The purpose of this study is to improve arm function in adults with hemiplegic cerebral palsy. Participants will receive transcranial direct current stimulation (or sham) in combination with upper extremity robotic therapy.

Therapy consists of 20 minutes of non-invasive, low-level brain stimulation (transcranial direct current stimulation, tDCS), followed by one hour of shoulder/wrist robotic training. Participants will be enrolled in therapy 3 times per week for 12 weeks (or 36 sessions). Before and after therapy, participants will receive and assessment of their arm function, as well as an assessment of their brain activity, using electroencephalography (EEG) and transcranial magnetic stimulation (TMS).

Inclusion Criteria:

• Participant willing and able to provide informed consent
• Diagnosis of hemiplegic Cerebral Palsy
• Joint mobility: wrist extention (20 degrees), metacarophalangeal and proximal interphalangeal joints (10 degrees)

Exclusion Criteria:

• Cognitive deficits that impede understanding of study protocol
• Current medical illness unrelated to CP
• Visual problems (uncorrected by glasses/contact lenses)
• High motor ability in affected arm
• Severe spasticity
• Lack of asymmetry in hand function
• Orthopedic surgery in affected arm within 2 years
• Dorsal root rhizotomy
• Botulinum toxin therapy in either upper extremity during last 2 months, or planned during study period
• Currently receiving intrathecal baclofen
• Seizure beyond age 2, use of anti-seizure medication, history of epilepsy (in self or first degree relatives), brain surgery, cranial metal implants, structural brain lesion, deices that may be affected by TMS (pacemaker, medication pump, cochlear implant, implanted brain stimulator)
• True positive response on the Transcranial Magnetic Stimulation Safety Screen
• Current use of medications known to lower the seizure threshold
• Previous episode of neurocardiogenic snycopy