Transcranial Magnetic Stimulation Exploration of Motor Cortex Functional Anatomy

The purpose of the proposed study is to explore the nature of the codes that are present in the primary motor cortex. All complex actions involves the contraction of multiple muscles, the timing and intensity of which is precisely modulated. The traditional view of this process is that an abstract representation of the action is coded in the posterior parietal lobe and this code informs premotor cortex which in turn contacts the primary motor cortex; crucially, on most accounts the primary motor cortex is "assigned to" a specific muscle such that when that neuronal population is stimulated a single muscle contraction is generated. An alternative account supported by recent studies involving primates and limited data from humans is that the primary motor cortex codes actions such as clenching the fingers that are generated by multiple muscles. We plan to address this question by stimulating primary motor cortex at multiple locations with Trascranial Magnetic Stimulation of the primary motor cortex and recording simultaneously from 6 muscles using surface electromyography.