Introduction. We are studying the dynamics of contrast-gain controls psychophysically using a probed-sinewave paradigm. In this probed-sinewave paradigm a background pattern's contrast is flickering sinusoidally over time. Threshold is measured for a short-duration probe-pattern superimposed at various phases with respect to the background flicker. The patterns are element-arrangement textures made of Gabor (2nd-order) or blob (1st-order) elements. Effects demonstrated with static versions of these patterns are consistent with a contrast-gain control produced by inhibition among channels in a normalization network (and are not consistent with a number of other models).

The Past. We and others have previously studied luminance-gain controls using a probed-sinewave paradigm with spatially homogenous background and probe. Probe thresholds at all phases increased with the frequency of the flickering background up to about 8 to 16 Hz. These results were very useful in distinguishing among models of light adaptation. These results show little interocular transfer, indicating that the luminance-gain control is very likely to be predominantly retinal.

The Present. In our current contrast-gain-control experiments -- using element-arrangement textures in the probed-sinewave paradigm -- we are seeing qualitatively different results. We think these new results will have a similar ability to distinguish among models. This time the models are of the dynamics of contrast-gain-controlling processes, e.g., inhibition among cortical cells, synaptic depression at LGN to V1 synapses, long-range horizontal connections, and so on.