how input to the gate control system occurs along the mechanoreceptor pathway

Answer 147

• Fibers from mechanoreceptors carry information about non-painful tactile stimulation
• An example of this type of stimulus would be signals sent from rubbing the skin
• When activity in the mechanoreceptors reaches the (–) neurons in the dorsal horn, inhibitory signals sent to the transmission cells “close the gate” and decrease the firing of the transmission cells
• This decrease in firing decreases the intensity of pain

Question 148

What are transmission cells?

Answer 148

• According to gate control theory, it’s the cell that receives + and − inputs from cells in the dorsal horn
• Transmission cell activity determines the perception of pain

Question 149

Describe how input to the gate control system occurs along the central control pathway

Answer 149

• These fibers, which contain information related to cognitive functions such as expectation, attention, and distraction, carry signals down from the cortex
• As with the mechanoreceptors, activity coming down from the brain also closes the gate, decreases transmission cell activity, and decreases pain

Question 150

How can top-down processes affect pain perception?

Answer 150

Modern research has shown that pain can be influenced by what a person expects, how the person directs his or her attention, the type of distracting stimuli that are present, and suggestions made under hypnosis

Question 151

Describe the hospital study on the effect of expectations on pain perception

Answer 151

In a hospital study in which surgical patients were told what to expect and were instructed to relax to alleviate their pain, the patients requested fewer painkillers following surgery and were sent home 2.7 days earlier than patients who were not provided with this information

Question 152

How does the placebo effect relate to the effect of expectations on pain perception?

Answer 152

• Studies have shown that a significant proportion of patients with pathological pain get relief from taking a placebo, a pill that they believe contains painkillers but that, in fact, contains no active ingredients (placebo effect)
• The key to the placebo effect is that the patient believes that the substance is an effective therapy
• This belief leads the patient to expect a reduction in pain, and this reduction does, in fact, occur
• Many experiments have shown that expectation is one of the more powerful determinants of the placebo effect

Question 153

What’s a placebo?

Answer 153

A substance that a person believes will relieve symptoms such as pain but that contains no chemicals that actually act on these symptoms

Question 154

What’s the placebo effect?

Answer 154

A relief from symptoms resulting from a substance that has no pharmacological effect

Question 155

Describe Ulrike Bingel and coworkers (2011) study on the effect of expectation on painful heat stimulation

Answer 155

• They demonstrated the effect of expectation on painful heat stimulation presented by an electrode on the calf of a person’s leg
• The heat was adjusted so the participant reported a pain rating of 70, where 0 corresponds to “no pain,” and 100 to “unbearable pain”
• Participants then rated the pain in a condition in which a saline solution was presented by infusion (baseline) and 3 conditions in which the analgesic drug remifentanil was presented, but the participants were told:
  1. That they were still receiving the saline solution (no expectation)
  2. That the drug was being presented (positive expectation)
  3. That the drug was going to be discontinued in order to investigate the possible increase in pain that would occur (negative expectation)
• The results indicate that pain was reduced slightly, from 66 to 65, in the no expectation condition when the drug infusion began, but dropped to 39 in the positive expectation condition, then increased to 64 in the negative expectation condition
• After the saline baseline condition, the participant was continuously receiving the same dose of the drug
• What was being changed was their expectation, and this change in expectation changed their experience of pain
• The decrease in pain experienced in the positive expectation condition is a placebo effect, in which the positive expectation instructions function as the placebo
• The negative effect caused by the negative expectation instructions is called a nocebo effect

Question 156

Describe Ulrike Bingel and coworkers (2011) findings on the participants’ brain activity during the study on the effect of expectation on painful heat stimulation

Answer 156

• They found that the placebo effect was associated with increases in a network of areas associated with pain perception, and the nocebo effect was associated with increases in activity in the hippocampus
• A person’s expectation therefore affects both perception and physiological responding

Question 157

What’s the nocebo effect?

Answer 157

A negative placebo effect, characterized by a negative response to negative expectations

Question 158

How has the technique of distracting a person’s attention from the source of the pain, as a way to decrease pain been used?

Answer 158

• It has been used in hospitals with virtual reality techniques as a tool to distract attention from a painful stimulus
• Ex: the case of James Pokorny
• Studies of other patients indicate that burn patients using this virtual reality technique experienced much less pain when their bandages were being changed than patients in a control group who were distracted by playing video games or who were not distracted at all

Question 159

Describe the case of James Pokorny

Answer 159

• He received third-degree burns over 42% of his body when the fuel tank of the car he was repairing exploded
• While having his bandages changed at the University of Washington Burn Center, he wore a plastic helmet with a computer monitor inside, on which he saw a virtual world of multicolored 3D graphics
• This world placed him in a virtual kitchen that contained a virtual spider, and he was able to chase the spider into the sink so he could grind it up with a virtual garbage disposal
• The point of this “game” was to reduce Pokorny’s pain by shifting his attention from the bandages to the virtual reality world
• Pokorny reports that “you’re concentrating on different things, rather than your pain. The pain level went down significantly”

Question 160

What’s a common way that we can see how attention affects pain perception?

Answer 160

Often people don’t feel pain from their injuries until they realize they have an injury

Question 161

What have many experiments on how pain perception can be influenced by a person’s emotional states shown?

Answer 161

That positive emotions are associated with decreased pain

Question 162

What are 2 ways that the idea of positive emotions being associated with decreased pain been shown?

Answer 162

• By having people look at pictures
• By having people listen to music

Question 163

Describe Minet deWied and Marinis Verbaten (2001) study on how looking at pictures can affect pain perception

Answer 163

• They had participants look at pictures that had been previously rated as being positive (sports pictures and attractive females), neutral (household objects, nature, and people), or negative (burn victims and accidents)
• The participants looked at the pictures while one of their hands was immersed in cold (2°C/35.6°F) water, and they were told to keep the hand immersed for as long as possible but to withdraw the hand when it began to hurt
• The results indicated that participants who were looking at the positive pictures kept their hands immersed for an average of 120 secs, but participants in the other groups removed their hands more quickly (80 secs for neutral pictures; 70 secs for negative pictures)
• Because their ratings of the intensity of their pain made immediately after removing their hands from the water was the same for all 3 groups, they concluded that the content of the pictures influenced the time it took to reach the same pain level in the 3 groups

Question 164

Describe Jaimie Rhudy and coworkers (2005) study on how looking at pictures can affect pain perception

Answer 164

• They found that participants gave lower ratings to pain caused by an electric shock when they were looking at pleasant pictures than when they were looking at unpleasant pictures
• They concluded from this result that positive or negative emotions can affect the experience of pain

Question 165

Describe Mathieu Roy and coworkers (2008) study on how music affected the perception of a thermal heat stimulus

Answer 165

• They measured how music affected the perception of a thermal heat stimulus presented to the forearm by having participants rate the intensity and unpleasantness of the pain on a scale of 0 (no pain) to 100 (extremely intense or extremely unpleasant), under one of 3 conditions: listening to unpleasant music (ex: Sonic Youth, Pendulum Music), listening to pleasant music (ex: Rossini, William Tell Overture), and silence
• The results of Roy’s experiment for the highest temperature used (48°C/119°F) indicates that listening to unpleasant music didn’t affect pain, compared to silence, but that listening to pleasant music decreased both the intensity and the unpleasantness of pain
• The pain relief caused by the pleasant music was comparable to the effects of common analgesic drugs such as ibuprofen

Question 166

What is the sense of taste created by?

Answer 166

Receptors on the tongue

Question 167

What is the sense of smell created by?

Answer 167

Receptors in the nose

Question 168

What 2 senses make up flavour?

Answer 168

Taste and smell, which is the dominant perception we experience when eating or drinking

Question 169

What’s anosmia?

Answer 169

• Loss of the ability to smell due to injury or infection
• This loss is associated with dramatic effects on a person’s quality of life

Question 170

Describe the findings of a study on anosmia and hazardous events (Cameron, 2018; Santos et al., 2004)

Answer 170

45% of people with anosmia had experienced at least one such hazardous event (ex: food poisoning or failure to detect fire or leaking natural gas) compared to 19% of people with normal olfactory function

Question 171

What are the 3 components of the chemical senses?

Answer 171

• Taste
• Olfaction (smell)
• Flavour

Question 172

What’s taste?

Answer 172

The chemical sense that occurs when molecules—often associated with food—enter the mouth in solid or liquid form and stimulate receptors on the tongue

Question 173

What’s olfaction?

Answer 173

-Sense of smell
- Usually occurs when airborne molecules enter the nose and stimulate receptor neurons in the olfactory mucosa, located on the roof of the nasal cavity

Question 174

What’s flavour?

Answer 174

The perception that occurs from the combination of taste and olfaction

Question 175

What’s a property that distinguishes the chemical senses from the other senses?

Answer 175

• While the receptors for the other senses are hidden in our bodies, protected from the environment (ex: in eyeball, in skin, in cochlea), for taste and smell, molecules stimulate receptors that are exposed to the environment
• In other words, the molecules have direct contact with the receptors for taste and smell

Question 176

How does the exposure of taste and smell receptors to the environment affect them?

Answer 176

• Because they’re constantly exposed not only to the chemicals they are designed to sense but also to harmful materials such as bacteria and dirt, they undergo a cycle of birth, development, and death over 5–7 weeks for olfactory receptors and 1–2 weeks for taste receptors
• This constant renewal of the receptors, called neurogenesis, is unique to these senses

Question 177

What’s neurogenesis?

Answer 177

• The cycle of birth, development, and death of a neuron
• This process occurs for the receptors for olfaction and taste

Question 178

Because the stimuli responsible for tasting and smelling are taken into the body, these senses are often seen as what?

Answer 178

“Gatekeepers”

Question 179

What are the gatekeeping functions of the sense of taste and smell?

Answer 179

1. They can identify things that the body needs for survival and that should therefore be consumed
2. They can detect things that would be bad for the body and that should therefore be rejected
   - This is especially true for taste because we often use taste to choose which foods to eat and which to avoid

Question 180

What’s another factor that aids the gatekeeping function of the sense of taste and smell?

Answer 180

• The gatekeeper function of taste and smell is aided by a large affective, or emotional, component -> things that are bad for us often taste or smell unpleasant, and things that are good for us generally taste or smell good
• In addition to creating “good” and “bad” affect, smelling an odor associated with a past place or event can trigger memories, which in turn may create emotional reactions

Question 181

What are the 5 basic taste sensations/qualities?

Answer 181

• Salty
• Sour
• Sweet
• Bitter
• Umami (which has been described as meaty, brothy, or savory, and is often associated with the flavor-enhancing properties of MSG, monosodium glutamate)

Question 182

Describe Donald McBurney’s study (1969) on the different taste sensations/qualities

Answer 182

• In an early experiment on taste quality, before umami became the 5th basic taste, he presented taste solutions to participants and asked them to make magnitude estimates of the intensity of each of the 4 taste qualities for each solution
• He found that some substances have a predominant taste quality and that other substances result in combinations of the 4 taste qualities
• Ex: sodium chloride (salty), hydrochloric acid (sour), sucrose (sweet), and quinine (bitter) are compounds that come the closest to having only one of the 4 basic tastes
• However, the compound potassium chloride (KCl) has substantial salty and bitter components, whereas sodium nitrate results in a taste consisting of a combination of salty, sour, and bitter
• Results such as these have led most researchers to accept the idea of basic tastes

Question 183

How does taste accomplish its gatekeeper function?

Answer 183

By the connection between taste quality and a substance’s effect

Question 184

Describe the qualities of sweetness

Answer 184

• It’s often associated with compounds that have nutritive or caloric value and that are, therefore, important for sustaining life
• Sweet compounds cause an automatic acceptance response and also trigger anticipatory metabolic responses that prepare the gastrointestinal system for processing these substances

Question 185

Describe the qualities of bitterness

Answer 185

• Bitter compounds have the opposite effect of sweet compounds
• They trigger automatic rejection responses to help the organism avoid harmful substances
• Examples of harmful substances that taste bitter are the poisons strychnine, arsenic, and cyanide

Question 186

Describe the qualities of saltiness

Answer 186

• Salty tastes often indicate the presence of sodium
• When people are deprived of sodium or lose a great deal of sodium through sweating, they often seek out foods that taste salty in order to replenish the salt their body needs

Question 187

Why are the connections we make between a taste’s quality and its function in the body not entirely accurate?

Answer 187

• People often make the mistake of eating good-tasting poisonous mushrooms, and there are artificial sweeteners, such as saccharine and sucralose, that have no metabolic value
• There are also bitter foods that aren’t dangerous and do have metabolic value
• People can also learn to modify their responses to certain tastes -> ex: when they develop a taste for foods they may have initially found unappealing, such as the bitter tastes in beer and coffee

Question 188

Where does the process of tasting begin?

Answer 188

With the tongue

Question 189

The surface of the tongue contains many ridges and valleys caused by what?

Answer 189

The presence of structures called papillae

Question 190

What are papillae?

Answer 190

• Ridges and valleys on the tongue, some of which containing taste buds
• Each papilla contains a number of taste buds

Question 191

What are the 4 types of papillae?

Answer 191

• Filiform
• Fungiform
• Foliate
• Circumvallate

Question 192

What are filiform?

Answer 192

• Type of papillae
• Shaped like cones and are found over the entire surface of the tongue, giving it its rough appearance

Question 193

What are fungiform?

Answer 193

• Type of papillae
• Shaped like mushrooms and are found at the tip and sides of the tongue

Question 194

What are foliate?

Answer 194

• Type of papillae
• A series of folds along the back of the tongue on the sides

Question 195

What are circumvallate?

Answer 195

• Type of papillae
• Shaped like flat mounds surrounded by a trench and are found at the back of the tongue

Question 196

Where does the taste stimulus enter?

Answer 196

Through the taste pore

Question 197

Where is the tip of the taste cell located?

Answer 197

It’s positioned just under the pore

Question 198

What’s the tongue?

Answer 198

• The receptor sheet for taste
• Contains papillae and other structures

Question 199

What are taste buds?

Answer 199

• A structure located within papillae on the tongue that contains the taste cells
• There are about 10,000 taste buds

Question 200

What are taste cells?

Answer 200

• Cells that make up a taste bud
• There are a number of cells for each bud, and the tip of each one sticks out into a taste pore
• One or more nerve fibers are associated with each cell
• Cause the transduction of chemical to electrical energy when chemicals contact receptor sites or channels located at the tip of these cells

Question 201

What are the receptor sites for taste?

Answer 201

• Sites located on the tips of the taste cells
• There are different types of sites for different chemicals
• Chemicals contacting the sites cause transduction by affecting ion flow across the membrane of the taste cell

Question 202

All kinds of papillae except for which contain taste buds?

Answer 202

Except the filiform papillae

Question 203

Why does stimulation of the central part of the tongue cause no taste sensations?

Answer 203

Because the filiform papillae are the only type of papillae located there and they contain no taste buds

Question 204

Each taste bud contains how many taste cells?

Answer 204

50 to 100

Question 205

What’s the taste pore?

Answer 205

• An opening in the taste bud through which the tips of taste cells protrude
• When chemicals enter a taste pore, they stimulate the taste cells and result in transduction

Question 206

Electrical signals generated in the taste cells are transmitted from the tongue toward the brain in what different nerves?

Answer 206

1. Chorda tympani nerve (from taste cells on the front and sides of the tongue)
2. Glossopharyngeal nerve (from the back of the tongue)
3. Vagus nerve (from the mouth and throat)
4. Superficial petrosal nerve (from the soft palete—the top of the mouth)

Question 207

The fibers from the tongue, mouth, and throat make connections where?

Answer 207

In the brain stem located in the nucleus of the solitary tract

Question 208

What’s the nucleus of the solitary tract?

Answer 208

• The nucleus in the brain stem that receives signals from the tongue, the mouth, and the larynx transmitted by the chorda tympani, glossopharyngeal, and vagus nerves
• This is where nerve fibers from the tongue and the mouth synapse in the medulla at the base of the brain

Question 209

Describe the central pathway to the brain for taste signals

Answer 209

1. The fibers from the tongue, mouth, and throat make connections in the brain stem in the nucleus of the solitary tract -> this is where nerve fibers from the tongue and the mouth synapse in the medulla at the base of the brain
2. From there, signals travel to the thalamus and the fibers synapse in the thalamus
3. They then travel to 2 areas in the frontal lobe—the insula and the frontal operculum -> where they synapse in the insula and frontal operculum

Question 210

What are the 2 areas in the frontal lobe that are considered to be the primary taste cortex (AKA cortical taste areas)?

Answer 210

• Insula
• Frontal operculum
• They are partially hidden behind the temporal lobe

Question 211

What’s the insula?

Answer 211

An area in the frontal lobe of the cortex that receives signals from the taste system and is also involved in the affective component of the perception of pain

Question 212

What’s the frontal operculum?

Answer 212

An area in the frontal lobe of the cortex that receives signals from the taste system

Question 213

What’s specificity coding?

Answer 213

The idea that quality is signaled by the activity in individual neurons that are tuned to respond to specific qualities

Question 214

What’s population coding?

Answer 214

• The idea that quality is signaled by the pattern of activity distributed across many neurons
• Population coding is generally favoured over specificity coding
• Population coding is involved in determining taste as well, especially at higher levels of the taste system

Question 215

Describe Robert Erickson’s (1963) study on population coding for taste

Answer 215

• He conducted one of the first experiments that demonstrated population coding
• He presented a number of different taste stimuli to a rat’s tongue and recorded the response of the chorda tympani nerve
• He found that 13 nerve fibers responded to ammonium chloride , potassium chloride (KCl), and sodium chloride (NaCl) -> 3 salts
• He called these patterns the across-fiber patterns, which is another name for population coding
  -The across-fiber patterns for ammonium chloride and potassium chloride are similar to each other but different from the pattern for sodium chloride

Question 216

What are across-fiber patterns?

Answer 216

• The pattern of nerve firing that a stimulus causes across a number of neurons
• AKA distributed coding or population coding

Question 217

What conclusion did Erikson make from his findings in his 1963 study about taste perception and how did he measure this?

Answer 217

• He reasoned that if the rat’s perception of taste quality depends on the across-fiber pattern, then 2 substances with similar patterns should taste similar
• The electrophysiological results would predict that ammonium chloride and potassium chloride should taste similar and that both should taste different from sodium chloride
• To test this hypothesis, Erickson shocked rats while they were drinking potassium chloride and then gave them a choice between ammonium chloride and sodium chloride
• If potassium chloride and ammonium chloride taste similar, the rats should avoid the ammonium chloride when given a choice
• This is exactly what the rats did
• When the rats were shocked for drinking ammonium chloride, they subsequently avoided the potassium chloride, as predicted by the electrophysiological results

Question 218

What did Susan Schiffman and Robert Erickson (1971) find when testing taste perceptions in humans?

Answer 218

• When they asked humans to make similarity judgments between a number of different solutions, they found that substances that were perceived to be similar were related to patterns of firing for these same substances in the rat
• Solutions judged more similar psychophysically had similar patterns of firing, as population coding would predict

Question 219

Most of the evidence for specificity coding comes from where?

Answer 219

From research that has recorded neural activity early in the taste system

Question 220

The evidence supporting the existence of receptors that respond specifically to a particular taste has been obtained by using what?

Answer 220

• Genetic cloning
• Which makes it possible to add or eliminate specific receptors in mice

Question 221

Describe Ken Mueller and coworkers (2005) series of experiments using a chemical compound called PTC

Answer 221

• PTC tastes bitter to humans but isn’t bitter to mice
• The lack of bitter PTC taste in mice is inferred from the fact that mice don’t avoid even high concentrations of PTC in behavioral tests
• Because a specific receptor in the family of bitter receptors had been identified as being responsible for the bitter taste of PTC in humans, Mueller decided to see what would happen if he used genetic cloning techniques to create a strain of mice that had this human bitter-PTC receptor
• When he did this, the mice with this receptor avoided high concentrations of PTC

Question 222

Describe Mueller’s experiment on cyclohexamide (Cyx)

Answer 222

• Mueller created a strain of mice that lacked a bitter receptor that responds to a compound called cyclohexamide (Cyx)
• Mice normally have this receptor, so they avoid Cyx
• But the mice lacking this receptor didn’t avoid Cyx
• Cyx also no longer caused any firing in nerves receiving signals from the tongue

Question 223

What did Mueller’s experiments demonstrate about taste receptors?

Answer 223

That when the taste receptor for a substance is eliminated, this is reflected in both nerve firing and the animal’s behavior

Question 224

TRUE OR FALSE: In Mueller’s experiments on taste receptors, he found that adding or eliminating bitter receptors had no effect on neural firing or behavior to sweet, sour, salty, or umami stimuli

Answer 224

TRUE

Question 225

Mueller’s and others’ experiments in which adding a receptor makes an animal sensitive to a specific quality and eliminating a receptor makes an animal insensitive to a specific quality have been cited as support for what?

Answer 225

• Specificity coding
• The idea that there are receptors that are specifically tuned to sweet, bitter, and umami tastes

Question 226

Describe Eugene Delay and coworkers (2006) findings on taste receptors

Answer 226

• They showed that with different behavioral tests, mice that appeared to have been made insensitive to sugar by eliminating a “sweet” receptor can actually still show a preference for sugar
• Based on this result, Delay suggests that perhaps there are a number of different receptors that respond to specific substances like sugar

Question 227

Research on how single neurons respond to taste stimuli has provided evidence for what?

Answer 227

• For specificity coding in taste
• Recordings from neurons at the beginning of the taste systems of animals (ex: from the cell bodies of chorda tympani nerve fibers), ranging from rats to monkeys, have revealed neurons that are specialized to respond to specific stimuli, as well as neurons that respond to a number of different types of stimuli

Question 228

What taste corresponds with sucrose?

Answer 228

Sweet to humans

Question 229

What taste corresponds with sodium chloride (NaCl)?

Answer 229

Salty

Question 230

What taste corresponds with hydrochloric acid (HCl)?

Answer 230

Sour in low concentrations

Question 231

What taste corresponds with quinine (QHCl)?

Answer 231

Bitter

Question 232

What’s amiloride?

Answer 232

• A substance that blocks the flow of sodium into taste receptors
• The sodium channel that’s blocked by amiloride is important for determining saltiness in rats and other animals, but not in humans

Question 233

Research on the effect of presenting amiloride to the tongue has provided evidence for what?

Answer 233

• Specificity coding
• Applying amiloride to the tongue causes a decrease in the responding of neurons in the rat’s brainstem (nucleus of the solitary tract) that respond best to salt but has little effect on neurons that respond best to a combination of salty and bitter tastes
• Thus, eliminating the flow of sodium across the membrane selectively eliminates responding of salt-best neurons but does not affect the response of neurons that respond best to other tastes

Question 234

Describe David Smith and Thomas Scott (2003) argument for population coding

Answer 234

They argue for population coding based on the finding that at more central locations in the taste system, neurons are tuned broadly, with many neurons responding to more than one taste quality

Question 235

Describe Smith and coworkers (2000) argument for population coding

Answer 235

• They point out that just because there are neurons that respond best to one compound like salty or sour, this doesn’t mean that these tastes are signaled by just one type of neuron
• They illustrate this by drawing an analogy between taste perception and the mechanism for color vision
• Even though presenting a long-wavelength light that appears red may cause the highest activation in the long-wavelength cone pigment, our perception of red still depends on the combined response of both the long- and medium-wavelength pigments
• Similarly, salt stimuli may cause high firing in neurons that respond best to salt, but other neurons are probably also involved in creating saltiness

Question 236

What’s one suggestion that settles the population coding VS specificity coding debate about taste signaling?

Answer 236

• That basic taste qualities might be determined by a specific code, but population coding could determine subtle differences between tastes within a category
• This would help explain why not all substances in a particular category have the same taste
• Ex: the taste of all sweet substances is not identical

Question 237

What kind of animal experiences “sweet blindness”?

Answer 237

• Domestic cats
• They don’t prefer the sweetness of sugar, even though they display human-like taste behavior to other compounds, such as avoiding compounds that taste bitter or very sour to humans
• Genetic research has shown that this “sweet blindness” occurs because cats lack a functional gene for formation of a sweet receptor and so, lacking a sweet receptor, have no mechanism for detecting sweetness

Question 238

What’s a factor that affects certain people’s ability to sense the taste of certain substances?

Answer 238

• Genetic differences
• Ex: Differences in people’s ability to taste the bitterness of PTC or not
• Ex: Differences in people’s perception of the sweetness of sucrose

Question 239

Describe the genetic differences in the detection of phenylthiocarbamide (PTC)

Answer 239

• The different reactions to PTC were discovered accidentally in 1932 by Arthur L. Fox, a chemist
• Fox had prepared some PTC, and when he poured the compound into a bottle, some of the dust escaped into the air
• One of his colleagues complained about the bitter taste of the dust, but Fox, much closer to the material, noticed nothing
• Albert F. Blakeslee, a geneticist of the era, pursued this observation

Question 240

Describe Albert F. Blakeslee study on the genetic differences in the detection of phenylthiocarbamide (PTC)

Answer 240

• At a meeting of the American Association for the Advancement of Science (AAAS) in 1934, Blakeslee prepared an exhibit that dispensed PTC crystals to 2,500 of the conferees
• The results: 28% of them described it as tasteless, 66% as bitter, and 6% as having some other taste

Question 241

What are the names used to describe people who can and people who cannot taste PTC?

Answer 241

• People who can taste PTC are described as tasters
• Those who cannot are called nontasters

Question 242

Describe the findings on the genetic differences in the detection of 6-n-propylthiouracil (PROP)

Answer 242

• PROP has properties similar to those of PTC
• Researchers have found that about 1/3 of Americans report that PROP is tasteless and 2/3 can taste it

Question 243

What causes the differences in people’s ability to taste 6-n-propylthiouracil (PROP)?

Answer 243

One explanation for these differences is that people who can taste PROP have higher densities of taste buds than those who can’t taste it

Question 244

What are factors that determine individual differences in taste?

Answer 244

• Receptor density
• The presence of specialized receptors

Question 245

What have advances in genetic techniques who have made it possible to determine the locations and identities of genes on human chromosomes that are associated with taste and smell receptors, helped identify about PTC and PROP?

Answer 245

They have shown that PROP and PTC tasters have specialized receptors that are absent in nontasters

Question 246

What are people who are especially sensitive to PROP called?

Answer 246

Supertasters

Question 247

What has research on supertasters (those who are especially sensitive to PROP) shown about their sensitivity to bitterness?

Answer 247

That these people may actually be more sensitive to most bitter substances, as if the amplification in the bitter taste system is turned up for all bitter compounds

Question 248

The next time you disagree with someone about the taste of a particular food, why should you not automatically assume that your disagreement is simply a reflection of your individual preferences?

Answer 248

Because it may reflect not a difference in preference (you like sweet things more than John does) but a difference in perception (you perceive sweet tastes as more intense than John does), which could be caused by differences in the types and numbers of taste receptors on the tongue or other differences in your taste systems

Question 249

What has video micrograph of the tongue showing the fungiform papillae of a “supertaster” vs a “nontaster” demonstrated?

Answer 249

That the supertaster has both more papillae and more taste buds than the nontaster

Question 250

How has the importance of olfaction been minimized in many textbooks?

Answer 250

These textbooks describe human olfaction as being microsmatic, while describing olfaction in other animals, and especially dogs, as macrosmatic

Question 251

What’s microsmatic?

Answer 251

• Having a weak sense of smell
• This usually occurs in animals, such as humans, in which the sense of smell is not crucial for survival

Question 252

What’s macrosmatic?

Answer 252

• Having a well-developed sense of smell
• Usually important to an animal’s survival
• Ex: in dogs

Question 253

What have recent measurements of the sensitivity of humans and animals to different odors indicated?

Answer 253

• That humans are more sensitive to many odors than a wide range of animals, including mice, monkeys, rabbits, and seals
• Also that although dogs are far more sensitive than humans to some odors, human’s sensitivity equals dog’s for others

Question 254

Describe Caroline Bushdid and coworkers (2014) study on the detection of different olfactory stimuli in humans

Answer 254

• They tested participants to determine how many components of a substance they could change before they could detect the difference between 2 substances
• Based on their results, plus an estimate of the number of possible odors, they proposed that humans can discriminate the difference in the smells of more than 1 trillion olfactory stimuli

Question 255

TRUE OR FALSE: humans can’t track scents in a field

Answer 255

FALSE: it has been shown that humans, like dogs, can track scents in a field

Question 256

List in order, the top 3 senses that can discriminate between the most stimuli

Answer 256

• Olfaction
• Vision
• Hearing

Question 257

What enables us to detect extremely low concentrations of some odorants?

Answer 257

Our sense of smell

Question 258

What’s the detection threshold for olfaction (odors)?

Answer 258

The lowest concentration at which an odorant can be detected

Question 259

What’s one method for measuring detection thresholds for olfaction?

Answer 259

The forced-choice method

Question 260

What’s the forced-choice method?

Answer 260

• Method in which 2 choices are given, and the subject has to pick one
• Ex: a subject is presented with blocks of 2 trials—a weak odorant on one trial, and no odorant on another trial, and has to pick the trial on which the odorant was presented (or which trial has a stronger smell)
• The threshold is determined by measuring the concentration that results in a correct response on 75% of the trials (50% would be chance performance)

Question 261

TRUE OR FALSE: there is a very large range of human odor detection thresholds

Answer 261

• TRUE
• Ex: the difference between T-butyl mercaptan and acetone or methanol
• T-butyl mercaptan, the odorant that’s added to natural gas to warn people of gas leaks, can be detected in very small concentrations of less than 1 part per billion in air
• In contrast, to detect the vapors of acetone (the main component of nail polish remover), the concentration must be 15,000 parts per billion, and for the vapor of methanol, the concentration must be 141,000 parts per billion

Question 262

Although humans can discriminate millions or perhaps trillions of different odors, what do they struggle with with regards to olfaction?

Answer 262

• They often find it difficult to accurately identify specific odors
• Ex: when people are presented with the odors of familiar substances such as mint, bananas, and motor oil, they can easily tell the difference between them. However, when they are asked to identify the substance associated with the odor, they are successful less than half the time
• However, when people are trained in identifying odors by being told the names of substances when they first smell them and then being reminded of the correct names if they fail to name them correctly on subsequent presentations, they can eventually identify 98% of the substances

Question 263

How does knowing the correct label for an odor affect us?

Answer 263

Knowing the correct label for the odor actually seems to transform our perception into that odor

Question 264

When we have trouble identifying odors, this trouble may occur not because of a deficiency in our olfactory system, but from an inability to do what?

Answer 264

From an inability to retrieve the odor’s name from our memory

Question 265

What causes individual differences in olfaction?

Answer 265

• Having a condition -> ex: people with anosmia who have lost their sense of smell
• Genetic conditions which cause selective losses of some smells -> ex: the chemical β-ionone
• Having a viral infection -> ex: decreases in olfaction is one of the symptoms of the viral infection COVID-19

Question 266

Describe genetic variation in olfaction with regards to the chemical β-ionone

Answer 266

• A section of the human chromosome is associated with receptors that are sensitive to the chemical β-ionone, which is often added to foods and beverages to add a pleasant floral note
• Individuals sensitive to β-ionone describe paraffin with low concentrations of β-ionone added as “fragrant” or “floral,” whereas individuals with less sensitivity to β-ionone describe the same stimulus as “sour,” “pungent,” or “acid”
• Genetically caused variation in sensitivity occurs for many other chemicals

Question 267

Genetically caused variation in olfactory sensitivity for many different chemicals led to what idea?

Answer 267

To the idea that everyone experiences their own unique “flavor world”

Question 268

What’s a predictor of Alzheimer’s disease?

Answer 268

Decreases in olfaction

Question 269

Describe the asparagus example of individual differences in smell

Answer 269

• After eating asparagus some people’s urine takes on a smell that has been described as sulfurous, much like cooked cabbage
• Some people, however, can’t detect this smell

Question 270

Describe the androsterone example of individual differences in smell

Answer 270

• The smell of the steroid androsterone, which is derived from testosterone, is described negatively (“sweaty,” “urinous”) by some people, positively by some people (“sweet,” “floral”), and as having no odor by others

Question 271

What are sustentacular cells?

Answer 271

Cells that provide metabolic and structural support to the olfactory sensory neurons

Question 272

Which sensory system appears to be much more sensitive than the visual system or auditory system to neural dysfunction?

Answer 272

• The olfactory system
• Although some visual loss precedes AD symptoms, the loss of olfactory function is the key sensory biomarker for predicting development of AD

Question 273

Describe Jayant Pinto and coworkers (2014) finding on loss of olfaction being associated with a higher risk of death

Answer 273

They found that in a group of older adults (57–87 years old), who were representative of the general U.S. population, people with anosmia (loss of smell) were 3x more likely to die within 5 years than people with normal smell

Question 274

What’s the olfactory stimuli for the sense of smell?

Answer 274

Molecules in the air

Question 275

What are reasons for why creating a way to organize odors and to relate odors to physical properties of molecules has proven extremely difficult?

Answer 275

1. We lack a specific language for odor quality
2. Some molecules that have similar structures can smell different and molecules that have very different structures can smell similar
3. The kinds of odors we routinely encounter in the environment consist of mixtures of many chemicals
4. Odors rarely occur in isolation (ex: all the odors in a kitchen)

Question 276

What’s an example of humans lacking a specific language for odor quality?

Answer 276

• When people smell the chemical α-ionone, they usually say that it smells like violets
• This description is fairly accurate, but if you compare α-ionone to real violets, they smell different
• The perfume industry’s solution is to use names such as “woody violet” and “sweet violet” to distinguish between different violet smells

Question 277

What’s an example of a kind of odor we routinely encounter in the environment that consists of mixtures of many chemicals?

Answer 277

• Coffee
• When you walk into the kitchen and smell freshly brewed coffee, the coffee aroma is created by more than 100 different molecules
• Although individual molecules may have their own odors, we don’t perceive the odors of individual molecules; we perceive “coffee”

Question 278

What are odor objects?

Answer 278

The source of an odor, such as coffee, bacon, a rose, or car exhaust

Question 279

Perceiving odor objects involves olfactory processing that occurs in what 2 stages?

Answer 279

1. The first stage, which takes place at the beginning of the olfactory system in the olfactory mucosa and olfactory bulb, involves analyzing
   - In this stage, the olfactory system analyzes the different chemical components of odors and transforms these components into neural activity at specific places in the olfactory bulb
2. The second stage, which takes place in the olfactory cortex and beyond, involves synthesizing
   - In this stage, the olfactory system synthesizes the information about chemical components received from the olfactory bulb into representations of odor objects

Question 280

What 2 cognitive processes have been proposed to be involved with the synthesis stage of olfactory processing for perceiving odor objects?

Answer 280

Learning and memory

Question 281

Describe the structure of initial structures in the olfactory system

Answer 281

1. Odorant molecules enter the nose and then flow over the olfactory mucosa, which contains olfactory receptor neurons (ORNs)
2. Stimulation of receptors in the ORNs activates the ORNs
3. Signals from the ORNs are then sent to glomeruli in the olfactory bulb, and then to higher cortical areas

Question 282

The perception of odor objects from hundreds of intermixed molecules is a feat of what?

Answer 282

Perceptual organization

Question 283

What’s the olfactory mucosa?

Answer 283

• Dime-sized region located on the roof of the nasal cavity just below the olfactory bulb
• Region inside the nose that contains the receptors for the sense of smell
• The human mucosa contains 400 types of ORNs and about 10,000 of each type, so the mucosa contains millions of ORNs
• All ORNs of a particular type send their signals to one or two glomeruli in the olfactory bulb

Question 284

What’s the olfactory bulb?

Answer 284

• The structure that receives signals directly from the olfactory receptors
• The olfactory bulb contains glomeruli, which receive these signals from the receptors

Question 285

How do odorant molecules come into contact with the olfactory mucosa?

Answer 285

Odorant molecules are carried into the nose in an air stream, which brings these molecules into contact with the mucosa

Question 286

What are olfactory receptor neurons (ORNs)?

Answer 286

Sensory neurons located in the olfactory mucosa and the supporting cells that contain the olfactory receptors

Question 287

The olfactory receptor neurons in the mucosa are dotted with what kind of molecules?

Answer 287

Olfactory receptors that are sensitive to chemical odorants

Question 288

What are olfactory receptors?

Answer 288

A protein string that responds to odor stimuli

Question 289

What’s a parallel between visual pigments and olfactory receptors?

Answer 289

• They’re both sensitive to a specific range of stimuli
• Ex: each type of visual pigment is sensitive to a band of wavelengths in a particular region of the visible spectrum and each type of olfactory receptor is sensitive to a narrow range of odorants

Question 290

What’s an important difference between the visual system and the olfactory system?

Answer 290

While there are only 4 different types of visual pigments (one rod pigment and 3 cone pigments), there are about 400 different types of olfactory receptors, each sensitive to a particular group of odorants

Question 291

What did Linda Buck and Richard Axel (1991) discover about olfactory receptors in humans and mice?

Answer 291

• They discovered that there are 350 to 400 types of olfactory receptors in the human and 1,000 types in the mouse
• They received the 2004 Nobel Prize in Physiology and Medicine for their research on the olfactory system

Question 292

What increases the challenges in understanding how olfaction works?

Answer 292

• The large number of olfactory receptor types
• One thing that makes things slightly simpler is another parallel with vision: Just as a particular rod or cone receptor contains only one type of visual pigment, a particular olfactory receptor neuron (ORN) contains only one type of olfactory receptor

Question 293

Describe the method of calcium imaging for olfactory receptors

Answer 293

• When an olfactory receptor responds, the concentration of calcium ions (Ca++) increases inside the OR
• Calcium imaging measures this increase in calcium ions by soaking olfactory neurons in a chemical that causes the ORN to fluoresce with a green glow when exposed to ultraviolet (380 nm) light
• This green glow can be used to measure how much Ca++ had entered the neuron because increasing Ca++ inside the neuron decreases the glow
• Thus, measuring the decrease in fluorescence indicates how strongly the ORN is activated

Question 294

What’s a method used to measure how the ORNs that blanket the olfactory mucosa respond to different odorants?

Answer 294

Calcium imaging

Question 295

Describe Bettina Malnic and coworkers (1999) study on olfactory receptor neurons with the use of calcium imaging

Answer 295

• ## They determined the response to a large number of odorants using calcium imaging

Question 296

What’s an odorant’s recognition profile?

Answer 296

• The pattern of olfactory activation for an odorant, indicating which ORNs (olfactory receptor neurons) are activated by the odorant
• From these profiles, we can see that each odorant causes a different pattern of firing across ORNs
• We know that when 2 odorants smell different, they usually have different profiles

Question 297

What kind of odorants often have similar profiles?

Answer 297

• Odorants that have similar structures
• Ex: octanoic acid and nonanoic acid
• However, this isn’t always the case -> ex: bromohexanoic acid and bromooctanoic acid

Question 298

Describe Malnic’s study on molecules having similar structures but smelling different

Answer 298

• When she compared such molecules, she found that these molecules had different recognition profiles
• Ex: octanoic acid and octanol differ only by one oxygen molecule, but the smell of octanol is described as “sweet,” “rose,” and “fresh,” whereas the smell of octanoic acid is described as “rancid,” “sour,” and “repulsive”
• This difference in perception is reflected in their different profiles

Question 299

The idea that an odorant’s smell can be related to different response profiles is similar to what aspect of vision?

Answer 299

• To the trichromatic code for color vision
• Each wavelength of light is coded by a different pattern of firing of the 3 cone receptors, and a particular cone receptor responds to many wavelengths
• The situation for odors is similar—each odorant is coded by a different pattern of firing of ORNs, and a particular ORN responds to many odorants
• What’s different about olfaction is that there are 350–400 different types of ORNs, compared to just 3 cone receptors for vision

Question 300

What does the activation of receptors in the mucosa cause?

Answer 300

• It causes electrical signals in the ORNs that are distributed across the mucosa
• These ORNs send signals to structures called glomeruli in the olfactory bulb

Question 301

What are glomeruli?

Answer 301

• Small structures in the olfactory bulb that receive signals from similar olfactory receptor neurons
• One function of each glomerulus is to collect information about a small group of odorants

Question 302

Describe a basic principle of the relationship between ORNs and glomeruli?

Answer 302

All of the ORNs of a particular type send their signals to just 1 or 2 glomeruli, so each glomerulus collects information about the firing of a particular type of ORN

Question 303

What creates different patterns of olfactory bulb activation for different odorants?

Answer 303

The targeting of specific areas of the olfactory bulb by certain receptors

Question 304

TRUE OR FALSE: different chemicals result in the same patterns of activity in the olfactory bulb

Answer 304

FALSE: Different chemicals result in different patterns of activity in the olfactory bulb

Question 305

The different patterns for different odorants create a map of odorants in the olfactory bulb that it is based on what?

Answer 305

Based on molecular features of odorants such as carbon chain length or functional groups

Question 306

What are chemotopic maps?

Answer 306

• AKA odor map or odotopic map
• The pattern of activation in the olfactory system in which chemicals with different properties create a “map” of activation based on these properties
• Ex: there’s evidence that chemicals are mapped in the olfactory bulb based on carbon-chain length

Question 307

The olfactory bulb represents an early or late stage of olfactory processing?

Answer 307

It represents an early stage of olfactory processing and is not where perception occurs

Question 308

What are the 2 main olfactory areas in the brain?

Answer 308

1. The piriform cortex (PC) -> primary olfactory area
2. The orbitofrontal cortex

Question 309

What’s the piriform cortex (PC)?

Answer 309

• AKA the primary olfactory area
• Area under the temporal lobe that receives signals from glomeruli in the olfactory bulb

Question 310

What’s the orbitofrontal cortex?

Answer 310

• AKA the secondary olfactory cortex
• Area in the frontal lobe, near the eyes, that receives signals originating in the olfactory receptors

Question 311

What’s the amygdala?

Answer 311

• A subcortical structure that’s involved in emotional responding and in processing olfactory signals
• Involved in determining emotional reactions not only to smell but also to faces and pain
• Has many connections to structures in both the taste and olfaction pathways
• Receives signals from vision, and the hypothalamus, which is involved in determining hunger

Question 312

What happens to the odotopic/chemotopic/odor map when we move up to the piriform cortex (PC)?

Answer 312

• The map vanishes
• Odorants that caused activity in specific locations in the olfactory bulb now cause widespread activity in the PC, and there is overlap between the activity caused by different odorants

Question 313

Describe the study by B. F. Osmanski and coworkers (2014), who used functional ultrasound imagery to measure patterns of activity in the olfactory bulb and in the piriform cortex to different odorants

Answer 313

• Functional ultrasound imagery, like fMRI, determines brain activation by measuring changes in blood flow
• They found that hexanal and pentyl acetate cause different patterns of activity in the rat olfactory bulb
• They also found that hexanal and pentyl acetate cause activity throughout the entire PC

Question 314

Describe the method used by Robert Rennaker and coworkers (2007), to study activity in the PC of rats

Answer 314

They used multiple electrodes to measure neural responding in the PC by recording from single neurons

Question 315

The compound isoamyl acetate causes what kind of activation in the brain?

Answer 315

• It causes activation across the cortex
• Other compounds also cause widespread activity and there is substantial overlap between the patterns of activity for different compounds

Question 316

Why does the orderly activation pattern in the olfactory bulb no longer exist in the piriform cortex?

Answer 316

This occurs because the projection from the olfactory bulb is scattered, so activity associated with a single chemical is spread out over a large area

Question 317

Describe the process of the formation of stable memories

Answer 317

• When a person witnesses an event, a number of neurons are activated
• At this point, the memory for the event isn’t completely formed in the brain; it is fragile and can be easily forgotten or can be disrupted by trauma, such as a blow to the head
• But connections begin forming between the neurons that were activated by the event, as time passes, the neural activity is replayed, and after these connections are formed, the memory is stronger and more resistant to disruption
• Formation of stable memories thus involves a process in which linkages are formed between a number of neurons

Question 318

How does odor perception relate to the formation of stable memories?

Answer 318

It has been proposed that formation of odor objects involves learning, which links together the scattered activations that occur for a particular object and create. a pattern of activation to represent the odor object
- Ex: you are smelling the odor of a flower for the first time. The odor of this flower, just like the odors of other substances, is created by a large number of chemical compounds. These chemical components first activate the olfactory receptors in the mucosa and then create a pattern of activation on the olfactory bulb that is shaped by the chemotopic map. This pattern occurs any time the flower’s odor is presented
- From research, we know that signals from the olfactory bulb are transformed into a scattered pattern of activation in the piriform cortex
- Because this is the first time you have ever experienced the flower’s odor, the activated neurons aren’t associated with each other
- This is like the neurons that represent a new memory, which aren’t yet linked. At this point you are likely to have trouble identifying the odor and might confuse it with other odors. But after a number of exposures to the flower, which cause the same activation pattern to occur over and over, neural connections form, and the neurons become associated with each other. Once this occurs, a pattern of activation has been created that represents the flower’s odor.
- Just as a stable memory becomes established when neurons become linked, odor objects become formed when experience with an odor causes neurons in the piriform cortex to become linked

Question 319

Describe Donald Wilson’s (2003) study on the role of learning in perceiving odors

Answer 319

• He measured the response of neurons in the rat’s piriform cortex to 2 odorants:
  1. a mixture of isoamyl acetate, which has a banana-like odor, and peppermint
  2. the component isoamyl acetate alone
• He was interested in how well the rat’s neurons could tell the difference between the mixture and the component after the rat had been exposed to the mixture
• He presented the mixture to the rat for either a brief exposure (10 secs or about 20 sniffs) or a longer exposure (50 secs or about 100 sniffs) and, after a short pause, measured the response to the mixture and to the component
• Following 10 secs of sniffing, the piriform neurons responded similarly to the mixture and to the component
• However, following 50 secs of sniffing, the neurons fired more rapidly to the component
• Thus, after 100 sniffs of the mixture, the neurons became able to tell the difference between the mixture and the component
• Similar experiments measuring responses of neurons in the olfactory bulb did not show this effect

Question 320

What were Donald Wilson’s (2003) conclusions for his study on the role of learning in perceiving odors

Answer 320

• He concluded from these results that, given enough time, neurons in the piriform cortex can learn to discriminate between different odors, and that this learning may be involved in our ability to tell the difference between different odors in the environment
• Numerous other experiments support the idea that a mechanism involving experience and learning is involved in associating patterns of piriform cortex firing with specific odor objects

Question 321

What are 2 relationships between memories and olfaction?

Answer 321

• Memory is involved in identifying odor objects
• Olfaction can, under some circumstances, create memories

Question 322

What’s the Proust effect?

Answer 322

• The elicitation of memories through taste and olfaction
• Named for Marcel Proust, who described how the taste and smell of a tea-soaked madeleine cake unlocked childhood memories

Question 323

What are some characteristics of Proustian memories (AKA odor-evoked autobiographical memories (OEAMs)?

Answer 323

1. Memories are realized not by seeing an odor object but by tasting it
2. The memory is vivid and leads to mental time travel
3. The memory is from early in someone’s life

Question 324

What are odor-evoked autobiographical memories (OEAMs)?

Answer 324

Memories about events from a person’s life that are elicited by odors

Question 325

Describe Rachel Herz and Jonathan Schooler’s (2002) study on odor-evoked autobiographical memories (OEAMs)

Answer 325

• They had participants describe a personal memory associated with items like Crayola crayons, Coppertone suntan lotion, and Johnson’s baby powder
• After describing their memory associated with the objects, participants were presented with an object either in visual form (a color photograph) or in odor form (smelling the object’s odor) and were asked to think about the event they had described and to rate it on a number of scales
• The result was that participants who smelled the odor rated their memories as more emotional than participants who saw the picture
• They also had a stronger feeling than the visual group of “being brought back” to the time the memory occurred

Question 326

Describe the findings of the experiment by Larsson & Willander (2009) that collected autobiographical memories from 65- to 80-year-old participants elicited by odors, words, or pictures

Answer 326

• Memories elicited by odors were most likely to be for events that occurred in the first decade of life, whereas memories elicited by words were more likely to be for events from the second decade of life
• The participants in this experiment also described their odor-evoked memories as being associated with strong emotions and feelings of being brought back in time

Question 327

What’s happening in the brain during odor-evoked autobiographical memories (OEAMs)?

Answer 327

• Clue to the answer: The amygdala, which is involved in creating emotions and emotional memories, is only 2 synapses from the olfactory nerve, and the hippocampus, which is involved in storing and retrieving memories, is only 3 synapses away
• It therefore isn’t surprising that fMRI brain scans have revealed that odor-evoked memories cause higher activity in the amygdala than word-evoked memories

Question 328

What’s flavor?

Answer 328

• The overall impression that we experience from the combination of nasal and oral stimulation
• Flavor is usually a combination of taste, from stimulation of the receptors in the tongue, and olfaction, from stimulation of the receptors in the olfactory mucosa

Question 329

The interaction between taste and olfaction occurs at what 2 levels?

Answer 329

1. In the mouth and nose
2. In the cortex

Question 330

How do chemicals in food or drink cause taste?

Answer 330

When they activate taste receptors on the tongue

Question 331

How does olfaction contribute to taste?

Answer 331

Food and drink release volatile chemicals that reach the olfactory mucosa by following the retronasal route, from the mouth through the nasal pharynx

Question 332

What’s the retronasal route and whats its contribution to flavor?

Answer 332

• The opening from the oral cavity, through the nasal pharnyx, into the nasal cavity
• This route is the basis for the way smell combines with taste to create flavor

Question 333

What’s the nasal pharynx?

Answer 333

A passageway that connects the mouth cavity and the nasal cavity

Question 334

Why does blocking your nose reduce sensations of flavor?

Answer 334

• Food and drink release volatile chemicals that reach the olfactory mucosa by following the retronasal route, from the mouth through the nasal pharynx
• Although pinching the nostrils shut does not close the nasal pharynx, it prevents vapors from reaching the olfactory receptors by eliminating the circulation of air through this channel
• The same thing happens when you have a cold—less airflow means the flavor of foods will be greatly reduced

Question 335

Why does the localization of flavor in the mouth occur?

Answer 335

Because food and drink stimulate tactile receptors in the mouth, which creates oral capture

Question 336

What’s oral capture?

Answer 336

The condition in which sensations from both olfactory and taste receptors are perceived as being located in the mouth

Question 337

What illusion does oral capture present?

Answer 337

When you “taste” food, you are usually experiencing flavor, and the fact that it is all happening in your mouth is simply due to oral capture

Question 338

What’s an example of a compound that’s not affected by olfaction?

Answer 338

• Monosodium glutamate (MSG), it has about the same flavor whether or not the nose is clamped
• In this case, the sense of taste predominates

Question 339

In general, solutions are more difficult to identify and are often judged to be tasteless when what occurs?

Answer 339

When the nostrils are pinched shut

Question 340

When is our perceptual experience of the combination of taste and olfactory stimuli created?

Answer 340

When they interact in the cortex

Question 341

How do vision and touch contribute to flavor?

Answer 341

By sending signals to the amygdala (vision), structures in the taste pathway (touch), and the orbitofrontal cortex (vision and touch)

Question 342

Flavor is created by interactions among what 4 senses?

Answer 342

• Taste
• Olfaction
• Vision
• Touch

Question 343

Where are signals sent from all 4 senses involved in flavor?

Answer 343

To the orbitofrontal cortex (OFC)

Question 344

Describe the multimodal nature of our experience of flavor

Answer 344

• The interactions among taste, olfaction, vision, and touch underscore the multimodal nature of our experience of flavor
• Flavor also includes not only what we typically call “taste,” but also perceptions such as the texture and temperature of food, the color of food, and the sounds of “noisy” foods such as potato chips and carrots that crunch when we eat them

Question 345

The orbitofrontal cortex contains many of what kind of neurons?

Answer 345

• Bimodal neurons
• Because of the convergence of neurons from different senses

Question 346

What are bimodal neurons?

Answer 346

• A neuron that responds to stimuli associated with more than one sense
• Ex: some bimodal neurons respond to both taste and smell, and others respond to taste and vision
• An important property of these bimodal neurons is that they often respond to similar qualities
• Ex: a neuron that responds to the taste of sweet fruits would also respond to the smell of these fruits
• This means that neurons are tuned to respond to qualities that occur together in the environment

Question 347

The orbitofrontal cortex is a cortical center for what?

Answer 347

For detecting flavor and for the perceptual representation of foods

Question 348

Research has shown that what 2 brain areas, other than the orbitofrontal cortex, are involved in the perception of flavor?

Answer 348

• Insula
• Primary taste cortex

Question 349

Why isn’t flavor a fixed response that is automatically determined by the chemical properties of food?

Answer 349

Because although the chemicals in a particular food may always activate the same pattern of ORNs in the mucosa, by the time the signals reach the cortex they can be affected by many different factors, including cognitive factors and the amount of a particular food the person has consumed

Question 350

Your expectations can influence what 2 things?

Answer 350

• What you experience
• Neural responding

Question 351

Describe Hilke Plassmann and coworkers (2008) study on how expectations can influence flavor perception

Answer 351

• They had participants in a brain scanner judge the “taste pleasantness” of different samples of wine
• Participants were asked to indicate how much they liked 5 different wines, which were identified by their price
• In reality, there were only 3 wines; 2 of them were presented 2x, with different price labels
• They found that when the wines are presented without labels, the taste pleasantness judgments are the same, but when tasting is preceded by a price label, the “$90 wine” gets a much higher taste rating than the “$10 wine”
• The labels also influence the response of the orbitofrontal cortex, with the $90 wine causing a much large response
• The response of the orbitofrontal cortex is being determined both by signals that begin with stimulation of the taste and olfactory receptors and by signals created by the person’s expectations

Question 352

Describe the findings of de Araujo et al. (2005) study on how expectations can influence odor perception

Answer 352

Participants rated the same odor as more pleasant when it was labeled “cheddar cheese” than when it was called “body odor,” and the orbitofrontal cortex response was larger for the cheddar cheese label

Question 353

List some examples of experiments that highlighted how flavor is influenced by factors in addition to the actual food that is being consumed

Answer 353

• The cheese vs body odor experiment
• The 90$ wine vs 10$ wine experiment
• The taste of a red frozen strawberry dessert was judged to be 10% sweeter and 15% more flavorful when it was presented on a white plate compared to on a black plate (Piqueras-Fiszman et al., 2012)
• The sweetness of café latte was almost doubled when consumed from a blue mug compared to a white mug (Van Doorn et al., 2014)
• Experiments have shown that perception of the flavor of wine can be influenced not only by information about its price but also by the shape of the wine glass (Hummel et al., 2003)

Question 354

Food consumed to ____ is often considered less pleasurable than food consumed when ____

Answer 354

• Satiety
• Hungry

Question 355

What’s satiety?

Answer 355

When you don’t want to eat any more

Question 356

Describe John O’Doherty and coworkers (2000) study that showed that both the pleasantness of a food-related odor and the brain’s response to the odor can be influenced by satiety

Answer 356

• Participants were tested under 2 conditions:
  1. When hungry
  2. After eating bananas until satiety
• Participants in a brain scanner judged the pleasantness of 2 food-related odors: banana and vanilla
• The pleasantness ratings for both were similar before they had consumed any food
• However, after eating bananas until satiety, the pleasantness rating for vanilla decreased slightly (but was still positive), but the rating for banana decreased much more and became negative
• This larger effect on the odor associated with the food eaten to satiety, called sensory-specific satiety, also occurred in the response of the orbitofrontal cortex
• The orbitofrontal cortex response decreased for the banana odor but remained the same for the vanilla odor
• Similar effects also occurred in the amygdala and insula for some (but not all) participants

Question 357

What’s sensory-specific satiety?

Answer 357

• The effect on perception of the odor associated with food eaten to satiety (the state of being satiated or “full”)
• Ex: after eating bananas until satiety, the pleasantness rating for vanilla decreased slightly (but was still positive), but the rating for banana odor decreased much more and became negative

Question 358

What part of the brain is involved in determining the reward value of foods?

Answer 358

The orbitofrontal cortex

Question 359

What’s the reward value of foods?

Answer 359

• Food is more rewarding when you are hungry and becomes less rewarding as food is consumed, until eventually—at satiety—the reward is gone and eating stops
• These changes in the reward value of flavors are important because just as taste and olfaction are important for warning of danger, they are also important for regulating food intake

Question 360

The orbitofrontal cortex sends signals to what brain structure, where neurons are found that respond to the sight, taste, and smell of food if hunger is present?

Answer 360

The hypothalamus

Question 361

What’s the purpose of the chemical senses?

Answer 361

• It extends beyond simply creating experiences of taste, smell, and flavor
• Their purpose is to help guide behavior—avoiding potentially harmful substances, seeking out nutrients, and helping control the amount of food consumed
• They have an ultimate purpose of guiding and motivating actions required for survival
• We eat in order to live, and our experience of flavor helps motivate that eating

Question 362

Neurons from where are sensitive to signals the body creates about hunger and satiety?

Answer 362

• In the olfactory bulb
• They respond to food odors in the context of signals from the body about how hungry you are

Question 363

How can the shutoff mechanisms of the chemical senses sometimes be overridden?

Answer 363

They’re sometimes overridden by manufactured foods that are rich in sugar and fat and by other factors, with obesity as an outcome

Question 364

What are multimodal interactions?

Answer 364

• Interactions that involve more than one sense or quality
• They’re all around us
• Ex: taste and smell combining to create flavor

Question 365

Give 2 examples of visual-auditory interactions

Answer 365

• Ventriloquism effect, in which the perceived location of the sound source is determined by vision
• McGurk effect, in which seeing a speaker’s lips move can affect what sound the listener hears

Question 366

What are correspondences?

Answer 366

They refer to how a property of a chemical sense—taste, olfaction, or flavor—is associated with properties of other senses

Question 367

Describe Crisinel & Spence (2012) study on how odors and Tastes Are Associated With Different Pitches and Instruments

Answer 367

• When participants were presented with odors like almond, cedar, lemon, raspberry, and vanilla and were asked to pick the auditory pitch that matched the odor, pitches were matched to different odors
• Fruits were matched by high pitches, and smells such as smoked, musk, and dark chocolate were matched by lower pitches
• In a study using taste stimuli, the tastes of citric acid and sucrose were matched to high tones, and coffee and MSG were matched to lower tones
• This study was titled “As Bitter as a Trombone,” because when also asked to match tastes and musical instruments, bitter substances, like caffeine, were more likely to be matched to brass instrument sounds, and sweet substances, like sugar, were more likely to be matched to piano or string sounds

Question 368

Describe Maric & Jacquot (2013) study on how Odors Are Associated With Different Colors

Answer 368

• When participants sniffed a wide range of odors and picked colors that matched them, they matched odors to specific colors
• Ex: pineapple was associated with red, yellow, pink, orange, and purple, whereas caramel was associated with brown, orange, and pale orange. Wild strawberry odor was matched by red, pink, and purple; “smoked” odor by brown, dark red, black, and gray

Question 369

Describe Dematte et al. (2006) study on how Odors Are Associated With Different Textures

Answer 369

When participants judged the texture of fabric while smelling different odors, they judged the fabrics to be slightly softer when smelling a pleasant lemon odor than when smelling an unpleasant animal-like odor

Question 370

Describe Spector & Maurer (2012) study on how Odors Are Associated With Different Textures

Answer 370

• They showed that different odors are associated with specific textures
• Ex: cinnamon and onion odors are associated with rough textures, whereas violet and peppermint are associated with smooth textures

Question 371

What are influences?

Answer 371

Influences occur when stimuli from one sense affect our perception or performance associated with another sense

Question 372

Describe Felipe Reinoso Carvalho and coworkers (2017) study on how Music Can Influence Flavor

Answer 372

• They demonstrated this by having participants taste samples of chocolate while listening to 2 different soundtracks
• The soft/smooth track consisted of long, consonant notes (consonants being notes that go well together), whereas the hard/rough track had staccato dissonant notes
• The results were clear-cut—when participants had eaten the chocolate while listening to the soft/smooth soundtrack they rated it as creamier and sweeter than if eaten during the hard/rough track

Question 373

Describe findings on how Color Can Influence Flavor

Answer 373

• Participants perceive a cherry-flavored drink as orange-flavored if it is colored orange (DuBose et al., 1980)
• Participants rate a strawberry-flavored drink as less pleasant if it is colored orange rather than red (Zellner et al., 1991).
• Charles Spence (2020), in a review of “wine psychology,” notes that there’s a large amount of evidence that color influences the aroma, taste, and flavor of wine. He also notes that even wine experts can be fooled by deliberately miscoloring wine. This was demonstrated in a paper by Qian Wang and Spence (2019) in which wine experts were asked to rate the aroma and flavor of a white wine, a rosé wine, and “fake rosé” wine, which was the white wine dyed with food coloring so it matched the color of the real rosé wine. The food coloring caused the experts to describe the aroma and flavor of the fake rosé as being very similar to the real rosé and very different from the white wine. The fake rosé and the real rosé received high ratings for “red fruit” aroma and taste, while the red fruit rating for the white wine was near 0

Question 374

Describe Holland et al. (2005) study on how Odors Can Influence Attention and Performance

Answer 374

• Participants sat in a cubicle, and were given the task of determining, as quickly as possible, whether a string of letters was a real word (like bicycle) or a non-word (like poetsen)
• 6 of the real words were related to cleaning (like hygiene)
• When the smell of citrus, which is often associated with cleaning products, was infused into the cubicle, participants responded faster to the cleaning words, but the smell had no effect on the words that weren’t related to cleaning

Question 375

Describe Madzharov et al. (2018) study on how Odors Can Influence Attention and Performance

Answer 375

Participants expected to perform better and actually did perform better on an analytical reasoning task when the testing room smelled like coffee, compared to when they took the test in an unscented environment

Question 376

TRUE OR FALSE: taste, smell, and flavor operate in isolation

Answer 376

FALSE: taste, smell, and flavor don’t operate in isolation. They share correspondences with other senses, interact with them, affect them, and are affected by them.

Question 377

Why do taste, smell and flavor share correspondences with other senses?

Answer 377

• One answer is “learning”
• Many associations are formed from everyday experiences
• Ex: Associating lemon flavor and yellow, strawberry and red. Also, odors of edible substances are likely to be associated with yellow, whereas odors that seem “inedible” are likely to be associated with blue, since blue is less likely to be associated with food
• Ex: our experience tells us that a large dog is likely to have a lower pitched bark than a small dog
• Some correspondences can be explained by pleasure or emotions
• Ex: bright colors, often associated with happiness, are associated with pleasant odors. Similarly, pleasant odors are associated with the pleasant feelings from stroking soft fabrics

Question 378

Much of perception is _____, and the different senses are all part of _____

Answer 378

Much of perception is multimodal, and the different senses are all part of a “community”

Question 379

How have researchers tackled the question of “do newborn infants perceive odors and tastes?”

Answer 379

One way researchers have answered this question is to measure newborn facial expressions

Question 380

Describe Rosenstein & Oster (1988) findings on whether newborns perceive odors and tastes

Answer 380

• They presented the sweet taste of sucrose and the bitter taste of quinine to the newborn approximately 2 hours after birth and before the first feeding
• They found that the newborn’s face remained calm after being presented the sucrose but made a grimace after being presented with the bitter quinine

Question 381

Describe Steiner’s (1974, 1979) findings on whether newborns perceive odors and tastes

Answer 381

Found that 3- to 7-day-old infants respond to banana extract or vanilla extract with sucking and facial expressions that are similar to smiles, and they respond to concentrated shrimp odor and an odor resembling rotten eggs with rejection or disgust

Question 382

What has research by Beauchamp et al. (1994) on how newborns and young infants respond to salt indicated?

Answer 382

• That there’s a shift toward greater acceptance of salty solutions between birth and 4 to 8 months of age that continues into childhood
• One explanation for this shift is that it reflects the development of receptors sensitive to salt during infancy
• But there’s also evidence that infants’ preferences are shaped by experience that occurs both before birth and during early infancy

Question 383

Describe findings on how pregnancy can affect the fetus’ perception odors and tastes

Answer 383

What the mother eats during pregnancy changes the flavor profile of the amniotic fluid, which affects the developing fetus, because by the last trimester, the taste and olfactory receptors are functioning and the fetus swallows between 500 and 1,000 ml of amniotic fluid a day (Forestell, 2017; Ross & Nijland, 1997)

Question 384

Describe the experiment by Julie Mennella and coworkers (2001) on how the flavor of the amniotic fluid can influence an infant’s preferences

Answer 384

• Mennella’s experiment involved 3 groups of pregnant women
• Group 1 drank carrot juice during their final trimester of pregnancy and water during the first 2 months of lactation, when they were breast-feeding their infants
• Group 2 drank water during pregnancy and carrot juice during the first 2 months of lactation
• Group 3 drank water during both periods
• The infants’ preference for carrot-flavored cereal versus plain cereal was tested 4 weeks after they had begun eating cereal but before they had experienced any food or juice containing a carrot flavor
• The results indicated that the infants who had experienced carrot flavor either in utero or in the mother’s milk showed a preference for the carrot-flavored cereal, whereas the infants whose mothers had consumed only water showed no preference
• Infants who had experienced carrot flavor in utero showed the highest preference for carrot cereal

Question 385

What’s the advantage of breast-feeding on influencing an infant’s taste/flavor preferences

Answer 385

• The advantage of breast-feeding is that the taste of mother’s milk is influenced by what she eats
• So if a mother eats a lot of vegetables, the infant is drinking “vegetable flavored milk” and becomes familiar with that flavor
• This translates into increased acceptance of vegetables when the child is older, which is a healthy food choice not always made by infants
• Bottle feeding, in contrast, teaches infants about the flavor of whatever milk is in the formula, so the infant is not sharing the mothers’ dietary choices

Question 386

Infants’ responses to tastes, odors, and flavors are determined by what factors?

Answer 386

• By innate factors, indicated by the fact that most newborns respond positively to sweet and negatively to bitter
• By experience indicated by the way the mother’s diet can influence the child’s preferences
• Thus, the first step toward insuring that young children develop good eating habits is for mothers to eat healthy foods, both when pregnant and while nursing

Question 387

When the child is weaned to solid food, its preferences are influenced by what?

Answer 387

First by what was experienced in the womb, then during nursing, and finally by exposure to the solid foods chosen by the child’s family

Question 388

Can somatosensory maps change throughout our lifetime?

Answer 388

Yes, these maps can change based both on how much a body part is used and in response to injury

Question 389

Describe the study by William Jenkins and Michael Merzenich (1987) showing that the somatosensory map changes with use

Answer 389

• They began by measuring the cortical areas devoted to each of a monkey’s fingers
• They gave the monkey a task that heavily stimulated the tip of finger 2 over a 3-month period and then remeasured the areas devoted to the fingers
• Comparison of the “before” and “after” cortical maps showed that the area representing the stimulated fingertip was greatly expanded (increased in size) after the training
• This change in the brain’s map is an example of experience-dependent plasticity (ex: similar to the effect of raising a kitten in an environment consisting only of vertically oriented stripes causing the cat’s orientation-sensitive neurons to respond mainly to verticals)

Question 390

An effect of experience-dependent plasticity has been demonstrated in humans by measuring what?

Answer 390

• By measuring the brain maps of musicians
• Ex: players of stringed instruments. A right-handed violin player bows with the right hand and uses the fingers of their left hand to finger the strings
• One result of this tactile experience is that these musicians have a greater than normal cortical representation for the fingers on their left hand
• Just as in the monkeys, plasticity has created more cortical area for parts of the body that are used more

Question 391

Give an example of how changes in the cortical map can also occur when part of the body is damaged

Answer 391

When a monkey loses a finger, the brain area representing that finger no longer receives input from that finger, so over a period of time that area is taken over by the fingers next to the one that is missing

Question 392

Describe the case of world-famous concert pianist Leon Fleisher

Answer 392

• Example of a possible change in mapping associated with dysfunction
• At the age of 36, he began experiencing hand dystonia, a condition which caused the fingers on his right hand to curl into his palm, making it impossible to play the piano with his right hand
• Fleisher developed a repertoire of left-handed piano compositions, and eventually, after 30 years of therapy, regained the use of his right hand and was able to resume his career as a 2-handed pianist
• Fleisher’s dystonia could have been due to a number of causes
• Fleischer came to believe that his problem was caused by overpracticing, which he described as “seven or eight hours a day of pumping ivory”
• One possible mechanism associated with this practicing is that using his fingers often and in close conjunction with each other could have changed the locations of their representation in the cortex

Question 393

Describe the study by William Bara-Jimenez and coworkers (1998) on hand dystonia

Answer 393

• They showed that the map of the fingers in area S1 is abnormally organized in some patients with dystonia.
• In their experiment, they measured the location of the areas in S1 representing the thumb and little finger in a group of 6 normal participants and 6 participants with dystonia of the hand
• The locations for these 2 fingers, which was determined by stimulating the fingers and measuring the brain activity with scalp electrodes, are separated in the normal participants but are close together in the patients with dystonia

Question 394

What kind of mapping allows us to see neural plasticity?

Answer 394

• Somatosensory maps
• With these maps, the plastic changes that occur due to stimulation or injury are easy to visualize