Role of the Intact Hemisphere in Recovery of Motor Function After Stroke

The purpose of this study is to better understand the role of the motor part of the brain in the recovery of motor function after stroke. The motor deficits that follow a stroke are compensated for over several months. It has been proposed that the ipsilateral motor cortex mediates these recovery processes. The results of this study will provide fundamental information on the role of ipsilateral M1 in recovery of motor function after chronic stroke.

A general patient evaluation will determine the location of the lesion site and assess the degree of impairment in motor and global cognitive functioning. An assessment of motor function will also be performed. Patients will be divided into two groups: well and poorly recovered. An MRI (magnetic resonance imaging) scan may also be done if one has not been performed in the past 6 months.

Two main procedures will be performed: transcranial magnetic stimulation (TMS) and test of motor performance. In the first procedure, a metal coil surrounded by a plastic mold will be placed on the head and electrical current will be pulsed through it. The electrical muscle activity will be recorded through these electrodes with a computer. The second procedure involves a reaction time test. The task will consist of reacting to a visual stimulus by performing a voluntary movement. TMS pulses will be given before each movement. This is done to determine whether this type of stimulation interferes with reaction time, which would indicated that it interferes with the brain centers executing the reaction to the visual Go-signal.

Patients with single ischemic hemispheric lesions at least 12 months after the stroke who initially had a severe paralysis of the arm will be recruited for the study. Healthy normal volunteers will also be included in the study. A special effort will be made to increase the participation of women and diverse racial groups.