Corticospinal excitability in human voluntary movement.

Abstract

The research described in this thesis addressed the neurophysiologic changes in the human corticospinal system during preparation and execution of voluntary hand movements. The experiments involved transcranial magnetic stimulation (TMS) of the motor cortex combined with electromyography (EMG) and electroencephalography (EEG). The thesis provides several new insights into the neurophysiology of the healthy human motor system: Excitability in human motor cortex and spinal cord is state dependent, and is adjusted to behavioural demands on a millisecond time scale. Excitability of movement agonists is facilitated during actual execution, but also in advance of a movement, when a movement is expected. Suppression of excitability is not only important to inhibit movement antagonists; it also prevents agonists to move prematurely, which is a critical in many motor preparation tasks. Finally, this thesis puts forward a fundamental mechanism through which neuronal excitability can be dynamically modulated, namely rhythmic neuronal synchronization