The 40 Hz gamma story
One frequency has produced the most striking brainwave research in a decade — clearing Alzheimer's proteins in mice and slowing brain shrinkage in early human trials. Here's what it really shows, and the part most headlines skip.
At MIT, exposing mice to 40 Hz flickering light and pulsing sound reduced Alzheimer's-related amyloid and tau, protected neurons, and preserved memory. Early human trials show slowed brain atrophy. It's genuinely exciting — but two caveats matter: this stimulation is pulsed light and sound (isochronic-style), not binaural beats, and it's Alzheimer's research, not a focus hack. A consumer audio track is not the therapy being tested.
A brain rhythm tied to attention
Your brain produces electrical rhythms at different speeds, grouped into bands. Gamma waves are the fastest, sitting above roughly 30 Hz, and 40 Hz is the value researchers return to again and again. Gamma activity is associated with attention, perception, and "binding" — the way separate details (a shape, a color, a sound) get stitched into a single conscious moment.
In people with Alzheimer's disease, this gamma activity is measurably disrupted. That observation is what led a team at MIT to ask a bold question: if you could push the brain to produce more synchronized 40 Hz gamma from the outside, would anything change? [1]
What the MIT studies found
The work comes from the lab of Li-Huei Tsai at MIT's Picower Institute, with collaborators including Ed Boyden and Emery Brown. They call the method GENUS — Gamma Entrainment Using Sensory Stimulation. [1]
Exposing Alzheimer's-model mice to light flickering at 40 Hz drove gamma activity in the visual cortex and reduced amyloid-beta, one of the proteins that builds up in the disease. It was the first sign that a purely sensory stimulus could shift brain pathology. [2]
Adding 40 Hz sound — and combining light with sound — extended the effect beyond the visual cortex to deeper memory regions like the hippocampus, reduced amyloid and tau more broadly, and improved performance on memory tasks. [3]
In early human studies, people with Alzheimer's who received daily 40 Hz light and sound showed slowed brain atrophy and preserved white matter versus controls, and one long-term study reported the routine was safe and feasible over two years, with signs of slower decline in some patients. A larger Phase III trial is underway. [4][5]
The proposed mechanism is striking: driving gamma appears to mobilize the brain's immune cells (microglia) and boost the glymphatic waste-clearance system, helping flush out the proteins that accumulate in Alzheimer's. [1]
Two things the headlines skip
Read this before you buy a "40 Hz" track1. This is not binaural beats. GENUS uses light that physically flickers and sound that physically pulses on and off 40 times a second — an amplitude-modulated stimulus. That's mechanically the same family as isochronic tones, not binaural beats, which create their beat as an illusion inside your auditory system. If you want to explore 40 Hz in the spirit of this research, a crisp pulsed tone is the closer match.
2. This is Alzheimer's research, not a productivity claim. The trials use specific medical-grade devices, careful dosing, and long daily sessions in people with a diagnosed disease. None of that transfers to "play this track and treat dementia," and it is not evidence that 40 Hz will sharpen a healthy person's focus. Gamma's link to attention is real and interesting, but the focus claim rests on a handful of small studies [6] — a much weaker footing than the pathology results.
Bottom line: the 40 Hz science is some of the most promising in the field, and it's worth being genuinely excited about. Just don't let a marketing page quietly upgrade "reduced amyloid in mice" into "cures brain fog in humans."
A reasonable, honest use
If you're curious about 40 Hz for yourself, treat it as an experiment, not a treatment. Gamma is associated with alert, engaged attention, so a 40 Hz session is a sensible thing to try during focused work — and many people simply find a steady rhythm helps them settle in, regardless of the exact frequency. Keep the volume comfortable, give it 15–30 minutes, and pay attention to whether it actually helps you.
Explore a clean 40 Hz gamma session. Because the MIT work uses pulsed sound, the isochronic studio is the closest match — sharp on/off pulses you can hear on speakers or headphones.
Open the Isochronic Studio →- MIT News (2025). Evidence that 40Hz gamma stimulation promotes brain health is expanding. Picower Institute / MIT. Link
- Iaccarino, H. F., et al. (2016). Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature, 540, 230–235. Link
- Martorell, A. J., et al. (2019). Multi-sensory gamma stimulation ameliorates Alzheimer's-associated pathology and improves cognition. Cell, 177(2), 256–271. Link
- Chan, D., et al. (2022). Gamma frequency sensory stimulation in mild probable Alzheimer's dementia patients: Results of feasibility and pilot studies. PLOS ONE, 17(12), e0278412. Link
- MIT News (2025). Study suggests 40Hz sensory stimulation may benefit some Alzheimer's patients for years. Link
- Ingendoh, R. M., Posny, E. S., & Heine, A. (2023). Binaural beats to entrain the brain? A systematic review. PLOS ONE, 18(5), e0286023 — context on the mixed EEG evidence for auditory gamma entrainment. Link
Brain Beats is an educational tool, not a medical device. Nothing here is medical advice or a treatment for any condition, including Alzheimer's disease. If you have epilepsy, a seizure disorder, or other neurological concerns, talk to a healthcare professional before using rhythmic light or sound.