Physiology of Voluntary Movement

National Institute Of Neurological Disorders And Stroke

Investigators

Linked publications & trials

Abstract

A number of efforts in the laboratory are devoted to understanding the physiology of volition. This includes the sense of willing to make a movement and the sense of agency, the sense of personal responsibility for the movement that has occurred. We have been trying to devise improved techniques to get quantitative measures of the timing of these subjective events. We have done studies trying to influence the decision of when or what to move, and to influence the subjective impression of volition, using non-invasive brain stimulation. New studies seek to evaluate the causal role of conscious intentions in the willing of movements. The ability to make selective movements, particularly of individual fingers, is a critical human function. Anatomical and physiological features of the motor system make this difficult since most neurons (other than alpha motoneurons in the spinal cord and brainstem) are not muscle specific. Our hypothesis is that selective motor action must require inhibitory mechanisms, and we are seeking to understand them using TMS. We refer to this process as surround inhibition, as muscles not intended for the selective action need to be inhibited. Many inhibitory processes in the cortex, such as short intracortical inhibition and short afferent inhibition, can be analyzed at rest and with movement. Such studies seem to indicate that networks within the motor cortex itself are responsible for surround inhibition. We continue to study the role of other brain networks in this regard, and have determined a role for the cerebellum in surround inhibition during tonic movements.