Changes of premovement field potentials in the cerebral cortex during learning processes of visually initiated hand movements in the monkey.

Field potentials on the surface and in the depth (2.5-3.0) mm from the surface) of several areas of the cerebral cortex were recorded with chronically implanted electrodes and with electronic averaging method, and changes of the potentials preceding visually initiated (reaction) hand movements were observed successively in the time course of leaning the movement in monkeys. Significant potentials in response to the light stimulus were found first in the frontal and occipital association cortices (area 8-10 and 19), and then in the premotor cortex (area 6) on bilateral sides. In the bilateral forelimb motor cortex (area 4), the early surface positive-depth negative premovement potentials became marked after the occurrence of the significant potentials in the frontal and occipital association cortices, and the later surface negative-depth positive premovement potentials mediated by the neocerebellum and the superficial thalamocortical projections emerged later in the forelimb motor cortex contralateral to the moving hand as the monkey became fast and skilled in the movement. Learning processes of the reaction movement were related to such changes of the premovement potentials in the cerebral cortical areas.