Professor Silvia Arber won the Brain Prize in 2022, together with Martyn Goulding and Ole Kiehn, for “revolutionizing our understanding of the fundamental cells and circuits underlying mammalian body movement and defining the importance of these elements in health and disease”.

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.

Always On the Move

Right now, as you read these words, you are moving. You might not even notice some of these movements, like your eyes scanning across the page or your chest rising and falling with each breath. Others might be intentional—like shifting in your seat or scrolling down the page. In fact, everything you ever do involves movement, from breathing to walking, talking, eating, grabbing objects, and typing on your phone.

How many different movements can you actually make? If you really think about it, there are countless ways of moving. Your body has over 600 muscles working together to make all these diverse movements possible. Even in so-called “simple” movements that you do not need to think about—like walking, for example—many muscles work together in incredible coordination.

How does the brain control all these movements? It turns out that there is not just one particular brain area that does this. Instead, essentially the whole brain helps to control movements, and millions of brain cells called neurons work together like a grand orchestra. Just as all the instruments in an orchestra must play in sync to create beautiful music, all these neurons must coordinate perfectly to produce the movements we make (Figure 1).

From Brain to Muscle: The Journey of Movement

Even though the many brain regions contribute to movement in some way, scientists have discovered that different parts of the motor system play distinct roles [1, 2]. The motor system is arranged in a hierarchy, which means that commands flow downward—from complex brain areas that plan and coordinate movement, to lower levels including the spinal cord that transmit those instructions to the muscles for execution.

At the top of this hierarchy is the motor cortex, the region that plans movements and sends instructions. Further down it is the brainstem, which acts like a switchboard translating the motor cortex’s commands into practical information about which muscles should move and when. Next is the spinal cord, that connects the nervous system to the muscles through motor neurons—cells that can transmit electrical signals to make muscles contract.

Let us use walking to illustrate how this works (Figure 2). Imagine standing at a crosswalk with a red light. Once the light turns green, information from your eyes ultimately reaches your motor cortex, which signals “start walking”. The brainstem figures out which muscles to activate, then motor neurons in your spinal cord make all the necessary muscles contract at the right time —not only in your legs, but also in your arms, torso, neck, and head. While you walk, your nervous system continuously tracks your movements to ensure you reach the other sidewalk safely.

Finding Patterns in the Brainstem’s “Sky”

Over the past 15 years, I have focused much of my research on understanding the brainstem’s role in the motor system. When I started, the brainstem was like a “black box”—nobody really understood what was going on in there. It was like looking at the night sky without a map and seeing many stars with no connecting pattern. Over time, we found patterns in the brainstem, which is in fact incredibly organized.

One key insight from studying the brainstem’s structure is that different areas control different movement types [3, 4]. One network connects to locomotion, while another handles specialized forelimb (arm and hand) movements, like grabbing your phone. From your brainstem’s perspective, these are completely different. Locomotion is considered “automatic movement”—requiring less conscious planning, even though many muscles must be coordinated. In contrast, skilled forelimb movements like typing or playing piano require fine-tuned planning, intention, and practice. For full body movements like locomotion, brainstem neurons send “branches” through the entire spinal cord to activate these programs. For skilled forelimb movements, other brainstem neurons connect only to specific spinal cord segments—like those controlling arm reaching and grasping—activating the small numbers of specific muscles needed for precise, specialized movements.

Interestingly, some movements can happen simultaneously while others cannot. For example, you can walk and type on your phone at the same time (even though this can be dangerous!), but you cannot play tennis and piano at the same time. This reveals more information about how groups of neurons are organized in the brainstem—some can work in parallel, while others must take turns.

Reading and Writing the Code of Movement

How do scientists like me figure out which brainstem neurons control which body movements? We do various types of experiments, and I want to share two with you here: “reading” and "writing” (Figure 3).

“Reading” means that we measure the electrical activity of neurons and listen to how they “talk” with each other. We do that using tiny electrical probes that record the brain activity of living animals, in our case mice. We know that an active neuron talks rapidly with many signals in a short time, something like “tu-tu-tu-tu-tu-tu” (you can hear an example in this video), while an inactive neuron goes “tu----tu----tu”, much more slowly. Using this recording method, we can identify which neurons are active at a particular moment and region of the brain.

In the lab, we listen to thousands of neurons, all chattering away. We record what they are saying while an animal performs different movements. Some neurons fire rapidly only when the animal is running. Others are active only when the animal is chewing food. By “reading” this neuronal conversation and watching what the animal does, we can start to crack the code of which neurons are responsible for which movements.

The other part of our experiments is “writing” or deliberately activating chosen neurons. After reading the code and understanding which neurons are likely to control a movement, we try to create that movement using optogenetics—a technique that lets us activate specific neurons using light [5]. If we have correctly identified the neurons for a specific movement—say running—then activating them with light should make the animal run. If that indeed happens, we can confirm that we identified the neurons that can produce this movement. Or we can inactivate them and find out whether then this movement no longer occurs or differently.

These methods are extremely useful. They have helped us to identify distinct regions within the brainstem, made of many different types of neurons. Using these “reading” and “writing” methods, we can accurately predict which neurons will control certain movements! It is like finally being able to see the constellations within the vast star systems of the brainstem and enjoying the beautiful order that is revealed.

Stepping Into the Future of Movement Research

The research I do is called basic science—it tackles fundamental biological questions like “How does the brain control movement?”. Though basic science does not directly aim to improve human health, it often brings unexpected discoveries that open new doors for medical uses. For example, in spinal cord injuries, neurons below the injury remain fully functional but receive no instructions from the brain. Understanding how brainstem neurons communicate with spinal cord neurons could help us develop ways to artificially stimulate the right neurons in the spinal cord and restore movement in previously paralyzed areas.

Despite everything we have learned, the biggest question remains: How does everything work together? Your nervous system does not just control your current movements—it simultaneously plans your future movements and tracks past movements that helped you learn something. In a sense, your nervous system is keeping track of your entire life! This raises another interesting question: How do life experiences shape your nervous system’s structure? Imagine duplicating a baby’s nervous system and placing it into another baby who went on to live a completely different life—after 50 years, how different would the two nervous systems be?

There is so much more we can study about the brainstem’s structure, the movement codes it contains, and how neurons communicate in amazing synchronization to coordinate everything we do—which is all movement. These mysteries keep scientists like me excited to continue their research every day.

Glossary

Motor System: ↑ The team of “players”, including the brain, spinal cord, and muscles, that work together to coordinate every movement that a person makes.

Motor Cortex: ↑ The part of the brain that plans movements and provides instructions.

Brainstem: ↑ A region at the base of the brain that processes signals between higher motor centers and the muscles and “codes” for different types of movements.

Spinal Cord: ↑ The main “highway” running down the spine that carries brain signals to muscles via motor neurons and controls reflexes.

Motor Neurons: ↑ Nerve cells that carry the final “move” signals from the spinal cord to the muscles, to make them contract.

Locomotion: ↑ Moving the body from one place to another, like walking, running, or swimming.

Optogenetics: ↑ An experimental tool kit that uses light to turn on or off specific brain cells, to study what functions they are responsible for.

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.

Additional Resources

1. The Brain Prize 2022: Circuits for Movement

2. The Brain Prize Explainer: How we move

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