Nobel Prize hails discoveries that allow scientists to control nerve cells with light

Karl Deisseroth, Peter Hegemann and Georg Nagel share the 2026 Nobel Prize in Physiology or Medicine for work that transformed the study of the brain

Three scientists whose discoveries turned a light-sensitive protein from algae into a powerful tool for neuroscience have been awarded the 2026 Nobel Prize in Physiology or Medicine.

Karl Deisseroth, of the Howard Hughes Medical Institute and Stanford University in the United States, Peter Hegemann, of Humboldt University of Berlin, and Georg Nagel, of the University of Würzburg in Germany, share the award ‘for their discoveries concerning light-gated ion channels and optogenetics’.

Their work allows researchers to control the activity of selected nerve cells using light, helping reveal how networks of cells contribute to memories, emotions and behaviour. The technique, known as optogenetics, has changed how scientists investigate the brain and the processes involved in neurological and psychiatric disorders.

The discoveries began with a question about a single-celled alga: how does it detect light and swim towards it?

Hegemann investigated the light-sensitive machinery of Chlamydomonas. Working with Nagel, he discovered and characterised channelrhodopsins, proteins in the alga’s cell membrane that act as light-gated ion channels.

When illuminated, these channels open and allow electrically charged ions to cross the membrane, changing the cell’s electrical activity. Crucially, the researchers showed that the proteins could also make other cells sensitive to light.

Deisseroth and his colleagues brought this principle into neuroscience. By introducing the gene for channelrhodopsin into rat nerve cells, they made it possible to trigger electrical signals with pulses of blue light. The breakthrough was published in 2005; by 2007, the approach had been extended to the brains of living mice.

Together, these advances established a way to investigate the workings of neural circuits with exceptional precision. Researchers could select particular groups of cells, alter their activity and observe the consequences.

That ability helped address a longstanding difficulty in brain research. Observing that a brain region becomes active during a task can reveal an association, but does not, by itself, establish what that activity causes. Optogenetics allows scientists to test more directly how particular cells contribute to a function.

“Optogenetics provides opportunities for mapping the brain in a way that we could once only dream of,” said Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine.

Scientists have used the technique to investigate circuits involved in memory, emotion and behaviour, as well as communication between the nervous system and organs such as the heart and gut. Different light-sensitive tools can be used to activate or suppress selected cells, helping researchers examine how those cells work together.

For Nagel, the award recognises a career connecting biophysics and plant physiology with neuroscience. He was professor of molecular plant physiology at Julius-Maximilians-Universität Würzburg from 2004 to 2021 and continued research and teaching as a senior professor until the end of June 2026. The university celebrated him as its 15th Nobel laureate. 

Optogenetics also has potential medical applications. Researchers are investigating whether light-sensitive proteins can help restore some vision in people with severe visual impairment. Such work remains distinct from the technique’s widespread use as a laboratory research tool; optogenetics is not a routine treatment for brain disorders.

The prize highlights how curiosity about a simple organism can lead to discoveries with far-reaching consequences. Understanding how an alga responds to light ultimately gave scientists a new way to explore one of biology’s most complex questions: how the activity of nerve cells produces the functions of the living brain.