Chapter 2-light sensitivity pt 2

Question 1

what is spatial summation

Answer 1

the ability of the visual system to add information over space

Question 2

the scotopic system has high ______ but poor ________

the photopic system has high ______ but poor ____

Answer 2

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

Question 3

what is Ricco’s Law

Answer 3

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

Question 4

there is a trade off between spatial resolution and what?

Answer 4

spectral sensitivity

Question 5

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

Answer 5

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

Question 6

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

Answer 6

10 photons

Question 7

how does the scotopic system sum up information

how does the photopic system sum up information

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

eccentricity, retinal illumination

Question 10

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?

Answer 10

50 min arc

30 min arc

2 degrees

Question 11

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

Answer 11

high, low, low

low, high, high

Question 12

what is temporal summation

Answer 12

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

Question 13

the scotopic system shows _____

Answer 13

high
high
low

Question 14

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

Answer 14

low
low
high

Question 15

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

Answer 15

10

Question 16

what is bloch’s law

Answer 16

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

Question 17

when is the critical duration for a rod

cone?

Answer 17

rod is 100ms

cone is 10ms

Question 18

what is stiles-crawford effect of the first kind

Answer 18

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

Question 19

cones show directionality, where will their outer segments point

Answer 19

to the center of the pupil

Question 20

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

Answer 20

perpendicular

perpendicular

Question 21

do rods show directionality?

Answer 21

no, able to detect light fron any direction or angle

Question 22

cone orientation can change over time is…

Answer 22

the entrance pupil changed