Nocturnal 
Three scientists have won this year’s Nobel Prize in Physiology or Medicine for working out how to switch individual brain cells on and off using nothing more than light.
Karl Deisseroth, a US psychiatrist and neurologist based at Stanford University and the Howard Hughes Medical Institute, shares the prize with German scientists Peter Hegemann of Humboldt University of Berlin and Georg Nagel of the University of Würzburg. The trio will split 12 million Swedish kronor, around £900,000, the Nobel Assembly at the Karolinska Institute in Stockholm confirmed on Monday, as reported by the BBC and the Guardian.
Their field is called optogenetics, and the Nobel Committee says it has “fundamentally altered our understanding of the brain”. Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine, said: “Optogenetics provides opportunities for mapping the brain in a way that we could once only dream of.”
The winners themselves said it was “absolutely wonderful” to get the award, and that it was an honour to share it with friends, according to the BBC.
How it all started with pond algae
The story begins decades ago with Hegemann trying to figure out why a green alga called Chlamydomonas swims towards light. According to Abdel El Manira, a professor of neuroscience at the Karolinska Institute and member of the Nobel assembly, Hegemann discovered the alga’s “eye spot” contains a light-sensitive protein that converts light almost instantly into an electrical signal, letting it move.
In the early 2000s, Hegemann and Nagel identified these proteins, known as channelrhodopsins. Working with frog egg cells, they showed that when the proteins were hit with blue light, they let charged particles flow into the cell, creating an electrical impulse. They later found that inserting the genetic code for one of these proteins into human or mouse kidney cells made those cells light sensitive too.
Deisseroth took it further, using rats to show that putting the channelrhodopsin gene into nerve cells let him produce electrical signals in them with light. He and colleagues then applied this to the motor cortex of mice, using tiny optic fibres threaded through the skull to trigger movement in the animals’ whiskers.
Why it matters
The technique means researchers can now switch specific neural circuits on or off in the brain, letting them bring memories to life, create feelings, drive behaviours and study which neurons are linked to psychiatric and neurological disorders, the Nobel Committee explained. It is also shedding light on how the nervous system interacts with other organs, including the heart and gut.
Jonathan Levin, president of Stanford University, said the discoveries had “deepened understanding of neural circuits and how they shape feelings, behaviour, and more”, adding: “Their implications are profound, not only for understanding the human brain, but for opening possibilities into new treatments for neurological and psychiatric disorders.”
The committee says scientists have already taken “the first steps” towards turning optogenetics into an actual treatment. In ongoing clinical trials, researchers have used the method to try to restore some vision in people left blind by retinitis pigmentosa, a disease that destroys the eye’s rods and cones, by inserting a light-sensitive protein into the damaged part of the eye.
This year’s award is the 117th time the Nobel Prize in Physiology or Medicine has been handed out. Of the 235 laureates to date, including this year’s trio, only 14 have been women, and none have been black scientists, according to the Guardian.
For now, optogenetics remains largely a research tool rather than a widely available treatment, but with clinical trials already under way, scientists say every day is bringing new discoveries about how the human brain actually works.
