Effect of Noninvasive Electrical Brain Stimulation on Memory at Different Times of Day in Younger and Older Adults

Inclusion Criteria: * Right-handed (according to the Edinburgh Handedness Inventory) * Normal or corrected vision * Fluent in English (started learning by age 6) * Ability to understand and provide informed consent for study procedures, and to comply - with study procedures for the entire length of the study. * For individuals in the 'younger adults' group, must be between 18 and 30 years of age * For individuals in the 'older adults' group, must be between 60 and 75 years of age * A score of 23 or above on the Montreal Cognitive Assessment (out of 30, education-corrected) is required. This is to minimize the inclusion of suspected mild cognitive impairment (MCI) or dementia, targeting individuals that score in the normal range according to the recent meta-analysis of MoCA's ability to differentiate normal aging from MCI in Carson et al. (2018, Int. J of Geriatric Psychiatry). * Performance above threshold on the episodic memory task during the baseline session. The threshold is defined as having a hit rate that is at least 5% greater than the false alarm rate, where hit rate is defined as the number of studied items identified as studied, divided by the total number of studied items, and false alarm rate is defined as the number of new items identified as studied, divided by the total number of new items. We don't anticipate this threshold to exclude many, if any subjects. Exclusion Criteria: * Neuropsychological conditions associated with cognitive decline or seizure * C…