Temporal Vision: Flicker Detection Flashcards
What is temporal vision?
Temporal vision is the ability to perceive changes in luminance over time.
What is temporal acuity?
Temporal acuity is the minimum interstimulus interval detectable by the visual system i.e. the fastest speed of flashing lights we can detect.
Which pathway is temporal vision mediated by?
The magnocellular pathway
True or False- We are unable to perceive stabilised retinal images.
True- Spatial vision impossible unless the retinal image changes with time. If there is no change the images fade in a few seconds Thus even when focussing we make small involuntary eye movements continuously so image does not stabilise on retina.
Why don’t we see the shadows of retinal vasculature on photoreceptors? Essentially these vessels are on the retina so would therefore obscure blood vessels
We don’t see them because vessels are stabilised relative to the retina (temporal frequency 0 Hz) i.e. the retinal image produced by the vessels i.e. the shadows do not move and any image on the retina that doesn’t move fades away.
How may one see a purkinje tree image and what is this?
A purkinje tree image is an image formed by the shadows of retinal blood vessels. In order to see this you would keep having to move a light around the eyes so that the retinal vessel shadows would keep falling in different places giving rise to the purkinje tree.
What is the Troxler Effect?
The disappearance of low temporal frequency stimuli –> temporary fading of image possible during steady fixation
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/588/871/a_image_thumb.png?1613153531)
What is the difference between a spatial sine wave and a temporal sine wave?
Spatial sine wave varies sinusoidally over space.
Temporal sine wave varies sinusoidally over time.
What is modulation amplitude/depth?
It is the temporal contrast of the stimulus i.e how bright and dark the flashing light gets. In the diagrams it is A.
Is visibility higher or lower if the modulation depth stimuli is greater?
The greater the modulation depth (temporal contrast) of a stimulus, the greater the visibility.
[Just as in spatial vision – the greater the spatial contrast the greater the visibility]
What is the difference between modulation depth and modulation amplitude?
Modulation amplitude is from the peak or from the trough to the midway average line.
Modulation depth is an equation which takes into account the modulation amplitude divided by the mean luminance.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/588/876/a_image_thumb.png?1613154073)
How do you calculate the percentage modulation?
Modulation depth x 100% = Percentage Modulation
What is temporal frequency?
Rate of flicker or rate of change of stimulus over time (in cycles per second i.e. Hz).
What does a low temporal frequency mean?
Low temporal frequency – stimulus appears to flicker/move slowly
What does a high temporal frequency mean?
High Temporal frequency – stimulus appears to flicker/move quickly
What is relative sensitivity in regards to luminance and describe what a high relative sensitivity means and a low relative sensitivity means?
Relative Sensitvity is 1/percentage modulation.
If sensitivity is high you can detect dim contrasts.
If sensitity is low you can only detect high/obvious contrasts.
What does the Temporal Contrast Sensitvity function look like and how do you interpret it?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/588/883/a_image_thumb.png?1613155990)