Contributions Of The Frontal Eye Field To Movement Coordination: Activity Of Neurons During Combined Eye-Head Gaze Shifts In The Rhesus Monkey

In primates, eye and head movements must be carefully coordinated for accurate vision; the neural basis for coordination in this model system is unclear. With the head free to move, eye saccades and head movements combine to produce large changes in the line of sight (gaze shifts), and microstimulation of the frontal eye field (FEF) can evoke combined eye and head gaze shifts. To test whether the FEF provides commands for the entire gaze shift or separate eye and head components, we recorded extracellular single-unit activity from 26 neurons in two monkeys trained to make head-unrestrained visually guided gaze shifts. We utilized behavioral dissociations of gaze, eye, and head movements and regression analyses to reveal the relations of unit burst parameters to gaze, eye, and head movement metrics. In 46% of these neurons, the number of spikes in the unit burst was predominantly correlated with head movement amplitude, and bursts of most of these units were also temporally correlated with eye movement. Fewer neurons were related to eye (19%) or gaze movements (12%). We conclude that the dorsomedial FEF participates in large amplitude gaze shifts, and that many neurons in this region may control the coordination of eye and head movements, while others separately control gaze, eye, or head movements. This work was supported by NIH grants EY00745 and RR00166 and the Graduate Neuroscience Training Grant GM07108.