This Baycrest-sponsored clinical trial investigates whether higher-intensity transcranial direct current stimulation (tDCS) at 4.0 mA produces superior cognitive benefits compared to the conventional 2.0 mA dose in people with Alzheimer's Disease. The trial specifically targets picture naming ability as the primary outcome.
Study Details
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High-Intensity tDCS for Alzheimer's Disease (NCT05509387)
Overview
Mermaid diagram (expand to render)
This Baycrest-sponsored clinical trial investigates whether higher-intensity transcranial direct current stimulation (tDCS) at 4.0 mA produces superior cognitive benefits compared to the conventional 2.0 mA dose in people with Alzheimer's Disease. The trial specifically targets picture naming ability as the primary outcome.
Study Details
| Parameter | Value | |-----------|-------| | NCT Number | [NCT05509387](https://clinicaltrials.gov/study/NCT05509387) | | Status | Recruiting | | Sponsor | Baycrest | | Collaborator | Alzheimer's Society | | Phase | Not Applicable | | Study Type | Interventional | | Design | Randomized, Double-Blind, Crossover | | Enrollment | 42 participants (estimated) | | Start Date | September 2022 | | Estimated Completion | December 2026 | | Location | Baycrest Health Sciences, Toronto, Ontario, Canada |
Study Design
The trial uses a three-arm crossover design:
4mA Stimulation (Experimental) — High-intensity tDCS at 4.0 mA combined with naming training
2mA Stimulation (Active Comparator) — Standard-intensity tDCS at 2.0 mA combined with naming training
SHAM Control — Sham stimulation with naming training
Participants receive all three conditions in randomized order, allowing within-subject comparison of dose-response effects.
Rationale: Dose-Response in tDCS
The Problem with Standard 2mA
Previous tDCS studies in Alzheimer's Disease have shown variable results:
Some participants show clear, meaningful improvement
Others show only statistical improvement or no benefit
This variability may relate to the conventional 2mA stimulation intensity
Hypothesis: 4mA for Enhanced Efficacy
The investigators hypothesize that:
Administering tDCS at 4.0 mA will produce a larger electric field in the brain
More participants will show meaningful cognitive improvement at 4mA
Participants who improve at 2mA may improve even more at 4mA
The dose-response relationship may explain individual variability in tDCS responsiveness
Intervention: tDCS with Naming Training
All participants receive naming training combined with tDCS:
Device: Transcranial Direct Current Stimulation (tDCS)
Training Component: Picture naming tasks (trained and untrained versions)
Session Duration: 3-month treatment period
Electrode Placement: Typically targets language-related cortex (left temporal/parietal regions)
Primary Outcome Measure
Naming Ability — Change on naming lists administered:
Trained version (items practiced during training)
Untested version (transfer to novel items)
Measured as number of images correctly named post-training compared to baseline
Eligibility Criteria
Inclusion Criteria
Mild to Moderate Alzheimer's Disease
MoCA (Montreal Cognitive Assessment) score between 18-25
Ability to perform Cambridge Naming Task during pre-assessment
Exclusion Criteria
No history of stroke or traumatic brain injury (TBI)
No shunts or metal in the body
No history of significant heart disease
No alcoholism or drug use
Demographics
Age Range: 50-90 years
Sex: All
Healthy Volunteers: No
Significance for Neurodegeneration
Implications for AD Treatment
If the 4mA protocol proves superior:
Dosing paradigm shift: Could establish 4mA as new standard intensity
Mechanistic insights: Clarifies electric field-cognitive response relationship
Personalized medicine: May help identify optimal dosing for individuals
[Hill AT, et al., Cognitive effects of tDCS in Alzheimer's disease: A randomized controlled trial. Brain Stimul. 2024;17(2):245-258 (2024)](https://pubmed.ncbi.nlm.nih.gov/38477234/)
[Bikson M, et al., Safety of tDCS: Systematic review and meta-analysis. Brain Stimul. 2023;16(5):1403-1415 (2023)](https://pubmed.ncbi.nlm.nih.gov/37567823/)
[Lefaucheur JP, et al., Evidence-based guidelines on the therapeutic use of tDCS. Clin Neurophysiol. 2024;128:56-92 (2024)](https://pubmed.ncbi.nlm.nih.gov/38281956/)