Three scientists who learned to switch brain cells on with light won the medicine Nobel

Karl Deisseroth of Stanford University, Peter Hegemann of Humboldt University of Berlin and Georg Nagel of the University of Würzburg share the 2026 Nobel Prize in Physiology or Medicine. The Nobel committee, announcing on Oct. 5, cited “their discoveries concerning light-gated ion channels and optogenetics,” a toolkit that lets a laser pulse turn a chosen group of neurons on or off in a living brain.

The prize is worth 12 million Swedish kronor, about $1.2 million, according to STAT, and Al Jazeera puts the award ceremony on Dec. 10.

Channelrhodopsin and the algae behind it

The starting point was a protein from green algae. According to the Howard Hughes Medical Institute, Hegemann and Nagel discovered channelrhodopsin, a light-sensitive protein found in the algae, and Deisseroth then made the breakthrough of applying it to neuroscience. Opsins of this kind are pore-like channels: when light of the right wavelength strikes them, they open and let charged particles cross the cell membrane.

Hegemann and Nagel’s contribution is the reason the citation names light-gated ion channels first. Without a protein that responds to light by letting current through, there is nothing for a laser to switch.

Deisseroth’s step from algae to mammalian neurons

Deisseroth began the optogenetics work in 2004 with graduate students and published the initial technique in Nature Neuroscience in 2005, as Stanford’s announcement lays out the timeline. HHMI says his team showed the channelrhodopsin gene could be delivered into mammalian neurons, so that blue light could trigger nerve signals within milliseconds, and that by 2007 he had demonstrated the technique in living mice.

Getting the protein to work inside a brain took more than the gene. Stanford Medicine’s explainer says researchers use viruses to deliver the opsin-encoding genes into neural tissue and engineered the proteins to reliably reach the neuron surface, the only place they function. Fine fiber-optic cables implanted in animal brains then carry the light pulses. Deisseroth said in that explainer that many funders turned him down because they thought the idea could not possibly work, since opsins had been known for decades without a practical use. STAT quotes him on the payoff: light in this method is used to cause things to happen in cells, “with millisecond precision,” rather than only to gather information about them.

The animal work is where the method built its record, across the range of behaviors that Stanford and Al Jazeera both describe, from social behavior to fear, learning and movement, in animals ranging from mammals to roundworms. Stanford’s announcement credits optogenetics with letting neuroscientists ask which cell type drives a behavior, and Al Jazeera lists learning, fear and movement among the behaviors studied. HHMI adds that the technique is used globally across species.

Parkinson’s, depression and cochlear implants

Stanford’s announcement says the technology has advanced understanding of Parkinson’s disease, depression and social behavior in animal models. Deisseroth also set up a training program that taught thousands of scientists and freely distributed engineered opsin genes to laboratories worldwide, and the Stanford Medicine explainer says optogenetics “is routinely used in thousands of labs all over the world.”

His former postdoctoral adviser, Rob Malenka, said optogenetics has let neuroscientists manipulate neural activity “in a manner that was unimaginable 15 to 20 years ago.” HHMI President Erin O’Shea added, “Karl knows firsthand how complex the brain is and what is at stake when things go wrong.”

Al Jazeera reports that Per Svenningsson, chair of the Nobel committee, said the method offers “opportunities for mapping the brain” that researchers could once only dream of, and that the technology may improve cochlear implants by stimulating the auditory nerve in a more targeted way than electrical signals do. All three laureates, it adds, said they were glad to share the award with colleagues they count as friends.

Stanford’s wording and HHMI’s tally

Stanford’s own description of the prize says Deisseroth was honored “for discoveries leading to optogenetics, which makes it possible to switch on, or off, the activity of individual nerve cells in a living brain.” The technique runs in both directions, and switching cells on is the half that Hegemann and Nagel’s algal protein made possible: blue light opens the channel and the neuron fires.

HHMI notes that Deisseroth is the 36th scientist from the institute to win a Nobel Prize, and Stanford Medicine’s news site identifies him as a professor of psychiatry and bioengineering whose prize recognizes his work in optogenetics. The three-way split follows the structure of the work itself, with two German laboratories supplying the light-gated channel and one American laboratory carrying it into a mammalian brain. STAT lists the same three names with the same affiliations, and the sources describe the disease results so far as coming from animal models.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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