Tactile Learning in Stroke Patients

This study will determine if stimulation of the stroke-injured side of the brain combined with stimulation to the paralyzed hand can temporarily improve the sense of touch in stroke patients. Healthy normal volunteers and people who have had a single stroke within 3 months of entering the study that affected one side of the brain may be eligible for this study. All participants must be between 18 and 90 years old and must be right-handed. Candidates are screened with a medical history, neurological examination and magnetic resonance imaging (MRI) of the brain if one has not been done within 1 year of entering the study. Participants undergo the following tests and procedures during four 2-day sessions over about 6 weeks:

• Peripheral high-frequency stimulation: Small loudspeakers are taped to the fingertips and simple tactile pulses are passed through the skin. Stimulation may be sham or real.
• Transcranial direct current stimulation: Two small rubber electrodes are taped to the head - one above the eye and the other on the back of the head. A current is passed between the two electrodes. Stimulation may be sham or real.
• MRI: The subject lies in the scanner, a metal cylinder surrounded by a magnetic field, for about 40 minutes, lying still for up to 40 minutes at a time. An electrical stimulation is applied to the fingers of the right and left hand in separate sessions. Earplugs are worn to muffle the loud noises during the scanning. Functional MRI measures blood flow changes in the brain during the performance of specific tasks.
• Behavioral measurements:
• Grating orientation task: The subject responds as quickly as possible to a touch stimulus to the finger by saying whether the direction of the stimulus is vertical or horizontal.
• Haptic object recognition task: The subject is given five categories of unfamiliar objects in the shape of cubes. During the task, identical objects are hidden in a sack. With eyes closed, the subject is asked to identify and find the objects from the sack as quickly as possible.
• Pegboard test: The subject is asked to place several pegs into a corresponding hole of a pegboard as soon as possible.
• Tapping task: The subject is asked to tap a metal stick on a metal plate as quickly as possible for 1 minute.
• Paired-pulse transcranial magnetic stimulation: This test measures changes in brain activity. A wire coil is held on the scalp and a brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. The subject hears a click and may fee a pulling sensation on the skin under the coil, and there may be a twitch in the muscles of the face, arm or leg. Subjects may be asked to tense certain muscles slightly or perform other simple actions.
• Paired-pulse somatosensory evoked potential mapping: This test measures brain activity in another brain area. The subject is seated in a chair with eyes closed. One electrode is placed above the eye and two others are placed on the back of the head. A short electrical stimulus is applied to a nerve in the wrist and brain activity is recorded while the stimulus is applied.
• Surface electromyography: This test measures the electrical activity of muscles. Electrodes are filed with a conductive gel and taped to the skin.
• Visual analog and mood scale: Subjects complete questionnaires about their attention, fatigue and mood.