Pre-microsaccadic Modulation in Foveal V1: Enhancement in the Current and Future Stimulus Locations

Abstract

Microsaccades are miniature saccades performed during visual fixation that were shown to play a pivotal role in active sensing. Recent studies suggested that pre-microsaccadic attention may underlie the enhanced visual processing at the stimulus site. However, the neuronal mechanism underlying this phenomenon at the foveal scale remains unknown. Using voltage-sensitive dye imaging, we investigated the neural responses to uninstructed, spontaneous microsaccades in the fovea of the primary visual cortex (V1) in behaving monkeys (macaque, male). We found that prior to microsaccades onset toward a small visual stimulus, the neuronal activity at the current and future landing stimulus sites was enhanced relative to microsaccades away from the stimulus. This enhancement was spatially confined to the current and future landing stimulus sites, which appeared to merge along the microsaccades (<1 deg) trajectory in V1. Finally, we found a pre-microsaccadic increased synchronization at the current stimulus site. Our findings shed new light on neural modulations preceding microsaccades and suggest a link to neural signatures of attention.