Objective:

To determine the efficacy of a noninvasive neuromodulation technique, called transcranial alternating current stimulation (tACS), in facilitating language abilities. 

Background:

Aphasia, an acquired language impairment following brain injury, is the most common focal cognitive disorder caused by stroke, affecting ~30% of stroke survivors. Speech-language therapy is the current mainstay of aphasia treatment, but residual language impairments persist, limiting quality of life. Transcranial electrical stimulation has garnered considerable attention as an alternative, noninvasive aphasia treatment. Emerging evidence suggests that tACS can manipulate and enhance endogenous cortical oscillations in a functionally specific way, inaccessible by direct current stimulation (tDCS). This ongoing study is investigating if tACS delivered in the alpha frequency band improves word retrieval abilities in healthy older adults by enhancing language network functional connectivity. 

Design/Methods:

Across two sessions, participants are randomized to receive placebo (sham) or active tACS to the frontotemporal cortex via a 5-electrode montage at a 4mA peak-to-peak intensity. Individual peak alpha frequency (8-13Hz) is identified during language task performance before tACS administration. Resting-state EEG is collected before, mid-way, and after tACS. During and immediately following stimulation, participants perform three naming tasks that involve retrieving words under two conditions: high competition (many possible responses) and low competition (single correct response). Of interest is the size of this interference effect (high minus low competition) following alpha vs. sham tACS. 

Results:

Conclusions:

Overall, this work will inform more precise noninvasive care compared to tDCS, laying the groundwork for employing tACS as an adjuvant to speech-language therapy.