Temporal Main Points (combined)

What is a sine wave grating?

A visual stimulus of alternating light and dark bars that vary sinusoidally in luminance and isolate a single spatial frequency

What is spatial frequency?

Number of cycles per degree (cpd), representing level of detail in a stimulus

What is temporal frequency?

Number of cycles per second (Hz), representing how fast a stimulus flickers or moves

What is phase in a grating?

Horizontal shift of a sine wave that determines alignment of peaks and troughs

What is Fourier synthesis?

Any complex visual image can be made by summing sine waves of different spatial frequencies, contrasts, and phases

What is the aperture problem?

Ambiguity in motion direction when viewed through a small aperture because only one component of motion is detected

What is critical flicker fusion (CFF)?

Frequency at which a flickering light appears steady

What is the typical range of CFF?

Approximately 30–90 Hz

What happens when frequency exceeds CFF?

Flicker is no longer perceived and appears continuous

What is Ferry-Porter law?

CFF increases linearly with the logarithm of luminance

What is Granit-Harper law?

CFF increases with the logarithm of stimulus area

How does luminance affect CFF?

Increasing luminance increases CFF (better temporal resolution)

How does retinal eccentricity affect CFF?

Peripheral retina has lower CFF unless stimulus size is scaled

How does color affect CFF?

Red/green pathways have higher CFF; blue (S-cone) pathway has lower CFF

Why do S-cones have low CFF?

They use slower koniocellular pathways

How do age and fatigue affect CFF?

They reduce CFF by slowing neural processing

What is heterochromatic flicker fusion?

Different colors appear steady at lower frequencies due to equiluminance and slow chromatic pathways

What is Talbot’s law?

Above CFF, perceived brightness equals time-averaged luminance

What is Bartley brightness enhancement?

Flickering light appears brighter than steady light at intermediate frequencies (~8–16 Hz)

What is Broca-Sulzer effect?

Brief flashes appear brighter than longer stimuli of the same luminance

What is Bloch’s law?

For brief stimuli, luminance × duration = constant at threshold

When does Bloch’s law apply?

For short durations before a critical duration

What happens after critical duration?

Increasing duration does not improve detectability

What is temporal contrast sensitivity function?

A plot of (contrast) sensitivity to luminance changes over time (temporal frequency)

Which pathway dominates temporal sensitivity?

Magnocellular pathway

What is visual masking?

One stimulus reduces visibility of another due to spatial or temporal interference

What is SOA (stimulus onset asynchrony)?

Time difference between target and mask onset

What is pattern masking?

Masking where the mask overlaps spatially with the target

When is pattern masking strongest?

At SOA = 0 (simultaneous presentation)

What causes pattern masking?

Spatial overlap and neural competition in same receptive fields

What does the pattern masking graph look like?

U-shaped curve with lowest visibility at SOA = 0

What is metacontrast masking?

Masking where mask does not overlap but is adjacent to the target

When is metacontrast masking strongest?

At short positive SOA (~30–100 ms after target)

What type of masking is metacontrast?

Backward masking

Why does metacontrast masking occur?

Mask interrupts or replaces processing of the target

What does the metacontrast masking graph look like?

U-shaped curve with minimum shifted to positive SOA

What is the key difference between pattern and metacontrast masking?

Pattern depends on spatial overlap; metacontrast depends on timing

Which masking peaks at SOA = 0?

Pattern masking

Which masking peaks at positive SOA?

Metacontrast masking

What is forward masking?

Mask appears before target and reduces detection

What is backward masking?

Mask appears after target and interferes with processing

Why is CFF clinically useful?

Detects early visual and neurological dysfunction

What conditions reduce CFF?

Glaucoma, cataracts, optic neuritis, multiple sclerosis, Alzheimer’s, TBI

Why is CFF useful in cataract patients?

Tests neural function without requiring spatial detail

What determines temporal resolution in vision?

Magnocellular pathway

What determines spatial resolution in vision?

Parvocellular pathway

What happens to flicker at very high frequency?

It fuses into steady light

What is the key cause of metacontrast masking?

Delayed interruption of target processing

What is the key cause of pattern masking?

Simultaneous spatial interference