Chapter 2-light sensitivity pt 2 Flashcards

1
Q

what is spatial summation

A

the ability of the visual system to add information over space

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2
Q

the scotopic system has high ______ but poor ________

the photopic system has high ______ but poor ____

A

scotopic: high spectral sensitivity but poor spatial resolution (visual acuity)
photopic: high spatial resolution (visual acuity) but poor spectral sensitivity

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3
Q

what is Ricco’s Law

A

for a small stimuli projected on the retina, the total number of photons needed for detection is constant at threshold

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4
Q

there is a trade off between spatial resolution and what?

A

spectral sensitivity

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5
Q

the rod pathway is convergent. what does this mean
what do rods connect to
what do rod bipolar cells connect to
where is there no direct contact

A

15-30 rods connect to rod bipolar cells
-rod bipolar cells are connected to multiple amacrine cells

-no direct contact btwn rod-bipolar cells and parasol ganglion cells

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6
Q

what is the threshold for each GC to respond to light and send a signal to LGN

A

10 photons

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7
Q

how does the scotopic system sum up information

how does the photopic system sum up information

A

scotopic: sums up info over a large area that results in high sensitivity but poor spatial resolution
photopic: sums up info over a small area that results in high spatial resolution but poor sensitivyt

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8
Q

in areas of complete summation, there is no loss of ________ on spreading the photons over a certain area instead of concentrating them on a much smaller one.
what can this mean

A

information

-if you want to find a threshold for a small spot, this threshold will be the same spot sizes that fall w/in the area of complete summation

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9
Q

the critical diameter (limit of complete spatial summation) varies w/ what

A

eccentricity, retinal illumination

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10
Q

for scotopic conditions at 6 degrees eccentricity, the critical diameter is how many min of arc?

what about for photopic conditions at 5-6degree?

photopic conditions at 35 degrees?

A

50 min arc

30 min arc

2 degrees

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11
Q

small receptive filed means ____spatial resolution and ______ spatial summation which in turns mean _____ sensitivity

large receptive field means _____ spatial resolution and ______ spatial summation which in turn means _______ sensitivity

A

high, low, low

low, high, high

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12
Q

what is temporal summation

A

the ability of the visual system to sum up information over time

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13
Q

the scotopic system shows _____

A

high
high
low

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14
Q

the photopic system shows ______ temporal summation, _____spectral sensitivty, and ____temporal resolution

A

low
low
high

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15
Q

the threshold of the scotopic system to detct a light is how many photons

A

10

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16
Q

what is bloch’s law

A

for a range of stiumus durations, the total # of photons needed for detection is constant at threshold
-up to critical duration, we always need the same # of photons to detect light

17
Q

when is the critical duration for a rod

cone?

A

rod is 100ms

cone is 10ms

18
Q

what is stiles-crawford effect of the first kind

A

the effect where light entering the eye near the edge of the pupil produces a lower photoreceptor response compared to light of equal intesnity entering the pupil near the eye

19
Q

cones show directionality, where will their outer segments point

A

to the center of the pupil

20
Q

light that enters the pupil through the center of the pupil falls where on the cone outer segment?

light that enters the eye not through the center of the pupil doesn’t fall _____ on the cone outer segment

A

perpendicular

perpendicular

21
Q

do rods show directionality?

A

no, able to detect light fron any direction or angle

22
Q

cone orientation can change over time is…

A

the entrance pupil changed