American scientist Karl Deisseroth and German scientists Peter Hegemann and Georg Nagel have won the 2026 Nobel Prize in Physiology or Medicine for their discoveries concerning light-gated ion channels and optogenetics.

The Nobel Assembly at the Karolinska Institutet announced the laureates on Monday, recognising research that has enabled scientists to control the activity of individual nerve cells in living brains using light.

Hegemann and Nagel discovered channelrhodopsin, a light-sensitive protein found in single-celled algae. The protein opens an ion channel when exposed to light, allowing charged particles to flow through cells and generate electrical signals.

Deisseroth subsequently introduced the gene responsible for channelrhodopsin into nerve cells, demonstrating that the cells could be activated with light. His work helped establish optogenetics, a technique that combines genetic and optical methods to control specific nerve cells.

The Nobel Assembly said optogenetics had transformed neuroscience by allowing researchers to investigate how individual neural circuits influence memories, feelings and behaviour.

The technique has also contributed to research into neurological and psychiatric disorders and is being investigated for potential medical applications, including efforts to restore sight in people with visual impairment.

The three laureates will share a prize sum of 12 million Swedish kronor.

Deisseroth is based at Stanford University in the United States, while Hegemann is affiliated with Humboldt University in Berlin and Nagel with the University of Würzburg in Germany.