The 2026 Nobel Prize in Physiology or Medicine has been awarded for a method that shows how nerve cells in the living brain shape feelings, memories and behaviours.
- Announcement: the Nobel Assembly at Karolinska Institutet announced the prize on 5 October 2026. The committee's citation reads: "for their discoveries concerning light-gated ion channels and optogenetics".
- Name of winners and prize: Karl Deisseroth (the Howard Hughes Medical Institute and Stanford University, USA), Peter Hegemann (Humboldt University of Berlin, Germany) and Georg Nagel (University of Würzburg, Germany) share 12,000,000 Swedish kronor, one third each.
- Nobel idea in one line: a protein from pond algae, channelrhodopsin, opens an ion channel when blue light hits it, so putting that protein into a nerve cell turns the cell into a switch that light can flip.
- Why it matters: researchers can now test cause and effect in a living brain. Before this, they could watch which brain areas were busy during a behaviour but could not switch one group of cells on and see what followed.
- What to watch: whether the attempts to restore sight in people with visual impairment report results, and the rest of Nobel week, with the physics prize on 6 October and chemistry on 7 October.
The three laureates were honoured by the Nobel Assembly at Karolinska Institutet for this remarkable work. Peter Hegemann and Georg Nagel discovered a protein called channelrhodopsin in a single-celled alga, and Karl Deisseroth turned that protein into a light switch for nerve cells. The alga, Chlamydomonas, swims towards light, and it carried a protein that nobody in neuroscience had asked for. That protein became the switch that let researchers test what a group of nerve cells actually does.
Whichever cell this algal protein is put into, that cell becomes sensitive to light. When blue light illuminates the protein, a channel opens through it, and charged ions flow into the cell. This method of controlling nerve cells with light is called optogenetics. Karl Deisseroth published a breakthrough in 2005, in which he put the gene for channelrhodopsin into nerve cells from rats and triggered a nerve signal by shining blue light on them. Two years later, he made the same light-controlled switch work in the brains of living mice.
Per Svenningsson, Chair of the Nobel Committee for Physiology or Medicine, says: "Optogenetics provides opportunities for mapping the brain in a way that we could once only dream of".
Optogenetics can help establish the causal relationship between a feeling and the brain's neural circuits. Using it, researchers have been able to reveal circuits relevant to neurological and psychiatric disorders. Researchers are also attempting to restore vision in people with visual impairment.