Inclusion Criteria:
1. Age \> 21
2. Limited ability to use upper limbs, based on neurological examination, due to stroke, amyotrophic lateral sclerosis (ALS), multiple sclerosis, cervical spinal cord injury, brainstem stroke, muscular dystrophy, myopathy or severe neuropathy.
3. Disability, defined by a 4 or greater score on the Modified Rankin Scale, must be severe enough to cause loss of independence and inability to perform activities of daily living.
4. If stroke or spinal cord injury, at least 1 year has passed since onset of symptoms
5. Must live within a two-hour drive of UCSF
Exclusion Criteria:
1. Pregnancy or breastfeeding
2. Inability to understand and/or read English
3. Inability to give consent
4. Dementia, based on history, physical exam, and MMSE
5. Active depression (BDI \> 20) or other psychiatric illness (active general anxiety disorder, schizophrenia, bipolar disorder, obsessive-compulsive disorder (OCD), or personality disorders (e.g. multiple personality disorder, borderline personality disorder, etc.)
6. History of suicide attempt or suicidal ideation
7. History of substance abuse
8. Co-morbidities including ongoing anticoagulation, uncontrolled hypertension, cancer, or major organ system failure
9. Inability to comply with study follow-up visits
10. Any prior intracranial surgery
11. History of seizures
12. Immunocompromised
13. Has an active infection
14. Has a CSF drainage system or an active CSF leak
15. Requires diathermy, electroconvulsive therapy (ECT), or transcranial magnetic stimulation (TMS) to treat a chronic condition
16. Has an implanted electronic device such as a neurostimulator, cardiac pacemaker/defibrillator or medication pump, or presence of any head or neck metallic foreign bodies
17. Allergies or known hypersensitivity to materials in the Blackrock NeuroPort Array (i.e. silicone, titanium) or the PMT Subdural Cortical Electrode (silicone, platinum iridium, nichrome)
