Short-Term Plasticity of Contrast Surround Suppression During Repeated Psychophysical Measurement

Perceptual surround suppression is commonly treated as stable within a testing session, but recent evidence for normalization reweighting suggests that suppressive interactions can be modified by recent visual input. Here, we asked whether surround suppression changes over minutes of repeated measurement and whether such change varies with stimulus and sampling conditions. Across four psychophysical experiments, we tracked contrast and motion surround suppression while varying center-surround orientation and stimulus spatiotemporal properties. With static gratings, contrast surround suppression increased early and then approached a plateau, with no evidence that this change depended on center-surround orientation. With dynamic gratings, an increase emerged only under finer temporal sampling and more sustained stimulation, and model-based analyses suggested a faster increase than with static stimulation. Motion surround suppression measured with drifting gratings showed no systematic change. Together, these findings show that contrast surround suppression can change within a single psychophysical session without a separate adaptation phase, and that its measured time course varies with stimulus and sampling conditions. The results are consistent with rapid, experience-dependent reweighting of contextual normalization.