Cortical field potentials preceding self-paced and visually initiated hand movements in one and the same monkey and influences of cerebellar hemispherectomy upon the potentials

Abstract

Field potentials in the premotor and forelimb motor cortices preceding hand movements were recorded with chronically implanted electrodes in the cortices. They were different between the same hand movements initiated at self-pace (‘voluntary’) and by visual stimulus (in reaction) in the same monkey. Ablation of the cerebellar hemisphere contralateral to the motor cortex suppressed both slowly increasing and relatively steep surface negative-depth (2.5–3.0 mm) positive potentials in the motor cortex prior respectively to self-paced and visually initiated movements. The results inferred the different central preparatory mechanisms (programs) for self-paced and reaction movements in the same individual, and revealed the direct neocerebellar participation in intiation of both self-paced and reaction movements by activating the motor cortex.