Local motion effects on form in radial frequency patterns.

Sinusoidal modulation of radial speed around a circular path of tangentially oriented Gabor patches results in the percept of modulation of the radius. These patterns have been called motion radial frequency (RF) patterns. Sensitivity to these patterns has been attributed to global summation of local speed by mechanisms, analogous to those proposed to explain sensitivity to spatial RF patterns, which are sensitive to particular radial frequencies of speed modulation. We demonstrate that: Adaptation to spatial RF patterns results in a phase specific after effect in motion RF patterns and vice versa; the rate of change of perceived displacement of a Gabor patch with a moving grating with increasing speed of that grating, is independent of whether the patch is or is not incorporated into a circular path; in the absence of local motion direction cues, global integration across 1, 2 and 3 cycles of motion and spatial RF modulation conforms to a power function with the same index; and finally that the magnitude of the motion position illusion is sufficient and necessary to account for sensitivity to motion RF patterns. We therefore propose that motion RF patterns are analyzed by the same mechanisms responsible for sensitivity to spatial RF patterns using perceived rather than actual local positions of the Gabor patches.