Abstract
During natural viewing the eyes scan the visual scene, leading to a continuous image motion over the retina. Yet, even during fixation periods, miniature fast eye movements (EM) known as microsaccades (MSs) displace the image across the fovea. Despite this constant image shift, our visual perception of the world is stable, suggesting the existence of an extra-retinal input to the visual cortex that can correct for the image motion and produce perceptual stability. Here we investigated the existence of an extra-retinal input into the primary visual cortex (V1) of fixating monkeys during MSs. We used voltage-sensitive dye imaging (VSDI) to measure the spatio-temporal patterns of neural population in V1 aligned on MSs onset, in the absence or presence of a visual stimulus. VSDI enables to measure the population response at a high spatial (meso-scale) and temporal (ms) resolution. Interestingly, in the absence of a visual stimulus, the VSD signal showed that MSs induced a spatio-temporal modulation in V1, comprised of two phases: an early suppression followed by an enhancement of the neural response. Interestingly, this modulation exhibited a non-homogenous pattern: foveal regions showed mainly the enhancement transient, whereas more parafoveal regions showed a suppression that was followed by a delayed enhanced neural activation. Neural synchronization increased during this modulation. We then compared the MSs modulation in the presence and absence of visual stimulus within stimulated and unstimulated sites at the imaged cortical area. Our results reveal a distinct extra-retinal source that can be involved in visual and perceptual stabilization.