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 guided eye movements: the frontal eye fields (FEF) and the medial eye fields (MEF) in dorsomedial frontal cortex. Previously, FEF lesions have revealed only mild deficits in saccadic eye movements that recovered rapidly. Deficits in eye movements after MEF ablation have not been shown. We report the effects of ablating these areas singly or in combination, using tests in which animals were trained to make saccadic eye movements to paired or multiple targets presented at various temporal asynchronies. FEF lesions produced large and long-lasting deficits on both tasks. Sequences of eye movements made to successively presented targets were also impaired. Much smaller deficits were observed after MEF lesions. Our findings indicate a major, long-lasting loss in temporal ordering and processing speed for visually guided saccadic eye movement generation after FEF lesions and a significant but smaller and shorter-lasting loss after MEF lesions.