Professor György Buzsáki won the Brain Prize in 2011, together with Péter Somogyi and Tamás Freund “for their wide-ranging, technically and conceptually brilliant research on the functional organization of neuronal circuits in the cerebral cortex”.

The Brain Prize is an international award that recognizes and celebrates highly original and groundbreaking advances in any area of brain research, from basic neuroscience to applied clinical research. Since it was founded in 2011 and up until 2025, The Brain Prize has been awarded to 49 scientists from 11 countries.

A Whole Spectrum of Brain Beats

In the natural world and in our bodies, there are many different rhythms which we call oscillations, forming a back-and-forth rhythm. The swing of a pendulum is an oscillation, and so is the cycle of day and night. Our bodies have many oscillations too—like our heartbeat (around 60 times per minute at rest), our breathing (about 12–30 per min at rest), and even the rise and fall of sugar levels in our blood.

The great power of oscillations is that they create balance in a system while using little energy. To understand this, think about the last time you went to a live performance. At the end of the show, people who enjoyed it start clapping. At first, everyone claps with their own rhythm—creating a jumbled mess of sounds. But then something amazing happens. When a few people accidentally by chance clap at the same time (in sync), suddenly the whole crowd joins in with the same rhythm. That rhythm is usually two–four claps per second, or 2–4 Hertz. Once clapping becomes synchronized, everyone’s actions align. This alignment amplifies the collective effect of clapping without increasing individual effort. This means it becomes easier—and costs less energy—to clap along with everyone else than to clap in your own rhythm. Similarly, the easiest and most energy-saving way for brain cells to stay in sync is by using oscillations. That is important, because the brain works hard to save energy wherever it can.

A similar phenomenon happens in brain cells called neurons. When information travels across the brain, millions of neurons need to be electrically active at the same time [1]. By using rhythmic oscillations, the brain coordinates large groups of neurons to be active (to beat) together using very little energy—much like turning many individual neurons “claps” into a synchronized collective “handclap”. This is crucial for helping brain areas communicate, share information, and work together efficiently.

The rhythms of these neural oscillations vary tremendously in different brain regions and different brain states. Fast rhythms can occur up to 200 times every second, at the frequency of 200 Hertz. These fastest transient oscillations are called hippocampal wave ripples and we will learn more about them later. Ultraslow rhythms in the brain might happen only once every 10 s, with a frequency of 0.1 Hertz. In between, there are many different oscillations with different frequencies and functions (Figure 1).

Looking across the whole body, we find very slow rhythms—such as the 24-h circadian rhythms, or even slower ones like the monthly menstrual cycle.

A rhythm like a menstrual cycle that happens once a month has a frequency of about 0.0000004 Hertz—which means it is hundreds of millions of times slower than the fastest rhythms in the brain!

Interestingly, brain oscillations have stayed the same across the evolution of all mammals. This means we have essentially the same brain rhythms as any other mammal—from tiny bats, whose brain weighs 0.16 g and is just a few hundred cubic millimeters in volume, to massive whales, with brains weighing up to 9 kg and up to 8,000 cm³ in volume. Is not it amazing that when brain sizes multiply tens of thousands of times, the fundamental rhythms stay the same?

To visualize this: imagine building one house the size of an apple and another house the size of New York City. You would need very specific building rules to ensure that the structure stays stable as the size becomes so vast (curious readers can read about the structure of geodesic domes). In the brain, timing—in the form of rhythmic oscillations—seems to be such a rule of “construction”.

The Brain’s Musical Grammar

Now that we know about the large collection of rhythms in the brain, we can explore: how do these rhythms relate to each other? The fascinating thing we discovered is that the various types of brain oscillations are very organized, in a hierarchical system [2]. Hierarchy means that the building blocks of the system are like a chain of command, where one rhythm controls another. In the brain, usually the slower oscillations control, or modulate, the faster ones. So the hierarchy flows from slow oscillations to fast oscillations.

Every oscillation has a phase and an amplitude. We can see this with a pendulum: the phase means its position in the cycle—whether it is to the left, right, or at the center, and the amplitude is how far it swings (Figure 2). In the brain, the phase of slower oscillations influences, or modulates, the amplitude of faster oscillations. This is called phase-amplitude modulation.

Phase-amplitude modulation is a brilliant mechanism that creates coupling, or tight connections, between different brain oscillations. To understand this, think about ocean tides. Every day, the ocean has two high tides when water levels peak (and two low tides of the least water levels (Figure 2C). This happens because of the gravitational pull between Earth and the moon (to learn more about the ocean’s tides, watch this video). Simply put, Earth’s rotation relative to the moon’s position determines ocean water levels. In phase modulation terms, the amplitude (water level) of the oceans is phase modulated by the Earth-moon relationship (24-h cycle).

This same principle occurs in the brain, where the phase of a slow oscillation modulates the amplitude of a faster one. Then the phase of that faster oscillation modulates an even faster one, and so on. This is how brain oscillations are coupled together—from the fastest ones occurring hundreds of times per second to slower ones happening once every few seconds, minutes, hours, or even days.

To understand what coupled brain oscillations can be used for, let me share a simple analogy. The language you are reading now is made of letters that bundle together to form words, which combine into meaningful sentences and convey information. You can think of the fastest brain oscillations as individual letters—“A”, “B”, and so on. The slower oscillations in the brain take several fast oscillations, arrange them in the right order, and create “words”. Finally, the slowest brain oscillations combine these “words” to create meaningful “sentences” and carry information across the brain. I call this way of studying brain oscillations “brain grammar”, and it is the main focus of my research.

The Poetry of Memory

One main area of research in my lab is memory—how our memories form in the brain. It turns out that memory formation is linked to the fastest brain oscillation called hippocampal sharp-wave ripples [3, 4] (Figure 3A). These ripples are a strong burst of activity in large groups of brain cells inside a part of the brain called the hippocampus (to learn more about the hippocampus, read this article by the Nobel Laureate Prof. John O’Keefe). They have a frequency of about 130–180 Hertz and last about one-tenth of a second. During sleep, they happen thousands of times throughout the night.

In our research, we discovered that these sharp-wave ripples contain small chunks of memories from events during the day. These ripples are a brain activity that “replays” daily events over and over again—like taking a movie and playing, rewinding and re-playing some parts. This is a mechanism that forms memories and stores them in our brains during sleep.

Like other brain oscillations, these fast ~200 Hertz ripples follow the brain’s hierarchical principle of oscillations. The hippocampal sharp-wave ripples are phase modulated by slower waves of about 10–15 Hertz called sleep spindles [5]. Sleep spindles are coupled to the phase of a ~1 Hertz oscillation that appears when we fall asleep. This ~1 Hertz brain wave, which helps with deep sleep and memory, is modulated by a ~0.1 Hertz wave that follows slow changes in blood flow and brain activity. That wave is modulated by a ~0.017 Hertz rhythm (about once a minute), linked to how awake or calm you feel. This in turn is modulated by a ~0.0011 Hertz rhythm (about every 15 min) coming from the body, which sets the brain’s overall mood and balance.

Going back to grammar terms, you can think of hippocampal sharp-wave ripples as letters representing small chunks of daily events (Figure 3B). The slower oscillations that modulate the ripples, organize these letters into words and sentences. These finally form a “poem” (a whole sequence of events) in our memory (Figure 3C). The letters (chunks of memory) were all there before, but they needed reorganization by an internal “poet” to create the final memory that the brain stores. That poet is the hierarchical system of brain oscillations. The final memory is like a daily movie that we can recall (“I had a lovely day with my family, we saw a beautiful view and ate lunch together”).

During your sleep tonight, your brain will generate thousands of hippocampal sharp-wave ripples. If these patterns were erased, you would not be able to remember anything you read in this article. When the ripples are impaired, for example in mouse models of Alzheimer’s disease, memory fails. Luckily, your brain is going to store meaningful memories from reading this. I hope that one of them will be that the brain uses an amazing internal grammar, made up of many interconnected oscillations—generated by the activity of large groups of brain cells—all dancing together in a very unique and hierarchical way.

Glossary

Oscillations: ↑ A back-and-forth, repeating activity, like tug-of-war.

Hertz: ↑ A unit that measures how many times something happens each second.

Transient Oscillations: ↑ Short bursts of brain waves that show up for a short moment and then disappear.

Hierarchical System: ↑ A structured system where some parts are “in charge” of the behavior of other parts.

Modulate: ↑ To change or adjust something, like its strength or speed.

Phase Modulation: ↑ A process where the timing (phase) of slow brain waves controls the strength (amplitude) of faster brain waves.

Hippocampal Sharp-Wave Ripple: ↑ A fast burst of spiking activity in the hippocampus at time when the brain is “idling”, serving to select and store personal memories.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

I wish to thank Or Raphael for conducting the interview that served as the basis for this paper, and for co-authoring the paper, Iris Gat for providing the figures, and Susan Debad for copyediting the manuscript. I also wish to acknowledge the young reviewers, Collette and Dito, both aged 13, for their valuable comments and contributions during the peer review. Supported by NIH grant U19 NS107616.

Further Reading

• Brain Prize 2011—Cerebral circuit organization
• György Buzsáki—Autobiography

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