Conditioning Neural Circuits to Improve Upper Extremity Function

Non-invasive brain stimulation has gained increasing popularity and research support over the past several years. Recent research indicates that it might have benefits for improving hand function in people with spinal cord injury. The purpose of this study is to evaluate the effects of a type of non-invasive brain stimulation, known as tDCS, on hand function.

Transcranial direct current stimulation (tDCS) is a technique in which low intensity electrical current is applied over the skull in order to excite the underlying brain tissue. It has been studied in many populations (stroke, spinal cord injury, learning disability, migraine, memory) and may be a useful counterpart to traditional rehabilitation of neurological injuries. Preliminary studies from members of the investigator's lab group have indicated beneficial, single-session effects of tDCS on hand function in people with spinal cord injury. Longer-term, multi-session trials are now warranted. Another approach that has research support for augmenting the effects of hand function training is peripheral nerve somatosensory stimulation (PNSS). Unlike tDCS, which excites brain tissue directly, PNSS excites the brain via an indirect approach. Members of the investigators' lab have found the combination of PNSS and fine motor training to be more effective in improving hand function than either intervention alone. Multi-session trials of PNSS have been conducted; however it has not yet been compared with another clinically accessible adjunctive therapy, like tDCS, in a multi-session trial. The investigators plan to study the comparative effects of tDCS and hand function training to PNSS and hand function training and hand function training alone in people with neck-level spinal cord injuries. People with both acute/subacute (<6 months post-injury) and chronic (>1 year post-injury) injuries will be enrolled, in order to look at responses to tDCS at different stages of recovery. Before beginning training, participants will complete approximately three hours of testing of their arm/hand function and self-reported perception of their overall function. Participants will then be randomly assigned to receive either tDCS, PNSS, or sham tDCS in combination with personalized fine motor training. This training will take place 3 times/week, for a total of 3 hours of training/week, for 4 weeks. Fine motor training will be based on principles that have been shown to optimize neuroplasticity (changes in the brain and/or spinal cord), yet customized, in order to allow participants to work towards individualized goals. At the end of 4 weeks, participants will complete a three-hour post-test using the same measures as before to examine any changes in arm and hand function. Participants will be asked to return to Shepherd Center 4 - 6 weeks following the post-intervention assessment to complete the post-intervention assessment.

This group of individuals with tetraplegia will receive transcranial direct current stimulation (tDCS) over the hand area of their primary motor cortex (M1). Stimulation at 2mA will be applied for 20 minutes while subjects complete a total of 1 hour of functional task practice (FTP) per session. (Only 20 minutes of functional task practice be be performed with stimulation on). 3 sessions will be completed per week for 4 weeks.

This group of individuals with tetraplegia will receive peripheral nerve somatosensory stimulation (PNSS) to the median nerve of the primary hand being trained. Stimulation will be set to elicit a sensory - not motor - response. Stimulation will be performed concurrently with the entire functional task practice (FTP) session. 3 sessions will be completed per week for 4 weeks.

This group of individuals with tetraplegia will receive sham transcranial direct current stimulation (tDCS) over the hand area of their primary motor cortex (M1) alongside functional task practice. Stimulation will be briefly turned on at the beginning of FTP and again after 20 minutes of practice in order to create a sham effect and maintain blinding of the participants. 3 sessions will be completed per week for 4 weeks.

High-definition transcranial direct current stimulation is applied over the hand area of the primary motor cortex (M1). Parameters= 2mA for 20 minutes. Functional task practice will be completed concurrently with tDCS and for approximate 40 minutes after the stimulation stops.

Electrical stimulation will be applied to the median nerve of the primary hand being trained at parameters that elicit a sensory but not motor response (called "peripheral nerve somatosensory stimulation"). Stimulation parameters are 100Hz with a 250uS pulse width. Stimulation intensity will vary between 1-10mA per participant. Stimulation will be applied for 1 hour and functional task practice will be completed concurrent with the stimulation.

During sham transcranial direct current stimulation (tDCS), a sham tDCS device will be used along with functional task practice. The sham tDCS unit will be used for the first 20 minutes of FTP, followed by an additional 40 minutes of FTP.

Inclusion Criteria: Be 18-65 years of age Have a cervical (neurological level C1-C8) SCI that occurred either <6 months ago (subacute) or >1 year (chronic) prior to the time of enrollment For subjects with acute/subacute SCI: the injury must be a traumatic injury (i.e. not the result of illness or a condition within the body) Have ISNCSCI severity classification (A, B, C or D) Have self-reported limitations in arm and hand function in at least one upper limb (a GRASSP quantitative score of no more than 26/30 in the hand that is the focus of treatment) Have the ability to pick up objects with at least one hand without using assistive devices (a GRASSP quantitative score of at least 4/30 in the hand that is the focus of treatment) Have shoulder strength lift an arm up to chest level Have the ability to sit for at least one hour at a time (e.g. good skin integrity, stable blood pressure) For subjects with acute/subacute SCI: adequate time remaining in their treatment at Shepherd Center to allow 5 weeks of participation For subjects with chronic SCI: active hand function is required (see Pre-intervention assessment) reliable transportation in order to complete the intervention in its entirety Ability and willingness to consent and authorize use of personal health information Exclusion Criteria: Pacemaker or a metal implant in the head Current pregnancy Severe shoulder weakness, injury, or pain that contraindicates repetitive fine motor training Lower motor neuron damage (as documented in medical record, per participant report, or as noted by in-person screening) Severe hypersensitivity or pain of the arm/hand Severe contractures of the arm/hand that would limit participation in fine motor training Prior tendon or nerve transfer surgery Have a history of seizures Have a history of frequent or severe headaches

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