Using Transcranial Direct Current Stimulation to Improve Cognitive Function in Mild Cognitive Impairment and Dementia
Year: 2020
Type: dissertation
Study design: Clinical Trial
Abstract: Introduction: Cognitive deficits are key clinical features of Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD). Current first-line pharmacotherapies demonstrate only modest efficacy in AD and lack efficacy in MCI. Transcranial direct current stimulation (tDCS), a non-invasive neuromodulatory technique, has been used to improve cognitive functions with positive results, but with wide variability in response. This research aims to optimize tDCS for cognition by evaluating the effects of electrode placement, the efficacy of exercise primed tDCS, and examining mechanistic correlates of tDCS response in MCI and mild AD patients. Methods and Results: Study 1. To evaluate the effects of electrode placement on cognition, MCI and mild AD participants (n=17) received a single session (2mA, 20 minutes) of bifrontal (F3/F4), bitemporal (T3/T4), and sham stimulations. There was a significant effect of stimulation condition on working memory (F(2,28)=5.28, p=0.01, ηp=0.27), with greater improvements following bitemporal tDCS compared to bifrontal and sham stimulations. Study 2. To investigate the efficacy of exercise primed tDCS on cognition, MCI and mild AD participants (n=19) were randomized to either exercise primed tDCS, exercise primed sham tDCS, or treatment as usual (exercise education only) with tDCS. Ten sessions of bitemporal (T3/T4, 2mA, 20 minutes) or sham tDCS were applied following personalized moderate-intensity aerobic exercise (30 minutes). The trial is ongoing and to maintain blindness, the treatment groups are named as Group A, B, and C. There was a significant effect of time (F(1,14)=11.40, p=0.005), but no group by time interaction on recognition memory (F(2,14)=1.00, p=0.38). However, post hoc analysis revealed significantly greater improvements on recognition memory over time within Group A only (t(5)=-3.70, p=0.02). Study 3. To examine mechanistic correlates of tDCS response, serum vascular endothelial growth factor (VEGF) and endostatin concentrations were analyzed from participants who completed Study 2 (n=18). After controlling for diagnosis, lower VEGF concentrations at screening predicted greater improvement in recognition memory following tDCS treatment with or without exercise priming (b[SE]=-0.66[0.004], p=0.03). Conclusion: Single-session and repeated-session exercise primed bitemporal tDCS may be effective at improving specific cognitive domains in MCI and mild AD patients. Angiogenic mechanisms may underlie tDCS-induced cognitive improvements in these patients.
Source: TSpace (University of Toronto)
Author: Celina Liu
Language: English
Subfield: Neurology
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W3148891113