The 2026 Nobel Prize went to optogenetics, a way to switch brain cells on and off with light

The Nobel Assembly at Sweden’s Karolinska Institute announced on Oct. 5, 2026, that the Nobel Prize in Physiology or Medicine goes to Karl Deisseroth of Stanford University, Peter Hegemann of Humboldt University of Berlin and Georg Nagel of the University of Würzburg. The citation reads “for their discovery of a molecular switch for nerve cells,” and the field it launched is optogenetics, which lets researchers turn chosen brain cells on and off with light. The prize is worth 12 million Swedish crowns, about $1.2 million, shared among the three.

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A protein from pond algae

The story starts with an organism that has no brain at all, and no nerves either. Hegemann and Nagel wanted to understand how Chlamydomonas, a tiny single-celled alga, senses light, and the answer turned out to be a single protein called channelrhodopsin. Robert Lucas, a professor of neuroscience at the University of Manchester, explained the mechanism in an explainer first published by The Conversation: when light hits the retinaldehyde inside channelrhodopsin, he wrote, it changes shape.

The explainer, carried by ScienceDaily on Oct. 19, describes what follows. The protein sits in the alga’s outer membrane with parts facing the water outside and inside the cell, and the shape change opens a passage through that membrane. Positively charged particles, including sodium, flow in, and the signal helps the alga swim. Lucas links the original discovery paper in the Proceedings of the National Academy of Sciences, which is where the protein’s behavior was described.

Switching nerve cells with a viral gene and a fiber

Nerve cells run on the same basic physics, using the movement of ions across their membranes to control their activity. The researchers realized that if channelrhodopsin could be put into nerve cells, light might be able to switch them on. In practice, scientists deliver the channelrhodopsin gene to a chosen group of cells, usually inside a disease-disabled virus, and in mice they send light into the brain through a thin optical fiber. The tool is used to turn specific groups of cells on and off to study memory, sleep, sensation and movement.

Thomas Perlmann, secretary-general of the Nobel Assembly, said the method makes it possible to switch the activity of individual nerve cells on or off in a living brain. Per Svenningsson, chair of the Nobel committee, said optogenetics offers a way of mapping the brain that researchers could once only dream of, according to the report of the announcement. The official Nobel press release carries the committee’s own account of the work.

The explainer picks one experiment to show what the technique can do. In a 2012 study at the Massachusetts Institute of Technology, mice received a mild shock in one cage and were later placed in a different cage. When the nerve cells tagged as holding the memory were lit, the animals froze in fear in the new cage, as if they remembered the shock. Deisseroth was an author on that 2012 paper in Nature, and Lucas uses it to show that light can reach a specific set of cells and change what an animal does.

Seeing a cause rather than a correlation is the point: switching cells on and watching behavior change shows that they matter.

Three laureates, three vantage points

Deisseroth, who is 54, is a psychiatrist and bioengineer at Stanford. Hegemann is 71 and Nagel is 73, and the two of them did the algal work that supplied the protein in the first place. According to Perlmann’s account of the call to the laureates, the three are friends who were pleased to share the award with one another. Coverage of the announcement also noted that researchers hope optogenetics could improve cochlear implants by stimulating the auditory nerve more precisely than current electrical devices do, though that is a hope rather than a demonstrated result, and the prize citation itself concerns the molecular switch rather than any therapy built from it.

From mouse brains to the clinic

Optogenetics is already in early-stage clinical trials for people with retinal degeneration, according to Lucas. In those trials, light-sensitive proteins are introduced into surviving nerve cells in the retina to restore some vision, as described in a report in Nature Medicine. Parkinson’s disease and epilepsy are being investigated as possible future targets, with a published review on Parkinson’s among the work Lucas points to, but those uses are still research questions rather than approved treatments.

Lucas ends his piece on the origin of the field, which began with algae in a pond rather than with a plan to treat any disease. He wrote that it is impossible to predict where knowledge will take people. The three laureates were honored for the discovery of the switch; what it will eventually do for patients remains the open part of the story. The clinical trials now under way in retinal disease are the first place that question is being tested in people, and the Parkinson’s and epilepsy work described in the published literature is further behind, still asking whether light-controlled cells can be made safe and useful outside the laboratory.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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