Brain Stimulation Paired With Structured Language Learning in Adults

Overview

This study investigates whether transcranial electrical stimulation (tES) delivered during structured language-learning sessions affects the rate and quality of second-language acquisition in adults. Adults who are learning or planning to learn a new language are randomly assigned in equal numbers to receive either active stimulation or sham (placebo) stimulation while completing structured language-learning content. Participants wear a non-invasive transcranial electrical stimulation headset that delivers a low-level electrical current through electrodes resting on the scalp, targeting cortical regions associated with language. Sessions typically last 20 to 30 minutes and may be completed at home or in person at a participating language program. Language proficiency is measured with a standardized assessment before and after the intervention period, with additional app-derived performance metrics and participant-reported measures collected throughout. A follow-up assessment may be conducted up to 12 months after the intervention ends to evaluate whether any observed effects persist. In this study the device is applied as a learning aid in healthy adults. It is not used to diagnose, treat, cure, or prevent any disease.

The study is a prospective, randomized, double-blind, sham-controlled investigation. Participants are randomized 1:1 to active or sham stimulation, with stratification by site or cohort as applicable. Neither participants nor the research team conducting outcome assessments are aware of assignment during data collection. Stimulation assignment is held by the Sub-Investigator and is not disclosed to the Principal Investigator until all outcome data are collected and locked and primary analyses are finalized. Sessions may be delivered by decentralized at-home administration, on-site administration at partner language programs and educational institutions, or a hybrid of the two. The protocol declares a bounded parameter envelope within which specific stimulation parameters, learning content, partner sites, and assessment instruments may be selected per cohort without protocol amendment. All parameters operate within the LOTES-2023 limited-output standard for transcranial electrical stimulation devices. For adult participants the declared envelope permits 0 to 4 mA average absolute current, a maximum current density of 2 mA/cm2 at the electrode contact area, and a maximum session duration of 60 minutes subject to a 6000 mC total-charge-per-session ceiling. Anticipated session durations are 20 to 30 minutes. Any modality within the transcranial electrical stimulation family may be used, including tDCS, tACS, tRNS, and tPCS. Intended cortical targets are the left perisylvian region and adjacent association cortex, including Broca's area and Wernicke's area. Montages use standard cephalic or extracephalic placements with at least one electrode positioned on the head. Because assessment instruments and specific stimulation parameters are selected per cohort within the declared envelope, each enrollment cohort has a cohort-specific Statistical Analysis Plan finalized and locked prior to unblinding of that cohort.