Stanford University psychiatrist and bioengineer Karl Deisseroth has won the 2026 Nobel Prize in Physiology or Medicine, sharing the award with German scientists Peter Hegemann and Georg Nagel. The Nobel Assembly at Karolinska Institutet honored the three on October 5 for their discoveries concerning light-gated ion channels and optogenetics, a technique that uses light to control brain cells.
Key Takeaways
- The prize recognizes discoveries that made it possible to switch individual nerve cells on or off in the living brain using light.
- Peter Hegemann and Georg Nagel discovered channelrhodopsins, light-sensitive proteins found in single-celled green algae.
- Karl Deisseroth turned those algae proteins into a light-controlled switch for neurons, with his first successful experiment recorded in his lab notebook in July 2004.
- Deisseroth has led his Stanford laboratory since 2004 and still practices psychiatry, specializing in major depression and autism-spectrum conditions.
- The three scientists previously shared major awards, with Deisseroth and Hegemann receiving the 2021 Lasker Award for Basic Medical Research.
- Deisseroth’s win is one of two U.S.-based Nobel science prizes this week, alongside physicist Francis Halzen of the University of Wisconsin–Madison.
A Discovery That Started in Pond Algae
The science behind this year’s medicine prize began far from the human brain. Single-celled green algae swim toward or away from light, and they do it using proteins called channelrhodopsins. When light hits these proteins, they open a channel that lets charged particles flow across the cell membrane, a basic electrical signal.
Peter Hegemann and Georg Nagel identified these light-gated channels in the early 2000s. Working with colleagues in Germany, they identified the gene for the first channelrhodopsin and, the following year, a second version called channelrhodopsin-2. In 2003, Nagel showed that channelrhodopsin-2 worked in a mammalian cell line, where blue light triggered a strong electrical response. That result hinted at something larger: a protein from algae could carry its light-switching ability into animal cells.
How Karl Deisseroth Turned Algae Proteins Into a Brain Switch
Karl Deisseroth took the decisive next step at Stanford. In July 2004, his lab recorded its first experiment showing that neurons carrying a channelrhodopsin gene could be activated by light. In 2005, his group, collaborating with Nagel and others, used a modified, harmless virus to deliver the algae gene into neurons, which then fired when exposed to light.
The result was a new kind of research tool. With optogenetics, scientists can make specific groups of neurons respond to light and then turn them on or off with millisecond precision. Before this technique, researchers could observe brain activity or disrupt it broadly with drugs or electrodes, but they could rarely control one type of cell at a time. Optogenetics allowed them to test cause and effect, switching on a particular circuit and watching what happens to behavior.
That capability transformed neuroscience laboratories worldwide. Researchers have used optogenetics to study circuits involved in movement, memory, motivation, fear and sleep, mostly in animal models. The Nobel recognition reflects how the method changed the questions neuroscientists can ask, not a finished medical treatment.
A Psychiatrist Who Still Sees Patients
Karl Deisseroth’s path to the prize is unusual among Nobel laureates. He holds the D.H. Chen Professorship of Bioengineering and of Psychiatry and Behavioral Sciences at Stanford University and is an investigator of the Howard Hughes Medical Institute. He also continues to practice as a psychiatrist at Stanford, specializing in major depression and autism-spectrum conditions.
That clinical work shapes his research. Deisseroth has written that psychiatry, more than any other field of medicine, lacks a physical explanation for the symptoms that disable patients. Optogenetics was, in part, an attempt to build tools that could connect brain activity to behavior and, eventually, to the conditions he treats. His Stanford work joins a broader wave of U.S. brain research, including University of Southern California research into brain inflammation in people at high risk for Alzheimer’s.
A Prize Long Anticipated by the Scientific Community
The Nobel caps a long run of recognition for the three laureates. Deisseroth received Japan’s Kyoto Prize in 2018 as its youngest recipient to date. Deisseroth and Hegemann shared the 2021 Lasker Award for Basic Medical Research and Columbia University’s 2022 Louisa Gross Horwitz Prize, an award whose past winners frequently go on to receive Nobel Prizes. Hegemann and Nagel shared the 2013 Louis-Jeantet Prize for Medicine for discovering channelrhodopsin.
For Stanford, the award adds to a list of Nobel laureates that includes structural biologist Roger Kornberg, who won the 2006 Nobel Prize in Chemistry. For the United States, it forms part of a strong week in science: a day after the medicine announcement, Francis Halzen of the University of Wisconsin–Madison received the physics prize for his work on the IceCube Neutrino Observatory in Antarctica.
The laureates will receive their medals and diplomas at the Nobel ceremony in Stockholm on December 10, the anniversary of Alfred Nobel’s death.
FAQs
Who won the 2026 Nobel Prize in Physiology or Medicine?
Karl Deisseroth of Stanford University, Peter Hegemann and Georg Nagel won the 2026 Nobel Prize in Physiology or Medicine for their discoveries concerning light-gated ion channels and optogenetics.
What is optogenetics?
Optogenetics is a technique that makes specific brain cells respond to light, allowing scientists to switch those cells on or off with millisecond precision. It is used mainly as a research tool to study how brain circuits control behavior.
What did Karl Deisseroth discover?
Deisseroth showed that light-sensitive proteins from algae could be placed into neurons and used to control their activity with light. His lab recorded its first successful experiment in July 2004 and published key findings in 2005.
When is the 2026 Nobel Prize ceremony?
The Nobel Prizes are presented in Stockholm on December 10, the anniversary of Alfred Nobel’s death.
