CORTICAL CONTROL OF SACCADES AND FIXATION IN MAN - A PET STUDY

To identify cortical regions activated during saccades and visual fixa tion, regional cerebral blood flow (rCBF) was measured in eight health y subjects using (CO2)-O-15 PET during the performance of three tasks: (i) central fixation; (ii) reflexive saccades to random targets; (iii ) remembered saccades to locations of recent target appearance. Signif icant rCBF increases were identified using analysis of covariance and the t statistic (P < 0.001). Compared with central fixation there was activation of striate and extra-striate cortex, posterior parietal cor tex (PPC) and frontal eye fields (FEF) during both reflexive and remem bered saccades. During remembered saccades there was additional activa tion of supplementary motor area (SMA), insula, cingulate, thalamus, m idbrain, cerebellum and right superior temporal gyrus (Brodmann's area 22). Compared with the individual saccadic tasks, central fixation ac tivated extensive regions of ventromedial (areas 10, 11 and 32) and an terolateral (areas 8, 9, 10, 45 and 46) prefrontal cortex, and foveal visual cortex. We conclude that FEF and PPC are associated with the ge neration of both reflexive and remembered saccades, with SMA additiona lly involved during remembered saccades. Sustained voluntary fixation is mediated by prefrontal cortex.