Project 8

Cortical control of voluntary movement

My lab is using transcranial magnetic stimulation (TMS) to study the function of motor cortex in controlling voluntary movement in conscious behaving humans. Brief high-intensity magnetic pulses delivered through a coil positioned on a subject’s scalp over the motor cortex excite underlying neurons and evoke a burst of electromyographic activity in the corresponding muscles (the motor-evoked potential , or MEP). The size of the MEP reflects the excitability of the corticospinal system. A variant of this procedure, using paired TMS pulses, shows the activity of inhibitory and excitatory circuits within motor cortex. These intracortical circuits control the output of motor cortex (and so shape and refine the movement that is produced) and are instrumental in the capacity of the motor cortex to reorganize with experience. Studies are in progress on the motor cortical mechanisms of manual dexterity and handedness (the asymmetry of manual dexterity) and on use-dependent reorganization of motor cortex.