The Nobel Prize in medicine has been awarded to three scientists whose work led to a tool that uses light to help unravel how the brain works.
Dr Karl Deisseroth, Peter Hegemann and Georg Nagel carried out research in optogenetics, combining light with genes to switch on and off neurons in living brains.
Separate research from the trio — one of whom lives in the US and two in Germany — resulted in a technique that helps to identify neural pathways responsible for behaviour and disease. It could lead to treatments, such as restoring some vision in people with a genetic form of blindness.
Experts said the advancements greatly expanded the understanding of how the brain is organised.
BREAKING NEWSThe 2026 #NobelPrize in Physiology or Medicine has been awarded to Karl Deisseroth, Peter Hegemann and Georg Nagel “for their discoveries concerning light-gated ion channels and optogenetics.” pic.twitter.com/pkDDEBWtkz
— The Nobel Prize (@NobelPrize) October 5, 2026
“It has let us go from a ‘Rand McNally’ road atlas of the brain to something more akin to ‘Google Earth’,” neuroscientist Patrick Forcelli, of Georgetown University, said.
Dr Deisseroth, 54, is a Howard Hughes Medical Institute investigator and Stanford University professor in California. Mr Hegemann, 71, is at Humboldt University in Berlin, and Mr Nagel, 73, most recently worked at the University of Wurzburg, also in Germany, the assembly said.
The breakthrough began when Mr Hegemann explored how a single-cell type of green algae can swim towards light. He and Mr Nagel discovered a particular protein that, when illuminated by blue light, opens a channel to create an electrical impulse. Putting that protein into other cells makes them light-sensitive.
Brain cells use electrical signals to communicate with each other, but normally they do not respond to light, Dr Deisseroth told the Associated Press. He used what he calls “a trick from nature”, putting the gene that controls that microbial protein into certain cells in the brains of living mice.
Beaming light at those cells — first by using tiny fibres, now with non-invasive methods — can turn neurons on or off while animals do various tasks.
“People usually think about light as a way of collecting information to observe things,” he told AP. “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.”
Optogenetics is mostly a research tool to learn how specific neurons and neural circuits work.
That “gives you, inevitably, ideas for how to correct things that go wrong”, Dr Deisseroth said. “Once you know the cells that are causal, that actually matter for a symptom or for correcting a symptom, you can devise medications or other methods that target those cells.”
Already companies have studies under way trying to treat inherited blindness called retinitis pigmentosa by inserting a light-activated protein into a patient’s retina and then outfitting the person with special light-emitting glasses.
Dr Deisseroth, a physician-scientist, pointed to other scientists pursuing possible treatments for autism and schizophrenia based on information gleaned from optogenetics, he said.
Experts say optogenetics has transformed neuroscience around the world, becoming a mainstay in labs trying to understand the brain pathways involved in behaviour and disease — and hopefully leading to ways to fix those that go awry.
“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,” said the University of Pittsburgh’s Jeremy Berg.
He was at the US National Institutes of Health in the early 2000s when it awarded Dr Deisseroth major funding for “this vision of optogenetics that was pretty much spot-on the way it played out”.
Dr Deisseroth, a self-described night owl, said he was up late in his Northern California home working on papers and emailing students. He had just gone to lie down when he got the call from the Nobel Assembly.
He was so surprised that “I almost couldn’t speak for a little bit”, he told AP. “I almost felt as if I’d lost the power of forming words.”
But he recovered quickly, pointing out that amid all the congratulations that morning, he still had to pack school lunches for his children once they woke up.
“That’s my one obligation I have in the next few hours, to make sure I make their sandwiches,” he said.
Thomas Perlmann, the secretary of the medicine committee, said he reached all three winners on Monday.
The prize was announced at the Karolinska Institute in Stockholm, kicking off Nobels week. The prize money this year is 12 million Swedish kronor (about £900,000), whether for an individual, small group of laureates or organisation.
Monday’s medicine prize is followed by the physics prize on Tuesday, chemistry on Wednesday and literature on Thursday.
After Friday’s peace prize is awarded, the Nobel Memorial Prize in economic sciences will be announced on October 12.
