Non-invasive Repetitive Paraorbital Alternating Current Stimulation Therapy for Aphasia

Inclusion Criteria: * stroke * lesion age at least 6 months * aphasia with at least moderate severity according to Aachener Aphasia Test (AAT) * age between 40 and 75 * German-speaking (at a native speaking level) Exclusion Criteria: * cognitive or speech-language therapy during the 2-weeks stimulation course * intensive language training when exceeding 1 hour, 2 times a week during the 2-weeks stimulation course and the follow-up period (60 days after stimulation was completed) * additional neurological diseases, e.g. surgical brain tumor removal, untreated tumor disease, acute traumatic brain injury, and/or craniotomy * (severe) dysarthria * untreated hypertension exceeding 160/100 mmHg (patients with treated hypertension and blood pressure below 160/100 mmHg can be included) * increased risk of vascular thrombosis * epilepsy, photo sensitivity, acute focal findings (patients without focal findings or epileptiform discharges can be included when they had only a single seizure more than 10 years ago) * dementias and neurodegenerative diseases * significant psychiatric disturbances, e.g. schizophrenia * major attention and/or memory deficits * major hearing loss * patients with uncorrected visual deficits * severe global aphasia * modality-specific disorders (pure speech apraxia, pure alexia, pure agraphia) * electric or electronic implants (e.g. heart pacemakers) * metal artefacts located at the head * medication with impact on the central nervous system (e.g. antidepressant or sedative drugs) * participation in another trial * pregnant or breastfeeding women