The 2026 Nobel Prize in Physiology or Medicine has been awarded to Karl Deisseroth, Peter Hegemann and Georg Nagel for their discoveries concerning light-activated ion channels and optogenetics, the Nobel Assembly at the Karolinska Institutet announced in Stockholm. The method allows researchers to switch individual nerve cells on and off in a living brain using light, opening a new era in neuroscience.
Optogenetics «reveals how nerve cells shape memory, emotions and behaviour in the brain», the Nobel Committee said. «Understanding how the brain forms memories, emotions and behaviours has long been a dream for researchers», the committee noted, adding that the three laureates «laid the foundation for a new era in neuroscience».
Karl Deisseroth, a professor of bioengineering and of psychiatry and behavioural sciences at the Howard Hughes Medical Institute and Stanford University, transformed the protein channelrhodopsin into a light-controlled switch for nerve cells. He introduced the channelrhodopsin gene into the nerve cells of rats. By illuminating the cells with blue light, he was able to activate a nerve signal. He published this discovery in 2005. Two years later, he made the light-controlled switch work in the brains of living mice.
Peter Hegemann, a professor of neuroscience at Humboldt University in Berlin, and Georg Nagel, a professor of molecular physiology at the University of Würzburg, discovered the extraordinary protein channelrhodopsin in a single-celled alga. Hegemann wondered how Chlamydomonas, a single-celled alga, is able to swim towards a light source. In the early 2000s, he and Nagel discovered channelrhodopsin, an algal protein with unique properties located on the cell surface. When illuminated by blue light, a channel opens through the protein. Charged ions then flow into the cell, creating an electrical impulse. The two German scientists found that regardless of the cell into which they inserted the protein, those cells became sensitive to light.
Thanks to optogenetics, researchers have been able to reveal the neural circuits that govern specific memories, feelings and behaviours relevant to neurological and psychiatric disorders. In clinical settings, researchers are using the method in attempts to restore sight in people with visual impairment. «Optogenetics has radically changed our understanding of the brain», the Swedish academics said. «Every day it brings new discoveries, helping to solve one of humanity's great mysteries: how our incredible brain works».
The prize, awarded by the Nobel Assembly at the Karolinska Institutet, recognises a body of work that began with basic questions about how a microscopic alga responds to light and grew into a tool now used in laboratories around the world. The method has become a standard technique for mapping the brain's circuitry, allowing scientists to link specific cells to specific behaviours and to test how those circuits go wrong in disease. The committee noted that the discoveries have already led to new insights into conditions such as Parkinson's disease, depression and addiction, and that the approach continues to yield fresh findings daily.
For the field of neuroscience, the award highlights how curiosity-driven research on a single protein can transform an entire discipline. The three laureates will share the prize, which was announced at a press conference in Stockholm. Their work stands as a reminder that fundamental questions about the natural world can lead to technologies that change how we understand ourselves.