The Karolinska Institute has awarded the 2026 Nobel Prize in Medicine to Karl Deisseroth, Peter Hegemann and Georg Nagel for research that led to optogenetics, a technique that uses light to control the activity of selected nerve cells. The method gives scientists a way to examine how specific neurons contribute to brain function and behavior.
The work began outside neuroscience. Hegemann studied how the single-celled alga Chlamydomonas detects light. Using electrodes, he found that it produced an electrical response within about 0.5 milliseconds of illumination. He proposed that a protein in the organism’s eyespot both sensed light and opened a channel through which charged particles, or ions, could pass. Later genetic research helped his team identify two candidate genes. Nagel tested them by placing each gene in frog eggs and exposing the resulting proteins to light. Both proved to be light-sensitive ion channels, named channelrhodopsin-1 and channelrhodopsin-2.
Channelrhodopsin-2, or ChR2, responded particularly quickly. When researchers introduced its gene into mammalian cells, those cells also produced electrical signals in response to light. Deisseroth then obtained the gene from Nagel and introduced it into rat neurons grown in dishes. In 2005, he showed that blue light could trigger electrical impulses in those neurons, demonstrating a way to control their activity. Subsequent work expanded the approach to proteins that activate or suppress neurons at different wavelengths.
The technique, named optogenetics in 2006, has since been used to investigate circuits involved in memory, emotion and behavior. Researchers are also exploring its possible use in restoring sight to people with visual impairment. Its development links observations in algae to experiments on nerve cells, illustrating how findings in microbiology can provide tools for studying the brain. The approach allows scientists to target cells with greater precision, though research applications and potential clinical uses remain distinct.