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.
| Parameter |
Value |
| NCT Number |
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 |
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.
¶ 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
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
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)
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
- Mild to Moderate Alzheimer's Disease
- MoCA (Montreal Cognitive Assessment) score between 18-25
- Ability to perform Cambridge Naming Task during pre-assessment
- 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
- Age Range: 50-90 years
- Sex: All
- Healthy Volunteers: No
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
This dose-response research extends to:
tDCS modulates cortical excitability through weak direct current delivery:
- Polarized neurons: Anodal stimulation depolarizes, cathodal hyperpolarizes
- Neuroplasticity enhancement: Promotes long-term potentiation (LTP)-like changes
- Network effects: Alters functional connectivity in targeted brain regions
- Neurotrophic support: May increase BDNF expression
- Anti-inflammatory: Modulates glial cell function
At higher intensities (4mA), the electric field strength increases, potentially:
- Penetrating deeper brain regions
- Engaging more neurons in the targeted network
- Producing more robust neuroplastic changes
| Trial |
Target |
Intensity |
Status |
| NCT05509387 |
Language cortex |
4.0 mA vs 2.0 mA |
Recruiting |
| NCT07291687 |
Motor cortex |
2.0 mA |
Recruiting |
| NCT06324448 |
Motor cortex |
2.0 mA |
Recruiting |