Transcranial Alternating Current Stimulation (tACS) in Aphasia

May 21, 2025 updated by: Priyanka Shah-Basak, PhD, Medical College of Wisconsin

Exogenous Tuning of Neural Oscillations as a Mode of Treatment in Post-stroke Aphasia

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

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

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.

The current study will investigate the efficacy of high-definition tACS (HD-tACS) to help restore neural oscillatory activity in aphasia. TACS differs from widely used transcranial direct current stimulation (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 and by the involvement of specific frequencies during a verbal short-term memory task. By exogenously tuning the neural oscillations with tACS, the investigators hope to up-regulate communication across regions within the language network and other connected areas to improve outcomes. 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 frequencies ranging from theta to low-gamma (4-40 Hz) combined with language tasks. Magnetoencephalography (MEG) or electroencephalography (EEG) will be used to determine tACS frequencies and to evaluate behavioral and neurophysiological changes in response to tACS. Investigators plan to recruit 200 participants: 100 stroke survivors with aphasia and 100 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 or sham-tACS over 3-4 sessions. 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. MEG will be collected prior to tACS sessions during a language task to determine tACS frequency. EEG may 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.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Wisconsin
      • Milwaukee, Wisconsin, United States, 53226
        • Recruiting
        • Medical College of Wisconsin
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

14 years to 81 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

Healthy Controls

  • 18 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
  • Right-handed
  • Fluent in English
  • 18 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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: tACS 10 Hz low frequency
All participants in a within-subject design will receive high-Definition-tACS, delivered via a battery operated alternating current stimulator (Soterix) using two 3x1 center-surround montages. Targets of stimulation will be localized based on the 10-10 International EEG system with center electrodes placed at a frontal and a temporoparietal site. The current is turned on and increased in a ramplike fashion over approximately 30 seconds. Participants will undergo tACS with frequencies ranging from 4-40Hz for 20-minutes with 2 milliampere (mA) peak-to-peak intensity. For sham stimulation, tACS is turned off after the first 30 seconds.
Device: tACS
Active or Sham tACS will be applied.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
tACS changes in language performance verbal STM tasks
Time Frame: Changes monitored over pre, during and immediately after 20 minutes of tACS
Improvement on verbal STM performance as determined by increases in span, accuracy or decreases in reaction time is expected with active tACS.
Changes monitored over pre, during and immediately after 20 minutes of tACS
tACS-dependent neurophysiological changes
Time Frame: Changes monitored over pre and immediately after 20 minutes of tACS
Concomitant frequency-specific EEG changes in spectral power and phase synchronization are expected.
Changes monitored over pre and immediately after 20 minutes of tACS

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Individual differences in tACS responsiveness
Time Frame: Based on immediate changes monitored after 20 minutes of tACS
tACS responsiveness depending on language impairment types, stroke lesion and language lateralization characteristics will be explored.
Based on immediate changes monitored after 20 minutes of tACS

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Medical College of Wisconsin

Investigators

  • Principal Investigator: Priyanka Shah-Basak, PhD, Medical College of Wisconsin

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 4, 2020

Primary Completion (Estimated)

January 1, 2030

Study Completion (Estimated)

December 1, 2030

Study Registration Dates

First Submitted

May 1, 2020

First Submitted That Met QC Criteria

May 1, 2020

First Posted (Actual)

May 5, 2020

Study Record Updates

Last Update Posted (Actual)

May 25, 2025

Last Update Submitted That Met QC Criteria

May 21, 2025

Last Verified

May 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 36878

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

Yes

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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