Investigation on the Bidirectional Cortical Neuroprosthetic System

Inclusion Criteria: Participants must meet all inclusion criteria, verified by medical evaluation, psychological evaluation, and review of medical history. Inclusion criteria include: * Participants with C4-C6 tetraplegia from any etiology except neurodegenerative disease (e.g. amyotrophic lateral sclerosis) or active cancer. * Complete or incomplete spinal cord injury classified by the American Spinal Injury Association (ASIA) as A or B or C if fewer than three muscle groups in the leg and foot (as identified in the ASIA Impairment Scale) can be contracted * Injury more than one year prior to enrollment * Participant has a life expectancy of greater than 5 years * Meeting surgical safety criteria, including surgical clearance by the participant's primary healthcare provider, study physicians, and any necessary consultants * Willingness and ability to provide informed consent * Screened by rehabilitation psychologist with a result showing that the participant has a stable psychosocial support system with caregiver capable of monitoring participant throughout the study * Ability and willingness to travel to up to fifty miles to study location up to three days per week for the duration of the study * Ability to understand and comply with study session instructions * Pain well controlled without narcotic medications * No other neurological, orthopedic conditions beyond the spinal cord injury * Participant consents to the study and still wishes to participate at the time of the study Exclusion Criteria: All interested participants will be reviewed for the presence of exclusion criteria by medical evaluation, review of medical history, self (or assistant) report and evaluation by a psychologist. Presence of any of the following criteria will exclude participants from eligibility to participate. In addition, the medical team has the right to withdraw the participant at any time if any of the exclusion criteria emerge and participants can withdraw at any time for any reason. Withdrawal details are outlined below exclusion criteria. Exclusion criteria include: * Neurological conditions: Impaired receptive and/or expressive verbal communication skills * Presence of memory impairment on the Rey Auditory Verbal Learning Test * Intellectual impairment: score of 26 or less on the Mini-Mental State Examination or history of Intelligence Quotient \< 80 * Chronic psychiatric illness, including psychosis and treatment-resistant major depression, as indicated by a diagnosis of Axis I or Axis II on the Symptom Checklist-90-Revised Test * Ventilator dependent * Implanted devices such as: pacemakers, cardiac defibrillators, spinal cord or vagal nerve stimulators, deep brain stimulators, cochlear implants or any other implantable device incompatible with MRI. * History of drug or alcohol dependence in past 24 months * Cerebral lesions affecting frontal and parietal lobes * Medical conditions contraindicating surgery of a chronically implanted device (e.g. osteomyelitis, diabetes, hepatitis, any autoimmune disease/disorder, epilepsy, skin disorders causing excessive skin sloughing or poor wound healing, blood or cardiac disorder requiring chronic anti-coagulation) * Other chronic, unstable medical conditions that could make control unsuitable (such as tremor or spasticity) * Presence of pre-surgical findings in anatomical, functional, and/or vascular neuroimaging that makes achieving implant locations within desired risk levels too challenging (to be decided by neurological and neurosurgical team) * Prior cranioplasty * Inability to undergo MRI or anticipated need for an MRI during the study period * Participants with active infections or unexplained fever * Participants with other morbid conditions making the implantation of the recording elements unsafe; not limited to: significant pulmonary, cardiovascular, or renal impairments making the surgical procedure unsafe * Pregnancy (confirmation through blood test) * Nursing an infant, planning to become pregnant, or not using adequate birth control * Corrected vision no worse than 20/30 * HIV or AIDS infection * Existing scalp lesions or skin breakdown * Chronic oral or intravenous use of steroids or immunosuppressive therapy * Active cancer within the past year or requires chemotherapy * Uncontrolled autonomic dysreflexia within the past 3 months * An implanted ventricular shunt * Suicidal ideation within the past 12 months * Medications that affect neuroplasticity: neuroleptics, Benzodiazepines (BDZ), Tricyclic Antidepressants (TCA).