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

Study Summary

Alzheimer's disease (AD) is the leading neurodegenerative disease of aging characterized by multiple cognitive impairments. Given the recent failures of disease-modifying drugs, the current focus is on preventing or mitigating synaptic damage that correlates with cognitive decline in AD patients. Transcranial Direct Current Stimulation (tDCS) is a safe, non-invasive, non-painful electrical stimulation of the brain that is shown to act as a primer at the synaptic level when administered along with behavioral therapy, mostly involving language, learning and memory. Previous studies have shown that tDCS over the left angular gyrus (AG) improves language associative learning in the elderly through changes in functional connectivity between the AG and the hippocampus. The investigators' previous clinical trial on the effects of tDCS in neurodegenerative disorders has also shown augmented effects of lexical retrieval for tDCS. In the present study the investigators will compare the effects of active vs. sham tDCS over the AG-an area that is part of the default mode network but also a language area, particularly important for semantic integration and event processing-in two predominant AD variants: probable AD with amnesic phenotype (amnesic/typical AD) and probable AD with non-amnesic (language deficit) phenotype also described as logopenic variant PPA with AD pathology (aphasic/atypical AD). The investigators aim to: (1) determine whether active high-definition tDCS (HD-tDCS) targeting the left AG combined with a Word-List Learning Intervention (WordLLI) will improve verbal learning; (2) identify the changes in functional connectivity between the stimulated area (AG) and other structurally and functionally connected areas using resting-state functional magnetic resonance imaging; (3) identify changes in the inhibitory neurotransmitter GABA at the stimulation site using magnetic resonance spectroscopy. Furthermore, the investigators need to determine the characteristics o

Primary Outcome

Each trained word-list (practiced during the intervention period) will consist of 12 semantically related words (e.g., birds). Word lists will be constructed using psycholinguistic databases. There will be 5 Trials to learn each list. The investigators will compute the raw score of items correctly recalled by summing all scores from Trial 1 to Trial 5 and transforming to percent correct (range: 0-100%) at each time point of the study. Increase in scores is considered a benefit.

Conditions Studied

Interventions

• DEVICE Sham
• DEVICE Active, in-person HD-tDCS or active remote tDCS
• OTHER Word List Learning Intervention (WordLLI)

Study Locations (1)