On the Capacity of Directionally Selective Mechanisms to Encode Different Dimensions of Moving Stimuli

Abstract

Direction-specific losses of contrast sensitivity for sinusoidal test gratings as a function of the contrast of a sinusoidal adapting grating were found to be similar to those measured previously with square-wave gratings. Furthermore, both relationships were similar to that between motion aftereffect duration and the contrast of sinusoidal adapting gratings, and all three sets of data can be fit by a single function. The function shows that the magnitude of direction-specific adaptation effects increases linearly with the logarithm of adapting contrast in the low contrast region, but is essentially independent of contrast once the contrast exceeds threshold by more than a factor of five—six. In addition, it was found that direction-specific losses of contrast sensitivity are restricted to limited ranges of spatial frequency.