Brain Stimulation Enhance Post-stroke Walking Survivors and Healthy Adults

Recent studies showed that a non-invasive, low-intensity brain stimulation called transcranial direct current stimulation (tDCS) can effectively increase motor neuron excitability in the brain and therefore promotes functional recovery after stroke. Thus, the overall purpose of this research project is to examine the effect of brain stimulation on motor skill learning in stroke survivors.

The specific aims and hypotheses are:

Aim 1: To explore the trends of locomotor skill acquisition in stroke survivors after anodal tDCS (a-tDCS, real brain stimulation), stroke survivors after sham tDCS (s-tDCS), and stroke with no brain stimulation (control; CON). Hypothesis (Aim 1): Stroke participants who receives a-tDCS will show a faster rate of learning a locomotor task compared to stroke participants who receive s-tDCS and stroke participants with no brain stimulation.

Aim 2: To explore different trends of stimulation-induced improvements in learning capacity and neural activities between three groups: stroke group, healthy young group, and healthy older group. Hypothesis (Aim 2): Healthy young adults will have a greater degree of stimulation-induced improvements in learning capacity and neural excitation compared to older adults and stroke participants.

Aim 3: To explore the trends of functional improvements post a-tDCS in stroke survivors. Hypothesis (Aim 3): Stroke participants who receives a-tDCS will show a greater improvements in functional performances compared to stroke participants who receive s-tDCS and stroke participants with no brain stimulation.

Aim 4: To explore the accumulated, longitudinal trends of a four-week visuomotor stepping training in conjunction with brain stimulation on treadmill walking training and gait improvements for persons with chronic stroke. Hypothesis (Aim 4): Stroke participants who receives a-tDCS will show a greater degree of gait improvements compared to stroke participants who receive s-tDCS and stroke participants with no brain stimulation.

Eligibility Criteria:
Inclusion Criteria:

* Age between 21 and 90 years
* Medical history of a unilateral stroke occurring ≥ 6 months prior to enrollment
* MRI or CT evidence from the imaging report shown that the stroke involves the corticospinal tract
* Hemiparesis involving the lower extremity (Fugl-Meyer Lower Extremity Motor Test)
* No passive range of motion limitation in bilateral hips and knees
* Limitation of ankle passive range of motion to 10 degrees of dorsiflexion or less
* Visual acuity can be corrected by glasses or contact lens to 20/20
* Able to walk independently with/without assistant devices for 10 meters
* Able to maintain standing position without any assistance \>= 30 sec (Short Physical Performance Battery)
* Evaluation of cognitive status: Mini-mental status examination (MMSE) score ≥ 24

Exclusion Criteria:

* Pregnant women
* MRI or CT evidence of involvement of the basal ganglia or cerebellum, evidence of multiple lesions, or evidence of any other brain damage or tumors
* Have any metal implants, cardiac pacemakers, or history of seizures
* Ongoing orthopedic or other neuromuscular disorders that will restrict exercise training
* Any vestibular dysfunction or unstable angina
* Significant cognitive deficits (inability to follow a 2-step command) or severe receptive or global aphasia