Stanford professor Karl Deisseroth, who helped develop a way to switch brain cells on and off with light, won the 2026 Nobel Prize in Physiology or Medicine on Monday, Oct. 5.

Deisseroth shares the prize with Peter Hegemann of Humboldt University of Berlin and Georg Nagel of the University of Würzburg. The Nobel Assembly at Karolinska Institutet awarded the three scientists for "their discoveries concerning light-gated ion channels and optogenetics," according to the Nobel Committee's announcement.

The prize carries 12 million Swedish kronor, roughly $1.2 million, split equally among the three laureates.

Deisseroth is the D. H. Chen Professor and a professor of bioengineering and of psychiatry and behavioral sciences in Stanford’s schools of engineering and medicine. He earned both his Ph.D. and M.D. from Stanford and has been an investigator at the Howard Hughes Medical Institute (HHMI) since 2014, according to HHMI.

What is optogenetics?

The technique lets researchers use pulses of light to activate or silence individual nerve cells in a living brain. Hegemann and Nagel discovered channelrhodopsin-2, a protein from algae that opens within 0.2 milliseconds of a light flash, in 2003. Two years later, Deisseroth's Stanford lab introduced that protein's gene into rat nerve cells and, by shining blue light on them, triggered a nerve signal that spread to neighboring cells, according to the Nobel Committee's summary.

The method got its name in 2006. By 2007, Deisseroth's team had threaded a thin optical fiber through a small hole in a mouse's skull and activated nerve cells in a living brain.

Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine, said the technique gives scientists a way to map the brain that was previously impossible.

Understanding depression, restoring sight

The Nobel Committee said optogenetics has deepened understanding of depression, anxiety, schizophrenia, Alzheimer's disease and Parkinson's disease. In a 2012 Nature study co-authored by Deisseroth and Nobel laureate Susumu Tonegawa, researchers used optogenetics to activate a hippocampal engram in mice, triggering recall of a fear memory and providing direct evidence that activating a specific population of neurons could evoke a particular memory.

Clinical trials are now underway to restore vision in people blinded by retinitis pigmentosa. In one case, a channelrhodopsin-like protein placed in a blind person's retina allowed the person to discern and grasp objects on a table while wearing special light-emitting glasses.

Deisseroth's motivation traces to his medical training in the 1990s at a psychiatric clinic, where he was struck by patients' suffering and the limited treatments available, Stanford Medicine reported.

A late-night call to Northern California

Deisseroth, a self-described night owl, was up late at his Northern California home working on papers and emailing students when the Nobel Assembly called. He had just gone to lie down. "That's my one obligation I have in the next few hours, to make sure I make their sandwiches," he told The Associated Press about packing school lunches for his children, who were still asleep, per a report carried by Fraser Valley Today.

The award ceremony is scheduled for Dec. 10 in Stockholm.