Reafferent head-movement signals carried by pursuit neurons of the simian frontal eye fields during head movements.

The smooth-pursuit system is important to precisely track a slowly moving object and maintain its image on the foveae during movement. During whole-body rotation, the smooth-pursuit system interacts with the vestibular system. The caudal part of the frontal eye fields (FEF) contains smooth pursuit-related neurons that signal eye velocity during pursuit. The majority of them receives vestibular inputs and signal gaze-velocity during passive whole-body rotation. It was asked whether discharge modulation of FEF pursuit neurons during head rotation on the stationary trunk could be accounted for by vestibular inputs only or if both vestibular and neck proprioceptive inputs contributed to the modulation. Discharge modulation during active head pursuit, passive head rotation on the stationary trunk, passive whole-body rotation, and passive trunk rotation against the stationary head were compared. The results indicate that both vestibular and neck proprioceptive inputs contributed to the discharge modulation of FEF pursuit neurons during head movements.