Behavioural state affects saccades elicited electrically from neocortex.

Reviewed is how behavioural context influences saccadic eye movements elicited electrically from the neocortex of monkeys. Factors found to affect stimulation-evoked saccades include (1) motor state, i.e. whether stimulation is delivered during free-viewing, or during or after active fixation, or before an animal is about to execute a saccade to a target location, and (2) reward delivery, i.e. the characteristics and timing of reward, which can promote or inhibit the evocation of saccades. We conclude that anyone using electrical stimulation in neocortex to study sensory and cognitive processes must control for the possibility that stimulation of cortex is merely generating a saccade vector whose expression is being obscured by the behavioural paradigm in use. Areas of neocortex from which saccades can be evoked using low currents (<100 microA) are surprisingly widespread and include regions traditionally considered within the sensory domain (e.g. V1, V2, V4, and MT), in addition to visuomotor regions such as the lateral intraparietal area, the dorsomedial frontal cortex, the frontal eye fields, and the prefrontal cortex. This is especially true once the behavioural state of a stimulated animal is put under experimental control.