Closed-Loop Brain Stimulation as a Potential Intervention for Cognitive Decline

Inclusion Criteria: * Cognitively normal younger adults 1. Ages between 18 to 35 years 2. Good general health 3. Normal or corrected vision 4. Completed elementary school education or able to understand middle school level experiment instructions * Cognitively normal older adults 1. Ages between 60 to 90 years 2. Good general health 3. Normal or corrected vision 4. Completed elementary school education or able to understand middle school level experiment instructions 5. Score of 23 or higher on the Montreal Cognitive Assessment, a brief formal cognitive screening test, which is used to indicate absence of cognitive impairment * Older adults with mild cognitive impairment (MCI) 1. Ages between 60 to 90 years 2. Diagnosis of MCI according to the National Institute on Aging - Alzheimer's Association (NIA-AA) criteria 3. Good general health 4. Normal or corrected vision 5. Completed elementary school education or able to understand middle school level experiment instructions Exclusion Criteria: 1. Neurological or psychiatric diseases (e.g., personal history of epilepsy/seizure brain damage, multiple sclerosis, schizophrenia, substance use disorder, etc.). 2. Current use of psychotropic medications with cognitive side effects (e.g., benzodiazepines, anticonvulsants, antipsychotics, etc.) 3. Current use of cognitive enhancing medications (e.g., Adderall, Memantine, etc.) 4. Factors hindering EEG acquisition and TMS delivery (e.g., skin infection, wounds, dermatitis, etc.) 5. Factors hindering MRI acquisition (e.g., implants, metallic tattoos, etc.)