Chapter 5 - Quiz 2

Question 1

The Eye and its connections to the brain: route within the retina

Where do messages go from the eye to the retina? (2)

Answer 1

-receptors at the back of eye to bipolar cells, then ganglion cells
-additional cells called amacrine cells get info from bipolar cels and send it to other bipolar, amacrine and ganglioln cells

-in the fovea, a single bipolar cell attaches to a single ganglion cell

Question 2

The Eye and its connections to the brain: route within the retina

What is the optic nerve made of?

Answer 2

-ganglion cells axons join to form it

-your brain fills in the gap of the blind spot and your other eye can see what the blind spot of the one eye cannot

Question 3

The eye and its connections to the brain: fovea and periphery

What is the midget ganglion cells?

Answer 3

-the ganglion cells in humans and primates

-each is small and responds to just a single cone

-each cone in the fovea has a direct route to the brain
-birds have two fovea

Question 4

Visual Receptors: Rods and Cones

What are rods functional for and where are they primarily located? (2)

Answer 4

-periphery
-not useful in daylight because bright light bleaches them

-rods outnumber cones but cones provide about 90% of the brain’s input

Question 5

Visual Receptors: Rods and Cones

Where are cones primarily located and what are their functions? (2)

Answer 5

-fovea
-less active in dim light, more useful in bright light and essential for color vision

Question 6

Color vision: the trichromatic (Young-Helmholtz) theory

What is the trichromatic theory/Young-Helmholtz theory?

Answer 6

-we perceive color through the relative rates of response by three different cones

-incomplete as a theory of colour vision

-each cone is sensitive to a different set of wavelengths (short is blue, medium is green yellow and long is orange red)

Question 7

Color: The trichromatic theory

What is a visual field?

Answer 7

-everything you can see in both fovea and peripheral vision with moving the head

Question 8

Color vision: the opponent-process theory

What is the opponent process theory? What is an example? (2)

Answer 8

-we percieve color in terms of opposites, brain perceives color on a continuum and after you stare at one color long enough you swing to the opposite
-for example, a bipolar cell receives excitation from short-wavelength cone and inhibiition from long and medium wavelength cone, after prolonged exposure the fatigued cell decreases its response and because a low level of response by that cell usually means yellow, you percieve yellow

-negative color afterimage (when you stare at something and look away and continue to see light within that shape)
-continuum includes red to green, yellow to blue and white to black

Question 9

Color Vision: Stop and check Pg 156

According to the trichoromatic theory, why do we see red?

Answer 9

-A perception of red occurs only if the long-wavelength cone has a high ratio of response relative to the other two types of cone.

-cpmparison is the key

-Activity of the long-wavelength cone is not sufficient.
-the long-wavelength cone responds to what we call yellow more than to what we call red.

Question 10

Color vision: stop and check Pg 156

According to the opponent process theory, under what circumstances would you perceive a white object as blue?

Answer 10

-If you stared at a bright yellow object for a minute or so and then looked at a white object, it would appear blue.

Question 11

Color vision: The Retinex Theory

What is color constancy? Which theories cannot explain it very well? (2)

Answer 11

-the ability to recognize colors despite changes in lighting
-trichoromatic theory and the oppnent-process theory

Question 12

Color vision: The Retinex theory

What is the retinex theory?

Answer 12

-the cortex compares information from various parts of the retina to determine brightness and color for each area

-examples include looking at two grey blocks that look like different shades of grey but when you put a finger in front of the border, they are actually the same color
-another example is when an object is under yellow vs. blue light. We can still perceive the correct color of a banana even if its under different lights

Question 13

Color vision: Stop and Check Pg 157

When a television set is off, its screen appears gray. When you watch a program, parts of the screen appear black, even though more light is actually showing on the screen than when the set was off. What accounts for the black perception?

Answer 13

-The black experience arises by contrast with the brighter areas around it.

Question 14

Color vision: stop and check Pg 157

Figure 5.9 shows light at about 510 nm as green. Why should we nevertheless not call it “green light”?

Answer 14

-Color perception depends not just on the wavelength of light from a given spot but also the light from surrounding areas.

Question 15

Color vision: color vision deficiency

What is color vision deficiency and what is it caused by? (2)

Answer 15

-people with certain genes fail to develop one type of cone or develop an abnormal cone
-colorblindness

Question 16

General Principles of Perception

What is the law of specific nerve energies?

Answer 16

-the nature of a sensation is determined by the specific type of sensory nerve that is stimulated, rather than the stimulus itself

-each type of sensory nerve is associated with a particular type of sensation
-the brain codes information largely in terms of which neurons are active and how active they are at any moment. Impulses in certain neurons indicate light, whereas impulses in others indicate sound, touch or other sensations.

Question 17

Visual Receptors 5.1: Summary

People who vary in their number of axons from the retina to the brain, specifically people who have more axons show a greater ability to what?

Answer 17

-detect brief, faint or rapidly changing stimuli

Question 18

5.1 Visual Receptors: End of Chapter Quiz

If you stare at a white circle surrounded by a green background, and then look at a white surface, you perceive a green circle surrounded by a red background. What does this observation imply about the opponent-process theory?

Answer 18

-Opponent-process color perception depends on the visual cortex, not just the cells in the retina.

-the afterimage effect requires higher level processing beyond the initial response of retinal cells

Question 19

5.2 An overview of the mammalian vsual systemi

What is the sequence of synaptic connections in the retina starting from the rods and cones? (3)

Answer 19

-Rods and cones synapse with horizontal and bipolar cells.
-Horizontal cells inhibit bipolar cells.
-Bipolar cells then synapse with amacrine and ganglion cells, all within the eyeball.

Question 20

An overview of mammalian visual system

Information for the nasal half of each eye and the temporal half of each eye cross to what side of the brain? (2)

Answer 20

-nasal half crosses to the contralateral hemisphere (otherside)
-temporal half crosses to the ipsilateral hemisphere (same side)

Question 21

An overview of the mammalian visual system

Where do most ganglion cells axons go to?

-this is also essentially asking where does the optic nerve go

-what part of the brain?

Answer 21

-lateral geniculate nucleus

-part of thalamus
-some cells go to hypothalamus and superior colliculus

-looks somewhat like a knee
-sends zons to other parts of the thalamus and the visual cortex

Question 22

Processing in the retina

What is the purpose of lateral inhibition and how does it work? (2)

Answer 22

-sharpens contrast and borders
-receptors send messages to excite nearby bipolar cells and also sends messages to horizontal cells that slightly inhibit those bipolar cells and the neighbors to their sides. The next result is to heighten the contrast between an illuminated area and its darker surround

Question 23

Processing in the retina: Stop and Check Pg 164

When light strikes a receptor, does the receptor excite or inhibit the bipolar cells? What effect does it have on horizontal cells? What effect does the horizontal cell have on bipolar cells? (2)

Answer 23

-The receptor excites both the bipolar cells and the horizontal cell.
-The horizontal cell inhibits the same bipolar cell that was excited plus additional bipolar cells in the surround

Question 24

Processing in the retina: Stop and Check Pg 164

If light strikes only one receptor, what is the net effect (excitatory or inhibitory) on the nearest bipolar cell that is directly connected to that receptor? What is the effect on bipolar cells to the sides? What causes that effect? (2)

Answer 24

-It produces more excitation than inhibition for the nearest bipolar cell.
-For surrounding bipolar cells, it produces only inhibition. The reason is that the receptor excites a horizontal cell, which inhibits all bipolar cells in the area.

Question 25

5.2 Further Processing

What is a receptive field?

Answer 25

-the area in visual space that excites or inhibits a cell in the visual system

-each cell has one

-the receptive field of a rod or cone is simply the point in space from which light strikes the cell
-other visual cells derive their receptive fields from the connections they receive
-if light from a particular spot excites the neuron, then that location is part of the neuron’s excitatory receptive field. If it inhibits activity, the location is in the inhibitory receptive field.

Question 26

Further Processing

Explain the three types of ganglion cells in primates: parvocellular, magnocellular and koniocellular (3)

Answer 26

-parvocellular neurons: small cell bodies and small receptive fields are mostly in or near fovea. respond to color and detailed shape
-magnocellular neurons: large cell bodies and receptive fields are distributed evenly through retina. do not respond to color and respond to movement and broad outlines of shape.
-koniocellular neurons: small cell bodies but theyt occur throughout the retina. Some respond to color and respond to varied stimuli

Question 27

Further processing: Stop and Check Pg 166

.As we progress from bipolar cells to ganglion cells to later cells in the visual system, are receptive fields ordinarily larger, smaller, or the same size? Why

Answer 27

-They become larger because each cell’s receptive field is made by inputs converging at an earlier level.

Question 28

The Primary Visual Cortex

Information from the lateral geniculate nucleus of the thalamus usually goes to where?

Answer 28

-primary visual cortex in the occipital cortex

-AKA as Area V1 or striate cortex

Question 29

The primar visual cortex

What happens if someone damages the primary visual cortex?

Answer 29

-they will report having no conscious vision, no visual imagery and no visual images in dreams

-can show blindsight

Question 30

The Primary Visual Cortex

What is blindsight?

Answer 30

-when people with damage to the primary visual cortex can respond to visual stimuli without consciously perceiving them

-could navigate around obstacles, detec movement or identify objects in the visual field
-indicates that some visual processing occurs outside of conscious awareness

Question 31

The Primary Visual Cortex

What does research around blindsight suggest? (2)

Answer 31

-small islands of healthy tissue remain in a damaged visual cortex that can support some visual functions
-the thalamus sends visual input to several other brain areas, including part of the temporal cortex

Question 32

The Primary Visual Cortex: Simple and Complex receptive fields

What is a simple cell? What shapes or movements does it respond best to? (2)

Answer 32

-a cell with a receptive field with a fixed excitatory and inhibitory zone
-bar-shaped and horizontal/vertical

-only in V1 area

Question 33

The primary Visual Cortex: Simple and Complex cells

What does a complex cell respond to?

Answer 33

-pattern of light in particular orientation anywhere within its large receptive field

-in V1 and V2 area

-a cell that responds to stimulus in only one location is a simple cell, one that responds equally throughout a large area is a complex cell

Question 34

The primary visual cortex: Simple and complex cells

What does an end-stopped or hyper complex cell respond to?

-resemble complex cell except?

Answer 34

-has strong inhibitory area at one end of its bar-shaped receptive field

-the cell responds to a bar-shaped pattern of light anywhere in its broad receptive field, provided the bar does not extend beyond a certain point

Question 35

The Primary Visual Cortex: The columnar organization

What do cells with similar properties in the visual cortex do?

Answer 35

-they group together in columns

-cells grouped together have the same orientation preference

Question 36

Primary Visual Cortex: are visual cortex cells feature detectors?

What is a feature detector

Answer 36

-neurons whose response indicate the presence of a particular feature

Question 37

Development of the visual cortex: deprived experience in both eyes

What is a sensitive period?

Answer 37

-when experiences have a particularly strong and enduring influence

Question 38

Development of the visual cortex: deprived experience in one eye

What happens if a young animal can see in one eye but not the other?

Answer 38

-synapses in the visual cortex gradually become unresponsive to input from the deprived eye and after a while, even if the eye works again the animal will not be able to see with it

Question 39

Development of the visual cortex: deprived experience in both eyes

What happens if both eyes of a kitten were sutured closed?

Answer 39

-if neither eye is active, no axon outcompetes another. For a while, the visual cortex remains responsive to visual input

Question 40

Development of the visual cortex: uncorrelated stimulation in the two ey

What is retinal disparity?

Answer 40

-the discrepancy between what the left and right eyes see

-stereoscopic depth perception requires this
-by comparing the inputs from two eyes, you achieve stereoscopic depth perception

Question 41

Development of visual cortex: uncorrelated stimulation in two eyes

What woud happen if a kitten had damaged eye muscles so that its eyes do not point in the same direction?

Answer 41

-cortical neurons do not consistently receive messages from one eye that match messages from the other, results in poor depth perception

-experience fine-tunes binocular vision

Question 42

Development of visual cortex: uncorrelated stimulation in two eyes

What is strabismus?

Answer 42

-lazy eye

-solution sometimes is to wear a patch over the active eye

Question 43

Development of visual cortex: early exposure to a limited array of patte

What causes astigmatism?

Answer 43

-assymetric curvature of the eyes

Question 44

5.3 Ventral and Dorsal Paths

Where does the V1 area send information to?

Answer 44

-secondary visual cortex

-processes the info furter and transmits it to additional areas
-anterior to V1 in the occipital cortex

Question 45

The ventral and dorsal pathway

What is the ventral stream? (2)

Answer 45

-through temporal cortex is known as perception pathway
-because of its importance for identifying and recognizing objects

-or what pathway
-damage to this area causes an inability to name the object, recognize faces etc but someone can still pick up objects appropriately and move them

Question 46

The ventral and dorsal paths

What is the dorsal stream through and why? (2)

Answer 46

-through parietal cortex and is action pathway or how pathway
-because of its importance for visually guided movements

-damage to this area causes people to be able to recognize objects but not accurately move out to touch them or move between them

Question 47

Detailed analysis of shape: Recognizing faces Stop and Check Pg 181

The brain has no specialized areas for perceiving flowers, clothes, or food. For what items does it have specialized areas?

Answer 47

-The temporal cortex has specialized areas for perceiving places, faces, and bodies, including bodies in motion

Question 48

Detailed analysis of shape: Recognizing faces Stop and Check Pg 181

The ability to recognize faces correlates with the strength of connections between which brain areas?

Answer 48

-Ability to recognize faces correlates with the strength of connections between the occipital face area and the fusiform gyrus.

Question 49

Motion Perception: The Middle Temporal Cortex

What are the two areas espcially important for motion perception?

Answer 49

-MT (middle temporal cortex)
-MST ( medial superior temporal cortex

-receive input mostly from the magnocellular path
-MT is color insensitive

Question 50

Motion Perception: The Middle Temporal Cortex

What do most cells in area MT respond to?

Answer 50

-They respond selectively to movement at a particular speed and direction, detect acceleration or deceleration, and respond to motion in all three dimensions.

Question 51

Motion Perception: The Middle Temporal Cortex

What type of stimuli do cells in the dorsal part of area MST respond best to?

Answer 51

-They respond best to complex stimuli like the expansion, contraction, or rotation of a large visual scene, as experienced when moving forward, backward, or tilting your head.

Question 52

Motion Perception: Motion Blindness

When you move your eyes, why does it not seem as if the world is moving?

Answer 52

-Neurons in areas MT and MST respond strongly when an object moves relative to the background, and not when the object and background move in the same direction and speed.