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PSYCH 2220 B Midterm > Lecture 5: Vision > Flashcards

Lecture 5: Vision Flashcards

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1
Q

retina

A

layer of neurons in back of eye

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2
Q

transduction

A

process of turning light into neural signals

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3
Q

cornea

A

bends light entering the eye

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4
Q

lens

A

changes shape to focus light on retina

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5
Q

refraction

A

the bending of light rays

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6
Q

ciliary muscles

A

adjust the focus by changing the shape of the lens

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7
Q

the process of accommodation

A

contraction of the ciliary muscles causes nearer or farther images to come into focus

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8
Q

eye movement is controlled by

A

three pairs of extraocular muscles

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9
Q

farsightedness

A

as mammals age, their lenses become less elastic and therefore less able to bring nearby objects into focus

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10
Q

nearsightedness

A

the most common vision problem in young people is myopia/nearsightedness, which is difficulty seeing distant objects

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11
Q

normal vision

A

the cornea and lens refract light to focus a sharp image of the outside world on the retina

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12
Q

myopia

A

eyeball is too long so images from distant objects are in focus in front of the retina. In this case, the image that reaches the retina is blurred

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13
Q

myopia with correction

A

eyeglasses refract the light before it reaches the cornea to bring the images into sharp focus on the retina

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14
Q

photoreceptors

A

sensory neurons in the retina that detect light:

rods - vision at low light levels
cones - colour vision

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15
Q

bipolar cells

A

receive input from photoreceptors and synapses on ganglion cells, whose axons form the optic nerve, which carries information to the brain

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16
Q

horizontal cells

A

in the retina contact photoreceptors and bipolar cells

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17
Q

amacrine cells

A

contact bipolar and ganglion cells

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18
Q

all cell types (in the retina) except ganglion cells generate:

A

only graded, local potentials, affecting each other through the graded release of neurotransmitters

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19
Q

ganglion cells conduct

A

action potentials

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20
Q

the humans eye contains about ___rods and______cones

A

100 million rods and 4 million cones, but only 1 million ganglion cells to transmit all that information to the brain

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21
Q

scotopic system

A

rods; highly sensitive to dim light; low acuity; insensitive to colour; more numerous in the periphery, absent in fovea

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22
Q

photopic system

A

cones; requires more light; sensitive to different wavelengths, enabling colour vision

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23
Q

photoreceptors in dark continually release

A

neurotransmitter

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24
Q

light triggers

A

hyperpolarization of the cell, causing it to release LESS neurotransmitter

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25
Q

hyperpolarization is just as much as a signal as

A

depolarization is

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26
Q

range refraction

A

uses different photoreceptors to handle different intensities

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27
Q

photoreceptor adaptation

A

each photoreceptor adjusts its level of sensitivity to match the average ambient level of light

28
Q

visual acuity

A

a measure of how much detail we see and is sharpest in the center of the visual field

29
Q

fovea

A

center region of retina has a high density of smaller, tightly packed cones with high acuity

this region receives direct light input that does not pass through other cells or blood vessels

30
Q

optic disc

A

where blood vessels and ganglion cell axons leave the eye

31
Q

blind spot

A

region on the retina that is sightless due to lack of photoreceptors in the optic disc

brain system fill in missing information so that we perceive an uninterrupted system

32
Q

occipital cortex

A

ganglion cells conduct action potentials along axons that make up the optic nerve, which extends to the occipital cortex

33
Q

optic chiasm

A

some or all of each optic nerve crosses the midline at the optic chiasm

after crossing, it is known as the optic tract

in humans, axons from the medial retina (closer to your nose) cross to the opposite side of the brain

axons from the lateral retina project to the same side of the brain

34
Q

Lateral geniculate nucleus

A

most axons of the optic tract terminate on the cells in the LGN of the thalamus

35
Q

Axons of the LGN neurons terminate in the:

A

primary visual cortex, aka the striate cortex of the occipital cortex

36
Q

visual cortical areas outside of V1 are called

A

the extrastriate cortex

37
Q

visual field

A

area that is visible without movement of the eye or head

38
Q

topographic projection

A

the retina represents a 2D map of the visual field

this organization is perserved as the information travels through the brain as a topographic projection - much of the projection corresponds to the fovea, making high visual acuity possible

39
Q

receptive field

A

consists of the stimulus features that excite or inhibit the cell

40
Q

both rod and cone photoreceptors release the synaptic neurotransmitter:

A

glutamate

light hyperpolarizes the photoreceptors causing them to release less glutamate

41
Q

on-center bipolar cells

A

turning on light in the center of its receptive field excites the cell because it receives less glutamate, which inhibits this type of bipolar cell

42
Q

off-center bipolar cells

A

turning off light in the center of the field excites the cells because they receive more glutamate and are depolarized

43
Q

on-center ganglion cells

A

on-center bipolar cells excite these cells when light is turned on

44
Q

off center ganglion cells

A

off-center bipolar cells excite these cells when light is turned off

45
Q

lateral inhibition

A

sensory receptor cells inhibit information from neighboring receptor cells, producing a contrast effect at the edges of regions

46
Q

Hubel and Wiesels theoretical model of visual analysis is:

A

Hierarchical: more complex receptor fields are built up from inputs of simpler ones

47
Q

simple cortical cells

A

also called bar detectors or edge detectors, respond to an edge or bar of a particular width, orientation, and location in the visual field

48
Q

complex cortical cells

A

respond best to a bar of a particular width and orientation that is in motion anywhere in the visual field

49
Q

spatial-frequency model

A

visual system analyzes the number of light-dark (or colour) cycles in any stimulus

Some cycles are narrow, others broad. Some cycles of light-dark are oriented vertically, others horizontally, and others somewhere in between. If cortical neurons are indeed optimized to detect light-dark cycles, then they should respond to repeating bars of light, even better than to a single bar of light.

50
Q

From area V1, axons extend to other cortical areas involved in perception to form:

A

V2, V4, and the inferior temporal lobe.

51
Q

V2 is adjacent to

A

V1; responds to illusory boundaries and to complex relations among the parts of their receptive fields.

52
Q

V4 cells generally have a strong response to

A

frequency gratings.
Some V4 cells produce strong responses to concentric, radial, or color stimuli.

visual contrast

53
Q

Area V5 neurons respond to

A

moving stimuli.

Woman with damage to V5: lost the ability to perceive motion

54
Q

Colour is perceived by the visual system as we detect differences in the

A

wavelength of photons within a certain range.

55
Q

Three dimensions of colour perception:

A

*Brightness–varies from dark to light
*Hue–varies throughout all colors *Saturation–varies from full color to gray

56
Q

Trichromatic hypothesis of colour perception:

A

Three different types of cones (blue-sensitive, green-sensitive, and red-sensitive)

*Each responds to a specific, different part of the spectrum
*Each has a separate pathway to the brain *Color recognized based on which receptors are activated

57
Q

Opponent-process hypothesis of color perception:

A

*Four unique hues (blue, green, yellow, red)
*Three opposed pairs of colors (blue versus yellow, green versus red, and black versus white)
*Three physiological processes with opposed positive and negative values are the basis of color vision

Neither of these old hypotheses are sufficient by themselves, but both are part of current colour-vision theory.

58
Q

Cones peak areas of wavelength sensitivity:

A

*Short (S)—420 nm
*Medium (M)—530 nm
*Long (L)—560 nm

59
Q

genes encoding photopigments are carried on the:

A

X chromosome—in those with female-typical chromosomes (XX) a normal copy can compensate for a defective gene.

males are more likely to inherit this

60
Q

second stage of colour processing:

A

Most ganglion cells and LGN cells fire in response to some wavelengths and are inhibited by others.

Spectrally opponent (color-opponent) cells have opposite firing responses to different regions of the spectrum.

A plus L/minus M (+L/–M) cell is stimulated above 600 nm and inhibited at shorter wavelengths.

61
Q

Spectrally opponent ganglion cells:

A

Receive input from two or three different types of cones through bipolar cells

Have excitatory connections from at least one input

Have inhibitory connections from at least one input

Record the difference in stimulation of different types of cones

62
Q

Spectrally opponent cells cannot be called color cells because

A

*They also send outputs to higher circuits for detection of form, depth, and motion *Their peak wavelength sensitivities do not correspond to the wavelengths we see as the principal hues

63
Q

Other spectrally opponent ganglion cells are stimulated or inhibited by

A

M and L cones and detect brightness or darkness.

64
Q

Two main processing streams originate in primary visual cortex:

A

Ventral stream: identifying objects (what) - - Damage causes problems in perceiving faces and objects.

Dorsal stream: assessing the location of objects (where), and guiding our movement toward them
- Opticataxia—difficulty using vision to reach for and grasp objects

65
Q

children who spend more time outdoors have a lower rate of:

A

myopia

66
Q

Misalignment of the eyes (lazy eye) can lead to

A

amblyopia— reduced visual acuity not caused by optical or retinal damage.
*If eyes are not aligned properly during development, the primary visual cortex suppresses information from one eye, and this eye becomes functionally blind.
*Eye muscles can be surgically adjusted to achieve better alignment.
*If the weak eye is used regularly (cover the good eye), vision can be preserved in both eyes.

67
Q
A

PSYCH 2220 B Midterm (3 decks)

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