MRI Guided Closed-loop TMS-EEG

Inclusion Criteria for Healthy participants: * Ages between 18 and 65 years; * Healthy with no history of neurological impairment; * Normal or correct-to-normal vision. Inclusion Criteria for aMCI patients: * Age 50-80 years; * MCI clinical criteria: (a) self- or informant-reported cognitive complaint; (b) preserved independence in functional abilities; and (c) absence of dementia; * Objective cognitive impairment supported by the following measures of general cognitive function: (a) Mini-Mental State Exam (MMSE) 24-27 (inclusive); (b) Montreal Cognitive Assessment (MoCA) 18-26 (inclusive); or (c) Clinical Dementia Rating Scale score of 0.5; * Normal or correct-to-normal vision. Exclusion Criteria for all participants: * Women who are pregnant or breastfeeding; * History of seizure (childhood febrile seizures are acceptable and these subjects may be included in the study), history of epilepsy in self or first degree relatives, stroke, brain tumor, brain surgery, head injury, known structural brain lesion; * Have metal in the eye or skull area, brain stimulator, surgical metal, clips in the brain, cochlear implants, mental fragments in the eye, as these make TMS unsafe; * Have non-MRI compatible metal in the body, for example metallic (forromagnetic) implants (e.g., cardiac pacemaker, aneurysm clip); * Subjects who are uncomfortable in small closed spaces (have claustrophobia), unable to lie comfortably supine for up to 1 hour, and would feel uncomfortable in the MRI machine; * Participation in any other study involving non-invasive brain stimulation less than two weeks ago; * Abnormal findings on neurological examination that we will perform.