The present study aims to assess the safety and feasibility of repeated transcranial alternating current stimulation (tACS) by the Miamind Neurostimulator in a cohort of healthy participants. Based on the findings of this investigation, subsequent clinical trials assessing the efficiency of tACS by the Miamind Neurostimulator for treatment of Alzheimer's Disease will be conducted.

The pathological hallmarks of Alzheimer's Disease (AD) are extracellular amyloid-β (Aβ) plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau deposition in the brain together with neuroinflammation and microglial activation. These alterations lead to synaptic dysfunction, neuronal loss, and subsequently to brain circuit and brain oscillation disruption, resulting in cognitive decline. Recent studies have shown a positive effect of neural entrainment at gamma frequency (30-80 Hz). Transcranial alternating current stimulation (tACS) utilizes low amplitude alternating currents, allowing for frequency and region-specific brain oscillation entrainment showing positive results regarding improvement of cognitive functions in healthy participants and Alzheimer's Disease patients. Miamind Neurostimulator is a patient specific MRI-based 3D printed medical device that permits electrical stimulation and recording on up to 32 electrode channels and thus allows for simultaneous, multifocal, and targeted brain stimulation. tACS is non- invasive, well tolerated by users and considered safe with no persistent adverse events reported.

Inclusion Criteria:

1. Participants who are overtly healthy as determined by medical evaluation including medical history and physical examination.
2. Able and willing to provide voluntary written Informed Consent and sign the ICF to participate in the study prior to any study-related procedure.
3. Must have the ability to comply with protocol-related tests, appointments, and procedures.
4. Age over 18 years old.
5. Knowledge of the German language (B1 or higher).
6. No history of intellectual or learning disability; at least 8 grades of school.
7. Non-disturbing hairstyle or headdress that enables electrode contact with the scalp judged by the investigator.

Exclusion Criteria:

1. Any acute or chronic disease/disorder (e.g., cerebral, psychiatric, cardiovascular, pulmonary, metabolic, skin etc.)
2. History of traumatic brain injury or other diseases of the central nervous system.
3. History of seizures, diagnosis of epilepsy, or abnormal (epileptiform) EEG, or immediate (1st-degree relative) family history of epilepsy.
4. Diagnosis of substance abuse.
5. Participant is under the influence of alcohol, and consumption of narcotics or benzodiazepines, or other sleeping medications prior to the procedure.
6. All female participants that are not post-menopausal (defined as at least 12 months of spontaneous amenorrhea in women over 45 years old) or surgically sterile (e.g. bilateral tubal ligation, hysterectomy, bilateral oophorectomy) will be required to have a pregnancy test; any participant who is pregnant or breastfeeding will not be enrolled in the study.
7. Metal implants (excluding dental fillings) or devices such as a pacemaker, cardioverter defibrillator, medication pump, nerve stimulator, Transcutaneous Electrical Nerve Stimulator (TENS) unit, ventriculoperitoneal shunt, and cochlear implant, unless cleared by the study MD.
8. Contraindications for undergoing MRI.
9. Ongoing participation in any other interventional clinical study with an investigational drug or another MD within the 30 days preceding and during the present investigation.
10. Participants not suitable for the study based on a holistic consideration of the participant's history and the PI's medical expertise.

No vulnerable subject is enrolled on this study