Transcranial direct current stimulation as a memory enhancer in patients with Alzheimer’s disease: a randomized, placebo-controlled trial

Abstract

BackgroundThe purpose of this study was to assess the efficacy of transcranial direct current stimulation (tDCS) on verbal memory function in patients with Alzheimer’s disease.MethodsWe conducted a randomized, placebo-controlled clinical trial in which tDCS was applied in six 30-minute sessions for 10 days. tDCS was delivered to the left temporal cortex with 2-mA intensity. A total of 25 patients with Alzheimer’s disease were enrolled in the study. All of the patients were diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s Disease and Related Disorders Association criteria. Twelve patients received active stimulation, and thirteen patients received placebo stimulation. The primary outcome measure was the change in two parallel versions of the California Verbal Learning Test–Second Edition, a standardized neuropsychological memory test normalized by age and gender. The secondary outcome measures were the Mini Mental State Examination, clock-drawing test, and Trail Making Test A and B.ResultsChanges in the California Verbal Learning Test–Second Edition scores were not significantly different between the active and placebo stimulation groups for immediate recall (p = 0.270), delayed recall (p = 0.052), or recognition (p = 0.089). There were nonsignificant differences in score changes on the Mini Mental State Examination (p = 0.799), clock-drawing test (p = 0.378), and Trail Making Test A (p = 0.288) and B (p = 0.093). Adverse effects were not observed.ConclusionsCompared with placebo stimulation, active tDCS stimulation in this clinical trial did not significantly improve verbal memory function in Alzheimer’s disease. This study differs from previous studies in terms of the stimulation protocol, trial design, and application of standardized neuropsychological memory assessment.Trial registrationClinicalTrials.gov identifier NCT02518412. Registered on 10 August 2015.

Non-Invasive Brain Stimulation in Dementia: A Complex Network Story

“…For studies with AD patients, roughly half of studies employed tDCS as the stimulation tool [81-87], the other using TMS [88-94]. Moreover, the majority of the studies have focused on memory, the core clinical symptom.…”

“…Moreover, the majority of the studies have focused on memory, the core clinical symptom. Ten studies were designed as multiple session paradigm [81, 83, 84, 86-88, 90, 92-94], and a cognitive training was combined with the stimulation protocol in 3 of the brain stimulation studies on AD [84, 93, 94]. …”

Transcranial Direct Current Stimulation as an Alternative Treatment in Patients with Alzheimer's Disease

“…In this study, both anodal and cathodal stimulation showed a change in cognitive function improvement and shortening of P300 latency. However, in other randomized parallelgroup clinical trials, tDCS stimulation did not show significant effects on enhancement of cognitive function [76][77][78] (Table 1). Most of these previous clinical studies were small, and the characteristics of subjects, conditions of stimuli and outcome measures were different from study to study.…”

Commentary: Transcranial direct current stimulation for depression in Alzheimer's disease: study protocol for a randomized controlled trial

“…Seven double-blind RCTs have been so far conducted for AD [20][21][22][23][24][25][26] . Here we review five of them that evaluated multiple-session effects 20,22,23,25,26 since a meta-analysis suggests that a larger number of sessions may be more effective 27 .…”

“…Here we review five of them that evaluated multiple-session effects 20,22,23,25,26 since a meta-analysis suggests that a larger number of sessions may be more effective 27 . Two of five controlled trials revealed significant effect on some domains in AD.…”