Brain Stimulation Paired With Structured Language Learning in Adults

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.

Inclusion criteria

• Adults aged 18 years or older
• Able to understand the consent materials and the informed consent process in English, or in another language for which an IRB-approved consent form is available
• Willing and able to participate in structured language-learning activities for the duration of the intervention period
• Able to provide written informed consent

Exclusion criteria

• History of epilepsy or any seizure disorder
• Active skin disease, open wounds, or significant skin irritation at electrode contact sites
• Implanted electronic medical devices where stimulation would be contraindicated per device manufacturer guidance or investigator judgment after individual risk assessment
• Significant cognitive impairment that would interfere with informed consent or study participation
• Any other condition that, in the investigator's judgment, would compromise participant safety or the integrity of the study data