Temporal dynamics of peri-microsaccadic modulations within the foveola

Microsaccades are small, rapid eye movements that shift the center of gaze by less than half a degree. While they have traditionally been associated with perceptual modulations and covert attention shifts in extrafoveal vision, recent evidence indicates that microsaccades also modulate perception within the central fovea in a spatially selective manner. However, the temporal dynamics of these modulations in fine spatial discrimination remain largely unexplored. Here we used high-precision eye tracking and gaze-contingent display control to achieve accurate localization of the line of sight and to restrict visual stimulation to selective locations within the central fovea during instructed microsaccades. Our results show that visual performance peaks approximately 70 milliseconds before microsaccade onset at the target location, while perception at equally eccentric, non-target foveal locations is concurrently impaired. This is followed by a generalized suppression phase while the microsaccade is in flight, when fine spatial discrimination drops to near-chance levels. Visual performance then recovers rapidly at the target location, returning to baseline within 100 milliseconds after microsaccade landing. Our findings demonstrate that visual discrimination within the central fovea is modulated following a distinct temporal profile and in a spatially selective way around the time of microsaccade execution.