Trio of Scientists Wins Medicine Nobel for a Method to Turn Nerve Cells On and Off With Light, Helping to Unravel the Brain’s Mysteries

Karl Deisseroth, Peter Hegemann and Georg Nagel received the 2026 award for their contributions to a revolutionary technique in neuroscience called optogenetics, which allows researchers to examine precise connections between neuronal activity and behavioral outcomes in live animals

Margherita Bassi | Daily Correspondent

October 5, 2026 3:33 p.m.

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This year’s Nobel Prize in Physiology or Medicine went to three scientists who laid the foundations for optogenetics, a revolutionary technique in neuroscience that illuminates—literally—direct connections between the brain’s nerve cells and behaviors, emotions and even memories. Neuroscientist Karl Deisseroth of Stanford University, biophysicist Peter Hegemann of the Humboldt University of Berlin and biophysicist Georg Nagel of the University of Würzburg in Germany were announced as the recipients on October 5.

“How does an organ composed of nearly 90 billion remarkably diverse neurons, connected through vast circuits, transform this complex interplay of perception, memory, prediction and decision-making into a single, purposeful behavior?” said Abdel El Manira, a member of the Nobel Prize committee and a neuroscientist at the Karolinska Institute in Sweden, during the award announcement. “Answering this question … requires establishing cause and effect.”

Deisseroth, Hegemann and Nagel’s work contributed to the creation of a tool that can do just that, serving as a sort of neuronal switch that can precisely turn specific nerve cells on and off. Optogenetics works by genetically modifying an animal’s targeted neurons to have special light-sensitive proteins. Shining a specific color of light on these cells makes them respond, allowing researchers to investigate what specific cells do in the brains of live animals.

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The story begins decades ago. In the early 2000s, Hegemann and Nagel discovered a protein called channelrhodopsin in a type of green algae named Chlamydomonas reinhardtii. These strange single-celled organisms were somehow able to sense and swim toward light, and the newfound protein held the key. When hit with blue light, channelrhodopsin—located on the cell surface—opens and allows charged ions to rush into the cell, generating an electrical impulse.

Adding the protein to other organisms’ cells made them light-sensitive, too. The pair inserted a gene for channelrhodopsin into embryonic human kidney cells and hamster kidney cells, giving the other species’ cells this unique property.

Around the same time, Deisseroth was starting his own lab at Stanford and searching for a way to trigger electrical impulses in specific neurons. These signals help nerve cells send messages to one another. He learned about Hegemann and Nagel’s work and asked them for access to the DNA that encoded channelrhodopsin. Once acquired, Deisseroth put it into rat neurons in a dish—and doing so made them react to blue light.

He had been examining multiple potential methods, but this one stood out. “It was the approach with the highest risk, but it turned out to be the one that worked best, and that was a valuable lesson,” Deisseroth says in a statement. “There were many additional steps in development, each one critical. It took years to really build into a whole technology.”

Deisseroth and his team soon figured out how to stimulate the altered brain cells in live animals, using an ultrathin, flexible optical fiber to deliver the light. They even made the whiskers of living mice move using the technique. Today, researchers can use several colors of light for optogenetics, thanks to the discovery of channelrhodopsin proteins sensitive to other hues.

“The ability to activate or silence neurons in the brain using laser light has opened the door to unprecedented precision,” Andrea Benucci, a neuroscientist at Queen Mary University of London, tells CNN’s Katie Hunt.

Over the years, optogenetics has shed light on how the brain operates and what can go wrong when someone has a condition such as depression, schizophrenia and Alzheimer’s disease, according to Nature’s Miryam Naddaf and Ewen Callaway. Some researchers are even testing whether it can restore vision in people with a type of blindness caused by the genetic disease retinitis pigmentosa, in which the eye’s light-sensitive cells in the retina gradually die.

Neuroscientists have long anticipated that the pioneers behind optogenetics would eventually be named Nobel laureates.

“Many of us had been waiting for this prize for years, because we always felt Peter [Hegemann] deserved it. He never cared much about other people’s opinions, but he was deeply interested in how things really work at the mechanistic level,” neuroscientist Jonas Wietek of Charité—University Medicine Berlin in Germany, tells Nature. He was previously a doctoral student in Hegemann’s lab.

The Nobel committee will continue revealing winners of its various award categories this week and early next week. Each award comes with 12 million Swedish kronor (about $1.2 million), which gets split among the laureates.

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.