Neurons in the caudal frontal eye fields of monkeys signal three-dimensional tracking

To maintain optimal clarity of objects moving in three dimensions, precise coordination of binocular eye movements is required in frontal-eyed primates. Caudal parts of the frontal eye fields (FEFs) contain smooth pursuit neurons and the discharge of the majority of them is related to vergence eye movements as well. However, whether or not those pursuit neurons carry true binocular signals has not been tested critically. Using dichoptic stimuli that dissociate horizontal movements of the left and right eyes, we found that all pursuit-related, FEF neurons tested carried binocular signals.