1. Howard Hughes Medical Institute, Department of Physiology, and W. M. Keck Foundation Center for Integrative Neuroscience, University of California , San Francisco, California 94143, USA

Correspondence to: Masaki Tanaka Correspondence and requests for materials should be addressed to M.T. (e-mail: Email: masaki@phy.ucsf.edu).

In studies of the neural mechanisms giving rise to behaviour, changes in the neural and behavioural responses produced by a given stimulus have been widely reported. This 'gain control' can boost the responses to sensory inputs that are particularly relevant^{1, 2, 3, 4}, select among reflexes for execution by motoneurons^{5, 6} or emphasize specific movement targets⁷. Gain control is also an integral part of the smooth-pursuit eye movement system^{8, 9, 10, 11, 12, 13}. One signature of gain control is that a brief perturbation of a stationary target during fixation causes tiny eye movements, whereas the same perturbation of a moving target during the active state of accurate pursuit causes large responses⁹. Here we show that electrical stimulation of the smooth-pursuit eye movement region in the arcuate sulcus of the frontal lobe ('the frontal pursuit area', FPA) mimics the active state of pursuit. Such stimulation enhances the response to a brief perturbation of target motion, regardless of the direction of motion. We postulate that the FPA sets the gain of pursuit, thereby participating in target selection for pursuit.