An area for vergence eye movement in primate frontal cortex

To view objects at different distances, humans rely on vergence eye movemen ts to appropriately converge or diverge the eyes and on ocular accommodatio n to focus the object(1,2). Despite the importance of these coordinated eye movements (the 'near response') very little is known about the role of the cerebral cortex in their control. As near-response neurons exist within th e nucleus reticularis tegmenti pontis(3), which receives input from the fro ntal eye field region of frontal cortex(4-6), and this cortical region is k nown to be involved in saccadic(7-9) and smooth-pursuit eye movements(10-12 ), we propose that a nearby region might play a role in vergence and ocular accommodation. Here we provide evidence from rhesus monkeys that a region of frontal cortex located immediately anterior to the saccade-related front al eye field region is involved in vergence and ocular accommodation, and i n the sensorimotor transformations required for these eye movements. We con clude that the macaque frontal cortex is involved in the control of all vol untary eye movements, and suggest that the definition of the frontal eye fi elds should be expanded to include this region.