Chapter 4-Temporal Vision Flashcards by Audrey Chu

what is temporal vision

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

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

our surroundings

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

luminance grating is always moving on our retina.

the retinal img always moves

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

eye movements

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what is the troxler effect

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

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how can temporal vision be measued

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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what is temporal luminance modulation

“flicker”

-has luminance modulating throughout time (not space)

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what is one cycle in temporal freq

the time from peak luminance to peak luminance

-or trough to trough luminance

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what is the unit for defining spatial freq

1 degree of visual angle

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what is the unit for defining temporal frq

1 sec

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what is temporal contrast of luminance modulation

differenc ein luminance exprssed as %contrast

-difference btwn the max and min values of a flicker

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what is low temporal contrast

waht is high temporal contrast

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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what is the spatial resolution limit

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

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what is the temporal solution limit

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

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what is the maximum flickering we can detect called

-what can it determine

critical flicker frequency (CFF) and dtermines the temporal VA

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for temporal freq above the CFF the stimulus appears how

steady or fused

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who is reponsible for temporal resolution

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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waht are factors that affect CFF

retinal illuminance
retinal location
stimulus size
retinal adaptation

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what does CFF increased w/

retinal eccentricity

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CFF is a function of _____ for different retinal eccentricities

retinal illuminance

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CFF is higher in fovea or peripheral retina?

peripheral retina

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mid or peripheral retina is more sensitive to flicker?

peripheral

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

what is granit harper law

CFF increases as the stimulus size increases

once rods are dark adapted, what happens to temporal resolution

decreases

what do dark adapted rods suppress

cone flicker sensitivity bc of the increase at the horizontal cell's response when the rods were desensitived

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

temporal contrast senstivity

what is the temporal contrast sensitivty function

temporal contrast sensitivity as a function of temporal freq

what is low freq drop off why?

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

waht is the troxler effect

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

what can explain the troxler effect

the low sensitivity to low tempoarl frequencies

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

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

what is the high freq cut off

due to the inability of neurons to signal high temporal freq

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

100% luminance modulation

what is the low freq drop off due to

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

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

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

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

btwn 10 and 20 Hz 60Hz 10Hz

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

magnocellular pathway

what does the freq doubling technology test

the sensitvity to low spatial freq gratings that flicker fast

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

5 and 40 Hz

what can discriminate pre-neovascular pts from normal pts

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

what is the broca-suzler effect

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

what phenomenon does the broc-suzler effect see

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

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

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

what is the brucke-bartley phen

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

what is the bruke bartley phen a direct consequence of

broca-suzler effect

what is the talbot plateau law

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

what is masking

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

masking vs adaptation

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

how can backward masking be explained

latency in the neuronal response to a near threshold test stiumulus

what can simultaneous and forwad masking be explained by

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

what do metacontrast and paracontrast suggest in masking

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

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

space

what is paracontrast what is metacontrast

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