Center-surround motion interaction between low and high spatial frequencies under binocular and dichoptic viewing.

Abstract

Motion discrimination of a stimulus that contains fine features is impaired when static coarser features are added to it. Previous findings have shown that this cross-scale motion interaction occurs under dichoptic presentation, where both components are spatially overlapped. Here, we used a center-surround spatial configuration where both components do not spatially overlap. We measured the strength of this motion interaction by assessing the cancellation speeds (i.e., the speed needed to cancel out the motion discrimination impairment) for different combinations of spatial frequencies, temporal frequencies, contrasts, durations, and under binocular and dichoptic presentations. The experiments revealed that cancellation speed is bandpass tuned to spatial frequency, increases with temporal frequency up to 12 Hz before slightly decreasing, and intensifies with contrast before stabilizing at higher levels. We found similar patterns of results for both dichoptic and binocular presentations, although the interaction was stronger in the binocular condition. These results confirm that this interaction mechanism can integrate fine and coarse scales when presented to different eyes, even when motion signals do not spatially overlap. Finally, we explain the differences between dichoptic and binocular cancellation speeds using a motion-sensing model that includes a cross-scale interaction stage. The model simulations suggest that an interocular gain control, followed by binocular summation and then by cross-scale interaction, accounts for the differences observed between binocular and dichoptic viewing.