Improvement of Memory in Mild Cognitive Impairment

Inclusion Criteria: Mild Cognitive Impairment (MCI) patients * age ≥ 55 years old * clinical diagnosis of mild cognitive impairment (MCI) based on a comprehensive clinical assessment and standard neuropsychological examination including tests of language, visuospatial thinking, executive functions, and memory * confirmation of diagnosis will be made by Prof. Paul Unschuld, the study MD, based on a participant's cognitive evaluation and history * understanding of the informed consent * able and willing to comply with all study requirements * informed consent form was signed * women of childbearing potential (WOCBP) must perform a pregnancy test during screening Caregiver * minimum 21 years of age * self-reported computer/tablet proficiency * willingness to learn how to use tACS * availability during the study period to administer tACS to the participant * informed consent form was signed * women of childbearing potential (WOCBP) must perform a pregnancy test during screening Exclusion Criteria: Mild Cognitive Impairment (MCI) patients * age \< 55 years old * any current diagnosis of a psychiatric disorder (e.g., schizophrenia, bipolar disorder, depressive disorder) * other than MCI, any history of other progressive or genetic neurologic disorder (e.g., Parkinson's disease, multiple sclerosis, tubular sclerosis) or acquired neurological disease (e.g., stroke, traumatic brain injury, tumor), including intracranial lesions * history of head trauma resulting in prolonged loss of consciousness * current history of poorly controlled headaches including chronic medication for migraine prevention * history of fainting spells of unknown or undetermined etiology that might constitute seizures * history of seizures, diagnosis of epilepsy * any unstable medical condition or chronic uncontrolled medical conditions that may cause a medical emergency in case of a provoked seizure (cardiac malformation, cardiac dysrhythmia, asthma, etc.) * contraindication for undergoing MRI or receiving tACS * any metal in the brain or skull (excluding dental fillings) or elsewhere in the body unless cleared by the responsible covering MD (e.g., MRI compatible joint replacement) * any skin problems, such as dermatitis, psoriasis, or eczema * any electrically, magnetically, or mechanically activated implanted devices such as a pacemaker, intracranial electrodes, implanted defibrillators, medication pumps, nerve stimulators, vascular clips, or any other prosthesis in the brain * any serious life-threatening disease such as congestive heart failure, pulmonary obstructive chronic disease, or active neoplasia * pregnant women * adults lacking capacity for consent Caregiver * insufficient understanding of study procedures * poor eyesight, severe arthritis in the hands, pain, deformity or other condition that interferes with successful administration of tACS