Karolinska awards the 2026 medicine Nobel to Deisseroth, Hegemann and Nagel 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 their discoveries concerning light-gated ion channels and optogenetics. The three will share 12 million Swedish kronor equally. The citation is the 117th medicine prize.

Deisseroth, born in 1971, is the D.H. Chen Professor of Bioengineering and of Psychiatry and Behavioral Sciences at Stanford University and an investigator at the Howard Hughes Medical Institute. He took a PhD at Stanford in 1998 and an MD there in 2000. Hegemann, born in 1954, is Hertie Senior Professor of Neuroscience at Humboldt University of Berlin. His doctorate, in 1984, came from the Max Planck Institute for Biochemistry at Martinsried, where the prize-cited algal work was done. Nagel, born in 1953, is professor of molecular plant physiology at the University of Würzburg. He took his doctorate at Frankfurt in 1988. The prize-cited work on the protein was done at the Max Planck Institute for Biophysics in Frankfurt.

The assembly's account starts with a single-celled alga, Chlamydomonas. Hegemann and Nagel found a protein on its surface, channelrhodopsin, that behaves unlike ordinary photoreceptors. Blue light opens a channel through the protein. Charged ions then flow into the cell and produce an electrical impulse. The pair showed that the same protein made other cells light-sensitive, regardless of the cell type into which it was placed. Nagel tested the idea by putting Chlamydomonas genes into frog eggs and identified channelrhodopsin-2 as a light-sensitive ion channel. In 2003 he and Hegemann reported that the protein could be introduced into human and hamster cells and used to generate electrical impulses with light.

Deisseroth took that protein into nerve cells. In 2005 he published the insertion of the channelrhodopsin gene into rat neurons, so that a flash of light triggered a nerve signal. In 2007 he made the switch work inside the brains of living mice. The method is now called optogenetics. 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 provides opportunities for mapping the brain in a way that could once only be imagined.

The practical difference from older brain maps is causal. Twentieth-century work could show that a region was active during a task. It could not prove that those particular cells produced the behaviour. Optogenetics lets a laboratory turn a defined set of cells on or off with light delivered through a fibre, then watch what the animal does. The assembly says researchers have used that control to pick out circuits tied to specific memories, feelings and behaviours that matter in neurological and psychiatric disorders. In the clinic, groups are trying the same proteins in attempts to restore sight in people with certain forms of visual loss. Those trials are attempts, not approved treatments, and the prize citation does not claim a licensed therapy.

The timeline matters for anyone reading the award as a sudden invention. The algal protein was characterised in the early 2000s. The first nerve-cell demonstration is two decades old. What the assembly is marking is the chain from a plant-physiology curiosity to a tool that laboratories now treat as standard. Hegemann and Nagel supplied the channel. Deisseroth supplied the method for using it in neurons and in living animals. Equal shares of the prize follow that division of labour, not a ranking of the three.

The money is 12 million kronor, about 1.2 million dollars at the rate Reuters used on Monday, or about 900,000 pounds in the Guardian's conversion. Each laureate therefore receives 4 million kronor before tax. Announcements for physics, chemistry, literature, peace and economics follow this week. The peace prize is due on Friday.

One concrete limit sits inside the praise. Optogenetics in a mouse brain requires genetic delivery of the protein and a light source at the cells. That is a laboratory setup, not a bedside switch. Clinical sight work has to solve delivery, immune response and the question of which human cells will express the channel. The prize recognises the switch. It does not settle how far the switch travels out of the animal lab.

For readers outside neuroscience, the usable fact is narrower than the phrase "control the brain with light". The control is cell by cell, and only in cells that have been given the gene. A circuit that stores a particular memory can be tagged and then replayed or silenced. A neighbouring circuit that was not tagged stays dark. That selectivity is why the method changed causal experiments. It is also why a headline about switching feelings on and off overstates what a fibre optic in a mouse skull actually does.