Psych 261 Midterm2 Ch5

Front 1

What is the pupil?

Back 1

Where light enters the eye through an opening in the center of the iris.

Front 2

What focuses the pupil? Are these parts adjustable or not?

Back 2

The lens (adjustable) and cornea (not adjustable)

Front 3

What is the retina?

Back 3

Light is projected onto this structure, and is lined with visual receptors.

Front 4

In the vertebrate retina, how are messages sent from the eye?

Back 4

Messages are sent from the receptors at the back of the eye to bipolar cells, who then send their messages to ganglion cells. The ganglion cells' axons join together and travel back to the brain.

Front 5

What do amacrine cells do?

Back 5

1) They get info from bipolar cells and send it to other bipolar, amacrine, and ganglion cells.

2) Refine the input to ganglion cells

Front 6

What do the axons of the ganglion cells form?

Back 6

The optic nerve

Front 7

What is the blind spot?

Back 7

The point at which ganglion cell axons leave (also where blood vessels enter and leave). Has no receptors.

Front 8

What is the fovea?

Back 8

A tiny area specialized for acute, detailed vision. Has nearly unimpeded vision due to the blood vessels and ganglion cell axons.

Front 9

What are midget ganglion cells?

Back 9

Ganglion cells in the fovea of humans and other primates. Small and responds to just a single cone. Therefore each cone in the fovea has a direct route to the brain.

Front 10

Why do birds have better eyesight compared to humans?

Back 10

They have a second fovea, enabling perception of detail in the periphery.

Front 11

What is a difference between foveal vision and peripheral vision?

Back 11

Foveal vision has better acuity (sensitivity to detail), whereas peripheral vision has better sensitivity to dim light.

Front 12

what are rods?

Back 12

Abundant in the periphery of the human retina, and respond to faint light but are not useful in daylight because bright light bleaches them.

Front 13

What are cones?

Back 13

Abundant near the fovea, and are less active in dim light, more useful in bright light, and essential for colour vision.

Front 14

What is more numerous? Rods or cones?

Back 14

Rods

Front 15

What provides more of the brain's input? Rods or cones?

Back 15

Cones

Front 16

What are photopigments?

Back 16

Chemicals that release energy when struck by light?

Front 17

What is the range of visible light?

Back 17

less than 400nm to more than 700nm

Front 18

What colour is the shortest wavelengths?

Back 18

Violet

Front 19

What colour is the longest wavelengths?

Back 19

Red

Front 20

What is Thomas Young known for?

Back 20

1) The first to start deciphering the Rosetta stone.

2) Founded the modern wave theory of light

3) Discovered much about the anatomy of the eye

Front 21

What is the trichromatic theory of colour vision?

Back 21

We perceive colour through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths. The ratio of these three cones determines a perception of a certain colour.

Front 22

What happens when the ratio of the three cones is the same and are equally active? What colour do we see?

Back 22

White or grey

Front 23

What is the opponent-process theory?

Back 23

We perceive color in terms of opposites. The brain has a mechanism that perceives color on a continuum. After you stare at one color in one location long enough, you fatigue that response and tend to swing to the opposite.

Front 24

What is the retinex theory?

Back 24

The cortex compares info from various parts of the retina to determine brightness and colour for each area.

Front 25

When a TV is off, its screen appears grey. 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?

Back 25

The black experience arises by contrast with the other brighter areas. The contrast occurs by comparison within the cerebral cortex, as in the retinex theory of color vision.

Front 26

What is color vision deficiency?

Back 26

Colorblindness.

Front 27

What is color deficiency a result of?

Back 27

People with certain genes failing to develop one type of cone, or develop an abnormal type of cone. The gene causing this deficiency is on the X chromosome.

Front 28

What is the general outline of the anatomy of the mammalian visual system?

Back 28

Rods & cones -> Horizontal cells -> bipolar cells -> amacrine cells & ganglion cells

Front 29

Where do the optic nerves from the two eyes meet?

Back 29

The optic chiasm

Front 30

What is the journey of visual input?

Back 30

It goes from the thalamus to the visual cortex. Another part also goes to the superior colliculus.

Front 31

What is the lateral geniculate nucleus (part of the thalamus)?

Back 31

Sends axons to other parts of the thalamus and the visual cortex. The cortex returns many axons to the thalamus, so the thalamus and cortex constantly feed info back and forth.

Front 32

what is lateral inhibition?

Back 32

The retina's way of sharpening contrasts to emphasize the borders of objects. The reduction of activity in one neuron by activity in neighboring neurons.

Front 33

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

Back 33

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

Front 34

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 side? What causes that effect?

Back 34

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.

Front 35

What is the receptive field?

Back 35

An area in visual space that excites or inhibits it.

Front 36

What is the receptive field of a rod or cone?

Back 36

The point in space from which light strikes the cell.

Front 37

What is the receptive field of any neuron in the visual system?

Back 37

The area of the visual field that excites or inhibits it.

Front 38

aWhat are parvocellular neurons?

Back 38

Small cell bodies and small receptive fields. Mostly in or near the fovea.

Detect visual details. Respond to color.

Front 39

What are magnocellular neurons?

Back 39

Larger cell bodies and receptive fields. Evenly distributed throughout the retina.

Responds strongly to movement and large overall patterns. Do not respond to color or fine details.

Front 40

What are koniocellular neurons?

Back 40

Small cell bodies. Occur throughout the retina.

Front 41

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?

Back 41

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

Front 42

Where does info from the lateral geniculate nucleus of the thalamus go to?

Back 42

The primary visual cortex. Area V1.

Front 43

What happens to people with damage to area V1 in comparison to people with eye damage?

Back 43

People with damage to area V1 report no conscious vision, no visual imagery, and no visual images in their dreams. People with eye damage lose their vision, but continue to have visual imagery and visual dreams.

Front 44

What is the phenomenon blindsight?

Back 44

The ability to respond in limited ways to visual info without perceiving it consciously.

Front 45

If you were in a darkened room and researchers wanted to "read your mind" just enough to know whether you were having visual fantasies, what could they do?

Back 45

Researchers could use fMRI, EEG, or other recording methods to see whether activity in your primary visual cortex increased.

Front 46

What is a simple cell?

Back 46

A cell in the visual cortex. Has a receptive field with fixed excitatory and inhibitory zones. More excitatory = more response. More inhibitory = less response.

Front 47

What are complex cells?

Back 47

Located in areas V1 and V2. Do not respond to the exact location of a stimulus. Responds to a pattern of light in a particular orientation anywhere within its large receptive field. Responds most strongly to a moving stimulus.

Front 48

What is the best way to classify a cell as simple or complex?

Back 48

To present the stimulus in several locations. A cell that responds to a stimulus in only one location is a simple cell. One that responds equally throughout a large area is a complex cell.

Front 49

What are end-stopped or hypercomplex cells?

Back 49

Resemble complex cells with one exception: It has a strong inhibitory area at one end of its bar-shaped receptive field. Responds to a bar-shaped pattern of light anywhere in its broad receptive field, provided the bar does not extend beyond a certain point.

Front 50

What do cells within a column of the visual cortex have in common?

Back 50

Respond best to lines in the same orientation. Similar in preference for one eye or the other, or both equally.

Front 51

What are feature detectors?

Back 51

Neurons whose responses indicate the presence of a particular feature.

Eg. Shape, or direction of movement

Front 52

After processing in areas V1 and V2 of the occipital cortex, where does the info go?

Back 52

It branches off in several directions into the parietal cortex and temporal cortex.

Front 53

What is the ventral stream?

Back 53

The "what" pathway through the temporal cortex. Identifying and recognizing objects.

Front 54

What is the dorsal stream?

Back 54

The "how" pathway through the parietal cortex. Importance for visually guided movements.

Front 55

What do cells in the inferior temporal cortex respond to?

Back 55

Meaningful objects.

Front 56

What is visual agnosia?

Back 56

An inability to recognize objects despite otherwise satisfactory vision.

Front 57

How does visual agnosia occur?

Back 57

Usually results from damage to the temporal cortex.

Front 58

what does the fusiform gyrus of the inferior temporal cortex respond to?

Back 58

Faces, more than anything else.

Front 59

What brain areas are responsible for face recognition?

Back 59

Part of the inferior occipital cortex, the amygdala, and parts of the temporal cortex.

Front 60

what is prosopagnosia?

Back 60

Impaired ability to recognize faces.

Front 61

What is area V4 important for?

Back 61

Color constancy. The responses of cells in V4 correspond to the apparent or perceived color of an object, which depends on the total context.

Front 62

What is color constancy?

Back 62

The ability to recognize something as being the same color despite changes in lighting.

Front 63

What are the two areas important for motion perception?

Back 63

MT (Middle temporal cortex /Area V5) and MST (medial superior temporal cortex)

Front 64

Where do MT and MST receive input from?

Back 64

The magnocellular path, which detects overall patterns. MT is color insensitive.

Front 65

What do cells in area MT respond to?

Back 65

When something moves at a particular speed in a particular direction. Central to the experience of seeing motion.

Front 66

What do cells in the area MST respond to?

Back 66

Complex stimuli, such as the expansion, contraction, or rotation of a large visual scene.

Front 67

What is motion blindness?

Back 67

The ability to see objects but impairment at seeing whether they are moving or, if so, which direction and how fast.

Front 68

What is saccades?

Back 68

When area MT and parts of the parietal cortex decrease activity during voluntary eye movements.