NEURAL CONTROL OF FAST-REGULAR SACCADES AND ANTISACCADES - AN INVESTIGATION USING POSITRON EMISSION TOMOGRAPHY

Regional cerebral blood flow changes related to the performance of two oculomotor tasks and a central fixation task were compared in ten hea lthy human subjects. The tasks were: (a) performance of fast-regular s accades; (b) performance of voluntary antisaccades away from a periphe ral cue; (c) passive maintenance of central visual fixation in the pre sence of irrelevant peripheral stimulation. The saccadic task was asso ciated with a relative increase in activity in a number of occipitotem poral areas. Compared with both the fixation and the saccadic task, th e performance of antisaccades activated a set of areas including: the superior and inferior parietal lobules, the precentral and prefrontal cortex, the cingulate cortex, and the supplementary motor area. The re sults of the present study suggest that: (a) compared with self-determ ined saccadic responses the performance of fast regular, reflexive sac cades produces a limited activation of the frontal eye fields; (b) in the antisaccadic task the inferior parietal lobes subserve operations of sensory-motor integration dealing with attentional disengagement fr om the initial peripheral cue (appearing at an invalid spatial locatio n) and with the recomputation of the antisaccadic vector on the basis of the wrong (e.g., spatially opposite) information provided by the sa me cue.