PET STUDY OF VOLUNTARY SACCADIC EYE-MOVEMENTS IN HUMANS - BASAL GANGLIA-THALAMOCORTICAL SYSTEM AND CINGULATE CORTEX INVOLVEMENT

1. The purpose of this work was to explore the cortical and subcortica l mechanisms underlying the execution of voluntary saccadic eye moveme nts in humans. 2. Normalized regional cerebral blood flow (NrCBF) was measured using positron emission tomography (PET) and (H2O)-O-15 bolus intravenous injections in four right-handed healthy volunteers at res t and while performing self-paced voluntary horizontal saccadic eye mo vements in total darkness. 3. Magnetic resonance imaging of each subje ct's brain was matched to PET images, allowing the detection of activa tion in individually defined anatomic regions of interest. Cortical re gions were drawn according to gyri limits; subcortical structures were also defined. 4. Self-paced saccadic eye movements elicited bilateral NrCBF increases in the lenticular nuclei, including putamen and globu s pallidus, and in the thalamus. At the cortical level, we found bilat eral NrCBF increases in the precentral gyrus, the superior part of the median frontal gyrus that corresponds to the supplementary motor area . There was also a significant NrCBF increase in the cerebellar vermis . 5. Right fusiform and lingual gyri, right insula, and left cingulate gyrus were also activated during the execution of saccades. 6. These results indicate that the classical basal ganglia-thalamocortical moto r loop previously described for skeletal movements may also be involve d in simple saccadic eye movements in humans.