THE EFFECTS OF FRONTAL EYE FIELD AND DORSOMEDIAL FRONTAL-CORTEX LESIONS ON VISUALLY GUIDED EYE-MOVEMENTS

In the frontal lobe of primates, two areas play a role in visually gui ded eye movements: the frontal eye fields (FEF) and the medial eye fie lds (MEF) in dorsomedial frontal cortex. Previously, FEF lesions have revealed only mild deficits in saccadic eye movements that recovered r apidly. Deficits in eye movements after MEF ablation have not been sho wn. We report the effects of ablating these areas singly or in combina tion, using tests in which animals were trained to make saccadic eye m ovements to paired or multiple targets presented at various temporal a synchronies. FEF lesions produced large and long-lasting deficits on b oth tasks. Sequences of eye movements made to successively presented t argets were also impaired. Much smaller deficits were observed after M EF lesions. Our findings indicate a major, long-lasting loss in tempor al ordering and processing speed for visually guided saccadic eye move ment generation after FEF lesions and a significant but smaller and sh orter-lasting loss after MEF lesions.