Effects of Transcranial Direct Current Stimulation in Post-stroke Aphasia

This study aims to determine whether behavioral word-retrieval therapy coupled with anodal
tDCS will improve the fluency and name retrieval performance of participants with post-stroke
aphasia more efficiently and for greater duration than language therapy alone (i.e. in the
sham condition).

tDCS neuronal targets will be selected in this order:

1. left posterior superior-middle temporal gyrus (an area critical for word retrieval and
word comprehension),

2. left posterior frontal areas found to be responsible for lexical selection if the first
area is infarcted, or

3. right cerebellum (important for learning, and consistently activated in naming task) if
both of the other areas are infarcted.

The same areas will be stimulated during the first tDCS and sham periods. If the participant
returns for a second period of tDCS and sham with language therapy, the right cerebellum will
be stimulated (if it was the only uninfarcted target area investigators will stimulate this
area again). For cerebellar stimulation, either anodal or cathodal will be used as studies
show that anodal or cathodal stimulation has an effect on cognitive functions.

Inclusion Criteria:

- Clinically diagnosed with with post-stroke aphasia and word-retrieval deficits

- Premorbid speakers of English

- Diagnosis will be based on neuropsychological testing, language testing (most commonly
the Western Aphasia Battery), MRI and clinical assessment

- Stroke size: any l

- Location: Left hemisphere strokes only from any etiology.

- Time since stroke onset: 1 day to 20 years.

Exclusion Criteria:

- uncorrected visual or hearing impairment by self report

- other premorbid neurological disorder affecting the brain

- any other language-based learning disorder or other neurodegenerative disorder such as
Alzheimer's Disease or Primary Progressive Aphasia

- premorbidly diagnosed with a developmental language disorder

- Pregnant women will also be excluded