Transcranial Direct Current Stimulation (tDCS) and Task-Specific Practice for Post-stroke Neglect

Examining the Effects of Transcranial Direct Current Stimulation and Task-specific Practice on Cortical Modulation Among Individuals With Unilateral Spatial Neglect Post Stroke

The purpose of this study is to test the effects of three different rehabilitation training sessions that combine non-invasive brain stimulation (transcranial direct current stimulation, tDCS) with arm rehabilitation training (repetitive task-specific practice, RTP) for individuals with unilateral spatial neglect following stroke. This study is designed to determine the effects of tDCS + RTP on the excitability in the brain, attention to the affected side, and arm movement ability.

Unilateral neglect (neglect) is common after stroke and is characterized by an inattention to one side of the body or environment. There is growing evidence that disconnections to fronto-parietal neural networks in the lesioned hemisphere not only cause neglect, but also cause these same networks to be hyperexcited in the non-lesioned hemisphere. Individuals with neglect typically experience motor impairments also since the regions of the brain that control attention also control movement.

Transcranial direct current stimulation (tDCS) when paired with repetitive task-specific practice (RTP) has the potential to modulate cortical activity (fronto-parietal networks) and facilitate motor and attentional recovery for individuals with neglect since tDCS can modulate the excitability of targeted cortical regions. tDCS is a form on non-invasive brain stimulation and RTP is the gold standard post-stroke motor recovery intervention.

It is particularly important investigators examine the effect of RTP + tDCS on cortical modulation in order to understand the underlying mechanism of the intervention and determine whether RTP+ tDCS (parietal or primary motor cortex [M1]) promotes greater neural modulation than RTP alone. Traditionally, electrodes are placed on M1 to facilitate motor recovery and on the parietal lobe to facilitate attentional recovery, however this intervention is designed to target each of these impairments (motor, attention) and enhance cortical modulation of fronto-parietal networks. Therefore, investigators must also determine the optimal electrode montage and placement for pairing tDCS with RTP for individuals with neglect.

The purpose of the proposed pilot project is to examine the effects of transcranial direct current stimulation (tDCS) paired with repetitive task-specific practice (RTP) on modulation of fronto-parietal network connectivity (measured by transcranial magnetic stimulation [TMS]), motor impairment (measured with kinematic assessment), and attentional impairment (measured with Behavioral Inattention Test) among individuals with unilateral neglect and hemiparesis post stroke. This three day cross-over design study will examine the optimal electrode placement and montage using 3 conditions: (1) tDCS to parietal lobe + RTP (2) tDCS to primary motor cortex + RTP (3) sham tDCS + RTP.

Inclusion Criteria:

• Unilateral hemispheric ischemic stroke or hemorrhagic subcortical stroke ≥3 months post stroke (lesion type and location to be confirmed with MRI)
• Neglect (Virtual Reality Lateralized Attention Test score <18)
• Upper extremity Fugl-Meyer score between 20-56/60
• Inducible motor evoked potential (MEP) of the abductor pollicis brevis (APB) on the affected side using transcranial magnetic stimulation (TMS)
• ≥18 years old

Exclusion Criteria:

• History of cortical hemorrhagic stroke
• Severe spasticity (Modified Ashworth Scale score ≥3) in paretic upper extremity
• Severe aphasia limiting participant's ability to follow 2 step directions
• History of seizures
• History of brain tumor
• History of skull defect
• Hardware in skull or spine (e.g. coils, clips)
• Implantable medical device (e.g. pacemaker)
• Metal in body that is not compatible with MRI
• Pregnant (women of child bearing age will be asked if they are pregnant or could possibly be pregnant)
• Unable to travel to Upper Extremity Motor Function Laboratory at the Center for Rehabilitation Research in Neurological Conditions
• Currently enrolled in another study using transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS)