The 2026 Nobel Prize in Physiology or Medicine has been awarded to three scientists who forged a new neuroscience technique that uses light to precisely flip chosen neurons on and off.
Karl Deisseroth, M.D., Ph.D., Peter Hegemann, Ph.D., and Georg Nagel, Ph.D., received this year’s highest scientific honor “for their discoveries concerning light-gated ion channels and optogenetics,” according to the Nobel Prize organization.
Now a widely used method in studies of the brain and behavior, the story of optogenetics started when Hegemann, now at Humboldt University of Berlin, was intrigued about how a species of algae called Chlamydomonas was able to detect and swim towards light. While working at the Max Planck Institute for Biophysics in Frankfurt, Hegemann deduced through experiments that a gene for a light-sensitive protein was responsible for the single-celled organism’s light sensitivity.
Teaming up with Nagel, now at the University of Würzburg but at that time also at the Max Planck Institute, the duo pinned down the key protein and named it channelrhodopsin. Rhodopsin is a channel that allows ions to flow into and out of the cell, but unlike other similar channels that are controlled by electricity, rhodopsin is opened by a certain wavelength of light.
Nagel, an ion channel expert, “used the gene provided by Hegemann to produce the protein in frog egg cells to study its function,” Abdel El Manira, Ph.D., a neuroscientist at the Karolinska Institutet and member of the Nobel committee, explained during the prize announcement this morning. “When exposed to light, the channel opens, allowing positively charged ions to rush in and rapidly generate an electrical signal.”
The pair described their award-winning findings in Science in 2002 and the Proceedings of the National Academy of Sciences in 2003.
“Francis Crick, who in 1953 co-discovered the DNA double helix, famously suggested in the late 90s that light might provide the speed and precision needed to control selected neurons,” El Manira said. “The solution didn't come from studying the brain. It came from a pond with a humble green alga as unlikely hero.”
U.S.-born Deisseroth, a psychiatrist and bioengineer based at Stanford University, then took things to the next level. Working with Nagel, in 2005 he published in Nature his successful efforts to genetically engineer rat nerve cells to express the light switch protein.
Using miniscule optical fibers that beam light into the rodents’ brains, Deisseroth’s team could precisely switch on specific neurons and study their functions.
“For the first time, causal links between specific brain circuits and behavior had been achieved,” El Manira said. “The technology, which soon became known as optogenetics, transformed neuroscience.”
This is the fourth year in a row that the winners of the Nobel Prize for Physiology or Medicine has included an American scientist. Last year’s prize was awarded to Mary Brunkow, Ph.D., Fred Ramsdell, Ph.D., and Shimon Sakaguchi, M.D., Ph.D., for their work on regulatory T cells. Numerous biotechs are currently working to turn the prize-winning cells into new medicines, with Orca Bio becoming the first to receive FDA clearance for a Treg cell therapy in July.
Optogenetics is primarily a basic research tool, used in animal models in research labs worldwide. But the discoveries unlocked by the method, in addition to fueling our growing understanding of the brain, can also prove relevant for fighting disease.
“There are mouse models of dementia, epilepsy, addiction, etc.,” Anna Wedell, M.D., Ph.D., a physician-scientist at the Karolinska Institutet, said during the announcement. “By understanding which cells are active in these diseases in the mouse, we can also understand where to look in the human.”
However, there are some efforts underway to directly apply the technique to diseases, particularly those involving vision loss. In 2021, researchers reported that they had used a viral vector to engineer a rhodopsin channel into the eye cells of a patient with retinitis pigmentosa. When the patient wore special goggles that stimulated the neurons with light, his vision improved.
“It's a little bit special treatment because the patients need to wear special goggles that record the environment and then transmit these recordings into light that is projected to the retina,” Per Svenningsson, M.D., Ph.D., a neurologist at the Karolinska Institutet and chair of the 2026 Medicine Nobel committee, said during the announcement.
Several biotechs are currently working to turn optogenetic therapy into reality for vision loss, including Ray Therapeutics, GenSight Biologics and Nanoscope Therapeutics, the last of which has a candidate awaiting a regulatory decision from the FDA. Big Pharma Novartis has also gotten involved in the field through a series of acquisitions.