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That is the observation that slips out of the MIT team when asked where Alzheimer's research stands today. The results obtained in animal models are spectacular. In humans, it is a different story. Slower, more complex, more humble too.
Memory · Free exploration
The Brain Going Dark
"a great time to have Alzheimer's if you are a mouse"
What brain waves reveal about Alzheimer's disease
Chapter 1
A great time to be a mouse
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It is in this space between promise and proof that one of the most compelling areas of current neuroscience sits: manipulating brain oscillations to slow, and perhaps one day stop, the progression of the disease.
Chapter 2
An electric brain
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The brain does not think in silence. At every moment, millions of neurons fire and synchronise, producing electrical waves that can be measured by electroencephalography (EEG). These rhythms have names: delta, theta, alpha, beta, gamma. Each frequency band corresponds to a particular cognitive state, and their balance reflects the overall health of the brain.
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In Alzheimer's disease, this balance breaks down in a characteristic way. Slow rhythms progressively invade the space vacated by fast ones. This is not a metaphor. It is a measurable, reproducible signal, observed for decades across dozens of independent laboratories.
Chapter 3
Alpha waves: something changes before symptoms appear
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Alpha waves oscillate between 8 and 12 Hz. They accompany the state of relaxed attention, working memory, and the ability to filter out what does not deserve focus.
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What makes their behaviour interesting in Alzheimer's is precisely their irregularity. They do not decrease in a linear, progressive way across disease stages. They fluctuate, differently across individuals and timepoints. This complexity, which might seem like an obstacle, is actually what makes them a potentially powerful biomarker: certain anomalies appear before the first clinical signs, before the visible formation of amyloid plaques.
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A systematic review published in Alzheimer's Research & Therapy in 2024 confirms it: EEG signatures of the disease are a serious avenue for early diagnosis and therapeutic monitoring. Clinical guidelines have not yet integrated these markers into routine practice, for lack of standardised measurement protocols. Research moves forward. Clinical practice follows, in its own time.
Chapter 4
Gamma waves: what the diseased brain is missing
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Gamma waves, above 30 Hz, are the signal of fast, integrated thinking. Episodic memory, sustained attention, coordination between distant brain regions. They are what allows the brain to hold several pieces of information at once and connect them.
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In Alzheimer's disease, they collapse. Their power decreases, their synchronisation fragments. And this deficit is not a late consequence of the disease: it appears early. Some research suggests it even precedes the formation of amyloid plaques and tau protein tangles.
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It was this observation that led neuroscientist Li-Huei Tsai and her team at MIT to ask a deceptively simple question: can these oscillations be restored from the outside?
Chapter 5
GENUS: the bold idea
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The GENUS protocol (Gamma ENtrainment Using Sensory Stimulation) is based on a principle of neural entrainment. When the brain is exposed to visual and auditory stimulations rhythmed at 40 Hz, meaning 40 cycles per second, it tends to synchronise its activity to that frequency. Like a metronome placed next to a clock.
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Results in mice were convincing enough to justify human trials. After three months of one-hour daily stimulation, participants receiving active stimulation showed less hippocampal atrophy, better brain connectivity, improved associative memory performance, and better daily activity rhythms.
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A study published in late 2025 in Alzheimer's & Dementia adds a further signal: gamma stimulation may reduce white matter loss and preserve myelination, a process that degrades precisely upstream of plaque formation in presymptomatic stages.
Chapter 6
What this sound actually sounds like
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The audio signal used in GENUS is not a pure 40 Hz tone, which would sit at the lower limit of human hearing and be inaudible on most speakers. It is an audible sound whose amplitude is modulated 40 times per second: a steady hum that pulses rhythmically.
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Illustration sonore
Son modulé à 40 Hz
Ce player illustre la nature du signal sonore utilisé dans les protocoles de recherche GENUS (MIT).
Ce n'est pas un protocole thérapeutique.
Ce n'est pas un protocole thérapeutique.
Appuyer pour démarrer
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Note scientifique
Les essais cliniques GENUS (MIT / Cognito Therapeutics) utilisent 1 heure de stimulation quotidienne sur plusieurs mois. Quelques minutes d'écoute n'ont aucune valeur thérapeutique documentée. Ce player illustre uniquement la nature du signal sonore étudié.
This player lets you hear a 40 Hz amplitude-modulated sound, as used in research protocols. A few minutes of listening has no documented therapeutic value. GENUS clinical trials use one hour of daily stimulation over several months, under controlled protocol.
Chapter 7
What we do not know yet, and what we will not claim
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Human sample sizes remain very small. The longest published follow-up to date involves five participants. Among them, the three women with late-onset Alzheimer's showed notable benefits, including reductions in plasma pTau217 of 47% and 19% for two of them. The two men with early-onset forms did not respond in the same way. This signal of difference by sex and disease subtype is significant. It calls for stratified studies that research has not yet conducted at scale.
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The exact cellular mechanisms remain partially unclear. The role of microglia in the response to gamma stimulation is an open question that the Tsai lab itself identifies as a priority.
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The MIT researchers put it bluntly: "It is a great time to have Alzheimer's if you are a mouse." Translating these effects into validated human therapy remains the central challenge of the coming decade.
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As for consumer applications claiming therapeutic effects through binaural beats or "40 Hz" videos, none of them rest on clinical validation. No device available outside a medical protocol reproduces the conditions of the GENUS trials. The visual flickering at 40 Hz, the other arm of the protocol, can also trigger seizures in photosensitive individuals and should not be reproduced without medical supervision.
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The gap between what science glimpses and what can be offered today is real. Naming it is the first form of respect toward those affected and their families.
Sources
- Chan D. et al. (2022). Gamma frequency sensory stimulation in mild probable Alzheimer's dementia patients. PLOS ONE. PMID: 36449516.
- Hajos M. et al. (2024). Safety, tolerability, and efficacy estimate of evoked gamma oscillation in mild to moderate Alzheimer's disease. Frontiers in Neurology.
- Hajos M. et al. (2025). Sensory evoked gamma oscillation reduces white matter loss and preserves myelin in Alzheimer's disease. Alzheimer's & Dementia.
- EEG biomarkers in Alzheimer's and prodromal Alzheimer's. Alzheimer's Research & Therapy (2024).
- Gamma sensory stimulation in mild Alzheimer's dementia: open-label extension study. Alzheimer's & Dementia (2025).
- MIT Picower Institute. Review: Evidence expanding that 40 Hz gamma stimulation promotes brain health (March 2025).
This exploration is educational. It does not replace individualised medical advice. Terms and conditions →