Transcranial Alternating Current Stimulation in Post Stroke Aphasia Therapy

Transcranial Alternating Current Stimulation in Post Stroke Aphasia Therapy. A Pilot Study

This study aims to investigate the efficacy of transcranial alternating current stimulation (tACS) combined with linguistic training for patients with chronic post-stroke aphasia. Thirteen patients will participate in a randomized crossover clinical trial. Their naming ability will be assessed before and after two-weeks of therapy (with 16 days of washout) supported by either 75Hz tACS or sham stimulation. The stimulated cortical area will be selected individually based on the results of functional magnetic resonance imaging.

Aphasia remains one of the most challenging long-term disabilities after stroke. Neuromodulation methods, such as transcranial electrical stimulation, may induce synaptic neuroplasticity processes and facilitate language restoration. Specifically, transcranial alternating current stimulation (tACS) may influence intrinsic cortical oscillations and GABA(A) inhibition.

This randomized, triple-blind, within-subject crossover pilot study aims to evaluate the feasibility and efficacy of tACS as an adjunct technique in the therapy of adults with chronic post-stroke aphasia.

Participants (>6 months post-stroke) will undergo 20 therapeutic sessions consisting of language training (with a focus on naming ability) combined with 75 Hz tACS over selected cortical areas. Stimulation targets will be identified individually prior to the first intervention session using functional magnetic resonance imaging (fMRI) during a naming task, selecting regions with the highest BOLD signal.

Participants will receive 10 sessions of active tACS and 10 sessions of sham stimulation in randomized order. Each intervention phase will last 2 weeks, resulting a total of 4 weeks of intervention. A 16-day washout period between the two intervention phases will be applied. The language training will include the vanishing cues method and a visual speech perception segment component to support language improvement and maintain a high level of participant motivation.

The primary outcome measure will be naming accuracy, assessed as the percentage of correctly named items in a picture-naming task (trained items), measured at three time points: immediately after completion of the intervention (last session), at 2-week, and 6-week follow-up.

Inclusion Criteria:

• presence of aphasia (Broca's or mixed)
• first ever stroke with one major lesion in left hemisphere
• chronic stage (at least 6 months since onset)
• right handedness
• capability to give an informed consent
• Native Polish speaker
• 5-80% correct responses in the first naming task

Exclusion Criteria:

• history of neurosurgical interventions
• history of other neurological or psychiatric conditions (including dementia, head trauma, alcohol abuse etc.)
• reports of seizures during last 36 months
• serious vision disorders
• medications increasing risk of seizures or influencing neuroplasticity
• electrically, magnetically or mechanically activated implants or other systems sensitive to electricity in the body
• history of language and/or speech disorders or intellectual disability in childhood
• bilingualism
• pregnancy
• claustrophobia