Can Subthreshold Transcranial Magnetic Stimulation (rTMS) to Motor Cortex and/or to Supplementary Motor Area (SMA) Improve Performance of Complex Motor Sequences in Parkinson's Disease?

The physiology of the motor disturbance in Parkinson's disease is not completely understood. One of the major and perhaps most disabling manifestations of PD is bradykinesia. It is particularly difficult for these patients to perform simultaneous, sequential and complex motor acts. Imaging studies have recently provided important information in reference to the brain regions associated with performance of these motor sequences in normal volunteers and in PD patients. These studies helped us to identify the brain regions active in association with task performance. It has been suggested that cortical regions, and particularly the SMA are less active in patients with PD than in controls in association with motor performance. We plan to study the effects of subthreshold rTMS delivered to SMA and primary motor cortex in patients with PD "on" and "off" medication. From this study, we expect to learn if stimulation of the scalp overlying primary motor cortex and SMA can ameliorate performance of simple and complex motor sequences in PD. Subthreshold rTMS has been proposed as a therapeutic tool in psychiatric disorders. In the motor domain, subthreshold rTMS delivered to primary motor cortex improves reaction times and motor performance in patients with Parkinson's disease. The mechanisms underlying this beneficial effect are not known. However, they may be related with subthreshold rTMS replacing the missing excitatory drive on the motor cortex.