Gamma Brainwaves Explained: The 40 Hz Frequency Behind Sharp Memory

In 2016, a team at MIT published a study in Nature that changed how neuroscientists think about brain rhythms. They showed that stimulating gamma-frequency oscillations — specifically the 40 Hz band — produced measurable cellular changes in animal models of Alzheimer's disease (Iaccarino et al., 2016, PMID: 27929004).

That single paper kicked off a decade of accelerating research into what is now called gamma entrainment — and it's also the underlying scientific premise of audio programs like The Brain Song. This article walks through what gamma brainwaves are, why the 40 Hz frequency matters, and what the published research actually shows.

What Are Brainwaves, Exactly?

Your brain runs on electricity. Neurons fire in synchronized patterns, and when many neurons fire together, they produce measurable electrical rhythms. These rhythms are called brainwaves, and they're typically grouped into five frequency bands:

• Delta (1–4 Hz) — deep, dreamless sleep
• Theta (4–8 Hz) — drowsy states, light meditation, deep relaxation
• Alpha (8–12 Hz) — relaxed but awake, eyes closed, calm focus
• Beta (12–30 Hz) — active thinking, problem-solving, alertness
• Gamma (30–100 Hz) — high-level cognitive processing, learning, attention, memory binding

Most of these bands are reasonably stable throughout adult life. Gamma is different — it's the fastest band, the most demanding metabolically, and the one that shows the most striking changes in conditions involving memory and cognitive function.

Why 40 Hz Specifically?

Within the gamma band, the 40 Hz frequency has drawn particular research attention. This isn't arbitrary. The 40 Hz oscillation appears repeatedly in studies of:

• Working memory tasks — holding information actively in mind
• Sensory binding — combining sound, sight, and meaning into a coherent perception
• Attention focus — selecting one stream of information out of many
• Conscious awareness itself — some researchers consider 40 Hz a marker of conscious processing

The 2016 MIT study found that 40 Hz stimulation specifically — not 25 Hz, not 100 Hz, but 40 Hz — produced the most reliable cellular effects in their animal model (Iaccarino et al., 2016).

Gamma Activity and Memory

A 2020 pilot study by Sharpe and colleagues looked at 40 Hz gamma entrainment in a small human cohort. Participants who received 40 Hz binaural beat stimulation showed mean improvements in cognitive scores from 75% to 85% over a 4-week period, alongside reported mood and memory improvements (Sharpe et al., 2020, PMID: 33226543).

It was a small study. The statistical significance was weak. The researchers were careful to call it exploratory. But the direction of the effect — gamma stimulation associated with improved cognitive performance — matches a broader pattern across the literature.

The Two Ways to Stimulate Gamma Activity

Research has identified two main non-invasive methods for encouraging gamma activity in the brain:

Visual stimulation (light flicker)

The original MIT studies used light flickering at 40 Hz delivered through goggles or a screen. This produces strong gamma responses in the visual cortex.

Auditory stimulation (sound)

Sound-based stimulation works through several mechanisms — binaural beats (slightly different tones in each ear), monaural beats (a single rhythmic beat), and isochronic tones (a pure tone pulsed on and off at the target frequency). All have been studied in the brain entrainment literature (Chaieb et al., 2015, PMID: 26029120).

The 2019 follow-up study in Cell extended the MIT work to auditory stimulation, showing that auditory 40 Hz stimulation also drove gamma activity in the auditory cortex and hippocampus, and improved spatial memory in animal models (Martorell et al., 2019, PMID: 30879788).

What Programs Like The Brain Song Are Doing

Audio programs built around gamma entrainment are essentially trying to deliver this kind of stimulation in a consumer-friendly format. The Brain Song is 12 minutes of structured audio that combines several entrainment techniques — binaural beats, monaural beats, harmonic backgrounds, and frequency sweeps — designed around the gamma band.

Whether this is as effective as laboratory protocols is an open question. Most published research has used controlled stimulation paradigms in lab settings, not commercial audio programs. The honest framing is: the underlying mechanism is real, the lab-based studies are encouraging, but the leap to specific consumer outcomes from a specific commercial audio file is not directly tested.

What Gamma Stimulation Won't Do

It's worth being clear about what the research does not show:

• It does not show that gamma stimulation cures Alzheimer's disease, dementia, or any other neurological condition.
• It does not show that any commercial audio program produces clinical effects.
• It does not replace the foundational habits — sleep, exercise, social connection — that drive most of the variance in brain health.

Gamma Activity Beyond Memory: Other Documented Effects

While memory is the most discussed application, gamma research has touched on several other dimensions of cognitive function. A 2019 paper in Neuron by Adaikkan and colleagues showed that gamma entrainment effects extend beyond primary sensory cortices into higher-order brain regions — including areas involved in attention, executive function, and the binding of disparate sensory streams into unified perception (Adaikkan et al., 2019, PMID: 31076275).

This matters because it suggests that gamma stimulation may produce effects that ripple outward from the auditory cortex into the broader cognitive network. The 2024 review by Liu and colleagues examined gamma wave stimulation across multiple brain disorders, surveying potential mechanisms in conditions ranging from neurodegenerative disease to mood-related conditions — though again, much of this research remains preclinical (PMID: 39695746).

How Gamma Differs From Other Brainwave Targets

Many wellness audio products target slower brainwave frequencies — alpha (around 10 Hz) for relaxation, theta (around 6 Hz) for meditative states, delta (around 2 Hz) for sleep. These have their place. But the gamma band is unique because it sits at the top of the frequency hierarchy, where active cognitive work happens.

Stimulating slower bands tends to produce relaxation effects — which can be beneficial, but typically don't address the memory and focus complaints that drove most people to look for cognitive support in the first place. Gamma stimulation is, in concept, more aligned with the active mental state most people are actually trying to support during their waking, working hours.

What the Honest Picture Looks Like

Gamma brainwave research is one of the more exciting areas of modern neuroscience. It is also still relatively young. The MIT papers from 2016 and 2019 opened the door, but the field is still working out exactly which protocols, durations, and individual factors matter.

For a healthy adult who wants to try a daily 12-minute audio practice grounded in this research — backed by a money-back guarantee — it's a reasonable experiment. For someone with a serious medical condition, the appropriate path is to talk to a qualified physician, not to rely on consumer audio.

References

1. Iaccarino HF, et al. Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature. 2016;540(7632):230-235. PMID: 27929004
2. Martorell AJ, et al. Multi-sensory Gamma Stimulation Ameliorates Alzheimer's-Associated Pathology and Improves Cognition. Cell. 2019;177(2):256-271.e22. PMID: 30879788
3. Sharpe RLS, et al. Gamma entrainment frequency affects mood, memory and cognition: an exploratory pilot study. Brain Inform. 2020;7(1):17. PMID: 33226543
4. Chaieb L, et al. Auditory beat stimulation and its effects on cognition and mood states. Front Psychiatry. 2015;6:70. PMID: 26029120