Final Exam - Temporal Vision

Spatial vision

changes in luminance across space

Temporal vision

changes in luminance across time. Closely related to motion perception.

hertz (cycles/second)

what is the unit for temporal frequency?

Magno retinocortical pathway

pathway that codes both temporal and motion information. Knowledge of this pathway is used in the diagnosis and management of certain diseases in the visual system.

Temporal acuity

the smallest time interval that can be resolved as a flickering light. Useful in assessing the magnocellular pathway. Measured by determining the critical flicker frequency.

Critical flicker frequency (CFF)

temporal acuity is psychophysically measured by determining this value. The frequency at which a flickering is detected as flickering 50% of the time and as fused the other 50% of the time.

Temporal sinusoids

stimulus whose luminance varies sinusoidally over time. The temporal equivalent of spatial sine wave gratings.

Depth of modulation

the temporal analogous of spatial contrast. Describes the detectability of a flickering stimulus. Ie) higher modulation, just like higher contrast, is easier to detect as flickering

Flicker

the perception that can be elicited by the temporal modulation of a stimulus.

higher

Higher or lower modulation the more flicker. Ie) fluorescent bulbs

lower

Higher or lower modulation the less flicker. Ie) incandescent bulbs

Temporal frequency

describes the rate of a flickering stimulus. Given in hertz.

60 Hz

Temporal frequency of north American households is

integrity of the retina

temporal acuity is useful for assessing the _____ before cataract surgery

myopes, central depressant use, and stimulant drugs

temporal acuities are decrease in these three cases

larger stimulus size

outside of the fovea temporal CFF increases with...

minimal

temporal CFF increases with ______ contrast

smaller targets

In the fovea, temporal CFF increases with...

wavelengths

temporal CFF is equal for all..

Ferry-Porter law

high frequency CFF is directly proportional to the log of the stimulus luminance (retinal illumination). Occurs due to increasing levels of light adaptation and speeding up of retinal processes.

Granit-Harper law

high frequency CFF is directly proportional to the log of the stimulus area. Due to the fact that the peripheral retina is better in detecting flicker than the central retina. Stimulus is more likely to appear as flickering if it is large.

Temporal contrast sensitivity function

a complete description of temporal vision obtained by measuring threshold of modulation over a large number of temporal frequencies.

flicker

Area below the curve of the temporal CSF is seen as

steady

Area above the curve of the temporal CSF is seen as

Lateral inhibitory process

process of the retina where sensitivity to low temporal frequencies is reduced. Ie) minute hand on a clock, watching the sun set, etc.

Purkinje tree

branch like pattern seen by patients due to lateral inhibitory processes of the retina.

Troxler phenomenon

phenomenon describing the disappearance of low temporal frequency, nonmoving stimuli in the periphery occurring due to neural adaptation.

Microsaccades

prevent the disappearance of peripheral stimulus. Lack of eye movements may make the stimulus fade and disappear.

neural constraints in coding

High frequency cutoff of the temporal CSF is due to

lateral inhibition

Low frequency cutoff of the temporal CSF is due to _____ of the peripheral retina.

Broca-Sulzer effect

suprathreshold flashes between 50-100 ms appear brighter than stimuli of shorter or longer durations.

Bruke-Bartley effect

flickering light of about 10 Hz appears brighter than a steady light of the same luminance.

Talbot-plateau law

light stimulus that is flickering at a frequency greater than the CFF appears equally bright as a non flickering stimulus of the same luminance.

Successive contrast

exposure to one stimulus affects the perception of a later stimulus if they are given in rapid succession.

Masking

the use of one stimulus to reduce the visibility of another stimulus. Provides information regarding both the spatial and temporal processing of visual information.

Simultaneous masking

masking where the mask and the target appear at the same time

amblyopia

Simultaneous masking is more pronounced in patients with _______. This is observed where VA measurements are worse for the standard eye chart versus an isolated optotype due to the experience of the crowding phenomenon.

Forward masking

masking where the mask is presented before the target

Paracontrast masking

form of forward masking where the mask appears first and the target appears second with both being close to each other in space.

Backward masking

masking where the mask is presented after the target. Occurs when the mask is substantially brighter than the targets.

Metacontrast masking

form of backward masking where the target appears first and the mask appears second with both being close to each other in space. Contributed by lateral inhibition within the retina and stimulation of the faster magnocellular pathway

Glaucoma

RP

ARMD

Temporal vision is affected in these three conditions

FDF (flicker defined form) perimetry

clinical machine measuring temporal vision. Dots on form a border in counterphase pattern and the patient is asked to detect the border which becomes more visible as the dots' contrast increases. Useful in detecting early stages of glaucoma. Ie) Heidelberg edge perimeter