Primate premotor cortex: dissociation of visuomotor from sensory signals.

1. If we assume adequate control for attention, memory, and stimulus location, a bona fide sensory response would be unaffected by whether a visuospatial stimulus instructs (1) one limb movement versus another or (2) limb movement versus a shift in spatial attention or memory. Two behavioral methods tested whether apparently sensory responses in the monkey's premotor cortex are strictly that, or, alternatively, whether they reflect the action instructed by a stimulus. 2. When an identical stimulus leads to two different responses, phasic discharge after a visuospatial stimulus is significantly, often dramatically, affected by the response. Similarly, premotor cortex neurons discharge more after a stimulus instructs a limb movement than after the same stimulus instructs a shift in spatial attention or memory. Thus, for the majority of premotor cortex neurons, the hypothesis that phasic poststimulus activity modulation represents a sensory response can be rejected.