Cross-coupled adaptation of eye and head position commands in the primate gaze control system.

Primates orient visual gaze using different eye-head coordination strategies. To test how these strategies are formed, we trained a macaque monkey to perform 'head-only' gaze shifts looking through a 10 degrees head-fixed aperture. When we suddenly relocated this aperture 15 degrees downward, the animal could orient initial eye position toward the new aperture, but during large gaze saccades the eye was mistakenly driven back to the original (now occluded) aperture. More importantly, this was accompanied by an opposite head movement, such that gaze (although blocked) pointed correctly. We conclude that the gaze control system acquires new strategies through separate but interdependent eye-head controllers, designed primarily to ensure that gaze is placed in the correct direction.