Peripheral Motion Detection Reflex: 3D Retinal Field

Stimulus

Eccentricity (° from fixation) 30°

Motion speed (°/s) 18°/s

Contrast 55%

Ambient light level 0.30

Reaction-Time Trial

Measured RT

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Predicted RT

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Trials avg (last 5)

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Detection P

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Cool = low motion sensitivity (fovea, fine detail)
Warm = high motion sensitivity (rod-pooled periphery)
Heatmap recomputes live from speed / contrast / light.

How it works

The fovea is cone-dominated: small receptive fields give sharp detail and color but pool little temporal signal, so it is a poor motion detector. Moving outward, rods take over, wired in large pooled receptive fields (the magnocellular pathway) that trade spatial detail for temporal resolution — the anatomical reason a flicker or a sudden movement at the edge of vision is often noticed before it is identified.

Rod pooling — sensitivity ∝ rod density(e) × √(pool size(e)); pool size grows with eccentricity.
Speed tuning — pooled peripheral units are band-pass, tuned to faster preferred speeds than foveal units.
Light dependence — rods saturate in photopic light, so the peripheral advantage shrinks as ambient light rises.
Detection / RT — probability is a sigmoid of the combined signal; reaction time falls as that signal strengthens.

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