Effects of Transcranial Direct Current Stimulation in Post-stroke Aphasia

Transcranial Direct Current Stimulation in Acute and Chronic Post-stroke Aphasia

This study aims to determine whether transcranial direct current stimulation (tDCS) paired with speech-language therapy is more beneficial than speech-language therapy alone in acute and chronic 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