An artist's concept illustrating optogenetics. (Photo: Nobel Prize)

How 2026 Nobel in Medicine winners decoded invisible brain circuits

How did a protein found in algae lead to optogenetics? Here's the simple science behind the 2026 Nobel Prize in Medicine.

by · India Today

In Short

  • Optogenetics allows scientists to switch specific nerve cells on, study brain functions
  • Method aids understanding of memories, feelings, behaviour, neurological disorders
  • Technique is also being explored for restoring sight in visually impaired people

Karl Deisseroth, Peter Hegemann and Georg Nagel have jointly won the 2026 Nobel Prize in Physiology or Medicine for their discoveries concerning light-gated ion channels and optogenetics, a method that uses light to control nerve cells and study how they shape memories, feelings and behaviour.

Their exemplary work gave scientists a new way to understand the brain.

An illustartion shows the three Nobel Prize in Medicine winners. (Photo: Noberl Prize)

Instead of only seeing which parts of the brain are active, researchers can now switch specific groups of nerve cells on and observe what happens.

HOW DID THE WORK START?

The discovery began with a rather basic question. How does a single-celled alga called Chlamydomonas swim towards light?

An alga is a simple organism that usually lives in water and makes its own food using sunlight.

Hegemann and Nagel found a protein called channelrhodopsin on the surface of the alga.

The alga Chlamydomonas senses light using its eyespot. (Photo: Nobel Prize)

Protein, as such, is a molecule that performs a specific job inside a living cell. In the case of channelrhodopsin, when blue light hits it, it opens a tiny passage in the cell's outer layer.

This allows electrically charged particles, called ions, to enter the cell and create an electrical signal.

The researchers also found that putting this protein into other cells could make those cells respond to light.

That discovery eventually caught Deisseroth's attention, and he took the baton.

FROM LIGHT TO A BRAIN SWITCH

Deisseroth introduced the gene that produces channelrhodopsin into nerve cells from rats. A gene is a section of DNA that carries instructions for making a particular protein.

Deisseroth successfully activated nerve cells in the brains of living mice. (Illustration: Nobel Prize)

When he shone blue light on the modified nerve cells, they produced a nerve signal. He published this breakthrough in 2005, and within two years, by 2007, he had shown that the same light-controlled switch could work inside the brains of living mice.

This technique became known as optogenetics, essentially, using light to control nerve cells.

HOW HAS OPTOGENETICS CHANGED BRAIN-STUDY?

The brain contains huge networks of nerve cells that constantly communicate with one another.

An illustration of Chlamydomonas genes in frog eggs. (Photo: Nobel Prize)

For decades, scientists could identify brain areas linked to certain activities, but it was much harder to show exactly which nerve cells were responsible for a particular memory, feeling or behaviour.

Optogenetics provided a way to test those connections.

Researchers can now use light to activate selected nerve cells and then observe the effect.

The technique has helped scientists identify groups of connected nerve cells, called nerve circuits, involved in specific memories, feelings and behaviours linked to neurological and psychiatric disorders.

Furthermore, the technique is also being explored as a way to restore sight in people with visual impairment.

The Nobel Assembly said the three scientists' work has laid the foundation for a new era in neuroscience, helping researchers tackle one of humanity's biggest scientific questions of how the brain works.

- Ends