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.Significance statement Microsaccades are miniature eye-movements that occur during visual fixation. Behavioral studies have suggested that pre-microsaccadic attention enhances visual processing in the fovea. However, the underlying neuronal mechanisms at the foveal scale remain unknown. Using voltage-sensitive dye imaging in monkeys, we investigated how microsaccades influence neural activity in the foveal region of the primary visual cortex. Just before a microsaccade toward a small visual stimulus, neural activity was enhanced at both the current and future landing stimulus locations, compared to microsaccades directed away. This enhancement appeared over the microsaccade path and was accompanied by increased synchronization at the current stimulus location. Our findings reveal novel neural modulations preceding microsaccades, and suggest a link between microsaccades and neural signatures of attention.