Neurostimulation for the Treatment of Post-Stroke Aphasia

There are about 15 million strokes worldwide each year. Of this group, about 30% suffer from aphasia. Aphasia is a speech-language disorder associated with exceptional difficulty performing daily communication activities. If no improvement is observed within the first months after the stroke, a complete recovery is unlikely, and the therapy can last for years. Up to date, speech and language therapy is a standard of care for post-stroke aphasia, however the process is long and demanding. In the past, several clinical trials aimed to verify the efficacy of language training paired with transcranial direct current stimulation (tDCS), however recent meta-analysis indicates only possible effectiveness (Level C evidence) of anodal tDCS in chronic post-stroke aphasia. To boost the effects of aphasia rehabilitation, effective brain stimulation protocol still needs to be developed. Transcranial alternating current stimulation (tACS) can be an interesting alternative to tDCS, as it is able to influence cortical excitability and activity. Stimulation within high gamma oscillations (60-500Hz) might allow for better speech-language processing, as this band is considered to be the cognitive index of linguistic processes. Moreover, a short period of 75Hz tACS over the motor cortex suggested the positive impact of high-gamma tACS on brain plasticity. The aim of this RCT is to determine whether 75Hz transcranial alternating current stimulation (tACS) paired with therapeutic linguistic tasks is an effective form of therapy for post-stroke aphasia, measured as an ability to name trained items at 12 weeks follow-up.