Functional localization of motor processes in the primary and supplementary motor areas.

Aspects of human brain activity were measured when subjects performed self-initiated voluntary movements, responded to external cues, or either executed or imagined performing sequential movements. Biophysical modeling of movement-related magnetic and electric fields of the brain succeeded in localizing focal activity in primary and supplementary motor areas, describing the temporal course of focal activation, and analyzing effects of type and consequences of movements on motor preparation. Positron emission tomography was used to test functional specializations of primary and supplementary areas by systematic variations of motor sequence tasks. Studies on functional brain imaging have been employed not only to contribute towards the understanding of brain physiology but also to investigate pathophysiology of movement disorders, principles of functional reorganization following brain lesions, and drug-induced changes of movement-related brain activity.