Could a zapping cap help Alzheimer's patients remember?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: For the aphasic/atypical AD participants: * Must be between 45-85 years of age. * Must be right-handed. * Must be proficient in English. * Must have a minimum of high-school education. * Must be diagnosed as logopenic variant Primary Progressive Aphasia (PPA) with Alzheimer's Disease (AD) biomarkers. Other possible diagnosis for the 'aphasic AD' variant would be Mild Cognitive Impairment (MCI) or 'possible AD' according to 2011 guidelines with AD biomarkers (CSF or positron emission tomography (PET) amyloid-beta or fluorodeoxyglucose (FDG)-positron emission tomography (PET) with unihemispheric atrophy). * Participants will be diagnosed from PPA and early dementias clinics at Johns Hopkins University or other specialized centers in US using current consensus criteria. Diagnosis will be based on neuropsychological testing, language testing (most commonly the Western Aphasia Battery), MRI and clinical assessment. The investigators will also use two new variant classification tests the investigators have developed at the lab which discriminate PPA variants with great accuracy (above 80%): a spelling test and a speech production test (i.e.,Cookie Theft picture description task). For the amnesic/typical AD participants: * Must be between 45-85 years of age. * Must be right-handed. * Must be proficient in English. * Must have a minimum of high-school education. * Must be diagnosed with 'probable AD' in specialized diagnostic centers with neuropsychological (e.g., RAVLT) and AD biomarkers according to 2011 guidelines. * The investigators will also perform extensive testing in the investigators' test battery including the Mnemonic Similarity Test (MST) that discriminates and measures the most salient hippocampal deficit-pattern separation (PS). Exclusion Criteria: * People with previous neurological disease including vascular dementia (e.g., stroke, developmental dyslexia, dysgraphia or attentional deficit). * People with hearing loss (\> 25 decibel, using audiometric hearing screen). * People with uncorrected visual acuity loss. * People with advanced dementia or severe language impairments (MMSE \< 15, or Montreal Cognitive Assessment \<10, or language Frontotemporal Dementia-specific Clinical Dementia Rating (FTD-CDR) = 3). * Left handed individuals. * People with pre-existing psychiatric disorders such as behavioral disturbances, severe depression, or schizophrenia that do not allow these people to comply or follow the study schedule and requirements such as repeated evaluation and therapy. Exclusion Criteria for MRI Participation: * People with severe claustrophobia. * People with cardiac pacemakers or ferromagnetic implants. * Pregnant women.