The purpose of this study is to assess the changes in language processing of patients with chronic, post-stroke aphasia following the application of brain stimulation. The brain stimulation the investigators administer is called transcranial direct current stimulation (tDCS). It involves passing a weak electrical current through the brain between two electrodes in the form of damp sponges. One sponge will be placed over a specified area on the damaged left hemisphere, while the other sponge will be placed on the right scalp. Computer-controlled speech-language treatment will be administered during the application of tDCS.

Stroke is the leading cause of adult disability in the United States. Approximately one-third of all strokes result in acute language impairment (aphasia), with approximately one-fifth suffering from chronic aphasia. Unfortunately, the prognosis for moderate to severe chronic aphasia remains grim, as current behavioral treatment approaches usually offer only limited-to-modest benefit. Recent advancements in understanding the relationship between low current electrical brain stimulation and cortical plasticity suggest that the effect of behavioral aphasia treatment could possibly be enhanced using anodal transcranial direct current stimulation (A-tDCS). Indeed, we have shown how A-tDCS can significantly boost the effect of behavioral aphasia treatment. Based on these results as well as our other studies aimed at understanding how favorable brain plasticity correlates with positive treatment outcome in aphasia, we propose to conduct a Phase II clinical trial utilizing a futility design. Consistent with the goals of Program Announcement PAR-08-204 by the National Institute on Deafness and Other Communication Disorders (NIDCD), we plan to "evaluate whether there is sufficient evidence of short term improvement in humans to justify a phase III trial."

Inclusion Criteria:

1. Patients must be willing and able to give informed consent.
2. Patients must be willing and able to comply with study requirements.
3. Patients must be between 25- and 80-years of age.
4. Patients must be native English speakers.
5. Patients must be pre-morbidly right-handed.
6. Patients must have sustained a one-time ischemic stroke in the left-hemisphere.
7. Patients must be greater than 6-months post-stroke.
8. Patients must have an aphasia diagnosis as confirmed by the Western Aphasia Battery-Revised.
9. Patients must be MRI-compatible (e.g., no metal implants, not claustrophobic, etc.).
10. Patients must achieve at least 65% accuracy on naming task during screening -

Exclusion Criteria:

1. History of brain surgery
2. Seizures during the previous 12 months
3. Sensitive scalp (per patient report)
4. Able to overtly name more than an average of 140 out of 175 items during the pre-treatment picture naming test (Philadelphia Naming Test) during Visits 2 or 3.
5. Unable to overtly name at least an average of 5 out of 80 items during the pre-treatment functional magnetic resonance imaging (fMRI) sessions during Visits 2 or 3.

Non-serious adverse events were collected until immediate post treatment testing sessions (2 weeks), and serious adverse events were collected until end of study (24 weeks).