Deisseroth, Hegemann and Nagel share the medicine Nobel for optogenetics

The Nobel Assembly at Karolinska Institutet awarded the 2026 Nobel Prize in Physiology or Medicine on Monday to Karl Deisseroth, Peter Hegemann and Georg Nagel for discoveries on light-gated ion channels and optogenetics. The three will share 12 million Swedish kronor, about 1.2 million dollars at the rate Reuters used in its dispatch from Stockholm.

Deisseroth, 54, works at Stanford University and the Howard Hughes Medical Institute. Hegemann, 71, is at Humboldt University of Berlin. Nagel, 73, is at the University of Würzburg. The assembly said Hegemann made the algal discoveries at the Max Planck Institute for Biochemistry in Martinsried, and Nagel made his at the Max Planck Institute for Biophysics in Frankfurt. Deisseroth was born in 1971, Hegemann in 1954 and Nagel in 1953.

Thomas Perlmann, secretary-general of the Nobel Assembly, said the method makes it possible to switch on, or off, the activity of individual nerve cells in a living brain. Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine, said optogenetics gives laboratories a way to map the brain that they could once only dream of. The official citation is short: discoveries concerning light-gated ion channels and optogenetics.

An algal protein became a switch

The starting point was not a brain. Hegemann studied how a single-celled green alga, Chlamydomonas, swims toward light. With Nagel he identified channelrhodopsin, a protein on the cell surface. Blue light opens a channel in that protein. Charged ions flow through. The flow is an electrical impulse. The protein does the same job in a host cell that is not an alga.

Nagel tested the idea by putting Chlamydomonas genes into frog eggs and found channelrhodopsin-2, a light-sensitive ion channel. In 2003 he and Hegemann reported that the protein could be introduced into human and hamster cells and made to fire an electrical impulse with light. That paper turned a plant-cell curiosity into a tool other laboratories could copy.

Deisseroth took the next step in animal tissue. In 2005 he put the channelrhodopsin gene into nerve cells from rats and triggered nerve signals with blue light. In 2007 he showed that the same switch worked inside the brains of living mice. A fibre or an implanted light source could then turn a chosen circuit on or off while the animal was awake. Older methods either killed cells, blocked them with drugs that spread, or stimulated a whole region at once. Optogenetics asks a narrower question: what does this cell type do in this circuit, at this moment.

What laboratories can now ask

The assembly said the method is now used in laboratories around the world to follow the pathways that lead to behaviour and disease. The press release framed the prize as a way to show how nerve cells shape memories, feelings and behaviours in the living brain. That is a claim about method, not a claim that any disease has been cured. A researcher can label one class of cells, shine light, and watch whether a mouse freezes, seeks a reward, or loses a memory. The same animal can be tested with the light off. The comparison is inside one brain, not between two groups of animals treated with a drug.

Clinical work is narrower than the basic-science use. The assembly said researchers are using optogenetics in attempts to restore sight in people with visual impairment. That line of work tries to make remaining cells in the retina respond to light when the normal photoreceptors have failed. It is not the same experiment as switching a memory circuit in a mouse. The prize citation does not list an approved therapy, a patient count, or a regulator. Anyone reading a hospital press release that treats the Nobel as a treatment announcement is ahead of what Karolinska actually said on Monday.

Money, calendar, and the rest of Nobel week

The 12 million kronor is split equally. Each laureate therefore takes 4 million kronor before tax, about 400,000 dollars on the Reuters conversion. The medicine prize is the first of the week. Physics, chemistry, literature and peace follow on the usual schedule. Reuters said the peace prize is due on Friday. The economics prize, awarded by the Swedish central bank in memory of Alfred Nobel, comes after that. The ceremony itself remains in December in Stockholm, with the peace prize presented in Oslo.

Optogenetics also has a practical constraint that the citation does not spell out but that every laboratory using it already knows. The gene has to be delivered, usually by a virus. The light has to reach the cells, which in a large brain means an implant or a very bright external source. Blue light does not travel far through tissue. Later work swapped in red-shifted channels and better fibres, but the 2005 and 2007 experiments that the assembly highlighted were blue-light experiments in rats and mice. The prize is for the switch, not for a finished map of the human brain.

Monday's announcement closes a twenty-year argument about whether the tool belonged to the biologists who found the algal protein or to the psychiatrist-neuroscientist who put it in a living brain. Karolinska answered by splitting the prize three ways. Hegemann and Nagel found the channel. Deisseroth made it a method for nerve circuits. Laboratories that already order channelrhodopsin plasmids will not change their Tuesday protocol because of the call from Stockholm. What changes is the public record of who is credited for a technique that now sits in ordinary methods sections, next to the patch clamp and the calcium dye.