• Subjects must have limited or no ability to use one or both hands due to cervical spinal cord injury, brainstem stroke, brachial plexus injury, above-elbow amputation, or spinal stroke. Individuals with intact limbs must have less than grade 2 strength in finger flexor and abduction on the contralateral side to the implant and a t-score \<35 on the PROMIS Upper Extremity Short Form. The non-functional hand(s) may be involved passively in functional tasks; for example, pushing an object or passively grasping an object placed into the hand. However, the participant must report that they have no functional use of their hand(s).

• Subjects must report that they are unable to perform functional activities with the hand contralateral to implantation.

• Subjects must be over 1 year post-injury at time of implantation. In addition, subject must report no worsening in neurologic status (strength, sensation) for the previous 6 months.

• Subjects must be between the ages of 22-70 years old at the time of enrollment and completion of the study. Participants outside this age range may be at an increased surgical risk and increased risk of fatigue during BMI training.

• Subjects must live within 2 hours of the research site during the study or be willing to travel to the research site at least once per week for BMI training.

• If subjects do not live in the area, they are expected to stay somewhere within 2 hours of the research site for at least 18 months after enrollment.

• Subjects must be able to communicate with the investigators in English because of the need to follow the instructions of the study team.

• Subjects must show an understanding of the study goals and have the ability to follow simple directions as judged by the investigators

• Subjects must have results that are within normal limits on neuropsychological and psychosocial assessment; psychosocial health and support will be assessed by interview with the psychologist.

⁃ Subjects must be able to activate distinct cortical areas during imagined or attempted movement tasks (i.e. hand movement and speaking or moving the mouth); this will be evaluated with functional magnetic resonance imaging (fMRI) as part of screening.

⁃ Subjects must have a stable psychosocial support and caregivers who are able to perform the necessary daily care of the participant's skin and pedestal site. This requires that the subject identify a caregiver and a backup who have been in place for greater than 6 months and are able to provide needed physical and psychosocial support. This will be assessed by the sponsor-investigator and study neurosurgeon.

⁃ Subjects must have a life expectancy greater than 18 months as assessed by the study investigator and neurosurgeon sub-investigator

⁃ Documentation of informed consent must be obtained from the participant or their legal representative.

⁃ Participants with transhumeral amputation must have been evaluated for a prosthesis, and if deemed appropriate, were fit with an optimized prosthesis. The prosthesis should be used/considered for the PROMIS evaluation.