Motor Performance in Chronic Stroke Patients

This study will determine in stroke patients whether stimulation of the injured side of the brain combined with stimulation of the weak hand can temporarily improve motor function of the paralyzed hand. It will also examine whether stimulation of the healthy side of the brain combined with stimulation of the weak hand can temporarily improve motor function in the paralyzed hand.

Healthy adult volunteers and adults who have had a stroke more than 3 months before entering the study may be eligible to participate. Candidates are screened with a physical and neurological examination. Stroke patients also have magnetic resonance imaging (MRI), a test that uses a strong magnetic field and radio waves to obtain images of the brain.

Participants perform several tasks (described below) in a practice session and then during five more sessions on separate days. They perform the tasks before and after undergoing transcranial direct current stimulation (tDCS) plus electrical stimulation (ES), and during a procedure that involves sham stimulation. For tDCS, small rubber electrodes are soaked with water and taped to the subject's head, one above the eye and the other on the back of the head. The current passes between the two electrodes. For ES, two pairs of electrodes are attached to the subject's wrist with a paste. A very short pulse of current is passed between the electrodes, creating an electrical field that stimulates the brain. For the sham stimulation, the electrodes are similarly placed, but there is no stimulation. The tasks are:

• Jebsen-Taylor test: Subjects write, lift small common objects like paper clips, and perform activities like turning pages, stacking checkers or lifting large objects. They do these tasks as fast as possible.
• Pinch force: Subjects press a wedged instrument between their thumb and index finger as hard as they can. There are several trials every 10 seconds.
• Speed tapping: Subjects press a key on a keyboard as quickly as possible for 10 seconds.
• Simple reaction time task: Subjects perform a quick wrist movement as quickly as possible in response to a "go" signal presented on a computer monitor. Muscle activity in the forearm is recorded using electrodes.
• Motor sequence learning/Learning a finger movement sequence: Subjects practice a finger movement exercise on a keyboard by pressing keys that correspond to a number displayed on a video screen.
• Visual analog scales: Subjects complete three questionnaires about their attention, fatigue, and mood.
• Sensory monitoring: Subjects are blindfolded and asked to judge the difference in various sensations, such as the feel of plastic domes with gratings, vibration, or a plastic hair applied to their fingertip.
• Scoring MRC scale: The muscle strength of the subject's hands is measured.
• Fugl-Meyer scale: The subject's ability to move his or her limbs is measured.
• Mini-mental state examination: The subject's mental ability is measured briefly.
• Handedness questionnaire: The subject's dominant hand is determined.

Participants also undergo transcranial magnetic stimulation (TMS) and electromyography (EMG) before, during and after these activities. For TMS, a wire coil is held on the scalp. A brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. The effect of TMS on the muscles is detected with small electrodes taped to the skin of the arms or legs. EMG measures the electrical activity of the muscles. For this test, small electrodes are taped to the skin over the muscle.