Physiology of Voluntary Movement

National Institute Of Neurological Disorders And Stroke

Investigators

Linked publications, trials & patents

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. To determine which areas of the brain are activated with the sense of agency when making voluntary movement, we have used an MRI-compatible dataglove which subjects wore while making hand movements in the scanner. Subjects viewed their movements in real-time and the visual feedback they received was varied during the experiment to simulate different degrees of voluntary control. Now both MRI and EEG results have been published that show the relevant brain networks. We have determined EEG methods to predict in real time when someone is going to move and what movement they will make. We have optimized features and classification methods for the prediction. We have completed studies identifying that persons are not necessarily thinking about movement when a movement prediction can be made. We are now trying to influence the decision of when or what to move using non-invasive brain stimulation. The learning of motor skills is an important function. We have been studying how movements become automatic, that is, the stage of learning where much attention does not need to be devoted to an action. We are carrying out studies on the learning of chunks, and on the influence of reward on learning. We will use information learned in these studies to investigate patients with different movement disorders. 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.