CORTICAL CONTROL OF SACCADES

A scheme for the cortical control of saccadic eye movements is proposed based partly on defects revealed by specific test paradigms in humans with discrete lesions. Three different cortical areas are capable of triggering saccades. The frontal eye field disengages fixation, and triggers intentional saccades to visible targets, to remembered target locations, or to the location where it is predicted that the target will reappear (i.e., saccades concerned with intentional exploration of the visual environment). The parietal eye field triggers saccades made reflexively on the sudden appearance of visual targets (i.e., saccades concerned with reflexive exploration of the visual environment). The supplementary eye field is important for triggering sequences of saccades and in controlling saccades made during head or body movement (i.e., saccades concerned with complex motor programming). Three other areas contribute to the preparation of certain types of saccades. The prefrontal cortex (area 46 of Brodmann) plays a crucial role for planning saccades to remembered target locations. The inferior parietal lobule is involved in the visuospatial integration used for calculating saccade amplitude. The hippocampus appears to control the temporal working memory required for memorization of the chronological order of sequences of saccades.