Midterm #1

Question 1

Perception definition

Answer 1

The process or result of becoming aware of objects/relationships/events, by means of senses (recognizing, observing). Enable organisms to organize and interpret the stimuli into meaningful knowledge and act in a coordinated manner.

Question 2

Sensation Definition

Answer 2

Experience produced by stimulation of a sensory receptor and the resultant activation of a specific brain centre, producing basic awareness.

Question 3

Subjective experience

Answer 3

Particular to a specific person and is intrinsically inaccessible to the experience or observation of others.

Question 4

Consciousness

Answer 4

An organism’s awareness of something either internal or external to itself.

Question 5

Easy problem

Answer 5

Explanation of mental phenomena that are testable by standard methods of science.

Question 6

Hard problem

Answer 6

What remains once the neurobiological mechanisms of a phenomenon have been explained. Eg: how do mechanisms give rise to subjective experience of colours?

Question 7

What is it like to be a bat?

Answer 7

Reducing the complex experience of being a bat to mere physical or neuroscientific terms, may miss the true essence of being a bat.

Question 8

The inverted spectrum thought experiment

Answer 8

There is no way to know that a person is experiencing the colour of something in a certain way.

Question 9

Steps of The Perceptual Process

Answer 9

1. Stimulus in the environment
2. Light is reflected and focused
3. Receptor processes
4. Neural processing
5. Perception.
6. Recognition
7. Action
   PLUS the knowledge in the person’s brain.

Question 10

Distal Stimulus

Answer 10

Environmental stimuli are all the objects in the environments that are available to the observer. Observer selectively attends to objects. Stimulus impinges on receptors resulting in internal representation. Step 1.

Question 11

Proximal Stimulus

Answer 11

The representation of the distal stimulus on the receptors. Stimulus is “in proximity” to the receptors. Step 2.

Question 12

Steps 1 and 2 of the Perceptual Process

Answer 12

Step 1: Information about the tree (the distal stimulus) is carried by light.
Step 2: The light is transformed when it is reflected from the tree, when it travels through the atmosphere, and when it is focused on by the eye’s optical system. The result is the proximal stimulus: the image of the tree on the retina, which is a representation of the tree.

Question 13

Principle of transformation

Answer 13

When stimuli and responses created by stimuli are transformed, or changed, between the environmental stimuli and perception.

Question 14

Receptor Processes: Step 3

Answer 14

Rod and cone receptors line the back of the eye, and they change light energy into electrical energy and influence what we perceive. Transduction occurs, which changes environmental energy to nerve impulses. End result is an electrical representation of the tree.

Question 15

Rods

Answer 15

3 types: long, medium, short. Responsible for black and white vision. More sensitive than cones. Good in low light conditions. Not good for detail.

Question 16

Cones

Answer 16

Colour vision. Good for detail. Not good in low light.

Question 17

Neural Processing: Step 4

Answer 17

Changes that occur as signals are transmitted through the maze of neurons. Each sense sends signals to different areas of the brain. Signal that reaches the brain is transformed so that it represents the original stimulus (but not an exact copy).

Question 18

Behavioural Responses (Steps 5-7)

Answer 18

Electrical signals are transformed into conscious experience.
Step 5: Perception occurs when electrical signals that represents object are transformed into experience of seeing object.
Step 6: Person recognizes it as the object (places object in category).
Step 7: Action.

Question 19

Bottom-up processing

Answer 19

Processing based on incoming stimuli from the environment. Also called data-based processing.

Question 20

Top-down processing

Answer 20

Processing based on the perceiver’s previous knowledge (cognitive factors). Also called knowledge-based processing.

Question 21

Psychophysical approach to perception

Answer 21

Use of quantitative methods to measure relationships between stimuli (physics) and perception (psycho).

Question 22

Physiological approach to perception

Answer 22

Measuring the relationship between stimuli and physiological processes and perception.

Question 23

Observing perceptual processes at different stages

Answer 23

Relationship A: the stimulus-perception relationship
Relationship B: the stimulus-physiology relationship
Relationship C: the physiology-perception relationship

Question 24

Example of the stimulus-perception relationship

Answer 24

Two coloured patches are judged to be different.

Question 25

Example of the stimulus-physiology relationship

Answer 25

A light generates a neural response in the cat’s cortex.

Question 26

Example of the physiology-perception relationship

Answer 26

A person’s brain activity is monitored as the person indicates what he is seeing.

Question 27

Absolute threshold

Answer 27

The smallest amount of energy needed to detect a stimulus

Question 28

Method of limits

Answer 28

Experimenter presents stimuli in either ascending order (intensity is increased) or descending order (intensity is decreased). Observer responds to whether she perceived the stimulus. Cross-over point is the threshold.

Question 29

Phenomenological method

Answer 29

A researcher asks a person to describe what he or she is perceiving or to indicate when a particular perception occurs. Describes what we perceive.

Question 30

Classical psychophysical methods

Answer 30

Limits, adjustment, and constant stimuli were the original methods used to measure the stimulus-perception relationship.

Question 31

Method of adjustment

Answer 31

The observer or the experimenter adjusts the stimulus intensity continuously until the observer can just barely detect the stimulus. Procedure can be repeated several times and the threshold determined by taking the average.

Question 32

Method of constant stimuli

Answer 32

The experimenter presents five to nine stimuli with different intensities in random order. The threshold is usually defined as the intensity that results in detection on 50% of the trials. Most accurate method, but time consuming.

Question 33

The Difference Threshold

Answer 33

The smallest difference between two stimuli that a person can detect.

Question 34

Determining the Difference Threshold

Answer 34

Participants are asked to determine whether they detect a difference between two stimuli. The DL is the difference between standard and comparison stimuli.

Question 35

The Weber Fraction

Answer 35

The ratio of the difference threshold (DL) to the weight of the standard stimulus. It is constant. He found that when the difference was small, observers had difficulty detecting differences, but they easily detected larger differences. He found that the size of the DL depended on the size of the standard weight. As the magnitude of stimulus increases, so does size of the DL.

Question 36

Magnitude Estimation

Answer 36

The experimenter first presents a “standard” stimulus, and assigns a value, they then present lights of different intensities, and observer is asked to assign a number to each light that is proportional to the brightness of the standard stimulus. Each light intensity has a brightness assigned to it by observer.

Question 37

Response compression

Answer 37

Result of magnitude estimation that indicates that doubling the intensity does not necessarily double the perceived brightness. As intensity is increased, the magnitude increases, but not as rapidly as the intensity.

Question 38

Response expansion

Answer 38

Result of magnitude estimation indicating that doubling the strength of a shock more than doubles the sensation of being shocked. As intensity is increased, perceptual magnitude increases more than intensity.

Question 39

The Power Function

Answer 39

The relationship between the intensity of a stimulus and our perception of its magnitude follows the same general equation for each sense. These functions are called power functions, and are described by the equation P=KS^n.

Question 40

Steven’s power law

Answer 40

Relationship of Perceived magnitude (P), equals a constant, K, times the stimulus intensity, S, raised to a power, n.

Question 41

How physical events influence affect perception

Answer 41

We begin with: seeing in focus, seeing in dim light, seeing in fine details

Question 42

Electromagnetic spectrum

Answer 42

A continuum of electromagnetic energy that is produced by electric charges and is radiated as waves. The energy in this spectrum ca be described by its wavelength.

Question 43

Wavelength

Answer 43

The distance between the peaks of the electromagnetic waves. They range from extremely short-wavelength gamma rays, to long-wavelength radio waves.

Question 44

Visible light

Answer 44

The energy within the electromagnetic spectrum that humans can perceive.

Question 45

The eye

Answer 45

Where vision begins. Light reflected from objects in the environment enters the eye through the pupil and is focused by the cornea and lens to form sharp images of the object on the retina, which contains the receptors for vision.

Question 46

Two kinds of visual receptors

Answer 46

Rods and cones.

Question 47

Visual pigments

Answer 47

Rods and cones contain light-sensitive chemicals called visual pigments that react to light and trigger electrical signals. These signals then flow through the network of neurones that make up the retina.

Question 48

Optic nerve

Answer 48

Signals emerge from the back of the eye in the optic nerve, which conducts signals towards the brain.

Question 49

How light is focused by the eye

Answer 49

Focus in retina. Cornea accounts for 80% of the eye’s focusing power, but can’t adjust its focus. The lens accounts for the last 20%, and can adjust the eye’s focus for stimuli located at different distances.

Question 50

Accommodation

Answer 50

A process that stops objects from being blurred. Accommodation increases the focusing power of the lens and brings the focus point for a near object back to point A on the retina, by bending the light rays passing through the lens.

Question 51

Near point

Answer 51

The distance at which your lens can no longer adjust to bring close objects into focus.

Question 52

Far point

Answer 52

The distance at which the spot of light become focused on the retina.

Question 53

Myopia (nearsightedness)

Answer 53

Trouble seeing distant objects. Refractive myopia: Cornea and lens overland the light. Axial myopia: Eyeball is too long.

Question 54

Hyperopia (farsightedness)

Answer 54

Trouble seeing near objects. Focus point beyond the retina. Eyeball is too short.

Question 55

Presbyopia

Answer 55

Trouble seeing near objects due to aging. Lens becomes more rigid with age.

Question 56

Isomerization

Answer 56

Before the light is absorbed, the retinal is next to the opsin. When a photon of light hits the retinal, it changes in shape, so it is sticking out from the opsin. Isomerization triggers the transformation of the light entering the eye into electricity in the receptors.

Question 57

What triggers transduction

Answer 57

When the light-sensitive retinal absorbs one photon of light.

Question 58

Hecht’s Psychophysical Experiment

Answer 58

Experiment enabled him to determine how many visual pigment molecules need to be isomerize for a person to see. He did this by using the method of constant stimuli to determine a person’s absolute threshold for seeing a brief flash of light. Conclusions: 1. A person can see a light if 7 rod receptors are activated simultaneously. 2. A rod receptor can be activated by the isomerization of 1 visual pigment molecule.

Question 59

Distribution of Rods and Cones

Answer 59

The small area of the fovea contains only cones - when we look directly at an object, its image falls on the fovea.
The peripheral retina (includes all of the retina outside of the fovea) contains both rods and cones. However, many more rods than cones in the peripheral retina.

Question 60

Blind Spot

Answer 60

Area in the retina where there are no receptors. Where the optic nerve leaves the eye. Because of the absence of receptors, it is called the blind spot.

Question 61

Why we are not aware of our blind spot

Answer 61

Located off to the side of our visual field, where objects are not in sharp focus. Most importantly: some mechanism in the brain “fills in” the place where the image disappears.

Question 62

Dark adaptation

Answer 62

Causes the eye to increase its sensitivity in the dark.Two stages: an initial rapid stage, and a later, slower stage.

Question 63

Dark adaptation curve

Answer 63

Function relating sensitivity to light to time in the dark. As adaptation proceeds, subjects become more sensitive to the light. Reveal the two stages of dark adaptation.

Question 64

Measuring cone adaptation

Answer 64

Have to ensure that the image of the test light stimulates only cones. Achieve this by having observer look directly at the test light so its image will fall on the all-cone fovea, and by making the test light small enough so that its entire image falls within the fovea.

Question 65

Measuring Rod Adaptation

Answer 65

Most use people who have rod monochromatic, who have no cones. Their all-rod retinas provide a way to study rod dark adaption without interference from cones. Once dark adaptation begins, the rods increase their sensitivity and reach their final dark-adapted level in about 25 mins.

Question 66

Process of dark adaptation summary with both cones and rods

Answer 66

As soon as the light is extinguished, the sensitivity of both the cones and the rods begins increasing. The cones determine the early part of the dark adaptation curve, meanwhile the rods are increasing their their sensitivity. After about 3-5 mins, the cones are finished adaption, so their curve levels off. The rods sensitive continues to increase until about 7 minutes of dark adaption, when they catch up to the cones, and then become more sensitive than the cones. Once the rods become more sensitive, they begin controlling the person’s vision.

Question 67

Rod-cone break

Answer 67

The place where the rods begin to determine the dark adaptation curve.

Question 68

Visual Pigment Bleaching

Answer 68

When light hits the light-sensitive retinal part of the visual pigment molecule, it is isomerize and triggers the transduction produces. It then separates from the opsin part of the molecule. This separation cause the retina to become lighter in colour.

Question 69

Visual Pigment Regeneration

Answer 69

In the light, as some molecules are absorbing light, isomerizing, and splitting apart, molecules that have been split apart are undergoing this process in which the retinal and opsin become rejoined.

Question 70

William Ruston’s procedure

Answer 70

Measured the reservation of visual pigment in humans by measuring the darkening of the visual pigment that occurs after adaptation. Showed that cone pigment takes 6 minutes, whereas rod pigment takes 30 minutes.

Question 71

Two important results demonstrated by Rushton

Answer 71

1. Our sensitivity to light depends on the concentration of a chemical - the visual pigment.
2. The speed at which our sensitivity is adjusted in the dark depends on a chemical reaction - the regeneration of the visual pigment.

Question 72

Spectral sensitivity

Answer 72

An observer’s sensitivity to light at each wavelength across the visible spectrum.

Question 73

Measuring spectral sensitivity

Answer 73

To determine special sensitivity, we use flashes of monochromatic light, which is light that contain only a single wavelength. We determine the threshold for seeing these monochromatic lights for wavelengths across the visible spectrum.

Question 74

Results of threshold sensitivity curve

Answer 74

The threshold for seeing light is the lowest in the middle of the spectrum: less light is needed to see wavelengths in the middle than to see wavelengths at either the short or long wavelengths at the end of the spectrum.

Question 75

Spectral sensitivity curve

Answer 75

Relative sensitivity versus wavelength. The cones are more sensitive the light, and the rods are more sensitive in the dark.

Question 76

Measuring spectral sensitivity curve

Answer 76

Measure the cone spectral sensitivity curve by looking directly at test light, so that it stimulates only the cones in the fovea, and presenting test flashes of wavelengths across the spectrum. Measure the rod: measuring the sensitivity after the eye is dark adapted and presenting test flashes off to the side of the fixation point.

Question 77

What does the difference in the sensitivity of the cones and the rods to different wavelengths mean?

Answer 77

As vision shifts from the cones to the rods during dark adaptation, we become relatively more sensitive to short-wavelength light. (near the blue and green end of spectrum)

Question 78

Rod and Cone Absorption Spectra

Answer 78

Plot of the amount of light absorbed by a substance versus the wavelength of light. The difference between the rod and cone spectral sensitivity curves is caused by differences in the absorption spectra of the rod and cone visual pigments.

Question 79

The three absorption spectra for the cones

Answer 79

Each of the three cone pigments are contained in its own receptor. They add together to result in a psychophysical spectral sensitivity curve that peaks at 560nm.

Question 80

Absorption of the rod visual pigment

Answer 80

Closely matches the rod spectral sensitivity curve.

Question 81

Five types of neurons that make up the retina’s layers

Answer 81

Signals generated in the receptors travel to the bipolar cells, and then to the ganglion cells. Receptors and bipolar cells do not have long axons, but the ganglia cells do. These axons transmit finals out of the retina in the optic nerve. There are also horizontal cells and amacrine cells, which connect neurons across the retina.

Question 82

Neural Convergence

Answer 82

Occurs when one neuron receives signals from many other neurons. A great deal of neural convergence occurs in the retina.

Question 83

Signal convergence in rods vs cones

Answer 83

Signals from the rods converge more than do the signals from the cones. 120 million rods in retina vs 6 million cones. 1) The rods result in better sensitivity than cones, and 2) the cones result in better detail vision than the rods/

Question 84

Why do Rods result in greater sensitivity than cones?

Answer 84

The rods’ greater convergence. Many rods summate their responses by feeding into the same ganglion cell, but only one or a few cones send their responses to a single ganglion cell.

Question 85

Why do we use cones to see detail?

Answer 85

The cones have better visual acuity because they have less convergence. Acuity is better in fovea than in the periphery.

Question 86

Lateral inhibition

Answer 86

Inhibition that is transmitted across the retina.

Question 87

What the Horseshoe Crab Teaches us About Inhibition

Answer 87

Used the Limulus (horseshoe crab) to demonstrate how lateral inhibition can affect the response of neurons in a circuit. The limulus eye is made up of hundreds of tiny structures called ommatidia, and each ommatidia has a small lens on the eye’s surface that is located directly over a single receptor. They found that illumination of the neighboring receptors inhibited the firing of receptor A, and this decrease is caused by lateral inhibition that is transmitted across the Limulus’ eye by the fibres of the lateral plexus.

Question 88

The Hermann Grid: Seeing Spots at Intersections

Answer 88

Because the response associated with receptor A (at the intersection) is smaller than the response associated with receptor D (in the corridor between the black squares), the intersection should appear darker than the corridor. And this is what happens - we perceive grey images at the intersection. Lateral inhibition therefore explains the dark images at the intersection.

Question 89

Mach Bands

Answer 89

Illusory light and dark bands near a light-dark border. Can be demonstrated using gray stripes, or by casting a shadow. You will see a dark Mach band near the border of the shadow and a light Mach band on the other side of the border. Because the intensities remain constant across the light stripe on the left and the dark stripe on the right, the small bands we perceive on either side of the border must be illusions. Can be explained by lateral inhibition.

Question 90

How can mach bands be explained by lateral inhibition

Answer 90

Each of the six receptors in this circuit sends signals to bipolar cells, and each bipolar cell sends lateral inhibition to its neighbours on both sides. Receptors A,B, and C fall on the light side of the border and so receive intense illumination; receptors D,E, and F fall on the darker side and receive dim illumination.

Question 91

Simultaneous Contrast

Answer 91

Simultaneous Contrast occurs when our perception of the brightness or colour of one area is affected by the presence of an adjacent or surrounding area.

Question 92

Simultaneous Contrast explained by lateral inhibition

Answer 92

The receptors under the two small squares receive the same illumination. However, the receptors under the light area surrounding one square are intensely stimulated, so they send a large amount of inhibition to the receptors under the left square. The receptors under the dark area surrounding the other square are less intensely stimulated, so they send less inhibition to the receptors under the right square. Because the cells under the first square receive more inhibition than the cells under the right square, their response is decreased more, they fire less than the cells under the right square, and so it looks darker.

Question 93

Reticular theory for the structure of the nervous system

Answer 93

The nervous system consisted of a larger network of fused nerve cells

Question 94

Neuron theory on the structure of the nervous system

Answer 94

The nervous system consisted of distinct elements or cells.

Question 95

Staining

Answer 95

A development that led to the acceptance of neuron theory. It is a chemical technique that caused nerve cells to become coloured so they stood out from surrounding tissue.

Question 96

Doctrine of specific nerve energies

Answer 96

Johannes Mueller proposed this, which stated that our perceptions depend on “nerve energies” reaching the brain and that the specific quality we experience depends on which nerves are stimulated. He proposed that activity in the optic nerve results in seeing, activity in the auditory nerve results in hearing…etc.

Question 97

Recording from Neurons

Answer 97

Recording from single neurons provides valuable info about what is happening in nervous system. Important to record from as many as possible because different neurons may respond differently to a stimulus or situation.

Question 98

Modular organization

Answer 98

Specific functions are served by specific areas of the cortex.

Question 99

Primary receiving areas

Answer 99

The first areas in the cerebral cortex to receive the signals initiated by each sense’s receptors. The primary receiving area for vision: occipital lobe, hearing: temporal lobe, skin senses: parietal lobe.

Question 100

Frontal lobe role

Answer 100

Receives signals from all of the senses, and plays an important role in perceptions that involve the coordination of information received through two or more senses.

Question 101

Receptors

Answer 101

Specialized to respond to environmental stimuli. Although receptors look different, they all have a part that reacts to environmental stimuli and triggers the generation of electrical signals, which eventually are transmitted to neurons with axons.

Question 102

Nerve

Answer 102

Such as the optic nerve, which carries signals out the back of the eye, consists of the axons of many neurons. They contain many nerve fibres.

Question 103

Resting potential

Answer 103

-70 millivolts. Stays the same as long as there are no signals in the neuron.

Question 104

Action potential

Answer 104

Happens when the neurons receptor is stimulated so that a signal is transmitted down the axon. There is a rapid increase in positive charge until the inside of the neuron is +40 mV compared to the outside, followed by a rapid return the baseline of-70 mV. These changes are caused by the flow of sodium and potassium ions across the cell membrane.

Question 105

Upward phase of the action potential

Answer 105

Change from -70mV to +40mV. Occurs when positively charged sodium ions rush into the axon.

Question 106

Downward phase of the action potential

Answer 106

Change from +40mV back to -70mV. Occurs when positively charged potassium ions rush out of the axon.

Question 107

Permeability

Answer 107

A property of the cells membrane that refers to the ease with which a molecule can pass through the membrane. The change in sodium and potassium flow that create the action potential are caused by changes in the fiber’s permeability to sodium and potassium.

Question 108

Selective permeability

Answer 108

Occurs when a membrane is highly permeable to one specific type of molecule, but not to others.

Question 109

Permeability during the action potential

Answer 109

Before the action potential occurs, the membrane’s permeability to sodium and potassium is low, so there is little flow of these molecules across the membrane. Stimulation of the receptor triggers a process that causes the membrane to become selectively permeable to sodium, so sodium flows into the axon. When the action potential reaches +40mV, the membrane suddenly becomes selectively permeable to potassium, so potassium flows out of the axon.

Question 110

Propagated response

Answer 110

The action potential is a propagated response - once the response is triggered, it travels all the way down the axon without decreasing in size. This enables neurons to transmit signals over long distances.

Question 111

Effect on action potential of changing the stimulus intensity

Answer 111

It does not affect the size of the action potentials, but it does affect the rate of firing.

Question 112

Refractory period

Answer 112

The interval between the time one nerve impulse occurs and the next one can be generated in the axon. This is the cause of there being an upper limit to the number of nerve impulses per second that can be conducted by an axon.

Question 113

Spontaneous activity

Answer 113

The action potentials that occur in the absence of stimuli from the environment. It establishes a baseline level of firing for the neuron.

Question 114

What is the action potentials function

Answer 114

To communicate information.

Question 115

Neurotransmitters

Answer 115

When action potentials reach the end of a neuron, they trigger the release of chemicals called neurotransmitters, that are stored in structures called synaptic vesicles in the sending neuron. The neurotransmitter molecules flow into the synapse to small areas on the receive neuron called receptor sites that are sensitive to specific neurotransmitters. When a neurotransmitter makes contact with a receptor site matching its shape, it activates the receptor site and triggers a voltage change in the receiving neuron.

Question 116

Excitatory transmitters

Answer 116

Cause the inside of the neuron to become more positive, a process called depolarization. To generate an action potential, enough excitatory neurotransmitter must be released to increase depolarization to a certain level. Increases the chances that a neuron will generate action potentials and is associated with high rates of firing.

Question 117

Inhibitory transmitters

Answer 117

Cause the inside of the neuron to become more negative, a process called hyper polarization. Hyperpolarization can prevent the neuron from reaching the level of depolarization needed to generate action potentials. Decreases the chances that a neuron will generate action potentials and is associated with lowering rates of nerve firing.

Question 118

Why does inhibition exist?

Answer 118

The functions of neurons is not only to transmit information but also to process it, and both excitation and inhibition are necessary for this processing.

Question 119

Convergence

Answer 119

The synapsing of more than one neuron into a single neuron.

Question 120

Receptive Field of a neuron

Answer 120

The area on the receptors that influences the firing rate of the neuron.

Question 121

Center-surround receptive field

Answer 121

The areas of the receptive field are arranged in a centre region that corresponds one way and a surround region that responds in the opposite way.

Question 122

Center-surround antagonism effect

Answer 122

The fact that the centre and the surround of the receptive field respond in opposite ways causes this effect. Shows what happens as we increase the size of a spot of light presented to the neuron’s receptive field. A small spot of light presented to the excitatory centre causes a small increase in the rate of nerve firing, and increasing the light’s size so that it covers the entire centre of the receptive field increase the cell’s response.

Question 123

When does centre-surround antagonism come into play

Answer 123

When the spot of light becomes large enough so that it begins to cover the inhibitory area. Stimulation of the inhibitory surround contracts the centre’s excitatory response, causing a decrease in the neuron’s firing rate. So, this neuron responds best to a spot of light that is the size of the excitatory centre of the receptive field.

Question 124

Problem of sensory coding

Answer 124

How does the firing of neurons represent various characteristics of the environment? One answer: specificity coding.

Question 125

Specificity coding

Answer 125

The representation of particular objects in the environment by the firing of neurons that are tuned to respond specifically to that object. There are neurons that are specifically tuned to each object in the environment.

Question 126

Grandmother cell

Answer 126

A neuron that responds only to a specific stimulus.

Question 127

Evidence from neurons that respond to specific stimuli

Answer 127

Recorded from eight patients with epilepsy who had electrodes implanted in their hippocampus or medial temporal lobe to help localize precisely where their seizures originated. A number of neurons responded to some of the stimuli that was showed to patients. But, some neurons responded to a number of different views of just one person or building. These neurons are not responding to visual features of the pictures, but to concepts. These neurons were in the hippocampus and MTL - areas associated with the storage of memories.

Question 128

Are the neurons that respond to specific stimuli grandmother cells?

Answer 128

According to Quiroga, the answer is no. It is unlikely that these neurons respond to only a single object or concept. First, it would be extremely difficult to find the one neuron that responded to a particular person or concept. Second, if they had had time to present more pictures, they might have found other stimuli that caused their neurons to fire.

Question 129

Distributed coding

Answer 129

The representation of a particular object by the pattern of firing of groups of neurons. Distributed coding allows the representation of a large number of stimuli by the firing of just a few neurons.

Question 130

Sparse Coding

Answer 130

The idea that a particular object is represented by the firing of a relatively small number of neurons. This concept is somewhere between specificity coding and distributed coding.

Question 131

Mind-body problem of perception

Answer 131

How do physical processes such as nerve impulses or sodium and potassium molecules flowing across membranes become transformed into the richness of perceptual experience?

Question 132

Lateral geniculate nucleus (LGN)

Answer 132

Most signals from the retina travel out of the eye in the optic nerve to the LGN in the thalamus. From here, signals travel to the primary visual receiving area in the occipital lobe of the cortex.

Question 133

Striate cortex

Answer 133

Other name for the visual receiving area, because of the white stripes that are created within this area by nerve fibres. From the striate cortex, signals are transmitted along two pathways, one to the temporal lobe, and the other to the parietal lobe.

Question 134

Receptive fields of LGN Neurons

Answer 134

LGN neurons have the same centre-surround configuration as retinal ganglion cells. Neurons in the LGN, like neurons in the optic nerve, respond best to small spots of light on the retina.

Question 135

Major function of LGN

Answer 135

Not to create new receptive field properties, but to regulate neural information as it flows from the retina to the visual cortex.

Question 136

Information flow in the LGN

Answer 136

The LGN does not just receive signals from the retina and then transmit them to the cortex. The LGN receives info from many sources, including the cortex, and then sends its output to the cortex. One of the purposes of the LGN is to regulate neural info as it flows from retina to cortex.

Question 137

Organization of LGN by Left and Right Eyes

Answer 137

The LGN is a bilateral structure, which means there is one LGN in left hemisphere and one in right hemisphere. Viewing one of the nuclei in cross section revels six layers. Each layer receives signals from only one eye. Layers 2,3,5 receive signals from ipsilateral eye (eye on same side of body), and layers 1,4,6 receive signals from contralateral eye (eye on opposite side of body from LGN).

Question 138

Organization of LGN as a spatial map

Answer 138

The correspondence between points on the LGN and points on the retina creates a retinotopic map on the LGN.

Question 139

Retinotopic map

Answer 139

A map in which each point on the LGN corresponds to a point on the retina. This correspondence means that neurons entering the LGN are arranged so that fibres carrying signals from the same area of the retina end up in the same area of the LGN, each location on the LGN corresponds to a location on the retina, and neighbouring locations on the LGN correspond to neighbouring locations on the retina.

Question 140

Finding of Hubel and Wiesel

Answer 140

Found cells in the striate cortex with receptive fields that, like centre-surround receptive fields of neurons in the retina and LGN, have excitatory and inhibitory areas. But these areas are arranged side by side rather than in the centre-surround configuration - these cells are called simple cortical cells.

Question 141

Simple cortical cells

Answer 141

Cells that are arranged side by side. We can tell from the layout of the excitatory and inhibitory areas of the simple cell that a cell with this receptive field would respond best to vertical bars.

Question 142

Orientation tuning curve

Answer 142

The relationship between orientation and firing is indicated by a neuron’s orientation tuning curve, which is determined by measuring the responses of a simple cortical cell to bars with different orientations. There are neurons that respond to all of the orientations that exist in the environment.

Question 143

Complex cells

Answer 143

Like simple cells, respond best to bars of a particular orientation. However, unlike simple cells, most complex cells respond only when a correctly oriented bar of light moves across the entire receptive field, and many respond best to a particular direction of movement.

Question 144

End-stopped cells

Answer 144

Cells that fire to moving lines of a specific length or to moving corners or angles. The neuron responds when the corner moves up-ward. The neuron’s response increases as the corner-shaped stimulus gets longer, but then stops responding when the corner becomes too long.

Question 145

What do Hubel and Wiesel’s finding that some neurons respond only to oriented lines indicate? And why does this make sense?

Answer 145

Indicates that neurons in the cortex do not simply respond to “light”; they respond to some patterns of light and not to others. Makes sense because: the purpose of visual system is to enable us to perceive objects in the environment, and many objects can be represented by lines of various orientations.

Question 146

Retinal ganglion cells respond best to

Answer 146

Spots of light

Question 147

Cortical end-stopped cells respond best to

Answer 147

bars of a certain length that are moving in a particular direction

Question 148

Selective adaptation

Answer 148

If the neurons fire for long enough, they become fatigued, or adapt. This adaptation causes two phycological effects: 1) the neuron’s firing rate decreases, and 2) the neuron fires less when that stimulus is immediately presented again. According to this idea: presenting a vertical line causes neurons that respond to vertical lines to respond, but as these presentations continue, these neurons eventually begin to fire less to vertical lines.

Question 149

Why is adaptation selective

Answer 149

only the neurons that respond to verticals or near-verticals adapt, and other neurons do not.

Question 150

Basic assumption behind a psychophysical selective adaptation experiment

Answer 150

If these adapted neurons have anything to do with perception, then adaptation of neurons that respond to verticals should result in the perceptual effect of becoming selectively less sensitive to verticals, but not to other orientations.

Question 151

Grating stimuli/contrast threshold

Answer 151

Alternating bars. High-contrast gratings are on the left, and lower-contrast on the right. A grating’s contrast threshold is the difference in intensity at which the bars can just barely be seen.

Question 152

Selective rearing

Answer 152

If an animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to these stimuli will become more prevalent.

Question 153

Neural plasticity/experience-dependent plasticity phenomenon

Answer 153

The response properties of neurons can be shaped by perceptual experience. According to this idea, rearing an animal in an environment that contains only vertical lines should result in the animal’s visual system have neurons that respond predominantly to verticals.

Question 154

Cortical magnification factor

Answer 154

The area representing the cone-rich fovea is much larger than one would expect from the fovea’s small size. The apportioning of the small fovea with a large area on the cortex is called the cortical magnification factor.

Question 155

Brain imaging

Answer 155

Refers to a number of techniques that result in images that show which areas of the brain are active.

Question 156

Positron emission tomography (PET)

Answer 156

A person is injected with a low does of radioactive tracer that is not harmful. The tracer enters the blood stream and indicates the volume of blood flow. Changes in the activity of the brain are accompanied by changes in blood flow, and monitory the radioactivity of the injected tracer provides a measure of this blood flow.

Question 157

fMRI

Answer 157

Based on the measurement of blood flow, like PET. Determines the relative activity of various areas of the brain by detecting changes in the magnetic response of the hemoglobin that occurs when a person perceives a stimulus or engages in a specific behaviour.

Question 158

Connection between cortical area and acuity experiment (Robert Duncan and Geoffrey Boynton)

Answer 158

Good acuity is associated not only with sharp focusing of images on the retina, and the small amount of convergence of the cones, but also with the relatively large amount of brain area devoted to the all-cone fovea.

Question 159

Location columns

Answer 159

Hubel and Wiesel concluded that the cortex is organized into location columns that are perpendicular to the surface of the cortex so that all of the neurons within a location column have their receptive fields at the same location on the retina.

Question 160

Orientation columns

Answer 160

The cortex is organized into orientation columns, with each column containing cells that respond best to a particular orientation. Also, adjacent columns have cells with slightly different preferred orientations.

Question 161

Ocular Dominance Columns

Answer 161

Neurons in the cortex are also organized with respect to the eye to which they respond best. Means that each neuron encountered along a perpendicular electrode track responds best to the same eye.

Question 162

Ocular dominance

Answer 162

Neurons having a preferential response to one eye than to another. The cortex consists of a series of columns that alternate in ocular dominance in a left-right-left-right pattern.

Question 163

Hypercolumns

Answer 163

All three types of columns could be combined into one larger unit called a hypercolumn. Each hypoercolumn contains a single location columns, left and right ocular dominance columns, and a complete set of orientation columns that cover all possible stimulus orientations from 0-180 degrees.

Question 164

Hubel and Wiesel’s “processing model”

Answer 164

They thought of a hyper column as a “processing model” that processes information about any stimulus that falls within the location in the retina served by the hyper column. They based this on: each hyper column contains a full set of orientation columns, so that when a stimulus of any orientation is presented to the area of retina served by the hyper column, neurons within the hyper column that respond to that orientation will be activated.

Question 165

How is an object represented in the striate cortex?

Answer 165

The pattern of activation of an object on the striate cortex is distorted compared to the actual object. The magnification factor allots more space on the cortex to the parts of the image that fall on the observer’s fovea. A large stimulus, which stretches across the retina, will stimulate a number of different orientation columns, each in a location in the cortex that is separated form the other columns.

Question 166

Brain Ablation experiment

Answer 166

Once the animals perception has been measured, a particular area of the brain is ablated (removed or destroyed), either by surgery or by injecting a chemical at the area to be removed. The monkey is then retrained to determine which perceptual capacities remain and which have been affected by the ablation.

Question 167

Brain ablation on monkeys experiment results (what/where pathways)

Answer 167

Part of temporal lobe was removed in some monkeys: testing showed that the object discrimination problem was difficult for them. Indicates that the pathway that reaches the temporal lobe is responsible for determine and object’s identify. Therefore, called the path leading from striate cortex to temporal lobe the what pathway.
Other monkeys had their parietal lobes removed, had difficulty solving landmark discrimination problems. This indicates that the pathway that leads to parietal lobe is responsible for determine objects location - called where pathway.

Question 168

Ventral pathway / dorsal pathway

Answer 168

What pathway is also called the ventral pathway, and where pathway is also called the dorsal pathway.

Question 169

Neuropsychology

Answer 169

The study of the behavioral effects of brain damage in humans.

Question 170

The behaviour of patient D.F

Answer 170

The method of determining dissociations used on DF, who suffered damage to her ventral pathway. She had trouble matching the orientation of a card held in her hand to different orientations of a slot. But, she was able to place the card through the slot. Thus, she performed poorly in the static orientation-matching task, but did well as soon as action was involved. This behaviour was interpreted as there being one mechanism for judging orientation and another for coordinating vision and action.

Question 171

How pathway suggestion

Answer 171

Dorsal pathway (where) should actually be called the how/action pathway, because it determines how a person carries out an action.

Question 172

Rod and frame illusion

Answer 172

Two small lines inside the tilted squares appear slightly tilted in opposite directions, even though they are parallel vertical lines. Observers were presented with a matching task and a grasping task. Results showed that observers had to adjust the matching stimulus in order to make it match their perception of the rod, but the tilted square did not affect the grasping task.

Question 173

Rationale behind rod and frame illusion

Answer 173

Because these two tasks involve different processing streams (matching task = ventral/what, grasping = dorsal/how), they may be affected differently by the presence of the surrounding frames. So, conditions that created a perceptual visual illusion (matching) had no effect on the person’s ability to take action (grasping). Supports the idea that perception and action are served by different mechanisms.

Question 174

Module

Answer 174

A structure that is specialized to process information about a particular type of stimulus is called a module.

Question 175

Fusiform face area (FFA)

Answer 175

Area located in the fusiform gyrus on the underside of therein directly below IT cortex. FFA is specialized to respond to faces.

Question 176

Prosopagnosia

Answer 176

Caused by damage to the temporal lobe. Difficulty recognizing the faces of familiar people.

Question 177

How can the nervous system achieve adaptation to the specific environment?

Answer 177

Through a process that causes neurons to develop so that they respond best to the types of stimulation to which the person has been exposed. This is the process of experience-dependent plasticity. Brain imaging experiments have also demonstrated a shift in responding of neurons in the FFA due to training.

Question 178

Greebles experiment

Answer 178

Observers were shown both human faces and Greebles. Results indicated that the FFA neurons responded poorly to the Greebles but well to the faces. The participants were then trained in “Greeble recognition”. After the training, participants had become “Greeble experts”. After the training, the FFA neurons responded about as well to the Greebles as to faces.

Question 179

How do neurons become specialized?

Answer 179

Specialized tuning is at least partially the result of experience-dependent plasticity. This makes it possible for neurons to adapt their tuning to objects that are seen often and that are behaviourally important.