Temporal Vision Ch. 7

Question 1

definition of temporal (resolution) acuity

Answer 1

the smallest time interval that can be resolved as flickering

Question 2

critical flicker (fusion) frequency, or CFF is:

Answer 2

how temporal (resolution) acuity is defined, the highest f you can still perceive flickering

Question 3

definition of period

Answer 3

the length of time for one complete cycle of light/ dark

Question 4

definition of flicker rate (frequency)

Answer 4

the number of cycles per second

Question 5

the talbot-plateau law is when the brightness of a light (strobe) is:

Answer 5

above the CFF

so it is steady, fused

Question 6

in the talbot-plateau law, if you were to ‘match’ a steady light, you would find the luminance to be:

Answer 6

strobe light’s average luminance

talbot brightness

Question 7

the brucke-bartley phenomenon is for flicker rates are:

Answer 7

below the CFF (between 5-20 Hz)

Question 8

in the brucke-bartly phenomenon, how can a flickering light can appear compared to mean luminance

Answer 8

it can appear brighter than steady light with equal mean luminance (may even be greater than Lmax)

Question 9

how can the temporal resolution limit (CFF) be reached?

Answer 9

due to neurons lagging in their responses

Question 10

when can the CFF be exceeded?

Answer 10

when the neural response doesn’t have time to stop between flashes

Question 11

what is the neural basis of the talbot-plateau law

Answer 11

above the CFF, flash duration is very short and the light is never on long enough to stimulate the neurons fully

Question 12

Ferry-Porter law states:

Answer 12

CFF is proportional to the log of stimulus luminance

Question 13

Ferry-Porter law means better temporal acuity will occur with ____ light levels

Answer 13

higher

Question 14

equation for Ferry-Porter law

Answer 14

CFF = k log L + b

k=10 for regular foveal vision

Question 15

for what range and conditions does Ferry-Porter law hold?

Answer 15

over about 4 log units (limit is at CFF- 50 Hz) foveal

Question 16

how does Ferry-Porter law change for periphery?

Answer 16

it has a greater slope in the periphery (k>10)

Question 17

FPF has a ____ effect in the periphery

Answer 17

stronger/greater

Question 18

FPF (at high luminance levels) has the highest CFF where?

Answer 18

mid-peripheral retina (about 35 degrees)

Question 19

where is the CFF on the FPF (at low luminance levels)?

Answer 19

CFF is nearly constant across the retina

Question 20

granit-harper law states

Answer 20

CFF is proportional to the log of stimulus area (size)

Question 21

grant-harper law states you have better temporal acuity with ____ stimuli

Answer 21

larger

Question 22

photopic CFF (foveal) is best at ___ Hz

Answer 22

50

Question 23

scotopic CFF is best at ___ Hz

Answer 23

20

Question 24

peak CS for temporal CSF

Answer 24

5-20 Hz

depends on light levels

Question 25

cutoff high flicker rate for temporal CSF

Answer 25

50-70 Hz

varies depending on curve

Question 26

how does the temporal CSF change with increase luminance?

Answer 26

peak and high cutoff shift right

Question 27

studies show glaucoma has a loss of what types of flicker rates?

Answer 27

loss of high flicker rate sensitivity

the neurons involved may be in Magnocellular pathway

Question 28

FDT has a ___ cpd grating and flickers at ___ Hz

Answer 28

20cpd grating at 25 Hz

Question 29

temporal summation (Bloch’s law) is a trade off between what 2 factors?

Answer 29

time an luminance

Question 30

in Bloch’s law, the time over which the law applies, the critical duration, can vary between

Answer 30

30 and 100 ms depending on luminance levels

Question 31

Bloch’s law: as the background luminance increases, the critical duration gets ____ and summation ___

Answer 31

critical duration gets shorter, less summation, more resolution

Question 32

in Bloch’s law, critical duration is shorter for higher luminance levels (about ___ ms)

Answer 32

30ms

Question 33

in Bloch’s law, critical duration is longer for lower luminance levels (about ___ ms)

Answer 33

100ms

Question 34

definition of Broca-Sulker effect

Answer 34

for supra threshold flashes, brightness depends on duration

Question 35

in the Broca-Sulker effect, we perceive what kinds of flashes differently?

Answer 35

50-100ms flashes brighter than flashes of other durations

Question 36

how does masking change threshold?

Answer 36

masking increases threshold for a task due to another stimulus being presented before, during, or after target

Question 37

forward masking is when:

Answer 37

mask presented BEFORE target

Question 38

backwards masking is when:

Answer 38

mask presented AFTER target

Question 39

where does masking have the biggest effect?

Answer 39

backward masking

Question 40

what is metacontrast?

Answer 40

type of backward masking when the target and mask do not overlap spatially

Question 41

what is paracontrast?

Answer 41

type of forward masking when mask and target do not overlap spatially

Question 42

how do we know masking is neural and NOT a retinal phenomenon

Answer 42

dichoptic masking tests- still get masking effects even when one target at each eye

Question 43

units of motion detection

Answer 43

degrees of visual angle/second

Question 44

temporal frequency=

Answer 44

velocity x spatial frequency

Question 45

you need at least two retinal points to distinguish between:

Answer 45

motion and static flicker rate

Question 46

motion detection is limited by:

Answer 46

temporal resolution

independent of velocity itself

Question 47

how can increasing velocity change the temporal CSF?

Answer 47

shifts the CSF left