This study will examine whether continuous use of transcranial direct current stimulation (tDCS) in combination with motor training can lead to long-term improvement in movement performance beyond what can be achieved with motor training alone.
Healthy normal volunteers 18-80 years of age who are clearly right- or left-handed may be eligible for this study. Each candidate is screened with a medical history, clinical and neurological examination, questionnaires to evaluate memory, attention, and handedness and a brain MRI, if one has not been done by NINDS within 12 months of entering the study. Pregnant women may not participate.
The study involves 10 sessions (in addition to the screening visit) over 3 months. Sessions 1-5 are completed over 5 consecutive days. Sessions 6-10 are divided over the remaining time. Participants are randomly assigned to one of three groups: 1) tDCS during motor training; 2) tDCS after training; or 3) training with sham tDCS. During these sessions, participants perform a pinch force task (squeezing a small device between the thumb and forefinger) and visuomotor tasks (using a device to move the cursor on a computer screen to various targets and holding the cursor in place for 1 second).
During the motor training and performance sessions, participants have the following procedures.
- TMS measurements: 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. During the stimulation, the subject may be asked to tense certain muscles slightly or perform other simple actions. The stimulation may cause a twitch in muscles of the face, arm, or leg, and the subject may hear a click and feel a pulling sensation on the skin under the coil.
- tDCS: Small, wet sponge electrodes are applied to the head - one above the eye and the other on the back of the head. A small electrical current is passed between them. The subject may feel an itching or tingling sensation under the electrodes or see light flashes. Some sessions are done with sham tDCS.
- Surface electromyography: Electrodes are filled with a conductive gel and taped to the skin over one small hand muscle to measure the electrical activity of muscles.
- Behavioral measurements: Evaluation of learned movement tasks
- Questionnaires to evaluate the subject's attention, fatigue and mood before and after testing