The effects of anterior arcuate and dorsomedial frontal cortex lesions on visually guided eye movements in the rhesus monkey: 1. Single and sequential targets

This study examined the effects of anterior arcuate and dorsomedial frontal cortex lesions on visually guided eye movements in three rhesus monkeys. Lesions of the anterior bank of the arcuate, where the frontal eye fields reside, produced major deficits in the execution of saccadic eye movements to sequentially presented targets that did not recover even after 1 year after the lesions. Ablations of the dorsomedial frontal cortex, wherein the medial eye fields reside, produced much smaller and shorter-duration deficits on this task. Deficits after paired lesions of the anterior arcuate and dorsomedial frontal cortex were of approximately the same magnitude as after single anterior arcuate lesions. Anterior arcuate lesions also increased saccadic reaction times to single visual targets and decreased saccadic velocities that recovered gradually over a period of 2-5 months. Dorsomedial frontal cortex lesions produced only small increases in saccadic latencies that recovered rapidly. None of the lesions produced deficits in executing combined saccadic and pursuit eye movements to moving targets. The results suggest that the anterior arcuate area plays a central role in the execution of sequences of eye movements to successively appearing targets. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.