What "40 Hz gamma" means
Gamma waves are the fastest brainwave band (roughly 30–100 Hz), linked to moments when many brain regions work together. The number 40 Hz matters because researchers found it's an especially effective frequency for entraining gamma activity using the senses — flickering a light and pulsing a sound at 40 times per second nudges the brain's own gamma rhythm upward. MIT's team calls this approach GENUS — Gamma Entrainment Using Sensory Stimuli.[1]
The mouse research (strong — but mice)
In mouse models of Alzheimer's, 40 Hz sensory stimulation produced striking results: it reduced the build-up of amyloid and tau proteins, helped preserve neurons and their connections, boosted the brain's waste-clearing "glymphatic" flow, and supported learning and memory. Several independent labs have since reproduced parts of this, though at least one 2023 study found no effect of 40 Hz light on amyloid in mice.[1] As the MIT researchers themselves wryly note, it's a great time to have Alzheimer's — if you're a mouse. Animal results are a beginning, not a promise for people.
The human trials (promising — but early)
Human testing is genuinely underway and the early signals are encouraging. A small MIT pilot trial in people with mild Alzheimer's found that three months of daily 40 Hz light-and-sound was safe and, compared with a control group, was associated with less brain atrophy, better performance on a memory recall test, and steadier daily rhythms.[2] Work at MIT and the spin-off company Cognito Therapeutics has reported slowed brain-volume loss and white-matter preservation, and a large pivotal trial (about 670 people) finished in 2026, with results still to come.[3]
A 2025 follow-up of five people who continued for two years reported a reduced Alzheimer's blood biomarker (pTau217) in the two who gave blood samples — but, importantly, the earlier brain-volume benefit was no longer statistically significant at 30 months, and two participants saw no clear benefit.[4] That mix of hopeful and sobering findings is exactly what "early science" looks like.
The honest caveats
Three things to hold onto:
- It's experimental. Nothing here is an approved therapy. The pivotal trial hasn't reported final results.
- It uses light and sound devices, at precise settings, under research supervision — not a casual audio track.
- Human samples are small and results mixed. Encouraging ≠ proven. Be sceptical of any product promising 40 Hz "cures."
What this means for you
If you find a 40 Hz tone pleasant or interesting, you're welcome to explore it in the player (try the Sharp preset) — as a listening experience, nothing more. It won't replicate a clinical GENUS device, and it isn't treating anything. If your real concern is brain health or memory, the best evidence-based steps are ordinary and boring: sleep, exercise, social connection, managing blood pressure — and speaking with a doctor.
Safety note: flickering light can trigger seizures in people with photosensitive epilepsy. If you have a seizure disorder, consult a doctor before using any entrainment audio, and don't use it while driving.
Frequently asked questions
Does 40 Hz sound treat or prevent Alzheimer's?
No. It's promising but experimental research, using specialized devices under study, with early and mixed human results. A web tone is not a treatment and not a substitute for medical care.
What is GENUS?
Gamma Entrainment Using Sensory Stimuli — MIT's method of using 40 Hz light and sound to raise gamma brain activity. Strong in mice; still being tested in people.
Is the human evidence conclusive?
Not yet. Early trials show encouraging signs, but samples are small, results are mixed, and a large pivotal trial has finished but not yet reported results.
Is listening to 40 Hz safe?
Listening at a low volume is low-risk for most people, but we can't promise it's safe for you. Flickering light, which some 40 Hz studies also used, can trigger seizures in people with photosensitive epilepsy. If you have epilepsy, a seizure disorder, a heart condition or a pacemaker, ask your doctor first, and don't listen while driving or operating machinery.
Sources
- Massachusetts Institute of Technology (2025). Evidence that 40Hz gamma stimulation promotes brain health is expanding. MIT News. news.mit.edu
- Chan, D., et al. (2022). Gamma frequency sensory stimulation in mild probable Alzheimer's dementia patients. PLOS ONE. journals.plos.org
- Picower Institute (2025). Review: Evidence expanding that 40Hz gamma stimulation promotes brain health. picower.mit.edu
- Chan, D., et al. (2025). Gamma sensory stimulation in mild Alzheimer's dementia: an open-label extension study. Alzheimer's & Dementia. alz-journals.onlinelibrary.wiley.com
This page is general education, not medical advice.