Stimulating Language in Subacute StrokE

The investigators will study the effects of transcranial direct current (tDCS) stimulation during language therapy for naming in individuals with aphasia in the acute and subacute post stroke period. Naming difficulties are a persistent and common symptom in aphasia after left-hemisphere (LH) stroke. Behavioral therapy (speech and language therapy; SALT) is the mainstay treatment for post stroke aphasia. Transcranial direct cortical stimulation (tDCS) is a promising adjunct to traditional SALT. tDCS is a safe, non-invasive, non-painful electrical stimulation of the brain which modulates cortical excitability by application of weak electrical currents in the form of direct current brain polarization. It is usually administered via saline-soaked surface sponge electrodes attached to the scalp and connected to a direct current stimulator with low intensities. Most studies are conducted in the chronic phase after stroke. Because neuroplasticity is greatest early after stroke, there is reason to believe tDCS might be most effective in the acute-subacute period. However, only two studies have evaluated tDCS paired with language therapy in group studies of acute to subacute aphasic stroke patients and only one of these was sham-controlled. Furthermore, no studies (of which we are aware) have combined tDCS with therapy to facilitate naming in post stroke aphasia, as shown to be effective in studies of chronic stroke. In this study, the investigators will evaluate whether tDCS combined with SALT improves naming in individuals with aphasia in the acute and subacute post stroke period, more than SALT alone in a randomized, double-blind, sham-controlled trial. The investigators will test the hypothesis that anodal tDCS (A-tDCS) over a targeted region and computer-delivered SALT is associated with greater gains in accuracy in naming pictures, compared to sham combined with the same computer-delivered SALT in post stroke aphasia.

After informed consent is received, a neurological examination will be performed and multiple screening assessments will be conducted including a tDCS and MRI safety screening. If the participant passes the initial screening portion, speech and language diagnostic testing will be conducted during the same visit (Visit 1). During the next visit (Visit 2), participants will undergo a second baseline assessment of naming ability and assessment of connected speech. On that visit, participants who have no contraindication for MRI (and agree to have MRI) will be randomized to (1) functional magnetic resonance (fMRI) electrode placement or (2) structural electrode placement. All participants who have no contraindication will have structural and resting state functional connectivity MRI (rsfcMRI). Those randomized to fMRI electrode placement will also participate in the naming paradigm during the MRI. The third visit will include electrode positioning and tDCS treatment administration. Participants will receive 15 sessions (Visits 3-17) of tDCS + SALT administration. At the beginning of Visit 3, eligible participants will be randomized to receive either A-tDCS (1 milli amp (mA)) or sham-tDCS (placebo) for 15 sessions (20-minutes per each 45-minute behavioral treatment session) over the course of three weeks. A computer-delivered naming treatment will be coupled with the stimulation. The computer-delivered treatment task will be 45-minutes in total length, so that it will commence at the same time as the tDCS administration and continue for another 25-minutes after the tDCS has ceased. To assess cardiovascular arousal, blood pressure and heart rate will be measured before and after each session. Additionally, discomfort ratings will be recorded following the end of each session using the Wong-Baker FACES Pain Rating Scale and a weekly neurological exam will be administered by a neurologist. Neither the participant nor the clinician monitoring and setting up the treatment will have knowledge of the treatment condition (A-tDCS versus sham). Utilizing a computerized picture naming assessment, all participants will be assessed at several different time points throughout the experiment: twice immediately before and twice the week immediately following the fifteenth and final treatment session; twice at five weeks follow-up after the end of treatment; and twice at 20 weeks after the end of treatment. Participants who agree to participate in the MRI portion of the study (and have none of the additional exclusion criteria for MRI) will have structural and rsfcMRI at Visit 2, following the 15th treatment session (Week 1 after the end of treatment), and at 5 weeks after the end of treatment.

Eligibility Criteria:
Inclusion Criteria:

* Participant Inclusion Criteria

Participants must satisfy the following inclusion criteria to be considered eligible for entry into this study:

1. Participants must have sustained an acute ischemic left hemisphere stroke.
2. Participants must be fluent speakers of English by self-report.
3. Participants must be capable of giving informed consent or indicating another to provide informed consent.
4. Participants must be age 18 or older.
5. Participants must be premorbidly right handed.
6. Participants must be within 3 months of onset of stroke.
7. Participants must have an aphasia diagnosis as confirmed by the Western Aphasia Battery-Revised.
8. Participants must achieve at least 65% accuracy on screening task (comparable to treatment task) on 1 of 3 attempts

Exclusion Criteria:

* Participant Exclusion Criteria

Participants with any of the following characteristics will not be eligible for entry into this study:

1. Previous neurological or psychiatric disease, including previous symptomatic stroke.
2. Seizures during the previous 12 months.
3. Uncorrected visual loss or hearing loss by self-report.
4. Use of medications that lower the seizure threshold (e.g., methylphenidate, amphetamine salts).
5. Use of N-methyl-D-aspartate (NMDA) antagonists (e.g., memantine).
6. History of brain surgery or any metal in the head.
7. Scalp sensitivity (per participant report).