Exploring the Effect of Single-Session Transcranial Direct Current Stimulation on Attention, Verbal Fluency, and Working Memory in Patients With Alzheimer's Disease-Related Dementia.

Abstract

Alzheimer's disease (AD) is a leading cause of morbidity and mortality among the elderly. Transcranial direct current stimulation (tDCS) applies low-intensity currents to the brain, resulting in short-term neurocognitive effects and long-term neuroplasticity enhancement. Limited research reported on the impact of tDCS on cognitive functions in dementia due to AD. This study aims to compare changes in verbal fluency and working memory following a single tDCS application to the left dorsolateral prefrontal cortex (DLPFC) in AD patients. Patients with mild dementia due to AD underwent cognitive assessment using the Standardized Mini-Mental Test, Clock Drawing Test, Rey Auditory Verbal Learning Test, Functional Activities Questionnaire, Informant Questionnaire on Cognitive Decline in the Elderly, and Montreal Cognitive Assessment Scale. A single-session tDCS was administered by applying anodal tDCS to the left DLPFC for a duration of 30 minutes. Verbal fluency and working memory were evaluated before and after tDCS using the WAIS-R Digit Span Test forward and backward subscales, Trail Making Test (TMT) A and B, and Verbal Fluency Test. Regarding cognitive test scores before and after tDCS application, there were statistically significant reductions in the durations of TMT-A and TMT-B. However, there were no significant differences observed for TMT B-A, VFT, DST-forward, and DST-backward performances. The findings indicate that a single anodal tDCS targeting the left DLPFC enhances attention and processing speed in AD patients but has no effect on working memory or verbal fluency.