Optogenetics pioneer Karl Deisseroth shares 2026 Nobel Prize in medicine

What the prize recognizes

The 2026 Nobel Prize in physiology or medicine was awarded to Karl Deisseroth, a Stanford professor of bioengineering and of psychiatry and behavioral sciences, together with Peter Hegemann of Humboldt University of Berlin and Georg Nagel of the University of Würzburg. The citation covers discoveries leading to optogenetics, which makes it possible to switch on or off the activity of individual nerve cells in a living brain.

Hegemann and Nagel identified channelrhodopsin, a cell-surface protein in single-celled algae that forms an ion channel in blue light, creating an electrical impulse. Deisseroth's contribution was to insert such light-sensitive microbial proteins, called opsins, into mammalian brain cells so selected cells could be controlled by light. Stanford President Jonathan Levin called him a defining figure in modern neuroscience.

From algal protein to brain circuit control

Deisseroth began the project in 2004 with two graduate students. The team engineered an opsin for expression on the surface of specified rodent nerve cells, publishing the technique in Nature Neuroscience in 2005, and designed an ultrathin flexible optical fiber for delivering light into live rodent brains. They also devised a yellow-light-triggered opsin that inhibited nerve-cell activity.

Using the method, Deisseroth and collaborators examined disorders including depression and Parkinson's disease, reversing Parkinson's symptoms in mice with Anatol Kreitzer of the University of California, San Francisco. His laboratory later developed CLARITY, which renders brain tissue transparent for high-resolution imaging, and in November 2023 he helped launch the Human Neural Circuitry program at Stanford Hospital to study brain activity in real time.

A field now widely shared

Deisseroth instituted an optogenetics training program that has taught thousands of scientists and distributed copies of the engineered opsin gene to labs worldwide, according to Stanford. The method has been adapted to other cell types, including heart and pancreas, and Stanford states it may eventually be used in humans with gene therapy. Stanford describes him as planning to return to work, saying more remains to be discovered.