Effects of Electrical Stimulation on Verbal Learning in Typical and Atypical Alzheimer's Disease

Stimulation will be delivered by a battery-driven constant current stimulator. The electrical current will be administered to a pre-specified region of the brain (angular gyrus). The stimulation will be delivered at an intensity of 2 milliamperes (mA) (estimated current density 0.04 mA/cm2; estimated total charge 0.048 Coulombs/cm2) in a ramp-like fashion for a maximum of 20 minutes. In the active, in-person HD-tDCS the current is delivered in a ring configuration. In the active remote tDCS current is delivered in one electrode patch.

Current will be administered in a ramp-like fashion but after the ramping the intensity will drop to 0 mA. Current under the Sham condition will last for a maximum of 30 seconds.

Participants will receive a word list learning intervention (WordLLI) of semantically related and unrelated word lists. Word lists are presented across 10 trials, with an additional trial after a 10-minute delay to assess delayed recall. Immediately following verbal presentation of word lists during each trial, participants will be instructed to recall as many of the words from the list as possible. Participants may use the written modality as a strategy during recall. Word lists include 12 words matched based on psycholinguistics attributes (e.g., imageability, frequency). This task is designed to help participants improve memory via enhancing list learning capabilities.