The Nobel-winning breakthrough that turned light into a remote control for the brain, allowing scientists to switch neurons on and off

Imagine being able to turn on and off specific brain cells with a ray of light. This was science fiction before, but today it is the most potent tool in neuroscience. The research leading to this breakthrough has brought Karl Deisseroth, Peter Hegemann, and Georg Nagel the 2026 Nobel Prize in Physiology or Medicine.

The innovation they pioneered is called optogenetics – a combination of genetics and light that allows switching specific neurons on and off. Rather than just observing which part of the brain is turned on or off, scientists can activate or deactivate specific cells and see what would happen.

This makes all the difference in neuroscience.


The method has been useful to scientists in mapping neural pathways associated with behaviour, perception, and disease. The method has also created possibilities in terms of therapies for inherited blindness, among others such as depression, addiction, autism, and schizophrenia.

The Nobel Prize-winning discovery, on the other hand, did not originate from an attempt to gain control over the brain but rather from a far more basic one: How does a tiny creature react to light?

A strange protein in green algae provided the key

The story began with Peter Hegemann's research into green algae and the way these single-celled organisms respond to light.

Hegemann and Georg Nagel identified proteins that can respond directly to light. One of the proteins acts as a channel in the cell membrane that activates upon exposure to blue light, enabling the transfer of charges across the cell membrane to produce an electrical signal.

This feature was fascinating since electrical signals are the basic principle behind neuron communication.

The brain cells in humans do not respond to bursts of blue light naturally. But researchers realised that the gene that causes production of the light-sensitive protein can be engineered into another cell type.

That insight became the foundation for optogenetics.

Karl Deisseroth helped turn the concept into a practical method for studying living brains.

Researchers would be able to make those neurons respond to light through the introduction of the appropriate gene from the microbe. This would mean that light could be used to affect their activities.

It was a paradigm shift from conventional neuroscience, where scientists could only observe the normal functioning of the brain. They would now be able to ask what happened when those specific neurons were stimulated.

Light became a precision tool for controlling neurons

The brain is made up of billions of neurons linked via incredibly complex neural networks. It is hard to know the function of every cluster since there are several neurons that can be stimulated at once.

Optogenetics provided scientists with an opportunity to isolate certain groups of neurons.

Early experiments involved the use of very thin optical fibres to shine light inside living creatures' brains. Depending on the type of light-sensitive proteins employed, shining the light would stimulate or silence neurons.

This was highly accurate.

The process of communication in neurons happens in milliseconds, and thanks to optogenetics, scientists were able to control neurons' activity on the same timescale.

It made it possible for scientists not only to see where activity happened but also to see if activation of a certain circuit led to a certain behaviour.

Optogenetics thus contributed to the transition of neuroscience from mapping the brain to understanding its functional connections.

In a brain area that controls a certain behaviour, there can be several neurons of different types, doing different things. With optogenetics, it is possible to distinguish between the roles of different populations of neurons.

From brain maps to circuits linked with disease

One of the major benefits of using optogenetics technology is the ability to determine whether certain neural circuits produce behaviours.

The mere fact that some group of neurons becomes activated during certain behaviour does not mean that these neurons control this behaviour. It might occur due to another activity in the brain.

Scientists can interfere with these neural circuits with the use of optogenetics technology.

For example, if turning certain neurons on affects the behaviour, scientists get proof that these neurons control the process in question. Turning neurons off can also provide additional proof.

This method has been used to study neural circuits associated with numerous activities and conditions.

Optogenetic circuits related to disorders like addiction, depression, dementia, autism, and schizophrenia, among others, are being studied. This method is basically used in research. However, knowing which cells and circuits are responsible for a symptom may eventually help scientists to find ways of treatment.

The reasoning behind this is rather clear. If it is known which cells are failing, scientists get closer to finding a way of therapy.

Optogenetics cannot be called a commonly used treatment method for neurological or psychiatric disorders at the moment. But the information gathered using optogenetics contributes to the development of new methods of treatment.

The same idea could help restore sight

One of the most direct demonstrations of the development of optogenetics into its use for therapeutic purposes concerns inherited blindness.

In an example of retinitis pigmentosa, cells in the retina responsible for reacting to light would be destroyed, ultimately resulting in vision problems. Scientists examine whether the introduction of genes allowing for the production of light-sensitive proteins could give the remaining cells the ability to react to light.

There are several ways of implementing such a procedure in practice when patients receive genetic therapy, making their retinal cells react to light, which then requires the use of special glasses for delivery of proper light signals to them.

The method is only at the stage of clinical trials, and it does not provide people with perfect vision; nevertheless, scientists see why the idea is so promising – because the cells, which cannot react to light in a natural way anymore, could gain a chance to receive visual information.

A discovery that began with proteins found in microorganisms has developed into a technology capable of manipulating biological signals in living tissue.

Why the Nobel committee chose this discovery

This is because the Nobel Prize acknowledges the impact that optogenetics has had on neuroscience research.

Without the method, there have always been many methods of measuring the electrical activity of neurons, but far fewer methods of manipulating a defined group of neurons using a similar level of precision.

With optogenetics, this deficiency was remedied.

A particular set of cells could be identified, an opsin protein injected into the neurons, and subsequently manipulated by the researchers during a behavioural experiment.

The technique also helped bridge several areas of science.

This technology combines genetics, molecular biology, neuroscience, engineering, and optics to turn a simple microbial light-sensing system into an instrument for exploring the most complicated organ in the human body.

In an interview with Science Magazine, neuroscientist Patrick Forcelli of Georgetown University used the example of going from a simple road map to something like Google Earth to explain the importance of this new technology for neuroscience – it allows you to move from the general anatomical location to specific neural circuits.

This example is quite apt, because the brain isn’t just a set of certain regions with certain functions. The brain is a huge network in which cells are constantly communicating with each other, and one area can be involved in various processes. It is extremely important to have an opportunity to explore such a complicated system through manipulating different circuits.

For now, the Nobel-winning breakthrough represents a remarkable shift in what scientists can do inside a living brain.

A protein that allows a microscopic organism to sense light became the basis for a technology that lets researchers control selected neurons with flashes of light.

The result is more than a new way to observe the brain. It is a way to test what individual cells and circuits actually do.

And that may ultimately be the most important step toward understanding what happens when those circuits stop working properly.