Deisseroth, Hegemann and Nagel Win the 2026 Nobel in Medicine for a Light Switch on Living Nerve Cells

STOCKHOLM — The 2026 Nobel Prize in Physiology or Medicine was awarded Monday to three scientists who turned a protein from light-seeking algae into a switch for nerve cells, giving laboratories a way to turn circuits in a living brain on and off with light.

The Nobel Assembly at Karolinska Institutet named Karl Deisseroth, Peter Hegemann and Georg Nagel "for their discoveries concerning light-gated ion channels and optogenetics." The prize is 12 million Swedish kronor, to be shared equally. Deisseroth, 54, is 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's summary was a single line of mechanism. "Light-seeking algae gave us a switch for nerve cells." Hegemann and Nagel found the protein, channelrhodopsin, in a single-celled green alga. Deisseroth put it to work in neurons. The method is now used in laboratories worldwide to trace how nerve cells shape memory, feeling and behavior, and to start mapping pathways tied to disease.

The biology began with a swimming cell. Hegemann studied how a green alga moves toward light. With Nagel, he identified a protein that, under blue light, opens a channel and lets ions through, producing an electrical impulse. Inserted into another cell, the same protein makes that cell respond to light. A neuron that does not normally care about a blue flash can be made to fire when the light comes on, and to stop when it goes off. That is optogenetics: a gene for the channel, a light, and a chosen set of cells.

Before the tool, brain activity was watched or broadly stimulated. Electrodes could record. Drugs could bathe a region. Neither could pick one cell type in a living animal and drive it on a millisecond clock. Channelrhodopsin, and later related switches that silence cells instead of firing them, made that possible. A mouse can be trained, a circuit switched, and the change in behavior timed to the light. The assembly called it a new era in neuroscience.

The work was done at Stanford and at the Max Planck Institutes for Biochemistry and Biophysics in Germany. The prize splits the credit the way the method splits. Hegemann and Nagel supplied the channel and the proof that light opens it. Deisseroth showed it could run inside nerve cells and be used as an experiment rather than a curiosity. Later refinements — different colors, switches that inhibit, genetic tricks that put the channel only in one class of neuron — built on that pair of steps.

Clinical use is narrower than the laboratory use, and the Nobel citation is for the discovery, not for an approved therapy. Researchers have tested the same idea in the eye, putting DNA for a light-sensing protein into remaining retinal neurons so they can send a signal when light hits, bypassing cells that have died. That is a repair attempt, not the prize. The prize is the switch itself, and what it has already let basic science see.

The medicine prize, first awarded in 1901, has gone to 232 laureates in 116 awards. Monday's is the first of this year's Nobels. Physics, chemistry, literature, peace and the economics prize follow on the usual schedule. Optogenetics sits in a line of method prizes: tools that changed what questions could be asked, rather than a single disease cured. Restriction enzymes, the PCR reaction and cryo-electron microscopy were honored on that logic. A light-gated channel belongs with them.

What the assembly did not claim is that the brain is solved. The method shows which cells are sufficient to drive a behavior in a given experiment. It does not, by itself, say those cells are the only cause, or that a human illness will yield to the same light. Translation still needs a way to deliver the gene and the light in people, and a reason to believe the circuit in the mouse is the circuit in the patient. Those are the next papers, not the citation.

The citation is specific. Light-gated ion channels, found in an alga that swims toward the sun, became a switch for nerve cells. Three scientists share the prize for making that switch and showing what it can do.