Prosaccades

Prosaccades are reflexive saccadic eye movements directed toward a suddenly appearing visual target. They reorient gaze to the target location and are among the fastest oculomotor responses to visual stimuli.

They arise from a sensorimotor network that links visual input to eye movement. The superior colliculus contributes to target selection; the frontal eye fields and supplementary eye fields help initiate the movement. Brainstem generators in the pons (PPRF) and in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) execute horizontal and vertical saccades, with the cerebellum refining accuracy and adaptive control.

Typical latencies range roughly 120 to 180 milliseconds; shorter, express-like saccades can occur with high predictability. The amplitude matches target eccentricity, and trajectories are generally accurate when the system functions normally. Eye movements are measured with infrared or video tracking in clinics and labs.

Clinically, prosaccades assess basic sensorimotor function and oculomotor integrity. Delays, hypometria, or reduced gain can indicate brainstem or cortical dysfunction and appear in several neurological disorders. Prosaccades are contrasted with antisaccades, which test inhibitory control by requiring gaze away from the stimulus.