Summation & Resolution

Question 1

Summation

Answer 1

the visual system’s ability to add up quanta over a certain area (spatial) or a period of time (temporal)

Question 2

Foveal Summation

Answer 2

low, cone photoreceptors have a 1:1 ratio with ganglion cells

Question 3

Periphery Summation

Answer 3

high, more cones converge onto a single ganglion cell

Question 4

Receptive Field

Answer 4

formed by the convergence of photoreceptors on a ganglion cell

Question 5

Summation Advantage

Answer 5

higher chance that the ganglion cell will respond to a stimulus (high sensitivity)

Question 6

Summation Disadvantage

Answer 6

the ganglion cell cannot distinguish where the response originates (not specific)

Question 7

High Summation = ____ Resolution

Answer 7

Low

Question 8

Low Summation = ____ Resolution

Answer 8

High

Question 9

What is the relationship between summation and resolution?

Answer 9

inverse

Question 10

Ricco’s Law Equation

Answer 10

I x A = constant

Question 11

Ricco’s Law

Answer 11

intensity and area inversely change but their product remains the same

Question 12

Critical Area

Answer 12

the point at which more stimulus area requires an increase in the IxA (stimulus area exceeds size for lowest intensity, must increase intensity if area is to increase)

Question 13

Piper’s Law Equation

Answer 13

I x sq(A) = constant

Question 14

Piper’s Law

Answer 14

when the stimulus size is slightly larger than the CA, threshold luminance still declines with increasing spot area, but at a slower rate

Question 15

Piper’s Law is also referred to as?

Answer 15

Partial Summation

Question 16

Ricco’s Law is also referred to as?

Answer 16

Spatial Summation

Question 17

What is the slope of partial summation?

Answer 17

m = 1/2

Question 18

What is the slope of complete summation?

Answer 18

m = 1

Question 19

Scotopic Summation

Answer 19

larger area -> improves sensitivity
poorer spatial resolution

Question 20

Photopic Summation

Answer 20

smaller area -> decreased sensitivity
higher spatial resolution

Question 21

Does the spatial summation area increase or decrease with eccentricity?

Answer 21

increases

Question 22

Temporal Summation

Answer 22

the visual system can summate photons that arrive at the same location over a period of time

Question 23

Bloch’s Law Equation

Answer 23

I x t = constant

Question 24

Bloch’s Law

Answer 24

number of quanta (I x t) is constant up until a certain duration, then more quanta per time is required

Question 25

High Brightness = ____ Duration

Answer 25

Low

Question 26

Low Brightness = ____ Duration

Answer 26

High

Question 27

How are intensity and duration related?

Answer 27

inversely

Question 28

High Temporal Summation = ____ Temporal Resolution

Answer 28

Low

Question 29

Pieron's Law Equation

Answer 29

I x sq(t) = constant

Question 30

Pieron's Law

Answer 30

when the stimulus duration is slightly longer than the critical duration, threshold intensity still declines as duration increases, but as a slower rate

Question 31

Critical Duration (Scotopic)

Answer 31

100-200 msec

Question 32

Critical Duration (Photopic)

Answer 32

10-50 msec

Question 33

When background intensity decreases, critical area increases or decreases?

Answer 33

increases

Question 34

How are background intensity and critical area related?

Answer 34

inversely

Question 35

When stimulus duration is longer, the critical area increases of decreases?

Answer 35

decreases

Question 36

When is summation desirable?

Answer 36

1. low light levels 2. detection > precision