Nobel in Medicine 2026 Honors Technology That Controls Neurons With Light

The Karolinska Institute has awarded the 2026 Nobel Prize in Medicine to three researchers: Karl Deisseroth of Stanford University, Peter Hegemann of Humboldt University in Berlin, and Georg Nagel of the University of Würzburg. Their discoveries paved the way for optogenetics, a technique that uses beams of light to turn individual nerve cells on or off.

Per Svenningsson, chair of the Nobel Committee for Medicine, said optogenetics offers a way to map the brain that could once only be dreamed of. No other method allows such precise study of a living brain, helping researchers understand both how the nervous system works and various neurological diseases and disorders.

From algae to neurons

The foundations lie in microbiology. Late in the last century, Hegemann began studying how the single-celled alga Chlamydomonas detects and reacts to light. The alga has an "eye spot" containing a light-sensing molecule called retinal. Using tiny electrodes, he found that it produced an electrical impulse about 0.5 milliseconds after illumination, 20 times faster than the human eye, which needs at least 10 milliseconds.

In the early 1990s he proposed that the eye spot contains a protein that both senses light and acts as an ion channel. The idea was controversial, since no known channel responded to light by itself. Isolating the proteins failed because they became unstable outside their natural environment. Later, Japanese researchers sequenced the alga's complete DNA, allowing Hegemann's team to identify two candidate genes.

Nagel introduced each gene into frog eggs. The eggs produced the proteins, which settled in cell membranes and, when illuminated, functioned as ion channels. He named the genes channelrhodopsin-1 and channelrhodopsin-2. The second, ChR2, was especially fast, with ion flow in just 0.2 milliseconds. When the gene was put into mammalian cells, which normally do not respond to light, they generated an electrical signal when illuminated.

Controlling neurons

Neurons communicate through electrical impulses mediated by the flow of ions, so controlling ion channels means controlling the neuron. Deisseroth sought a way to toggle specific nerve cells in a living brain, hoping to better understand brain function and open new routes to treating conditions such as depression and schizophrenia. He obtained the ChR2 sequence from Nagel and introduced it into rat nerve cells grown in dishes. Under blue light they reacted immediately, sending an impulse to other neurons. This 2005 result was decisive.

The three later collaborated to find proteins that activate or silence neurons with different wavelengths of light. The term optogenetics was coined in 2006. The Nobel Assembly says the method has revealed neural circuits behind specific memories, feelings and behaviors, and that researchers are using it in attempts to restore sight.