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TMTV > Chapter 4-Temporal Vision > Flashcards

Chapter 4-Temporal Vision Flashcards

1
Q

what is temporal vision

A

concerned w/ the ability to perceive temporal modulations of light or changes in luminance over time

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2
Q

w/out temporal changes, we wouldnt be able to detect what

A

our surroundings

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3
Q

how is it possible to detect a luminance grating that is static/doesnt move?

A

luminance grating is always moving on our retina.

the retinal img always moves

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4
Q

there is some temporal modulation on sptial luminance gratings due to what

A

eye movements

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5
Q

what is the troxler effect

A

small movements do not move the retinal image and this system fails

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6
Q

how can temporal vision be measued

A

w/ flashes with a time interval btwn them

  • usually studied w/ luminance gratings that alternate btwn min adn max luminance over time
  • FLICKERING
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7
Q

what is temporal luminance modulation

A

“flicker”

-has luminance modulating throughout time (not space)

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8
Q

what is one cycle in temporal freq

A

the time from peak luminance to peak luminance

-or trough to trough luminance

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9
Q

what is the unit for defining spatial freq

A

1 degree of visual angle

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10
Q

what is the unit for defining temporal frq

A

1 sec

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11
Q

what is temporal contrast of luminance modulation

A

differenc ein luminance exprssed as %contrast

-difference btwn the max and min values of a flicker

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12
Q

what is low temporal contrast

waht is high temporal contrast

A

diff btwn max and min luminace of this flicker is small

-high temp: the diff btwn the max and min luminace of this flicker is greater

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13
Q

what is the spatial resolution limit

A

the max spatial cycles per degree of visual angle somebody can detect

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14
Q

what is the temporal solution limit

A

the max temporal cycles per 1 sec someone can detect or the fastest flickering

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15
Q

what is the maximum flickering we can detect called

-what can it determine

A

critical flicker frequency (CFF) and dtermines the temporal VA

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16
Q

for temporal freq above the CFF the stimulus appears how

A

steady or fused

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17
Q

who is reponsible for temporal resolution

A

determined at an early stage at the visual pathway as it can be described by the temporal prop of the photoreceptors and ganglion cells

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18
Q

waht are factors that affect CFF

A

retinal illuminance
retinal location
stimulus size
retinal adaptation

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19
Q

what does CFF increased w/

A

retinal eccentricity

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20
Q

CFF is a function of _____ for different retinal eccentricities

A

retinal illuminance

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21
Q

CFF is higher in fovea or peripheral retina?

A

peripheral retina

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22
Q

mid or peripheral retina is more sensitive to flicker?

A

peripheral

bc of diff temporal properties of parvocelluar and magnocellular pathways
-central: mostly midget ganglion cells

23
Q

what is granit harper law

A

CFF increases as the stimulus size increases

24
Q

once rods are dark adapted, what happens to temporal resolution

A

decreases

25
Q

what do dark adapted rods suppress

A

cone flicker sensitivity

bc of the increase at the horizontal cell’s response when the rods were desensitived

26
Q

what is the minimum contrast that we still see the light flickering?

A

temporal contrast senstivity

27
Q

what is the temporal contrast sensitivty function

A

temporal contrast sensitivity as a function of temporal freq

28
Q

what is low freq drop off

why?

A

our sensitivyt to low temporal freq below this point decreases and we can no longer detect them

bc of troxler effect

29
Q

waht is the troxler effect

A

when one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point will fade away and disappear

30
Q

what can explain the troxler effect

A

the low sensitivity to low tempoarl frequencies

31
Q

what does the peak sensitivty show that the neurons respond maximally to

A

that the majority of the neurons respond maximually at stimuli w/ intermediate temporal freq

32
Q

what is the high freq cut off

A

due to the inability of neurons to signal high temporal freq

33
Q

the point where the fucntion intersects the x axis is the maximum CFF we can perceive at ….

A

100% luminance modulation

34
Q

what is the low freq drop off due to

A

due to a lag btwn the center and the surround of a receptive field

35
Q

for every luminance modulation there are 2 CFF. what are they for

A

one for low end and one for the high end of the freq range

ex. for 5% luminance mod we arent able to perceive flicker for freq lower than low CFF 3Hz and higher than high CFF 50Hz

36
Q

for everyday life, where does the peak sensitivity of temporal contrast sensitivty range

  • for everyday life, the max CFF is what
  • for low light levels the max CFF can be as low as what
A

btwn 10 and 20 Hz
60Hz
10Hz

37
Q

which pathway that is sensitive to low spatial freq and high temporal freq believed to be early affected in glaucoma and IOP w/o vision loss

A

magnocellular pathway

38
Q

what does the freq doubling technology test

A

the sensitvity to low spatial freq gratings that flicker fast

39
Q

patiends w/ AMD who have a reduced temporal sensitivty btwn _______Hz are at risk for developing neovascular AMD (wet AMD)

A

5 and 40 Hz

40
Q

what can discriminate pre-neovascular pts from normal pts

A

temporal sensitivty to just 2 temporal freq (5 and 10 Hz)

41
Q

what is the broca-suzler effect

A

brightness is a perceptual phen and not something that can be measured w/ an instrument

42
Q

what phenomenon does the broc-suzler effect see

A

that short duratoin light appear brighter than another steady light w/ the same avg luminance

43
Q

what happens to the brightness of a flickering light? does it change with temporal freq?

A

yes, flicker of approx 10Hz appear brigher than flicker of lower or higher temporal freq

44
Q

what is the brucke-bartley phen

A

if a light is flickering w/ a temporal freq equal to CFF and we start reducing its temporal freq then there will be a point where the flickering light appears brighter than b4

-point of enchancemnt is around 10Hz

45
Q

what is the bruke bartley phen a direct consequence of

A

broca-suzler effect

46
Q

what is the talbot plateau law

A

a fused flickering light appears the same in brightness as a steady light w/ luminance equal to the time avged luminance of the fused light

47
Q

what is masking

A

the effect a ‘masking’ stimulus has on the detection of a test stimulus that is presented before, during, or after the masking stimulus

48
Q

masking vs adaptation

A

adatation: long process, adapting stimulus is presented for a long time and the effect of adaptation lasts long
masking: short. short stimulus and the effect lasts a couple of hundrend millisecs

49
Q

how can backward masking be explained

A

latency in the neuronal response to a near threshold test stiumulus

50
Q

what can simultaneous and forwad masking be explained by

A

signal detection theory

-masking stim generates lots of neuronal activity while the test stim generates lower

51
Q

what do metacontrast and paracontrast suggest in masking

A

there are lateral interactions btwn the neurons and that there is also some overlap of their receptive field

52
Q

masking occurs not only when flashes are separted in time, but also in…

A

space

53
Q

what is paracontrast

what is metacontrast

A

when it is presented before the masking stimulus (backward masking)

-when it is presendted after the masking stimulus (foward masking)

TMTV (5 decks)

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