Transcranial Alternating Current Stimulation (tACS) for the Recovery of Phonological Short-Term Memory in Patients With Aphasia After Stroke

Study Overview
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Brief Summary
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This study will assess the effects of transcranial alternating current stimulation (tACS) on language recovery after stroke.

Detailed Description
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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. 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, potentially with 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 stroke survivors with aphasia. TACS differs from trancranial direct current stimulation (tDCS), a widely used brain stimulation paradigm, in that sinusoidal or alternating currents are delivered rather than direct currents. TACS is shown to manipulate ongoing oscillatory brain activity and also to modulate synchronization (or connectivity) between targeted brain areas. This feature of tACS is quite attractive, given the new body of evidence suggesting that language impairments stem from diminished brain connectivity and ensuing disruptions in the language network due to stroke. The study will employ high-definition tACS (HD-tACS) in a parallel, double-blinded, sham-controlled design combined with language therapy targeting phonological short-term memory (STM) function in stroke survivors with aphasia. Magnetoencephalography (MEG) and fMRI BOLD data collection will occur to determine tACS parameters and to evaluate stimulation-induced neural changes, respectively. The investigators plan to recruit 120 stroke survivors with aphasia in a 2-group tACS study design.

Official Title
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TACS for the Recovery of Phonological STM After Stroke

Conditions
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Stroke, Aphasia

Intervention / Treatment
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* Device: HD-tACS
* Device: Sham HD-tACS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Diagnosed with left hemisphere stroke/aphasia Consent date >= 1 month after stroke onset 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 Contraindications to MRI or tACS, e.g. patients with metallic implants, and/or history of skull fractures, pregnancy, skin diseases History of ongoing or unmanaged seizures History of dyslexia or other developmental learning disabilities

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High Definition tACS with Short-term Memory Focused Speech Therapy<br>High-Definition-tACS will be delivered via a battery operated alternating current stimulator (Soterix) using two 3x1 center-surround montages.The current is turned on and increased in a ramplike fashion over approximately 30 seconds. Participants will undergo tACS stimulation for 20-minutes with 2 milliampere (mA) peak-to-peak intensity. Stimulation will be maintained no longer than 20 minutes. This will be paired with short-term memory focused speech therapy. | Device: HD-tACS<br>* High definition tACS will be applied during speech therapy.<br>|
| Sham Comparator: Sham-High Definition tACS with Short-term Memory Focused Speech Therapy<br>High-Definition-tACS will be delivered via a battery operated alternating current stimulator (Soterix) using two 3x1 center-surround montages. The current is turned on and increased in a ramplike fashion for 10 to 30 seconds and then ramped down. In this way, the participants experience the same initial sensations (mild tingling) as the active tACS groups. This will be paired with short-term memory focused speech therapy. | Device: Sham HD-tACS<br>* Sham high definition tACS will be applied during speech therapy.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Accuracy on a phonological STM task | Accuracy changes in a delayed sample-to-match task assessing phonological STM after tACS. | Upon the completion of therapy cycle (a cycle consists of 10 intervention days) and 10 weeks post | 
| fMRI measures of language network activation after tACS | Activation in the language network regions involved in phonological STM will be assessed before and after tACS | Upon the completion of therapy cycle (a cycle consists of 10 intervention days) and 10 weeks post | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Functional Communication Outcome | Improvements in using language in daily life or functional communication as assessed by patient reported measure of Communication Effectiveness Index (CETI) | Upon the completion of therapy cycle (a cycle consists of 10 intervention days) and 10 weeks post |