[Noninvasive study of cortical neuronal mechanism in voluntary movements: role of basal ganglia and cerebellum]

Abstract

Voluntary movements can be classified into the two categories depending on how those are initiated; ones initiated internally, and others triggered or paced by external stimuli. Central neuronal mechanisms involved in those preparation and execution could be represented by movement-related cortical potentials (MRCP) or Bereitschaftspotential (BP), and contingent negative variation (CNV), respectively. The both potentials, as the field potentials, can be recorded with long time constant, and represent transient changes of the membrane potentials of the cortical neurons. In patients with the lesion at the cerebellar efferent system, the BP disappeared completely whereas the late CNV was normally seen. In patients with parkinsonism, in contrast, the late CNV was significantly smaller in amplitude in severe than in mild symptom group. Recent subdural recording in epilepsy patients demonstrated that the BP and late CNV were commonly generated from the primary and supplementary motor areas, and that late CNV also arose from the frontal association cortices (mesial, basal and lateral prefrontal areas). It is therefore suggested that subcortical generating mechanism is different for the late CNV and BP although both commonly share at least some cortical generators, and that the basal ganglia are most likely responsible for the generation of the late CNV and the cerebellar efferent system for the generation of the BP.