Temporal Vision (Sensory)

Question 1

The length of time for one complete cycle of light and dark of a flickering stimulus is what?

Answer 1

Period

Question 2

The number of light-dark cycles per second of a flickering stimulus is what?

Answer 2

Flicker rate (or flicker frequency)

UNITS: Herts (cycles/second)

Question 3

The highest flicker frequency at which the flicker is perceived is what?

Answer 3

Critical Flicker Frequency (CFF)

Question 4

The brightness of a fused flickering stimulus is equal to the brightness of a steady stimulus with the same time-averaged luminance is what law?

Answer 4

Talbot-Plateau Law

NOTE: a strobe lights time-averaged luminance is also known as TALBOT brightness

Question 5

Brightness enhancement in which a flickering stimulus appears brighter than the Talbot brightness at some flicker frequencies below the CFF (5-20 Hz) is considered what law?

Answer 5

Brucke-Bartley Phenomenon

NOTE: even though the time-average luminance of 2 lights is the same, the flickering light is perceived to be brighter without adjustment

Question 6

Why is the temporal resolution limit (CFF) reached?

Answer 6

Due to retinal neurons lagging in their responses

NOTE: NT travelling from pre-synaptic to post-synaptic cleft does NOT occur instantly

Question 7

CFF is proportional to log luminance (as one goes up, the other goes up too) according to what law?

Answer 7

Ferry-Porter Law

Describes relationship btwn CFF and stimulus luminance

Question 8

The slope for the Ferry-Porter law in the periphery is steeper or shallower?

Answer 8

STEEPER out in the mid-periphery or periphery

The Ferry-Porter function is STRONGER out there UNLESS in scotopic levels where CFF is flat and the same across entire retina

NOTE: the FP law works EVERYWHERE though

Question 9

CFF is proportional to the log of stimulus area is described as which law?

Answer 9

Granit-Harper Law

NOTE: larger the stimuli = better temporal acuity and the FP function shifts UP!!!! Slope does NOT change

Question 10

Do cones or rods follow flicker well?

Answer 10

Cones > Rods

Cones greatest in mid-periphery

NOTE: 30 Hz flicker ERG ONLY measures cone function bc rods cannot perceive flicker > 20 Hz

Question 11

Michaelson Contrast equation?

Answer 11

(Lmax-Lmin)/(Lmax+Lmin)

Question 12

Peak contrast sensitivity for temporal CSF?

Answer 12

5-20 Hz

Question 13

What is the longest flash duration for which bloch’s law holds true called?

Answer 13

Critical Duration which varies from 30ms (photopic) to 100ms (scotopic)

NOTE: the critical duration DEC as luminance of background OR area INCREASES

Question 14

Increased temporal resolution at shorter or longer critical durations?

Answer 14

SHORTER critical duration

NOTE: resolution and summation are inversely related

Question 15

A short-duration (50-100 ms) suprathreshold flash can appear bright than a longer or shorter flash of the same physical intensity is explained by what effect?

Answer 15

Broca-Sulzer effect

10 Hz to 5 Hz basically

Question 16

Masking is a _____ phenomenon while crowding is a ____ phenomenon

Answer 16

Temporal; spatial

Question 17

Masking does what to threshold?

Answer 17

Increases threshold bc there is another stimulus presented before, during, or after a target

Question 18

If test stimulus is brought closure to the mask during forward masking, how is threshold effected?

Answer 18

It is elevated

Question 19

Which has greater threshold elevation: forward masking or simultaneous masking?

Answer 19

Simultaneous masking bc a test flash is presented while the masking flash is turned on

Question 20

Which type of masking has the greatest threshold elevation?

Answer 20

Backwards masking bc the mask comes so quickly after the target that both the target and mask are temporally summed!!!

Question 21

Metacontrast involves:

a. Backwards masking
b. Simultaneous masking
c. Forward masking

Answer 21

a. Backwards masking

Question 22

Paracontrast involves:

a. Backwards masking
b. Simultaneous masking
c. Forward masking

Answer 22

c. Forward masking

Question 23

What is the spatial extent of masking?

Answer 23

~3 degrees

Falls off after that

Question 24

Which type of masking occurs when the test flash is presented to one eye and the masking flash to the other?

Answer 24

Dichoptic masking

NOTE: this indicates that masking is a cortical phenomenon and not at the retinal level

Question 25

You need at least how many retinal points to detect motion?

Answer 25

At least TWO!!!

Question 26

Dynamic visual acuity (DVA) breaks down above what for 20/40 letters?

Answer 26

60 degrees/sec

NOTE: for smaller letters, DVA may break down earlier (~30 degrees/sec)

Question 27

Which direction are neurons MOST sensitive?

Answer 27

UP!!!

79 AP’s

Makes sense something falling on you

Question 28

Which direction are neurons LEAST sensitive?

Answer 28

DOWN!!

2 AP’s

Question 29

What is 1st order motion?

Answer 29

Motion detection due to LUMINANCE changes

NOTE: example is TV

Question 30

What is 2nd order motion?

Answer 30

Motion detection due to CONTRAST or TEXTURE changes

NOTE: nothing is actually moving the contrast change makes it look like things are. EX boxes change from black to white, giving appearance of a bar moving

Question 31

What is the minimum displacement threshold (detection of displacement) threshold?

Answer 31

10”

Hyperacuity bc center-to-center PR spacing is 30”

Question 32

The % of dots needed to move for perception of movement in a direction is called what?

Answer 32

Motion coherence

NOTE: threshold is 5-10% in order to tell

Question 33

Where is motion processed in the brain?

Answer 33

Middle temporal region of the cortex known as V5

NOTE: MT contains specialized neurons for detection of motion

Question 34

What is Akinetopsia?

Answer 34

Loss of motion perception, but other visual functions are intact (i.e. spatial vision, color vision, etc)

NOTE: can occur due to a stroke in the MT