Nobel Medicine Prize goes to trio who taught scientists to switch brain cells on and off with light

When Karl Deisseroth finally lay down in his Northern California home in the early hours of Monday morning, he had been up late working on papers and emailing students. The call from Stockholm came before any real sleep arrived — and within the hour he was on the phone with the Associated Press, a Nobel laureate, with school lunches still to make.

Deisseroth, a Stanford University professor and Howard Hughes Medical Institute investigator, was named alongside Peter Hegemann of Humboldt University in Berlin and Georg Nagel, most recently of the University of Würzburg, as winners of the 2026 Nobel Prize in Physiology or Medicine. The Nobel Assembly at the Karolinska Institute in Stockholm awarded the prize for their discoveries leading to optogenetics — a method that uses light to switch individual nerve cells in a living brain on or off with precision that was previously impossible.

People usually think about light as a way of collecting information to observe things. But this is the opposite of that. This is using light to control things, to make things happen, and to do it in a very precise way.— Karl Deisseroth, Nobel laureate and Stanford University professor

The story of optogenetics begins not in a neuroscience lab but in a pond. Hegemann, 71, studied how a single-celled green algae navigates toward light. He and Nagel, 73, identified a specific protein that, when hit by blue light, opens a channel in the cell membrane and generates an electrical impulse. Crucially, they showed that inserting that protein into other cells makes those cells light-sensitive too.

Deisseroth, 54, took that discovery into living animals. Working with the gene that controls the algal protein, he created a light-controlled switch for nerve cells in the brains of mice, then developed tiny fibers to deliver light directly to the modified cells. The result was a tool that lets researchers activate or silence specific neurons — and the circuits connecting them — on demand, in a living brain.

It's a very precise set of tools for doing experiments about how the brain works that are pretty hard to do any other way.— Jeremy Berg, University of Pittsburgh

Berg, who was at the U.S. National Institutes of Health in the early 2000s when it awarded Deisseroth major funding for the optogenetics concept, said the work played out almost exactly as Deisseroth had envisioned it.

The Nobel Assembly said optogenetics opened a new era in neuroscience and is now used in laboratories around the world. Its applications reach well beyond basic research: other scientists are pursuing treatments for autism and schizophrenia based on insights from the technique, and a direct optogenetics approach is already being tested as a treatment for retinitis pigmentosa, a genetic form of vision loss.

It has also helped reveal how specific brain circuits are disrupted, with implications for conditions such as blindness, depression, addiction and dementia. Yet despite these extraordinary advances, the brain still holds countless mysteries, with much more left to learn and discover. And optogenetics has given us a powerful means to take on these challenges.— Abdel El Manira, member of the Nobel Assembly

The prize is worth 12 million Swedish kronor — roughly $1.2 million — shared among the three laureates. Nobel week continues with the physics prize on Tuesday, chemistry on Wednesday, literature on Thursday, the peace prize on Friday, and the Nobel Memorial Prize in Economic Sciences on October 12.

Why it matters — Optogenetics gives scientists an unprecedented ability to probe the brain circuits behind memory, emotion and disease, with early clinical applications already underway for conditions including blindness, depression and addiction.

Reported by abcnews.com, nobelprize.org, reuters.com