On Wednesday, April 29, two research groups in the Lake Geneva region received the 2026 Leenaards Science Prize, which comes with a total of nearly CHF 1.4 million in award money. One of the projects aims to reduce the impact of the hepatitis E virus. The other, including EPFL professor Friedhelm Hummel, an international expert in neuroscience and neurological rehabilitation, seeks to restore cognitive functions through electrical stimulation.

People’s ability to orient themselves in their surroundings – an essential function of the human brain – can be temporarily or permanently altered by even a mild traumatic brain injury (like a concussion) or some forms of epilepsy. Around 80% of traumatic brain injuries can be classified as mild to moderate and, of these, nearly 15% result in a disorder that continues more than six months after the trauma. This disorder includes impaired spatial memory, an inability to situate oneself and disorientation. “Even simple tasks like getting your bearings in a city, finding your way and remembering familiar routes can become a real challenge,” says Elena Beanato, a project manager at the HUG Outpatient Clinic for Brain and Mental Health. She is leading the second winning project, in collaboration with Friedhelm Hummel, head of EPFL’s Hummel Lab and associate professor at the UNIGE Faculty of Medicine, and Pierre Mégevand, a neurologist at HUG and researcher at the Human Neuron Lab at the UNIGE Faculty of Medicine.

For now, few options are available for treating this condition. Beanato’s cross-disciplinary research group is working to change that by developing an innovative method for deep brain stimulation without invasive surgery. The team has designed a procedure that uses temporal interference to stimulate areas deep inside the brain. In their method, two high-frequency electric fields are applied to a patient’s scalp. “The two fields intersect deep within the patient’s brain and produce a modulation that can influence neural activity in a targeted way – particularly in the hippocampus, which is a key region for memory and spatial orientation,” says Beanato.

Potential applications for other neurodegenerative diseases

To better understand how their new method affects cognitive function, the research team is working with epilepsy patients who received intracranial electrode implants as part of their treatment. In the second phase of the research, the team is testing their method on patients who have suffered brain trauma. These patients are placed in an immersive virtual reality environment, and scientists measure their ability to orient themselves and move around, both before and after receiving the stimulation. “Our initial tests seem to confirm that the electric-field stimulation improves patients’ spatial orientation capabilities,” says Prof. Hummel. “We hope to eventually develop rehabilitation strategies as well as new therapeutic approaches.”

More information on 2026 Leenaards Science Prize

The 2026 Queen Elizabeth Prize for Engineering honours nine engineers whose pioneering work on modern neural interfaces has restored lost human function and had a lasting impact for people around the world. Among them, UNIL/CHUV and EPFL researchers Jocelyne Bloch and Grégoire Courtine, whose work over the last two decades allowed several impaired patients to regain voluntary movement or to stop suffering from hypo- or hypertension consecutive to spinal cord injuries. “Professors Jocelyne Bloch and Grégoire Courtine are recognised for their development of electronic spinal stimulation technology, which reactivates neural circuits controlling locomotion. By combining targeted electrical stimulation with advanced rehabilitation approaches, their work has enabled individuals with spinal cord injuries to regain voluntary movement”, says the committee of the Prize.

They receive the prestigious award along with seven fellow researchers, all active in the field of neural interfaces: Graeme Clark, Erwin Hochmair, Ingeborg Hochmair, Blake Wilson, John Donoghue, Alim Louis Benabid and Pierre Pollak.

“Our collective effort to build a world in which paralysis is no longer a life sentence has been neither swift nor easy. This prize does not mark the end of the journey, but the responsibility — and the encouragement—to continue the fight against paralysis. Onward!,” declares Grégoire Courtine. “Neurosurgery teaches humility. Innovation demands audacity. This journey has required both—and this prize recognises that this unlikely combination was essential to advance treatments for people with paralysis,” says Jocelyne Bloch.

EPFL President Anna Fontcuberta i Morral is delighted with the announcement: "This prestigious award highlights the excellence, long history and remarkable achievements of the .NeuroRestore team, while giving it international visibility. Big dreams for a better world are based on ambitious vision, courage and interdisciplinary collaboration – in this case between neurosurgery and engineering – which is the strength of teamwork in the service of a common mission. I warmly thank Grégoire and Jocelyne for their exceptional commitment and congratulate them on this global recognition. Above all, this award is a powerful message of hope and encouragement for the future."

One field, many approaches

This year’s Laureates have delivered pioneering achievements in neuroengineering, demonstrating the extraordinary power of engineering to overcome physical limitations. Their work enables technology to interact directly with the brain and nervous system to restore abilities such as hearing, movement, and communication for people affected by sensory loss, paralysis, and neurological disease.

Together, these advances mark a new frontier in neuroprosthetics, where engineering and medicine converge to restore capabilities once thought lost forever. Spanning several decades of research and clinical translation, the Laureates’ contributions have transformed complex neuroscience into practical technologies that have restored independence and improved quality of life for growing numbers of people worldwide.

Modern neural interfaces encompass a range of technologies that connect engineered systems with the nervous system to restore function. Among the most established of these are cochlear implants, which convert sound into electrical signals that directly stimulate the auditory nerve, enabling people who are profoundly deaf to regain functional hearing.

Read the full press release on the Queen Elisabeth Prize for Engineering homepage.

Being able to distinguish individual animals – including their unique history, movement patterns and habits – can help scientists better understand how their species function, and therefore better manage habitats and study population dynamics. Today, most computer vision systems for tracking animals are effective on species with patterns and markings, such as zebras, leopards and giraffes. The task is much more complicated for unmarked species where individual differences are harder to spot. Distinguishing a particular brown bear from its peers in a non-invasive way requires an incredible eye for detail and years of viewing the same bears over time. What’s more, these bears emerge from hibernation in the spring with shaggy fur and having lost quite a bit of weight and then substantially increase their body weight feasting on salmon, as well as fully shedding their winter coat – that’s enough to throw off experts as well as AI algorithms. A team of scientists from EPFL and Alaska Pacific University has developed an AI program that can recognize individual brown bears over time in photos, despite changes in the bears’ appearance and the difficulties associated with image capture for these elusive and far-ranging animals.

Our biological intuition was that head features combined with pose would be more reliable than body shape alone, which changes dramatically with weight gain. The data proved us right – PoseSwin significantly outperformed models that used body images or ignored pose information

Machine learning based on head and posture

The McNeil River State Game Sanctuary in Alaska is home to the world’s largest seasonal population of brown bears. Every summer, nearly 150 of these animals move through this area undisturbed over 500 km² of pristine land. They gather on high-protein sedge meadows, and at large, low-grade waterfalls to catch salmon, providing an opportunity for the few humans allowed in the sanctuary to observe them. “The latter are strictly supervised; this is bear territory!” smiles Alexander Mathis, a professor at EPFL’s Brain Mind Institute and Neuro-X Institute. This remote area is also home to Beth Rosenberg, a researcher at the Fisheries, Aquatic Science, and Technology Laboratory at Alaska Pacific University, for four months of the year. She has built up an extraordinary database of brown-bear images: between 2017 and 2022, she took over 72,000 photos of 109 different brown bears under all sorts of conditions – in the rain, in varying times of day, and with bears in every available behavior and posture (or angle) – in order to fully depict the bears in their natural habitat.

To develop their AI program, called PoseSwin, the scientists drew on their biological expertise to focus on four characteristics of bears that change surprisingly little over time: the shape of the muzzle (which has minimal fatty tissue), the brow bone angle, and the placement of the ears. Crucially, they incorporated pose information – analyzing photos of bears from various angles including frontal, profile, and tilted views. "This pose-aware approach enabled us to use as many pictures as possible, even those that do not clearly show the bear's face perfectly," says Mathis. "Our biological intuition was that head features combined with pose would be more reliable than body shape alone, which changes dramatically with weight gain. The data proved us right – PoseSwin significantly outperformed models that used body images or ignored pose information. "

Capturing a bear’s true identity

The architecture behind the scientists' program is based on transformers – the same fundamental technology that powers large language models like ChatGPT – but adapted specifically for image analysis. “We used a technique called metric learning to train a transformer to understand the relationships between different parts of the images,” says Mathis. That means the algorithm learned not only to recognize individual bears based on the characteristics mentioned earlier, but also to compare two images of bears. The team exposed the algorithm to groups of three photos: two of the same bear taken at different times and one of another bear. The algorithm projected the images onto a multidimensional mathematical space, placing the photos of the same bear near each other and pushing those of the other bears further away. “It is a real game of attraction and repulsion, a digital tug-of-war where images shuffle around until they form coherent groups,” says Mathis. “Each bear ended up being represented as a unique constellation of points, which suggests the AI program was able to capture something fundamental – not just a bear’s appearance but something closer to its identity.” PoseSwin can also flag bears that it has never seen before, which is a major advantage for studies in unenclosed areas where new individuals can appear regularly.

The next step was to apply the program in a new environment. For that, the scientists turned to citizen science: they collected photos taken by visitors to Katmai National Park and Preserve, located just over 60 km from McNeil River, and fed them into the PoseSwin algorithm. The program clearly recognized several of the bears, indicating specifically where the animals move seasonally in search of food. “This is a concrete example of the PoseSwin model’s potential,” says Beth Rosenberg. “The technology could eventually be used to analyze the thousands of pictures that visitors take every year and help to build a map of how brown bears use this expansive area. This helps us to understand what they need, how their population dynamics work, and many other important ecological questions.”

“A bear is a complicated version of a mouse”

Thanks to photos of the bears and some virtual measurements of their morphology, scientists are now able to track Sloth, Rocky, That Bear and around 100 of their peers without interfering with them physically. “The better we can distinguish individual bears, the better we can understand them and their behaviors at the species level,” says Rosenberg. “Bears are at the top of the food chain and ensure the proper functioning of their ecosystem. They are critical to maintaining healthy systems.”

PoseSwin will make field work more broadly applicable for the scientists involved in the study, as well as for other scientists working in other contexts. It also achieved excellent accuracy on benchmark datasets of macaques, suggesting its broad applicability beyond bears. “Bears are perhaps the hardest species to recognize individually,” says Mathis. “We focused on them first with the idea that our program could be adapted to other species from mice to chimps, which seem to exhibit much less visual variation.” The team has provided open-source access to their algorithm and the data used to develop it so that other researchers can use and adapt it as needed.

The scientists plan to continue developing PoseSwin for Alaskan brown bears. Because the program is scalable, they are already able to add data collected in other seasons and from other locations. Their goal is to automate much of the system so that it can help monitor wild animal populations over the long term.

“I have my life back,” says Julie, a participant in the clinical study. After a spinal cord injury left her with chronic bouts of dizziness and fatigue, she had little energy to pursue even basic daily tasks. “Now I can go back to school and finish my PhD.” Daniel, another participant, has spent decades navigating life in a wheelchair after a skiing accident. Thanks to a new type of implant, he was able to pursue his love of para-alpine sit skiing with greater confidence and stability this past winter.

These personal stories, though striking, reflect a lesser-known reality for people living with spinal cord injuries (SCI): the inability to regulate blood pressure. While much of the focus in SCI care has been on restoring movement, a majority of patients—over 70%, according to a survey in 1’479 people conducted for the study—live with chronic hypotension, a condition that leaves them exhausted, cognitively dulled, and prone to fainting.

This is because the projections from the brainstem to the region of the spinal cord that regulates blood pressure are disrupted, leaving the body unable to adjust vascular tone and heart rate in response to daily activities. And if hypotension was not debilitating enough, this deregulation can also lead to life-threatening peaks in blood pressure, known as autonomic dysreflexia.

A major discovery to stabilize blood pressure

In a rare double publication in both Nature and Nature Medicine, a pair of landmark studies led by Grégoire Courtine (EPFL), Jocelyne Block (University of Lausanne/CHUV) and Aaron Phillips (University of Calgary) describe the development of a targeted therapy to address blood pressure regulation in SCI patients. Working with the EPFL spin-off ONWARD Medical, the team has demonstrated how an implanted neurostimulation system successfully restored blood pressure stability.

“First, in the study we’ve published in Nature, we were able to identify the entire neuronal architecture of the spinal cord that is responsible for uncontrolled, life-threatening elevation of blood pressure, called autonomic dysreflexia. We also showed that spinal cord stimulation can compete with this neuronal architecture to safely and precisely regulate blood pressure. This competition occurs over a specific region of the spinal cord that we call the hemodynamic hotspot,” says Grégoire Courtine, director of .NR along with Jocelyne Bloch. He goes on to say, “in the Nature Medicine study, we leveraged this understanding to engineer an implantable system capable of targeting this hemodynamic hotspot with electrical stimulation in order to prevent chronic low blood pressure.”

Over the past decade, a series of patents on this technology were filed by the Swiss and Canadian teams as their discoveries and development progressed. Developed by ONWARD Medical, this implantable system, known commercially as ARC-IM, consists of a new class of electrode arrays, carefully shaped and spaced to target the hemodynamic hotspot. These arrays connect to a purpose-built pulse generator—similar to a cardiac pacemaker—that delivers finely tuned electrical stimulation, calibrated to each patient’s needs. The result is a compact, adaptable system capable of restoring blood pressure stability through targeted neuromodulation.

Safe and effective deployment across multiple clinical studies

The therapy for hypotension involved 14 patients and was validated across four clinical studies in Switzerland, the Netherlands, and Canada, each treated by independent clinical teams.

“The international deployment shows that the surgery and therapy are safe and effective regardless of local practices. It’s a key milestone toward making this technology widely available,” says Jocelyne Bloch.

“Our mechanistic discoveries in Nature were crucial in bridging the gap from foundational neuronal mapping to clinical application and allowed us to move quickly from theory to therapy. The Nature Medicine study demonstrates that low blood pressure after a spinal cord injury has serious medical consequences that must not be clinically ignored and that our neuromodulation therapy for blood pressure instability after SCI can be deployed effectively in diverse clinical settings,” says Aaron Phillips, neuroscientist and director of the RESTORE Network at the University of Calgary.

The results were consistent: once activated, the system restored blood pressure to a functional range, often within minutes. “Based on our experiences with this novel treatment, participants report experiencing less brain fog, having more energy, being able to speak louder, and suffering less from a postprandial dip. In addition, once the surgery was performed by neurosurgeon Erkan Kurt at Radboudumc, this system proved relatively easy to use in their home environment,' says Dr. Ilse van Nes, who successfully deployed the system at the rehabilitation center Sint Maartenskliniek in Nijmegen, Netherlands.

“Its impact extends beyond physical health: by stabilizing blood pressure, the therapy improves mood and independence—elements of daily life that are often compromised after spinal cord injury,” adds Bloch.

Towards large-scale testing

“The goal now is to move toward widespread clinical adoption,” says Professor Grégoire Courtine. “ONWARD Medical has recently received Investigational Device Exemption (FDA IDE) approval to initiate a pivotal trial of this therapy, which is expected to involve approximately 20 leading neurorehabilitation and neurosurgical research centers across the United States, Canada, and Europe. This multicenter study will be crucial to demonstrating the safety and efficacy of the system at scale. If successful, it will pave the way for regulatory approval and reimbursement—bringing this therapy within reach for the broader SCI community.”

As summer winds down, many of us in continental Europe are heading back north. The long return journeys from the beaches of southern France, Spain, and Italy once again clog alpine tunnels and Mediterranean coastal routes during the infamous Black Saturday bottlenecks. This annual migration, like many systems in our world, forms a network—not just of connections, but of communities shaped by shared patterns of origin and destination.

This is where network science — and in particular, community detection — comes in. For decades, researchers have developed powerful tools to uncover communities in networks: clusters of tightly interconnected nodes. But these tools work best for undirected networks, where connections are mutual. Graphically, it looks like these node maps that most of us have already seen:

These clusters can mean that a group of people are all friends on Facebook, follow different sport accounts on X, or all live in the same city. Using a standard modularity algorithm, we can then find connections between different communities and begin to draw useful conclusions. Perhaps users in the fly-fishing community also show up as followers of non-alcoholic beer enthusiasts in Geneva. This type of information extraction, impossible without community analysis, is a layer of meaning that can be leveraged to sell beer or even nefariously influence elections.

When it comes to directed networks — where influence, information, or traffic flows from one point to another — the concept of a “community” becomes much harder to define. Existing methods often ignore direction or use it inconsistently. A new work out of EPFL and University of Geneva redefines what a community means in a directed graph — capturing both who belongs together and how information flows between them.

Enter bimodularity. By using a clever mathematical maneuver, researchers at Dimitri Van De Ville’s Laboratory of Medical Image Processing and Analysis have broken the code. In one elegant, algorithmic sweep, they have added the ever-elusive directionality to network analysis. In other words, they could now detect not only which cities empty out in summer, but where these communities tend to go to find a beach and parasol.

“With bimodularity, we can finally distinguish senders from receivers in a network. That means finer-grained detail in how communities interact — who’s sending, and who’s receiving,” says Van de Ville. And when we can detect who is sending and receiving, we can discover where someone is going — or who is following and who is being followed.

Bimodularity allows for bicommunity detection

“What truly sets this method apart is how it identifies communities — not by clustering nodes, as is typically done, but by clustering edges,” says Van De Ville. In other words, instead of asking which individuals belong together, the algorithm asks which interactions behave similarly in terms of directionality. This edge-based approach allows the researchers to reveal pairs of communities: one that sends information and one that receives it — a new organizational structure they call bicommunities.

The end result is a graph that looks like this:

We now not only have the community of nodes represented by red, blue and yellow clusters with conventional community detection, but we also can detect a second type of community represented by the directional arrows green, orange and purple. This is an important new layer of information, for we can now know who is connected in each community as well as if they are equally part of another community of senders or receivers, influencers or followers, commuters or vacationers.

And while this new discovery has not arrived in time to save us this year from the summer traffic jams, the researchers are optimistic about its imminent implementation in network analysis for a wide swath of applications. To test the theory, they applied it to a well-known data set of neuronal activity that comes from the roundworm C. elegans. The new algorithm not only organized the neural network in a way that perfectly lines up with the anatomical data, but it also even revealed certain new groupings of neurons that shed light on functionality within the nervous system.

“What’s exciting is that bimodularity doesn’t just confirm the known flow from sensory input to motion — it also reveals the intermediate steps in between, like sensory to processing and processing to motion. These could point to causal pathways, which opens up new possibilities for interpreting how information moves through the nervous system. It could, for example, help us understand how brain plasticity reorganizes the network to restore function after a stroke,” says first author and PhD student Alexandre Cionca.

If you’ve accidently cut yourself – a minor cut – then your body would likely heal itself by generating new skin cells at the wound in a phase of healing called proliferation. It’s a whole other story if you cut off a body part. Unlike salamanders who can grow back their tails, we humans are unable to regenerate body parts, even relatively small parts like a finger. That’s because the cells responsible for generating fingers, so-called stem cells, are only actively growing whole fingers during embryotic development.

Similarly, our bodies have a limited ability to heal damage to the nervous system because the stem cells responsible for growing a functioning nervous system are likewise only fully active in the embryo. If you were to zoom into parts of the nervous system, you would see a network of billions of interconnected cells called neurons, the fundamental building blocks of the nervous system responsible for transmitting electrical signals throughout the body. The number of neurons in the body peaks before birth, at roughly 86 billion units, and slowly declines throughout one’s lifetime.

That doesn’t mean that new neurons can’t be made. There is evidence that points to neuron birth in specific regions of the brain, albeit at a slower rate as we age. But unlike skin cells that can regenerate to heal a small wound, there is no way of spontaneously growing new neurons to heal a lesion of the nervous system. So how do you fix a damaged nervous system if the body can’t heal the lesion with new neuron cells?

The importance of neuroplasticity

“In the brain, there is no regeneration or repair, but neuroplasticity,” says Defitech Chair of Clinical Neuroengineering Friedhelm Hummel, who specializes in noninvasive deep brain stimulation. “Rehabilitation is about getting neurons to rewire their branches and make connections across a lesion. The nervous system’s capacity to adapt is called neuroplasticity.”

Neuroplasticity is what gives us the ability to learn new information and adjust to new situations. From childhood to adulthood, those 86 billion neurons that we are born with are constantly firing electrical signals, connecting and rewiring as we learn and adapt, and they do so thanks to the various branches that extend from the neuron’s cell body. The branches that transmit signals from one neuron to the next are called the axons, and those that receive signals from another neuron are called dendrites. In other words, neuroplasticity is the ability of these branches to change the way they connect to each other, essentially adjusting the way the network of neurons fire and transmit electrical signals.

When neurons are no longer functional, or die, neuroplasticity will attempt to rewire the surrounding, intact neuron branches to reestablish communication channels. For large lesions, like blunt trauma or illness or a spinal cord injury leading to paralysis, the gap may simply be too big for neuroplasticity alone to renew meaningful communication channels.

At EPFL, researchers, engineers, doctors and scientists are exploring ways to restore communication pathways of the damaged nervous system, be it in the brain, the spinal cord or the peripheral nervous system. The nervous system may still output useful information, and may also be capable of receiving input thanks to artificial stimulation of the nervous system, both fundamental in the development of rehabilitation protocols of the nervous system for translation into meaningful clinical therapies with life-changing potential.

Prosthetic approach to rehabilitation

Current state-of-the-art prosthetic technology for neurorehabilitation involves interfacing the nervous system with surgically implantable electrodes, usually printed on a flexible material, directly in contact with the brain or the rest of the nervous system. The noninvasive approach to rehabilitation involves placing an electronic device, such as an electrode, on the skin to deliver signals to the nervous system. The pharmaceutical approach involves the use of drug therapy to increase neuroplasticity conducive to learning new tasks. Then there is iontronics, a system based on ion transport instead of electrons, developed at EPFL by Yujia Zhang. As an emerging approach for neurorehabilitation, researchers are exploring ways to communicate with the nervous system by controlling the movement of ions and small molecules.

Neuroprosthetics are devices that aim to restore lost or impaired neural function by interacting with the nervous system. The role of neuroprosthetics is to replace sensory or motor functions, or modulate brain activity.

“There is no one-size-fits-all solution,” explains Silvestro Micera, head of EPFL’s Translational Neural Engineering Laboratory and neuroengineer at both EPFL and Scuola Sant’Anna. His specialty is in the restoration of hand sensory-motor control in people with different disabilities. “Where you interface with the nervous system depends on the function you want to restore, the neurophysiology of that function, and the specifics of the patient’s lesion.”

Among Micera’s expertise is the development of neuroprosthetics that restore touch sensation in hand amputees by interfacing with the peripheral nervous system, specifically the nerves in the arm. “We can simulate the sensation of touch from the missing hand by electrically stimulating the residual nerves in the arm. In practice, we’ve been interfacing with rather large nerves, so we’ve opted to use intraneural electrodes to deliver the stimulation in order to intercept multiple nerve bundles to simulate sensory feedback from the missing hand.”

Where you interface with the nervous system depends on the function you want to restore, the neurophysiology of that function, and the specifics of the patient’s lesion.

Intraneural electrodes are essentially minute electrode arrays, less than 0.3 mm by 3 mm in size, that traverse a section of the nerve fiber. The insertion of intraneural electrodes requires precision neurosurgery and has been successfully performed on amputees in collaboration with Italian partners. Lately, Micera and colleagues have been working to repurpose the intraneural electrodes to make them capable of delivering electrical impulses to restore hand function in people with spinal cord injury.

Neuroscientist Grégoire Courtine and neurosurgeon Jocelyne Bloch, both at EPFL and the Lausanne University Hospital (CHUV), and co-founders of NeuroRestore, are developing a “digital bridge,” a neuroprosthetic system that bridges the gap created by lesions disrupting signals between the brain and the rest of the body, such as in cases of paralysis.

“With our digital bridge, we are translating the paralyzed patient’s intention to move into action,” explains Courtine. “We have successfully helped five individuals who were paralyzed after an accident: three who were able to walk again, and two who were able to move their arms,” says Bloch.

Their digital bridge strategy involves interfacing the patient’s brain to detect brain signals, and translate them to the affected parts of the body such as the arms or the legs via the spinal cord.

At the interface of the brain, Courtine and Bloch are using electrodes, about 5 cm in diameter, which are surgically implanted at the surface of the brain. “I like to call these electronic bones. We simply remove part of the skull, just above the brain region that controls the legs, and replace it with the electronic bone that will listen to those brain cells,” explains Bloch.

Electrical stimulation of the spinal cord

At the spinal cord interface, the duo has opted for a flexible electrode array, about 1 cm by 6 cm in size, developed by Courtine and Bloch’s spin-off ONWARD Medical. This array is expertly inserted by Bloch beneath the vertebrae and wraps around the back of the spinal cord.

ONWARD Medical has recently obtained FDA approval to commercialize their spinal cord stimulation technology in the United States. “It’s the first time in the history of humanity that a therapy has been approved to improve rehabilitation after a spinal cord lesion,” says Courtine.

Electrical stimulation of the spinal cord has also proven useful for treating patients suffering from Parkinson’s disease. “We looked at a group of patients who had tremendous difficulty walking. We applied the same principle of spinal cord stimulation, this time without the digital bridge, and we were able to correct deficits in the patients’ gait and reduce the rate of falling,” says Bloch.

Courtine and Bloch have also investigated use of deep brain stimulation probes, specifically of the lateral hypothalamus, and found improved recovery of lower limb movements in two individuals with partial spinal cord injury.

Most electrodes that interface with the human body – such as the ones used by Micera, or Courtine and Bloch – consist of a circuit printed on a flexible polymer, which despite being flexible, is still relatively rigid compared to the organic nature of the nervous system. Stéphanie P. Lacour, an interdisciplinary neuroengineer at EPFL, is developing a whole new field of stretchable electrodes. She made a breakthrough discovery about stretchable metal films and their applications in soft devices. “I was exploring how to design electrodes that could conform to objects of irregular curvature. The first idea was to deposit metal on a compliant polymer carrier. I started with gold, a ductile metal, and silicone, an elastomer. To my surprise, the metal could be evaporated on the silicone, was electrically conductive, and could retain its conductivity when stretched.”

With our digital bridge, we are translating the paralyzed patient’s intention to move into action.

Driven to connect these stretchable electrodes with biology, she has since been developing innovative, stretchable electrodes at the intersection of robotics: with deployable electrodes that open like a flower 4 cm across to ensure maximum coverage on the surface of the brain while passing through a minimally invasive 1 cm hole in the skull; to auditory implants that closely conform to the curved surface of the brainstem for high-resolution prosthetic hearing; to enhancing electrodes that could interface with potentially any part of the nervous system.

Noninvasive approach to rehabilitation

For treating brain injury, Hummel is investigating ways to stimulate deep structures within the brain and he decided years ago to explore noninvasive solutions. “Deep brain stimulation with a probe is the most established interface for the brain, and yet only two to four percent of Parkinson’s patients can benefit from it,” he explains. “In contrast, noninvasive brain stimulation has the potential to reach a large number of patients.”

By tuning electrical signals delivered via electrodes placed on a patient’s head, Hummel is able to target deep structures within the brain. “Neurons respond to low frequency signals, between one and one hundred Hertz, yet remain unresponsive to high frequency signals in the kilo Hertz range. We’ve taken advantage of these characteristics to target and stimulate very precise regions of the brain, located with the help of magnetic resonance imaging and computational modelling,” explains Hummel.

“In humans, we’ve demonstrated that our non-invasive deep brain stimulation enhances plasticity of the targeted deep brain area,” explains Hummel. Although rehabilitaion studies have yet to be published, several clinical trials are ongoing to demonstrate the potential for improving motor and cognitive functions in impaired populations, such as stroke and traumatic brain injury.”

Micera and his research team have also been exploring non-invasive technology for restoring thermal sensation in amputees. By delivering hot and cold directly on the amputee’s residual arm through a specialized interface, the researchers were able to restore sensations of warmth and cold in the missing hand.

Pharmaceuticals and neuroplasticity

Drug therapy may capitalize on the nervous system’s incredible ability to adapt, specifically its neuroplasticity. Courtine, Bloch and team are exploring how gene therapies may promote nerve growth after spinal cord injury in animal models. The scientists activated growth programs in the identified neurons in mice to regenerate their nerve fibers, upregulated specific proteins to support the neurons’ growth through the lesion core, and administered guidance molecules to attract the regenerating nerve fibers to their natural targets below the injury. Mice with anatomically complete spinal cord injuries regained the ability to walk, exhibiting gait patterns that resembled those quantified in mice that resumed walking naturally after partial injuries.

Iontronics, communicating with the language of cells

For the past two decades or so, researchers around the world have been exploring how to communicate with the nervous system, and printed circuits of electrodes have been used time and again in neuroprosthetics. But electrodes use electrons to produce signals, while neurons use a complex biological mechanism based on ion movements. For example, essential ions used in cell function include potassium and sodium, which are positively charged ions actively controlled by cell membranes to form the molecular basis for all cellular activities. Yujia Zhang, who leads EPFL’s Laboratory for Bio-Ion­tronics, is pioneering the development of droplet-based ionic devices in the emergent field of iontronics.

Electrodes are electronic conductors, and reactions at the electrode-tissue interface are required to mediate the transition from electron flow in the electrode-to-ion flow in the tissue. “Electrodes are inefficient at interfacing with the nervous system. High currents are used to counteract the effect of ion accumulation on the electrodes, known as the electric double layer, which can decrease stimulation efficacy. So, I’ve been exploring ways to develop biocompatible bio-inspired electronics to overcome this issue,” explains Zhang.
He and his team are deploying microfluidic technology to print miniature biocompatible droplet-based iontronic devices, termed dropletronics, which include iontronic diodes, transistors and logic gates, the building block analogues of electronic components. One iontronic transistor measures roughly 250 micrometers in size. “Our iontronic transistor can serve as a biocompatible sensor to record ion movements from sheets of human cardiomyocytes, revealing their beating patterns. Our dropletronics will pave a way to the assembly of miniature bioiontronic systems,” explains Zhang.

Over the last couple of decades, many people have regained hearing functionality with the most successful neurotech device to date: the cochlear implant. But for those whose cochlear nerve is too damaged for a standard cochlear implant, a promising alternative is an auditory brainstem implant (ABI). Unfortunately, current ABIs are rigid implants that do not allow for good tissue contact. As a result, doctors commonly switch off a majority of the electrodes due to unwanted side effects such as dizziness or facial twitching—leading most ABI users to perceive only vague sounds, with little speech intelligibility.

Designing a soft implant that truly conforms to the brainstem environment is a critical milestone in restoring hearing for patients who can’t use cochlear implants.

Now, a team at EPFL’s Laboratory for Soft Bioelectronic Interfaces has developed a soft, thin-film ABI. The device uses micrometer-scale platinum electrodes embedded in silicone, forming a pliable array just a fraction of a millimeter thick. This novel approach, published in Nature Biomedical Engineering, enables better tissue contact, potentially preventing off-target nerve activation and reducing side effects.

“Designing a soft implant that truly conforms to the brainstem environment is a critical milestone in restoring hearing for patients who can’t use cochlear implants. Our success in macaques shows real promise for translating this technology to the clinic and delivering richer, more precise hearing,” says Stéphanie P. Lacour, head of Head of the Laboratory for Soft Bioelectronic (LSBI) Interfaces at EPFL.

Probing “prosthetic hearing” with a complex behavioral task
Rather than simply relying on surgical tests, the researchers ran extensive behavioral experiments in macaques with normal hearing. This allowed them to measure how well the animals could distinguish electrical stimulation patterns as they would with natural acoustic hearing.

“Half the challenge is coming up with a viable implant, the other half is teaching an animal to show us, behaviorally, what it actually hears,” says Emilie Revol, co-first author on the project and a former PhD student at EPFL. She meticulously trained the animals to perform an auditory discrimination task: the monkeys learned to press and release a lever to indicate whether consecutive tones were the “same” or “different.”

“We then introduced stimulation from the soft ABI step by step, blending it with normal tones at first so the monkey could bridge the gap between acoustic and prosthetic hearing,” says Revol. “Ultimately, the goal was then to see if the animal could detect small shifts from one electrode pair to another when only stimulating the soft ABI. Our results suggest that the animal treated these pulses almost the same way it treated real sounds.”

Why a soft array?
“Our main idea was to leverage soft, bioelectronic interfaces to improve electrode-tissue match,” explains Alix Trouillet, a former postdoctoral researcher at EPFL and co-first author of the study. “If the array naturally follows the brainstem’s curved anatomy, we can lower stimulation thresholds and maintain more active electrodes for high-resolution hearing.”

Conventional ABIs rest on the dorsal surface of the cochlear nucleus, which has a 3 mm radius and a complex shape. Rigid electrodes leave air gaps, leading to excessive current spread and undesired nerve stimulation. By contrast, the EPFL team’s ultra-thin silicone design easily bends around the tissue.

Beyond conformability, the soft array’s flexible microfabrication means it can be reconfigured for different anatomies. “The design freedom of microlithography is enormous,” says Trouillet. “We can envision higher electrode counts or new layouts that further refine frequency-specific tuning. Our current version houses 11 electrodes—future iterations may substantially increase this number.”

Improved comfort and fewer side effects
A crucial outcome of the macaque study was the absence of noticeable off-target effects. The researchers report that, within the tested range of electrical currents, the animal showed no signs of discomfort or muscle twitches around the face—common complaints from human ABI users. “The monkey pressed the lever to trigger stimulation itself, time and again,” explains Revol. “If the prosthetic input had been unpleasant, it probably would have stopped.”

Path to clinical translation
Although these findings are promising, the path to a commercially available soft ABI will require additional research and regulatory steps. “One immediate possibility is to test the device intraoperatively in human ABI surgeries,” says Lacour, noting that the team’s clinical partners in Boston regularly perform ABI procedures for patients with severe cochlear nerve damage. “They could briefly insert our soft array before the standard implant to measure if we truly reduce stray nerve activation.”

In addition, every material in an implant destined for human use must be fully medical grade and show robust, long-term reliability. Yet the researchers are confident, thanks to the demanding tests the device has already withstood: “Our implant remained in place in the animal for several months, with no measurable electrode migration,” notes Trouillet. “That’s a critical step forward given how standard ABIs often migrate over time.”

Spinal cord injuries are life-altering, often leaving individuals with severe mobility impairments. While rehabilitation robotics—devices that guide movement during therapy—have improved training for those with spinal cord injuries, their effectiveness remains limited. Without active muscle engagement, robotic-assisted movement alone does not sufficiently retrain the nervous system.

A team at .NeuroRestore, led by Grégoire Courtine and Jocelyne Bloch, has now developed a system that seemlessly integrates an implanted spinal cord neuroprosthesis with rehabilitation robotics. The researchers’ device delivers well-timed electrical pulses to stimulate muscles in harmony with robotic movements, resulting in natural and coordinated muscle activity during therapy. The neuroprosthetics innovation leveraged the the robotic expertise of Professor Auke Ijspeert’s lab at EPFL. This advancement not only enhances immediate mobility but also fosters long-term recovery.

“The seamless integration of spinal cord stimulation with rehabilitation or recreational robotics will accelerate the deployment of this therapy into the standard of care and the community of people with spinal cord injury,” says Courtine. This adaptability ensures that rehabilitation professionals can incorporate this technology into existing rehabilitation protocols worldwide. Combining therapies also presents significant challenges, as each requires precise synchronization. Spinal cord stimulation strategies must be modulated in both space and time to match the patient’s movement, and integrating them with widely used robotic rehabilitation systems requires a flexible and adaptable framework.

The technology relies on a fully implanted spinal cord stimulator that delivers biomimetic electrical epidural stimulation (electrical epidural stimulation). Unlike traditional functional electrical stimulation, this method activates motor neurons more efficiently by mimicking natural nerve signals.

The researchers integrated electrical epidural stimulation with various robotic rehabilitation devices—including treadmills, exoskeletons, and stationary bikes—ensuring that stimulation is precisely timed with each phase of movement. The system uses wireless sensors to detect limb motion and automatically adjust stimulation in real time, allowing for a seamless user experience.

In a proof-of-concept study involving five individuals with spinal cord injuries, the combination of robotics and electrical epidural stimulation resulted in immediate and sustained muscle activation. Not only did participants regain the ability to engage muscles during robotic-assisted therapy, but some also improved their voluntary movements even after the stimulation was turned off.

The researchers also worked closely with rehabilitation centers to test how well the stimulation system integrated with widely used robotic devices. “We visited multiple rehabilitation centers to test our stimulation technology with the robotic systems they routinely use, and it was incredibly rewarding to witness their enthusiasm,” say .NeuroRestore researcher Nicolas Hankov and BioRob researcher Miroslav Caban, the study’s first authors. “Seeing firsthand how seamlessly our approach integrates with existing rehabilitation protocols reinforces its potential to transform care for people with spinal cord injury by providing a technological framework that is easy to adopt and deploy across multiple rehabilitation environments.”

The study also showed the potential of this approach beyond clinical settings, as participants used the system to walk with a rollator and cycle outdoors, validating its real-world impact.

This innovative technology offers new hope for individuals with spinal cord injuries, presenting a more effective rehabilitation approach than robotics alone. By making rehabilitation more dynamic and engaging, it has the potential to significantly enhance recovery outcomes. Future clinical trials will be needed to establish long-term benefits, but the initial results suggest that integrating neuroprosthetics with rehabilitation robotics could redefine mobility restoration after paralysis.

List of contributors

• EPFL Neuro X
• Lausanne University Hospital (CHUV) and University of Lausanne (UNIL)
• Defitech Center for Interventional Neurotherapies (.NeuroRestore)
• EPFL Biorobotics Laboratory
• ONWARD Medical
• Bern University of Applied Sciences
• VAMED Management and Service Switzerland AG
• ETH Zurich Sensory-Motor Systems Lab
• University of Zurich Spinal Cord Injury Center
• Hocoma AG
• Medtronic
• Oxford University
• GBY (Go-by-Yourself) SA
• Université de Bordeaux Institut des Maladies Neurodégénératives
• Zurich University of Applied Sciences (ZHAW)
• MyoSwiss AG

Press kit

Electrical stimulation of the spinal cord is a promising strategy for reestablishing walking after spinal cord injury, recent studies show. But for patients suffering from muscle spasms, the stimulation protocols have a limited effect due to the unpredictable behaviour of involuntary muscle stiffness related to spasticity. Muscle spasticity affects almost 70% of spinal cord injured patients

Now, scientists at EPFL, Università San Raffaele and Scuola Sant’Anna have found a promising way to address and reduce muscle spasticity in patients with incomplete spinal cord injury. It involves zapping the spinal cord with high-frequency electrical stimulation that blocks the abnormal muscular contractions. This high-frequency treatment gives patients suffering from spasticity access to rehabilitation protocols that were previously inaccessible to them with a very good clinical outcome. The results are published today in Science Translational Medicine.

“We’ve found that high frequency electrical stimulation of the spinal cord, coupled with the usual continuous, low-frequency spinal stimulation, is effective during rehabilitation after spinal cord injury, overcoming muscular stiffness and spasms in paralyzed patients and effectively assisting the patients during locomotion,” explains Silvestro Micera, professor at EPFL’s Neuro X Institute and Scuola Sant’Anna.

“This is a safe and effective surgical procedure that offers a new perspective in the treatment of patients with severe damage to the spinal cord. We are planning to extend the indications to different clinical conditions we will define in the next month. We are deeply grateful to the patients who trusted us,” says Pietro Mortini, Head of the Neurosurgery and Stereotactic Radiosurgery Unit at IRCCS Ospedale San Raffaele (Milan) and full professor of Neurosurgery at the University Vita-Salute San Raffaele.

Electrical stimulation of the spinal cord is an indirect way to reach the motor neurons that make muscles move. That’s because the backside of the spinal cord contains sensory neurons which in turn communicate with the motor neurons. In muscle spasticity, it is known that the spinal sensory-motor circuits are overreactive. In fact, the spinal cord is naturally overreactive to stimuli, which is good since it leads to fast reflexes. Normally, that over-reactivity is balanced out by the brain that inhibits the motor circuits. In spinal cord injury, the patient loses messaging from the brain and these inhibitory mechanisms. By indirectly stimulating the motor circuits, the research team has found that high-frequency stimulation of the spinal cord is an artificial and safe way to inhibit that over-reactivity without producing discomfort in patients.

During the clinical trial at San Raffaele Hospital, coordinated by Mortini and Micera, Simone Romeni, first author of the study and researcher at EPFL and Università San Raffaele, proposed to implement high-frequency stimulation taking inspiration from previous work on high-frequency kilohertz blocks of motor circuits by stimulating peripheral nerves.

“At this stage, we can only speculate that high-frequency stimulation acts as a kilohertz block that prevents muscle spasticity," says Micera.

"The clinical data with the two patients point to the benefits of implementing high-frequency stimulation for reducing muscle stiffness and spasms in paralysis. More experiments will be necessary to confirm the potentials of this approach,” concludes Mortini.

Researchers at EPFL and Lausanne University Hospital (CHUV), led by professors Grégoire Courtine and Jocelyne Bloch, have achieved a major milestone in the treatment of spinal cord injuries (SCI). By applying deep brain stimulation (DBS) to an unexpected region in the brain—the lateral hypothalamus (LH)—the team has improved the recovery of lower limb movements in two individuals with partial SCI, greatly improving their autonomy and well-being.

Last year on vacation, it was no problem to walk a couple of steps down and back to the sea using the stimulation.

Wolfgang Jäger, a 54-year-old from Kappel, Austria, has been in a wheelchair since 2006 after a ski accident left him with a spinal cord injury. Participating in the clinical trial, he experienced firsthand how deep brain stimulation could restore his mobility and independence. “Last year on vacation, it was no problem to walk a couple of steps down and back to the sea using the stimulation,” Jäger shared, describing the newfound freedom DBS has given him. Beyond walking, the therapy has improved everyday tasks. “I can also reach things in my cupboards in the kitchen,” he added.

DBS is a well-established neurosurgical technique that involves implanting electrodes into specific brain regions to modulate neural activity. Traditionally, DBS has been used to treat movement disorders like Parkinson’s disease and essential tremor by targeting areas of the brain responsible for motor control. However, applying DBS to the lateral hypothalamus to treat partial paralysis is a novel approach. By focusing on the LH, the researchers at .Neurorestore tapped into an unexpected neural pathway that had not been considered before for motor recovery.

In the study published in Nature Medicine, not only did the DBS show immediate results to augment walking during rehabilitation, but patients also showed long-term improvement that persisted even when the stimulation was turned off. These findings suggest that the treatment promoted a reorganization of residual nerve fibers that contribute to sustained neurological improvements.

This research demonstrates that the brain is needed to recover from paralysis.

“This research demonstrates that the brain is needed to recover from paralysis. Surprisingly, the brain is not able to take full advantage of the neuronal projections that survive after a spinal cord injury. Here, we found how to tap into a small region of the brain that was not known to be involved in the production of walking in order to engage these residual connections and augment neurological recovery in people with spinal cord injury,” says Courtine, professor of neuroscience at EPFL, Lausanne University Hospital (CHUV) and UNIL and co-director of the .NeuroRestore center..

Fundamental neuroscience combined with neurosurgical precision

The success of this DBS therapy hinged on two complementary approaches: discoveries enabled by novel methodologies in animal studies and the translation of these discoveries into precise surgical techniques in humans. For the surgery, the researchers used detailed brain scans to guide the precise locations of the small electrodes into the brain, performed by Bloch at CHUV, while the patient was fully awake.

At this moment, I knew that we were witnessing an important discovery for the anatomical organization of brain functions.

“Once the electrode was in place and we performed the stimulation, the first patient immediately said, ‘I feel my legs.’ When we increased the stimulation, she said, ‘I feel the urge to walk!’ This real-time feedback confirmed we had targeted the correct region, even if this region had never been associated with the control of the legs in humans. At this moment, I knew that we were witnessing an important discovery for the anatomical organization of brain functions,” says Bloch, neurosurgeon and professor at the Lausanne University Hospital (CHUV), UNIL and EPFL, and co-director of the .NeuroRestore centre. .

The lateral hypothalamus’ role in walking recovery

The identification of the LH as a key player in motor recovery after paralysis is in itself an important scientific discovery, given that this region has traditionally only been associated with functions like arousal and feeding. This breakthrough emerged from the development of a novel multi-step methodology that began with whole-brain anatomical and functional mapping to establish the role of this region in walking, followed by experiments in preclinical models to establish the precise circuits involved in the recovery. Ultimately, these results led to clinical trials in human participants.

Without this foundational work, we would not have uncovered the unexpected role this region plays in walking recovery.

“It was fundamental research, through the creation of detailed brain-wide maps, that allowed us to identify the lateral hypothalamus in the recovery of walking. Without this foundational work, we would not have uncovered the unexpected role this region plays in walking recovery," says Jordan Squair, a lead author of the study.

The advanced imaging platform at the Wyss Center played a critical role in this research by providing high-resolution imaging capabilities that enabled the team to map the anatomical and functional activity of neurons across the brain, enabling the identification of the lateral hypothalamus.

Combining DBS with spinal implants for enhanced recovery

These remarkable results pave the way for new therapeutic applications to augment recovery from SCI. Future research will explore integrating DBS with other technologies, such as spinal implants that have already shown their potential in restoring movement after SCI. “Integrating our two approaches—brain and spinal stimulation—will offer a more comprehensive recovery strategy for patients with spinal cord injuries,” says Courtine.