Announcement of the 2026 Nobel Prize in Physiology or Medicine
The prize was awarded for their discoveries of light-gated ion channels and
optogenetics — a revolutionary technique that allows scientists to study how
nerve cells control memories, emotions and behaviour in the living brain.
It began with a simple question: How does a single-celled alga know which way to swim
when it senses light?
Peter Hegemann became fascinated by Chlamydomonas, a microscopic alga that moves
towards a light source. In the early 2000s, his research led to the discovery of
channelrhodopsin, a light-sensitive protein found on the surface of the algal cell.
When exposed to blue light, channelrhodopsin opens a channel that allows charged ions
to flow into the cell, generating an electrical impulse. Hegemann and his
collaborators discovered that the protein could make other cells sensitive to light,
laying the foundation for a revolutionary way of controlling cells with light.
Working alongside Peter Hegemann, Georg Nagel helped reveal the remarkable properties
of channelrhodopsin.
The discovery showed that this protein could act like a light-controlled switch. When
blue light hits channelrhodopsin, a channel opens and charged ions flow through it,
producing an electrical signal. Crucially, the researchers found that the protein
could make different types of cells respond to light.
This insight would prove transformative for neuroscience: if a light-sensitive
protein could be introduced into nerve cells, scientists could potentially switch
their activity on or off with light.
Karl Deisseroth took the discovery of channelrhodopsin from algae into the world of
neuroscience.
He introduced the gene for channelrhodopsin into nerve cells from rats. When he
illuminated these cells with blue light, the cells generated nerve signals.
Published in 2005, the breakthrough demonstrated that light could be used to control
the activity of nerve cells with remarkable precision.
Two years later, Deisseroth took the technique a crucial step further, showing that
this light-controlled switch could work in the brains of living mice.
The method became known as optogenetics. It gave researchers an unprecedented way to
control specific groups of nerve cells and investigate how neural circuits shape
memories, feelings and behaviours.
