Chapter 5 : Sensation & Perception

Question 1

Sound

Answer 1

Physical form of energy, travels in waves
- Requires medium like air or water to move through space
- Vibrating air molecules colliding with one another, pressure travels across a distance

Question 2

Frequency

Answer 2

Determined by rate of vibrations
- High-frequency sounds = higher pitch
- People can hear between 20 - 20,000 Hz, but hear best between 1000–5000 Hz (range of speech)

Question 3

Intensity of Wave

Answer 3

Determines loudness
- Increased intensity → Increased amplitude of wave (Wave arrives at our ear with more force)
- Amplitude measured in decibels (dB)
- Sound above 100 dB can cause damage to middle & inner structures of ear bc of the force of pressure

Question 4

The ear can be called a ______ ?

Answer 4

Pressure sensor
e.g. We feel discomfort in our ears with rapid elevation shifts, such as when we are on planes

Question 5

How does sound enter the ear ?

Answer 5

1. Sound enters your _OUTER EAR_ through your pinna – Outer portion of the ear, made of mostly cartilage
- Shaped in way to help funnel sound into ear canal
2. Sound reaches tympanic membrane (eardrum) in the _MIDDLE EAR_
3. Energy transfers to auditory ossicles in the middle ear – 3 smallest bones in the body (malleus, incus, stapes), help amplify the vibrations as sound waves travel further into ear
- Stapes is connected to a small membrane called the oval window
4. Oval window – Small, thin membrane of cochlea connected to the stapes, connects middle ear to _INNER EAR_
- Movement of the stapes concentrates the pressure of the sound waves to transmit vibrations into cochlea
5. Cochlea – Snail-shaped, bony sound processor of the inner ear, receives vibrations from an oval window and transfers sound into neural language of the brain
- Contains the basilar membrane – Fluid tissue inside cochlea, where the auditory hair cells are located
- Placement of hair cells corresponds to our perception of pitch
- When hair cells are displaced by the moving fluid, they allow an electrochem signal to be sent to the auditory cortex to form a perception of sound

Question 6

How is sound transduced into the brain ?

Answer 6

1. Vibrations against the stapes in the oval window causes fluid inside the cochlea to move
2. Fluid pushes against cilia attached to sensory hair cells
3. Sound causes the basilar membrane to “ripple”
4. Motion causes the cilia to bend
5. Causes an excitatory message to cascade from the ear to the brain via auditory nerve
6. Medial geniculate nucleus of the thalamus organizes / analyzes auditory info
7. Majority info arrives at the auditory cortex (located in temporal lobes), where it is combined with other info (e.g. expectations & knowledge) to create perception of sound

Question 7

Do hair cells in the ear operate independently ?

Answer 7

NO All hair cells in the ear are the same & do not operate independently

Question 8

What is place theory ?

Answer 8

Brain uses location of neural firing to understand sound, we hear a specific pitch because cells fire at a specific place on basilar membrane
- Higher frequency uses cells closest to oval window to excite (beginning of basilar membrane)
- Lower frequency excites cells deeper in cochlea (end of basilar membrane)

Question 9

What is frequency theory ?

Answer 9

Brain uses info related to the AP firing rate of cells
- More rapid firing → Higher pitch

Question 10

Auditory Cortex

Answer 10

• Receives auditory message in temporal lobes
• Simpler sounds (pure tones) processed in lower regions
• More complex sounds (speech) processed higher up

Auditory system : Tonotopic organization from the basilar membrane to → Auditory cortex
“What” & “Where” stream
Has specialized neurons for transmitting sound
Cells with particularly rapid APs & LARGE terminal buttons to help relay temporal components of message
Hierarchical organization

Question 11

Auditory System

Answer 11

Tonotopic (hierarchical) organization from basilar membrane → Auditory cortex
- “What” & “Where” stream
- Has specialized neurons for transmitting sound
- Cells with particularly rapid APs & LARGE terminal buttons to help relay temporal components of message

Question 12

Sound Localization

Answer 12

Brain is able to locate objects from sound by comparing info arriving in both ears

Binaural Cues : Cues requiring comparisons between info from both ears used for localization
- Interaural time differences – Comparisons made between arrival time of a sound in each ear, right / left & both (sound is in front)
- Interaural level differences – Intensity difference of sound between ears, monitored by brain. Ear closest to the sound will perceive the noise as louder. Some sound absorbed by head / skull as it travels to furthest ear → furthest less quiet

Question 13

Do humans have high, low or medium acuity for music & speech ?

Answer 13

HIGH

Question 14

Music

Answer 14

• Psychological effects on body : Influencing mood, heart rate, muscle tension, respiration
• Blood flow within the brain sent to regions associated with reward + motivation

Involuntary musical imagery (Earworm) – Song is stuck in your head (no more than 24h), duration longer than average auditory memory, triggered by only few notes of song or memory

Question 15

Speech & Language

Answer 15

Uniquely human ability, although speech perception NOT unique

3 basic components :
- Respiration from lungs
- Vocal cords
- Vocal tract
→ Works with somatosensory system

• Rapid perception in brain (10–15 sounds produced /s)
• Use variations in sounds to capture meaning
• Brain uses context & info from visual system to help interpret information, distinguish similar sounds

Question 16

What is the McGurk Effect ?

Answer 16

Participants hear the term “ba” but see a person making lip movements to “ba” or as if they were saying “fa.” When you look at the person saying “ba,” you hear the term “ba”; when you look at his lips when he says the word “fa”
- Changes the perception of what you hear

Question 17

What are chemoreceptors ?

Answer 17

Sensory cells that respond to properties in air molecules → Interpreted as _smell_ & _taste_

Question 18

How are smell & taste similar ?

Answer 18

• They both use chemoreceptors
• They both are “Gatekeepers”→ Only senses that require you to ingest physical stimuli in order to analyze incoming information. Decide what we should ingest VS what we should leave alone

Question 19

Smell

Answer 19

• Only sense that does NOT first go through thalamus
• Evolutionarily OLD
• Plays role in behaviour – Adaptive response to how we evaluate food (evokes emotional response), choose mates (female preferences for the smell of particular types of men changes as their chances of becoming pregnant increase)
• Humans poor smellers → Need a higher concentration of odorants to perceive a smell relative to other animals
• Dogs at least 100 x more olfactory receptors than us + Highly developed olfactory cortex & olfactory bulb
• Salmon use olfaction for migration hundreds of miles each year
• Bear smell sensitivity x7 that of a dog
• Giant rats in Africa use olfaction to clear landmines + detect TB

Question 20

Chemical Process of Smell

Answer 20

1. Airborne molecules interact with receptor sites in the mouth & nose → Drawn into upper nasal cavity
2. Olfactory receptors bind to the cilia of hair cells embedded in the olfactory mucosa – Tissue contains chemoreceptors of nose
3. In olfactory mucosa, odorants come into contact with olfactory receptor neurons (ORN) – Neurons specifically responsive to odorants, humans have over 350 types (each responding to specific mol range) → can identify 1 trillion different smells
4. ORNs send messages to glomeruli in the olfactory bulb in the brain – Cells consolidate messages from particular receptor type
- Some mol with similar structures create different perceptions of smell & molecules with different structures can be interpreted as similar
- Smell highly dependent on expectation
5. Message becomes complex (reaches different parts of the brain, e.g. Limbic system)

Question 21

Taste

Answer 21

Relies on correlation between the mol properties of a substance & the effect of that substance on the body
e.g. Many nutritious & high-calorie foods are sweet. When the brain perceives sweetness on tongue → We decide to eat more, GI tract begins to prepare for ingestion of sweet foods. Conversely, consider your response if you taste something rotten or bitter. It is unlikely that you will continue to eat it

Question 22

5 Basic Tastes

Answer 22

Used in conjunction with smell) to evaluate food :
- Sweet
- Salty
- Sour
- Bitter
- Umami (savoury)

Question 23

Process of taste

Answer 23

1. Taste begins on the tongue, with papillae – Where taste buds are located, 4 categories :
- Filiform papillae – Found over the entire surface of the tongue, give “fuzzy” appearance, ONLY papillae that do NOT contain taste buds
- Fungiform papillae – Tips + sides of tongue, mushroom-like
- Foliate papillae – Little folds along back of tongue
- Circumvallate papillae – Little mounds on back of your tongue
2. Each taste bud contains 50–100 taste receptor cells, which protrude into a taste pore
- Taste receptor cells – Primary sensory receptor for the gustatory system, different types detect different tastes
3. Transduction occurs when chemicals bind to receptor sites on the taste pore
4. Messages are sent through system of _afferent nerves_ to the brain & stomach → Body begins to metabolically prepare for food
5. Eventually, info processed in the orbitofrontal cortex (OFC) – Region processes sensation from both smell & taste, receives info from visual “what” pathway.
- Contains bimodal neurons – Respond to more than 1 sense,
specialize in determining sensations that occur simultaneously → Flavor perception (smell, taste combine)

Question 24

Skin

Answer 24

• Largest organ
• Helps with thermoregulation
• Protects us from environment
  -Source of info about surface qualities of objects (e.g. texture)

Question 25

Body Senses

Answer 25

• Able to understand info about where our body is in space ← Receiving information about the position of your limbs
• Pressure – Physical message of touch

Question 26

Processing Touch

Answer 26

1. Object makes contact with the body
2. Receptor cells embedded in skin respond

Mechanoreceptor – Gather most info about texture

Close to surface of skin, respond to “quick” pressure that is applied then removed :
- Merkel receptor – Fire continuously as long as the skin is making contact with an object, sending information about fine details → High concentration of Merkel receptors in the skin
- Meissner corpuscle – Fires when the skin first encounters the stimulus and when it is removed

Located deeper in skin :
- Ruffini cylinder – Stretching of skin
- Pacinian corpuscle – Vibration + texture

Other receptors gather info about temperature, pressure, intermittent pressure, etc

3. Message travels up the spinal cord to the somatosensory cortex of the parietal lobe – Where touch + motion are processed, info about different qualities / inputs of touch is interpreted (different fibers carry info about different qualities) & combined to form perception of touch
- Somatotopic organization – 2 adjacent points of contact on your skin map to 2 adjacent points of neural activity on the cortex
- Brain does not prioritize messages from all parts of the body equally – Large portion of cortex devoted to analyzing info from your hands & your face VS Small portion of cortex analyzes info from the torso & limbs (makes less contact with world)

Question 27

Temperature Perception

Answer 27

• RELATIVE, dependent on what we are comparing the current stimulus to
• e.g. Cold water hand will feel warm in room temp, hot water hand will feel cool in room temp

Changes in temp sensed through both hot & cold thermoreceptors in skin
- Cold fibers – Increase firing rate to objects that are cool to the touch
- Warm fibers – Increase firing to heat
- Also fire in response to chemical stimuli (e.g. menthol has a cooling effect)

Question 28

Pain Perception

Answer 28

Adaptive response to tissue damage
- *Highly subjective8 (Different thresholds, dependent on person’s expectation & enculturation)
– Robbins (2000) case : Patient at Uni of Washington Burn Center reported less pain during bandage changes while playing VR
– Susceptible to placebo effect (e.g. pain alleviation after placebo pill, expectation of pain reduction)

• Serves a purpose – When limb has been damaged, we reduce use of it bc of pain – ESSENTIAL TO SURVIVAL
• Context dependent (e.g. marathon runners completing races with injuries)
• Nociceptors – Nerve endings in skin detect pain → send signals to brain

Question 29

What is Gate-Control Theory ?

Answer 29

• Pain only adaptive if helps to keep organism alive, suggests that impulses indicating painful stimuli can be blocked in the spinal cord by signals sent from the brain (e.g. when you are deeply engaged in a physical task like running from a predator, brain prioritizes mobility over responding to source of pain)
• Suggests that input happens along 3 pathways :
  Small diameter fibers (S-fibers) – Fire to damaging + painful stimuli
  Transmission cells (T-cells) – Activate with S-fibers, their excitation determines the intensity of pain perception
  Large diameter fibers (L-fibers) – Send signals to the brain about stimulation that is not painful. When activated, they inhibit the activation of T-cells → This CLOSES the gate, decreases the perception of pain
• Theory CANNOT explain some aspects of _chronic pain_ (e.g. phantom limb pain)

Question 30

Congenital Analgesia

Answer 30

Congenital insensitivity to pain, 2 features :
- Inability to perceive pain
- Inability to perceive temperature
→ Results from recessive allele on chromosome 2
- Can be a dangerous condition resulting in unrecognized burns, injuries, and infection → Common to die in childhood because they become ill / injured & do not recognize it

Question 31

Kinesthetic Sense

Answer 31

• Provides with understanding of where our body is in space & how to move our bodies to accomplish specific tasks
• Relies heavily on sense of touch & receptors in the joints and muscles (Info from receptors → Sent to the somatosensory cortex)
• Neural organization works like visual system – Cells that fire when specific body parts are oriented in specific positions

Question 32

Vestibular Sense

Answer 32

Sense of balance
- Sensory cells located in cochlea, 2 structures in inner ear that respond to movement, posture & acceleration :
- Semicircular canals – Sense changes in acceleration + rotation of the head. Filled with hair cells (sensory neurons) that respond to the force of gravity → convert to neural firing
- Vestibular sacs – Respond to cues associated with balance & posture
Closely integrated with the visual system (e.g. optical illusions make u feel dizzy)

Question 33

Stimulus Detection

Answer 33

Technique that attempts to answer “What is the minimum amount of stimulus required to generate a sensation?”

**Absolute threshold stimulus **– Level of intensity required to create a conscious experience, can differ across indiv. + circumstances
- Point of intensity required for a participant to detect the stimulus 50% of the time
- e.g. Imagine sitting in a room that is completely dark, display a dim light. Although you may not be able to perceive the light when it is at its lowest level, if I gradually make the light brighter, you will eventually see it. The point where you will see the light is known as the absolute threshold for the stimulus.

Question 34

Signal Detection (Individual Biases)

Answer 34

High “hit rate” – Some will report the presence of a stimulus even when none has been presented
- Likely to detect more stimuli when they are presented
- Because of their bias, they are also likely to say that a stimulus was present when it was not
- False alarms, individuals have a more _liberal response bias_

High “miss rate” – Some individuals prefer to be certain that a stimulus was presented before they say they heard/saw/felt it.
- Tend to say they did not perceive a stimulus even when one was presented
- BUT they also have a higher correct rejection rate, so are more likely to say there was no stimulus when no stimulus was presented
- _Conservative bias_

Question 35

Difference Threshold

Answer 35

Smallest amount of a particular stimulus required for a difference in magnitude to be detected
- e.g. You are holding 1 pound weight in both hands. You would not notice the difference if I increased the weight in your right hand by 0.01 ounces. BUT you would notice one weight wass much heavier if I increased to 2 pounds. How small a weight can we add for you to just notice the difference?

• Just noticeable difference (jnd) – Not absolute (differs across individuals), depends on amount of stimuli already present
  e.g. Difference of 2 oz not noticeable if holding 100 lbs

Question 36

What is Weber’s Law ?

Answer 36

• Ability to notice the difference between 2 stimuli is a constant proportion of the intensity or size of the stimulus (ratio)
• More intense the stimulus → Larger required change to notice a difference