Some conceptual remarks about supraspinal mechanisms in the control of voluntary and reflex motor activities

The present paper analyses the supraspinal control of motor functions and sensorimotor integrations. Attention was paid mainly to three phenomena involved in these mechanisms: the Bereitschaftspotential, the long latency reflex responses and the short latency somatosensory evoked potentials (SEPs). The study includes the problems of long loop motor control and dyscontrol, the gating process of SEPs by movement, the role of N18 component of SEP and the analysis of supraspinal modulation of the H-reflex excitability curve in healthy subjects and in patients with some cerebral dysfunction. It was found that the amplitude of the Bereitschaftspotential increased with peripheral nerve stimulation. The experiments have shown a positive relationship between the long latency reflex latencies and the distance of the corresponding muscle from the brain. The amplitude of the long latency reflex response was found to be higher and its synchronization better in phasic movements than in a slightly sustained contraction. The short latency somatosensory evoked potentials were distinctly attenuated by movement gating. By its wide spread negativity, the N18 component probably facilitates the cortical transfer of the long latency muscle response. The H-reflex excitability curves in patients with various cerebral dysfunction exhibited a characteristic course corresponding approximately to the degree of dysfunction in focal cerebral lesions, arterial hypertension and neurasthenias.