VISUAL PROCESSING IN BRAINS FOLLOWING CORTICAL ABLATION

Monkeys were prepared with unilateral frontal eye field ablations. They were then trained on a series of oculomotor tasks. They could easily perform visually guided saccadic eye movements but were impaired in learning to make eye movements to remembered points. To see if this deficit were primarily a learning deficit or a motor performance deficit, monkeys were trained on remembered saccade tasks then underwent unilateral frontal ablations. These monkeys had no difficulty retaining the ability to make remembered saccades. However, for several weeks after surgery all of their saccades into the field contralateral to the lesion were slower and less accurate than saccades into the ipsilateral field. Saccades to briefly flashed targets were slower and less accurate than saccades to stable targets, and saccades to remembered targets were far slower and less accurate than those to briefly flashed targets. Thus ablation of the frontal eye fields causes both a learning and a motor performance deficit for saccades to briefly flashed or remembered targets. Unilateral ablation of the superior colliculus caused short-lived deficits in saccade latency and motor performance, but no differential effect between saccades to visual targets and saccades to remembered targets.