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

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)