Neurostimulation & neurofeedback
40Hz Gamma Sensory Stimulation
Graded on: structural brain change; cognition unestablished.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
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How this letter has changedLatest: October 2026 · Corrected.
The record carried a 'not replicated' flag while describing 11 controlled trials; the flag is removed and the checklist corrected (several small trials, null clinical endpoints The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score., one positive imaging endpoint). Wu 2025 (PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 40855942), a meta-analysis reporting large cognitive gains, is now cited with the reason it is not relied on: it pools transcranial brain stimulation with sensory stimulation. Letter unchanged.PMID 40855942
Funding stated in the evidence. The largest sham-controlled trial, OVERTURE, Hajós 2024, and the MRI paper from the same trial, Da 2024 (PMID 38073386), are now cited; both were funded by Cognito Therapeutics, maker of the device, and written mostly by its employees. OVERTURE missed its primary clinical outcome. The meta-analysis the letter rests on, Ang 2025 (PMID 41381439), was publicly funded. Letter unchanged.PMID 38073386 PMID 41381439
Every change to a letter on this site is dated and published. The full evidence log →
This treatment uses lights and sounds that flicker 40 times a second. In people with Alzheimer's disease or mild memory loss, a review found some changes on brain scans. But memory, thinking and daily living did not improve, and ringing in the ears became more common. The largest study, paid for by the device maker, missed its main goal. It has never been tested in healthy adults.
A letter describes the human evidence, not the product, the manufacturer, or the intervention's worth.
See the full evidence record →Graded on Structural brain change; cognition unestablished.
Why this gradeGrade C, small or unreplicated trials. The reasoning, and what the grade does not cover.
Grade C on structural brain change in Alzheimer's disease and mild cognitive impairment. A meta-analysis of 11 controlled trials in 341 adults aged 50 and over found structural improvement (SMD 1.74), while cognition and daily living were null, and tinnitus rose by 16 percentage points (Ang et al., 2025; PMID 41381439). The largest sham-controlled trial, OVERTURE, missed its primary clinical outcome (Hajos et al., 2024; PMID 38515445), and both it and the imaging paper (PMID 38073386) were funded by the device maker.
WHAT THIS GRADE DOES NOT COVERcognition, which was null; healthy adults, never tested; and consumer devices, none of which meets the trial parameters. Tinnitus is a reported harm, not a graded outcome.
A grade describes the human evidence for a named use. It is not advice, and it is not a judgment on any individual prescription. How the letters are decided →
The evidence, in fullFour papers, each linked to its PubMed record.
Ang et al. (Translational Psychiatry, 2025; PMID 41381439): systematic review A review that searches for every study on a question using a method set in advance, then assesses them together. and meta-analysis of gamma-frequency auditory and visual stimulation in Alzheimer's disease and mild cognitive impairment, 11 controlled trials, 341 participants; publicly funded in China. The largest sham-controlled trial, OVERTURE (Hajós et al., Front Neurol, 2024; PMID 38515445, n=74), missed its primary clinical outcome, and the structural MRI finding that drives the positive imaging endpoint (Da et al., J Alzheimers Dis, 2024; PMID 38073386) came from the same trial. Both papers state funding by Cognito Therapeutics, maker of the device, and most of their authors are Cognito employees with stock options and patent applications assigned to the company. Grade C reflects null cognitive and functional endpoints against a positive imaging endpoint that has been reported only by the device maker's own staff, high heterogeneity How much the results of the pooled trials differ from each other. High heterogeneity makes a combined estimate less reliable., and a tinnitus safety signal. A second 2025 meta-analysis, Wu et al. (Neurorehabil Neural Repair, 2025; PMID 40855942), reports large cognitive gains across 8 trials, but it pools transcranial electrical and magnetic brain stimulation with sensory stimulation, so it does not grade this modality and is not relied on here.
A validated cognitive battery (ADAS-Cog, MoCA) at baseline and every 12 weeks: the MIT Tsai lab trials used 40Hz combined audiovisual stimulation for 1 hour/day. Sleep quality and subjective cognitive function monthly. Daily session duration and compliance: the published protocol requires 1 hour/day; shorter sessions have not been validated.
Evidence notes: meta-analysis
Endpoint graded: Structural brain change; cognition unestablished (surrogate)
Last reviewed: July 2026
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
Primary evidenceFour papers, each linked to its PubMed record.
Ang et al. (Translational Psychiatry, 2025; PMID 41381439): systematic review and meta-analysis of gamma-frequency auditory and visual stimulation in Alzheimer's disease and mild cognitive impairment, 11 controlled trials, 341 participants; publicly funded in China. The largest sham-controlled trial, OVERTURE (Hajós et al., Front Neurol, 2024; PMID 38515445, n=74), missed its primary clinical outcome, and the structural MRI finding that drives the positive imaging endpoint (Da et al., J Alzheimers Dis, 2024; PMID 38073386) came from the same trial. Both papers state funding by Cognito Therapeutics, maker of the device, and most of their authors are Cognito employees with stock options and patent applications assigned to the company. Grade C reflects null cognitive and functional endpoints against a positive imaging endpoint that has been reported only by the device maker's own staff, high heterogeneity, and a tinnitus safety signal. A second 2025 meta-analysis, Wu et al. (Neurorehabil Neural Repair, 2025; PMID 40855942), reports large cognitive gains across 8 trials, but it pools transcranial electrical and magnetic brain stimulation with sensory stimulation, so it does not grade this modality and is not relied on here.
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