Invariant tuning of motion aftereffect.

Motion aftereffects (MAE) to drifting gratings were measured with a cancellation technique. For a constant adapting grating, MAE cancellation velocity increased linearly with visual field eccentricity. The slope of the function was dependent upon adapting temporal frequency. MAE velocity was independent of spatial frequency (2-16 c/deg) and approximately constant when expressed as an M-scaled velocity. The MAE was broadly tuned to temporal frequency and temporal tuning was independent of spatial frequency and eccentricity. Reducing contrast over the range 1.0-0.1 reduced the magnitude of the MAE at high temporal frequencies but had no influence at low and moderate temporal frequencies. The results support a ratio model of velocity coding whose spatial reference varies with eccentricity in approximate accordance with the human cortical magnification factor.