Effect of Increasing Motor Cortex Inhibition on Task Specific Dystonia

Dystonia is a disease where muscles in the affected body part are abnormally active. This may result in abnormal postures. The underlying mechanisms are not known. One proposed mechanism is located in the motor area of the brain that controls the coordination of muscles, called the motor cortex. It is well known that the motor area of one hemisphere of the brain (motor cortex) controls the movement of the opposite side of the body. When people perform tasks such as picking up an object or writing there are mechanisms in motor cortex that focus the level of activity so that they can do these tasks with a high level of precision. Focusing activity in motor cortex seems to be disturbed in people with dystonia. Transcranial magnetic stimulation (TMS) is a device that allows the non-invasive stimulation of the brain. When applied to the motor cortex it can upregulate or down regulate its activity. In the present study the investigators will conduct experiments on subjects with task specific focal hand dystonia (such as writers cramp) using TMS to decrease unwanted motor activity. The investigators will assess the effects of this intervention using objective, subjective and kinematic measures. This is a pilot study and will require further research to assess the long-term effects of repetitive TMS on task-specific focal hand dystonia.