2026 Nobel Prize in Medicine Light-Seeking Algae Provided a Switch for Nerve Cells

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The Nobel Assembly at the Karolinska Institute has decided to award the 2026 Nobel Prize in Physiology or Medicine “for their discoveries concerning light-controlled ion channels and optogenetics” to the following individuals: Karl Deisseroth, Howard Hughes Medical Institute and Stanford University, USA; Peter Hegemann, Humboldt University of Berlin, Germany; Georg Nagel, University of Würzburg, Germany.

The 2026 Nobel Prize in Physiology or Medicine is awarded for optogenetics—a method that can be used to demonstrate how nerve cells in the living brain form memories, emotions, and behaviors. Peter Hegemann and Georg Nagel discovered a remarkable protein, channelrhodopsin, in a single-celled alga. Karl Deisseroth transformed the protein into a light-controlled switch for nerve cells. The laureates have laid the foundation for a new era in neuroscience.

How the brain controls emotions, behaviors, and bodily functions was a mystery for a long time. In the 20th century, researchers began to investigate which areas of the brain influence which functions, but due to the methods they used, they were unable to establish causal relationships. The picture they formed of the brain resembled a sketch, full of question marks and unknowns. Now, all of that is changing.

“Optogenetics opens up possibilities for mapping the brain that we could only dream of in the past,” says Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine.

It all began with Peter Hegemann’s curiosity. He wondered how Chlamydomonas, a single-celled alga, is able to swim toward a light source. In the early 2000s, he and Georg Nagel discovered channelrhodopsin, an algal protein with unique properties located on the cell surface. When exposed to blue light, a channel opens through the protein. Charged ions then flow into the cell, generating an electrical impulse. They found that the cells into which they introduced the protein—regardless of the cell type—became light-sensitive.

Karl Deisseroth introduced the gene for channelrhodopsin into rat nerve cells. By exposing the cells to blue light, he succeeded in triggering a nerve signal. He published this breakthrough in 2005. Two years later, he succeeded in making this light-controlled switch function in nerve cells in the brains of living mice.

This method of controlling nerve signals using light is now known as optogenetics and has rapidly gained prominence worldwide. Using optogenetics, researchers have succeeded in identifying neural circuits that control specific memories, emotions, and behaviors relevant to neurological and psychiatric disorders. In clinical medicine, researchers are using this method to restore vision in people with visual impairments.

Optogenetics has fundamentally changed our understanding of the brain. Every day, new discoveries are made that help solve one of humanity's greatest mysteries: How does our incredible brain work?

• Karl Deisseroth, born in 1971. Received his Ph.D. in 1998 and his M.D. in 2000 from Stanford University, USA. D.H. Chen Professor, Professor of Bioengineering and of Psychiatry and Behavioral Sciences at the Howard Hughes Medical Institute and Stanford University, USA.
• Peter Hegemann, born in 1954. Received his Ph.D. in 1984 from the Max Planck Institute for Biochemistry in Martinsried, Germany. Hertie Senior Professor of Neuroscience at Humboldt University in Berlin, Germany. The discoveries recognized by the award were made at the Max Planck Institute for Biochemistry in Martinsried, Germany.
• Georg Nagel, born in 1953. Received his Ph.D. in 1988 from the University of Frankfurt am Main. Professor of Molecular Plant Physiology at the Chair of Molecular Plant Physiology and Biophysics – Botany I at the University of Würzburg. The discoveries recognized by the award were made at the Max Planck Institute for Biophysics in Frankfurt am Main. 

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