EFFECTS OF ANTERIOR CINGULATE CORTEX LESIONS ON OCULAR SACCADES IN HUMANS

Cerebral blood flow studies in humans suggest that the anterior cingul ate cortex (ACC) could be involved in eye movement control. In two pat ients with a small infarction affecting the posterior part of this are a (on the right side) and in ten control subjects, we studied several paradigms of saccadic eye movements: gap task, overlap task, antisacca des (using either a 5 degrees or 25 degrees lateral target), memory-gu ided saccades with a short (1 s) or long (7 s) delay, and sequences of memory-guided saccades. Compared with controls, patients had normal l atency in the gap task but increased latency in the other tasks. The g ain of memory-guided saccades was markedly decreased, bilaterally, wha tever the duration of the delay. Patients made more errors than contro ls in the antisaccade task when the 5 degrees lateral target was used, and a higher percentage of chronological errors in the sequences of s accades. These results show that the posterior part of the right ACC p lays an important role in eye movement control and suggest that this a rea could correspond to a ''cingulate eye field'' (CEF). The role of t his hypothetical CEF could be an early activation exerted on the front al ocular motor areas involved in intentional saccades and also a dire ct action on brainstem ocular premotor structures.