Grasping Function After Spinal Cord Injury

Grasping behaviors, which are essential for daily-life functions, are largely impaired in
individuals with cervical spinal cord injury (SCI). Although rehabilitative interventions
have shown success in improving the ability to grasp following injury their overall effects
remain limited. The goals of this proposal are to examine the contribution of physiological
pathways to the control of grasping behaviors after cervical SCI, and to maximize the
recovery of grasping by using tailored non-invasive stimulation protocols with motor
training. The investigators propose to study two basic grasping behaviors: a precision grip
and a power grip. These behaviors are crucial because they provide the basis for a number
human prehensile manipulations and are also necessary skills for eating, writing, dressing,
and many other functions. Thus, the study results may have a direct impact on the quality of
life for Veterans and their caregivers by enhancing their independence and level of care.

In Aim 1, the investigators will investigate the contribution of corticospinal and brainstem
pathways to the control of hand muscles involved in precision and power grip after cervical
SCI. Transcranial magnetic stimulation (TMS) will be used to examine transmission in
corticospinal and intracortical pathways targeting finger muscles and an acoustic startle
stimulus with and without TMS will be used to examine the contribution from brainstem
pathways. In Aim 2, the investigators propose to enhance the recovery of grasping by using
novel tailored protocols of non-invasive repetitive TMS targeting late indirect (I)
descending volleys (iTMS) and an acoustic startle stimuli. iTMS and startle will be used
during precision and power grip movements in a task-dependent manner to induce cortical and
subcortical plasticity and enhance voluntary output of hand muscles. Later, iTMS and startle
will be applied in a task-dependent manner during a motor training task that involves
precision and power grip. These unique approaches aim at promoting neuroplasticity during
functionally relevant grasping movements has not been used before.

Inclusion Criteria:

Participants who are unimpaired healthy controls:

- Male and females between ages 18-85 years

- Right handed

- Able to complete precision grips with both hands

- Able to complete full wrist flexion-extension bilaterally

- Able to walk unassisted

- Able to complete full ankle flexion-extension bilaterally

Participants who have had a spinal cord injury:

- Male and females between ages 18-85 years

- SCI ( 2 months of injury)

- Spinal Cord injury at or above L5

- The ability to produce a visible precision grip force with one hand

- Able to perform some small wrist flexion and extension

- The ability to perform a small visible contraction with dorsiflexion and hip flexor
muscles

- No subjects will be excluded based on their race, religion, ethnicity, gender or HIV
status.

- ASIA A,B,C, or D

Exclusion Criteria:

Exclusion criteria for enrollment For SCI and Healthy Control Subjects (4-8 exclusion for
non-invasive brain stimulation only):

- Uncontrolled medical problems including pulmonary, cardiovascular or orthopedic
disease

- Any debilitating disease prior to the SCI that caused exercise intolerance

- Premorbid, ongoing major depression or psychosis, altered cognitive status

- History of head injury or stroke

- Metal plate in skull

- History of seizures

- Receiving drugs acting primarily on the central nervous system, which lower the
seizure threshold (see appendix 2)

- Pregnant females

- Ongoing cord compression or a syrinx in the spinal cord or who suffer from a spinal
cord disease such as spinal stenosis, spina bifida, MS, or herniated disk

- Individuals with scalp shrapnel, cochlear implants, or aneurysm clips.