Is the Feedback Primarily due to Sensors Measuring the Movement of the Head in Space?
In daily life where the head is free to move, eye and head movements are coordinated during tracking of a moving visual target. As described in the Introduction, there have been 2 competing hypotheses for the neural mechanisms of the eye-head coordination; one proposes an integrated gaze command driving both eye and head movements, and the other proposes independent eye and head commands together with different coordinating mechanisms such as vestibular feedback (for reviews, see Chen 2006; Leigh and Zee 2006). Single neuron- and electrical stimulation- studies have suggested involvement of the FEF in saccadic gaze shifts that consist of rapid eye and head movements (Bizzi and Schiller 1970; Tu and Keating 2000; Knight and Fuchs 2007; see however, Chen 2006). In these studies, the head movements elicited by electrical stimulation of the FEF are directed to the side contralateral to the stimulus, consistent with preferred directions of FEF saccade neurons. Lesion studies (van der Steen
