Inclusion Criteria:  Diagnosed with mild cognitive impairment by modified Peterson's criteria Identified as amyloid positive by amyloid PET result Insomnia severity index of more than 15 or diagnosed with insomnia disorder by Diagnostic Statistical Manual-5  Exclusion Criteria:  Subjects with active psychiatric or neurological disorders Unstable medical conditions (Myocardial infarction, cerebral infarction, congestive heart failures etc.) Moderate to severe obstructive sleep apnea (apnea hypopnea index of more than 15), rapid eye movement disorder, narcolepsy On regular hypnotic medication (can enroll if there was 2-week wash out period) Currently receiving or having a past history of cognitive behavioral therapy for insomnia Patients who received transcranial magnetic stimulation (TMS), transcranial direct current stimulation, within 2 weeks before enrollment Who are on cognitive enhancers (choline alfoscerate, acetylcarnitine, acetylcholinesterase inhibitors, NMDA receptor antagonist) History of cerebral infarction or Parkinson's disease History of facial or brain trauma A subject with allergy to acrylic acid A subject who is sensitive to electrical devices A subject who are uncooperative to MRI process