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Perception 351 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

more technical definition of acuity

A

smallest spatial detail that can be resolved

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2
Q

three ways to test acuity

A

minimum visible (absolute threshold)
minimum resolvable (stripes)
minimum recognizable (snellen test)
minimum discriminable (JND)

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3
Q

Snellen Eye Chart

A

eye doctor chart, show letters (or orientations of letters for universal use)

operationalized visual acuity based on distance relative to “average” people

20/20 - average
20/15 - above average (you can read from 20 ft away what others read at 15 ft)
20/30 - below average

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4
Q

acuity tests the size of _____ ______ at which you can identify a _____ in a striped grating

A

visual angle; cycle

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5
Q

cycle of acuity

A

one full rotation from black to white

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6
Q

sine wave grating

A

gradation between colors

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7
Q

smallest angle you can see shift in light = _____

A

acuity

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8
Q

why does an oriented grating appear to be gray if you are far enough away?

A

your cones are picking up both light and dark luminance, combining them to make gray due to a smaller cycle/frequency

this is because our photoreceptor responses are graded, so some light and some dark = medium

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9
Q

two factors that affect acuity

A

spatial frequency
- visual angle of a change from light to dark (cycle)
- aka the rate at which the luminance changes

contrast
- the amount of difference between a change in luminance
- aka the sharpness of that change in luminance

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10
Q

Contrast sensitivity function (CSF)

A

chart contrast and frequency and see where cycles become invisible on that spectrum

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11
Q

CSF can be _____, impacted by changes in _____ ________ and ___ _____

A

shifted; overall luminance and temporal frequency

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12
Q

temporal frequency

A

how fast the cycle moves

the faster the cycles go, the less acuity you have

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13
Q

gabor patches

A

grading adjusting spatial frequency and contrast

squares with a circle of vision in the middle which is impacted by spatial frequency and contrast

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14
Q

how do we measure ganglion activity?

A

rate of action potential

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15
Q

really low and high frequency yields ___ response for action potential, while medium frequency yields ____ response

A

weak; strong

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16
Q

phase

A

portion of sine wave

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17
Q

leaving the eye tract

A

optic nerve
optic chiasm
optic tract to LGN

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18
Q

thalamus

A

primary relay center of the brain

inhibited when you sleep, lowering your responses to most external stimuli

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19
Q

at the optic chiasm, vision is divided by ___ ____, not by ____

A

visual field; eye

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20
Q

at the optic chiasm, regardless of eye;

information for the left side of space goes _____
information for the right side of space goes ____

visual fields represented ____________

A

right; left; contralaterally

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21
Q

how many layers in the LGN

A

6

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22
Q

each side of the LGN receives input from _______ and _________ eye, meaning …

A

ipsilateral - same eye
contralateral - opposite eye

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23
Q

LGN layers 1, 4, 6 receive ______ eye input

A

contralateral

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24
Q

LGN layers 2, 3, 5 receive ______ eye input

A

ipsilateral

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25
Q

the inner two layers of the LGN are the ___________ layer

A

magnocellular (what M ganglion cells are named after), receiving info from periphery

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26
Q

outer two layers of the LGN are the ________ layer

A

parvocellular (what P ganglion cells are named after), receiving info from fovea

27
Q

why do parvocellular layers in the LGN get more representation?

A

because they are receiving information from fovea which means more cells report to it

28
Q

Retinotopic Map

A

map of what is hitting your retina

29
Q

if one eye or one optic nerve is damaged, what is affected?

A

vision is lost only on the affected side

30
Q

if the optic chiasm is damaged, what is affected?

A

the outer part of the visual field in both eyes is lost

31
Q

if the visual pathways from the optic chiasm to the visual cortex are damaged, what is affected?

A

one side of the visual field is lost in both eye

ex) damage on the right side of the brain causes loss of the left visual field in both eyes

32
Q

which factors influence our ability to perceive a cycle between black and white?

1) spatial frequency
2) overall luminance
3) contrast
4) all of the above

A

4

33
Q

Dr. Rafay is an eye doctor. A patient comes to him complaining that they cannot see the right side of their visual space. Their eyes aren’t damaged at all though. What might be wrong with Dr. Rafay’s patient?

a) They have damage to their left optic nerve before the optic chiasm
b) They have damage to their left optic tract after the optic chiasm
c) They have damage to their right optic nerve before the optic chiasm
d) They have damage to their optic chiasm

A

B

34
Q

which layer(s) of the LGN receives input from M ganglion cells of the ipsilateral eye?

a) 1
b) 2
c) 3 and 5
d) 4 and 6

A

B

35
Q

what is the saying to remember what layers of the LGN are contralateral or ipsilateral?

A

seasick

1 - C
2 - I
3 - I
4 - C
5 - I
6 - C

36
Q

striate cortex

A

aka primary visual cortex or V1

part of the occiptial lobe of your brain

receives bottom-up inputs from the LGN

maintains a retinotopic map

37
Q

bottom-up

A

info from sensory system up into the brain

38
Q

first part of cortex to receive visual input

A

v1/primary visual cortex

39
Q

how many layers is in the striate/cellular layer

A

6 but DO NOT correspond to LGN layers

40
Q

fovea is represented at the _____ of the retinotopic map for the striate cortex

VF is then represented extending out based on ________ from the fovea

A

back; eccentricity

41
Q

eccentricity

A

distance from fovea, measured in degrees of VF

42
Q

what three features are shown in the retinotopic map for the striate complex

A

contralateral VF (like LGN)
inverted from reality
cortical magnification of fovea

43
Q

cortical magnification

A

dramatic scaling of information from different parts of visual fields

proportionally more cortex devoted to fovea than periphery, causing loss of acuity

susceptible to visual crowding

44
Q

visual crowding

A

stimuli are harder to perceive because there are other stimuli around than compared to when they are in isolation

ex) being able to see a key on the left side (since it is the only item there) but not on the right side (since it is surrounded by multiple items) when staring at a red dot in the center of the image

45
Q

v1 cells respond better to _________ rather than cicular/center-surround like the LGN

A

lines/bars

46
Q

what can V1 cells code for (depending on LGN cells that feed input)?

A

any orientation
edges vs. bars
gratings of various frequencies
motion direction

47
Q

simple cells in V1

A

respond to specific orientation and location

48
Q

complex cells in V1

A

respond to specific orientation

unlike simple, respond to any location

49
Q

end stopping cells in V1

A

respond to orientation, location and length

50
Q

cortical neurons tend to have a _____ eye, called ______ ________

A

preferred; ocular dominance

V1 cells have an eye they prefer, but will still receive information from both eyes

51
Q

cells in the V1 are grouped in ________

A

columns

line of cells the run perpendicular to the surface of the brain

52
Q

orientation columns in the V1 reflect sets of cells that all respond to … each column is then …

A

the same line orientation; adjacent to columns that are of slightly shifted angle

53
Q

ocular dominance organization

A

also columnar, but overlaps with orientation columns to form hypercolumns

54
Q

hypercolumns

A

represent all possible orientations across both eyes for a given part of the visual field

since all orientations represent .5 mm and each eye represents .5mm, a hypercolumn is 1 mm

55
Q

inside each hypercolumn are _________

A

CO blobs

full role unclear, part tied to color

56
Q

adaption in columns of striate cortex

A

cells/columns are tuned for specific things (orientation, location, etc.) but they do not fire forever to that sustained stimulus

response is reduced due to sustained/prior exposure to stimulus

57
Q

selective adaption

A

when you can downregulate responding to a specific stimulus by sustaining it

58
Q

due to selective adaption: after staring at lines slanted to the left for 30 seconds, if you look at straight lines they will appear … why?

A

slanted to the right due to your cells becoming adapted to them

59
Q

selective adaption effects for _____ and ___________

A

orientation; spatial frequency

60
Q

high spatial frequency = ________

low spatial frequency = _________

A

edges are defined; shadows are defined

61
Q

How is the retinotopic map of V1 organized relative to the image on the fovea?

a. The fovea is at the back of V1, and the retinotopic map stretches forward based on eccentricity
b. The fovea is at the front of V1, and the retinotopic map stretches backwards based on accommodation
c. The fovea is at the back of V1, and the retinotopic map stretches forward based on accommodation
d. The fovea is at the front of V1, and the retinotopic map stretches backwards based on eccentricity

A

a

62
Q

We know bars of light can activate V1 Simple Cells. Which factor CANNOT influence Simple Cell firing?

a. Orientation of Bar of Light
b. Position of Bar of Light
c. Length of Bar of Light
d. Extended duration of Bar of Light
e. All of these factors can influence Simple Cell firing rate

A

e

63
Q

Which statement the organization of columns for a given hypercolumns in V1 is TRUE?

a. Each hypercolumn contains all orientations, but with ocular dominance divided across layers
b. Each hypercolumn contains all orientations, organized based on ocular dominance
c. Each hypercolumn is coded so that columns of a given orientation are always adjacent to their opposite eye column
d. Each hypercolumn is coded based on color, organized based on ocular dominance

A

b

Perception 351 (21 decks)

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