On October 5, Stockholm local time, the Nobel conference of Karolinska Institute announced that the 2026 Nobel Prize in physiology or medicine would be awarded to Karl deisseroth, Peter hegemann and Georg Nagel in recognition of their "discovery of light gated ion channels and pioneering optogenetics".

This technology enables researchers to use light to turn on or off the activities of specific nerve cells in the living brain, thus revealing with unprecedented accuracy how nerve cells shape memory, emotion and behavior.

Per svenningsson, chairman of the Nobel Committee for physiology or medicine, commented: "optogenetics provides us with the opportunity to map the brain in a way we could only dream of."

01、 From algal eye point to neural switch

How the brain governs emotion, behavior, and physical function has long been a mystery. In the 20th century, researchers began to study which regions of the brain affected which functions, but limited by the methods at that time, they could not prove causality. Their brain picture is like a sketch, full of question marks and unknowns. Now, all this is changing.

It all started with Peter hegemann's curiosity. He wondered how the unicellular alga Chlamydomonas could swim towards the light source. In the early 1990s, hegemann began to study the phototaxis behavior of this green alga. He found that only half a millisecond after the algae eye point was irradiated by light, it would produce an electric pulse, which was surprisingly fast - the reaction of human eyes to light took at least 10 milliseconds.

Hegemann thus proposed a bold hypothesis: there may be a single protein complex in algae, which can not only capture light, but also directly act as an ion channel. This was met with many doubts at that time, because it was known that none of the ion channels could respond to light by themselves.

At the beginning of the 21st century, hegemann and Georg Nagel discovered channelrhodopsin, an algal protein with unique properties, which exists on the cell surface. When it is irradiated by blue light, a channel opens in the protein. Charged ions then flow into the cell, generating an electrical pulse. They found that no matter what kind of cells they put this protein into, these cells will become sensitive to light.

If hegemann and Nagel found the "light control part", Karl deisseroth turned it into the "control panel" of neuroscience. Deisseroth is a psychiatry trained doctor. After establishing a laboratory at Stanford University, he has always hoped to have a deeper understanding of how nerve cells operate in the living brain to help those patients with mental diseases who have limited treatment options and are often troubled by side effects.

In 2005, deisseroth team introduced ChR2 gene into cultured rat neural cells. After blue light irradiation, these neurons immediately generate action potentials and can propagate to other neurons. This is the first demonstration that ChR2 can faithfully drive neuronal firing.

In 2007, they further developed an optical fiber neural interface, which couples the laser diode with the optical fiber to accurately deliver light to the deep brain region of freely moving mice, and successfully controlled the movement of tentacles through light stimulation. Since then, researchers can not only control neurons in the Petri dish, but also "write" nerve signals in the awake and behaving animal brain.

This method of controlling neural signals with light is now known as "optogenetics" and has rapidly had a global impact.
 

02、From "reading brain" to "writing brain"

The core value of optogenetics is to promote neuroscience from an observational discipline to a causal intervention discipline. Traditional electrophysiological, injury, pharmacology and imaging methods can establish the correlation between neural activity and behavior, but it is difficult to manipulate specific cell types with millisecond accuracy in the complete circuit.

Optogenetics has spatial targeting, genetic selectivity and temporal accuracy at the same time: researchers can turn on or off these cells by simply introducing the light-sensitive protein gene into specific neurons and then irradiating them with light.

With the help of optogenetics, scientists have been able to reveal the neural circuits that control specific memories, emotions and behaviors. For example, labeling and reactivating fear memory related neurons in the mouse hippocampus can trigger fear recall; After the active neurons are reactivated by optogenetics when exploring a safe environment, the mice will show fear in the originally safe environment, indicating that the memory content can be causally manipulated in the imprinted cell population.

In emotion research, optogenetics has helped to analyze how projection specific circuits in amygdala, bed nucleus of stria terminalis (BNST) and other regions drive anxiety, reward and avoidance, respectively. In motion control, the midbrain motor area is proved to be composed of multiple parallel, projection defined modules, which control speed, posture and fine motion respectively.

In addition, inhibitory optogenetic tools are also constantly developing, from the chloride pump nphr to the natural light gated anion channel gtacr, which provides an important tool basis for researchers to achieve bidirectional regulation of neural activity.

Clinical translation has also made progress. In patients with retinitis pigmentosa, researchers introduced photosensitive proteins into retinal ganglion cells through viral vectors, and then transmitted light pulses with the help of engineered goggles, which has achieved partial vision recovery. A number of relevant clinical trials are ongoing. Moreover, optogenetics has also promoted the development of complementary technologies such as chemical genetics, providing a richer toolbox for the study of neurological and psychiatric diseases.

Introduction of winners

• Karl Deisseroth， Born in 1971, he received his Ph.D. from Stanford University in 1998 and his M.D. in 2000. He is currently the named Professor of Howard Hughes Institute of medicine and Stanford University D.H. Chen, and professor of bioengineering and psychiatry and behavioral sciences. He introduced ChR2 into neurons, proved that light can trigger action potentials, and promoted the application of optogenetics in living animals, formally proposed and defined the term "optogenetics".

• Peter Hegemann， Born in 1954, he received his doctorate from the Max Planck Institute of biochemistry in Martinsried, Germany, in 1984. He is now a senior professor of Neuroscience at hertie, Humboldt University, Berlin. He was curious about the phototaxis behavior of algae, put forward the hypothesis of a single protein complex, and found that the channelopsin gene was the key promoter of the discovery of channelrhodopsin.

• Georg Nagel， Born in 1953, he received his doctorate from the University of Frankfurt, Germany, in 1988. He is currently a professor in the Department of molecular plant physiology and Biophysics at the University of Wurzburg. He made his award-winning discovery at the Max Planck Institute for Biophysics in Frankfurt. With his expertise in frog oocyte heterologous expression systems, he proved that chr1 and ChR2 are true light gated ion channels, providing a core tool for optogenetics.

Reference article: https://www.nobelprize.org/prizes/medicine/2026/press-release/