Probing correlates of saccadic suppression in the primate superior colliculus and primary visual cortex using simulated and real saccades

Visual sensitivity is strongly impaired around the time of saccades, in a phenomenon known as saccadic suppression of visual sensitivity. Recently, the origins of perceptual saccadic suppression were linked to the rapid visual flow that appears on the retina during saccadic eye movements (Idrees et al. 2020, Idrees et al. 2022). Specifically, these authors found that the visual appearance of the background (e.g. low or high spatial frequency content) that is translated on the retina can affect both the strength and duration of saccadic suppression, and that this effect already starts in the retina. Here, we investigated how visual flows created by rapid image shifts affect the superior colliculus (SC) and primary visual cortex (V1), both downstream of the retina. We recorded SC and V1 neural activity from two monkeys. The monkeys fixated while we presented a rapid image displacement of different textured backgrounds (similar to Idrees et al., 2020). At different times after texture displacement, we presented a brief probe flash (luminance pedestal) within the visual receptive fields (RF’s) of recorded neurons. The monkeys also performed the same experiment with real horizontal saccades (SC RF’s were away from the saccade endpoint, allowing us to place probe flashes within these RF’s and only assess visual responses). Both brain areas responded to texture displacements (whether shifted by saccades or externally) and probe flashes. Moreover, probe flash responses were suppressed in both areas, depending on presentation time relative to image shifts, consistent with (Idrees et al., 2020). However, the two areas exhibited important differences: V1 probe flash responses were similar whether texture displacements were saccade-induced or external; on the other hand, SC responses were much more suppressed by external texture displacements than by saccade-induced image shifts. These results suggest that SC distinguishes between self-induced and external visual stimulation significantly better than V1.