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

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. 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. 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 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.