Transcranial Alternating Current Stimulation (tACS) in Aphasia

  • End date
    Jan 22, 2025
  • participants needed
  • sponsor
    Medical College of Wisconsin
Updated on 7 October 2022
Accepts healthy volunteers


This study will assess the effects of transcranial alternating current stimulation (tACS) on language recovery after stroke as well as healthy language functions.


Aphasia is a debilitating disorder, typically resulting from damage to the left hemisphere, that can impair a range of communication abilities, including language production and comprehension, reading, and writing. Approximately 180,000 new cases of aphasia are identified per year, and approximately 1 million or 1 in 250 are living with aphasia in the United States (NIH-NIDCD, 2015). Treatments are limited and provide modest benefits at best. The current emphasis in aphasia rehabilitation is to formulate intensive speech and language therapies and augment therapeutic benefits by providing brain stimulation concurrent with therapies. Transcranial direct current stimulation (tDCS) is one of the most widely used such technique. While tDCS has had relative success in chronic aphasia (>6 months after stroke), it has not been efficacious during subacute stages (<3 months after stroke). But enhancing language recovery early after stroke is desirable because of its potential impact on long-term language outcomes and quality-of-life.

The current study will investigate the efficacy of high-definition tACS (HD-tACS) to help restore neural oscillatory activity in aphasia. TACS differs from tDCS in that sinusoidal, alternating currents are delivered rather than constant currents. TACS can manipulate the ongoing oscillatory neuronal activity and potentially increase functional synchronization (or connectivity) between targeted areas. This feature of tACS is quite attractive, given the new body of evidence suggesting that language impairments stem from diminished functional connectivity and disruptions in the language network due to stroke. The selection of tACS frequencies in this study is guided by our preliminary work examining pathological neural oscillations found near stroke-lesioned areas (or perilesional) in aphasia. By exogenously tuning the perilesional oscillations with tACS, the investigators hope to up-regulate communication across these areas and other connected areas to improve language outcome. If successful, tACS will be a powerful and novel treatment approach with reverberating positive impact on long-term recovery.

The study will employ HD-tACS in a within-subject and sham-controlled design, using two frequencies (alpha/10 Hz and low-gamma/40 Hz) combined with language tasks and electroencephalography (EEG) to evaluate subsequent behavioral and neurophysiological changes. Investigators plan to recruit 50 participants: 25 stroke survivors with aphasia at lease 1 month after stroke, and 25 healthy controls.

Participants will complete language testing that covers a broad range of language functions, medical history, and MRI. Eligible participants will undergo active tACS at 10 Hz or 40 Hz, or sham-tACS. All participants will receive all three stimulation types during separate visits. The tACS administrator and participants will be blinded to the stimulation type. The order of stimulation type will be counterbalanced across participants. Washout period between visits will be at least 48 hours to minimize potential carryover effects. EEG will be acquired before and after tACS during periods of rest (resting-state) and during language tasks. Participants will complete a questionnaire at the end of stimulation visits to assess potential side effects of tACS. Total time enrolled in the study is expected to be 2-3 weeks, which may be longer depending on participant's availability.

Condition Aphasia, Stroke
Treatment tACS 10-Hz, tACS 40-Hz, tACS sham
Clinical Study IdentifierNCT04375722
SponsorMedical College of Wisconsin
Last Modified on7 October 2022


Yes No Not Sure

Inclusion Criteria

Healthy Controls
years of age or older
Fluent in English
No history of neurological or psychiatric disorders
Stroke Patients
Diagnosed with post-stroke aphasia by referring physician/neuropsychologist
Consent date >=1 months after stroke onset
Fluent in English
years of age or older

Exclusion Criteria

Severe cognitive, auditory or visual impairments that would preclude cognitive and language testing
Presence of major untreated or unstable psychiatric disease
A chronic medical condition that is not treated or is unstable
The presence of cardiac stimulators or pacemakers
Any metal implants in the skull
Contraindications to MRI or tACS
History of seizures
History of dyslexia or other developmental learning disabilities
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