On October 5, the Nobel Assembly at the Karolinska Institute announced the recipient of the 2026 Nobel Prize in Physiology or Medicine, recognizing significant contributions in the field of optogenetics. This innovative technique enables the activation of nerve cells using light.

The award comes with a prize pool of 12 million Swedish kronor (approximately $1.2 million), which will be shared equally among the laureates: Karl Deisseroth, Peter Hegemann, and Georg Nagel.

Source: The Nobel Prize.

"Hegemann and Nagel discovered an extraordinary protein — channelrhodopsin — in a single-celled algae. Deisseroth transformed this protein into a light-controlled switch for nerve cells. The researchers have laid the groundwork for a new era in neurobiology," the press release stated.

This pioneering method holds promise for tracking how specific neurons contribute to memory, emotions, and behavior.

Further Insights into Optogenetics

The journey of optogenetics began with the Chlamydomonas algae, which can swim toward light sources. In the 20th century, researchers connected various brain regions to specific functions, but they struggled to prove that certain types of nerve cells were responsible for particular actions or feelings.

The Chlamydomonas cell moves toward light. Source: The Nobel Prize.

Nobel laureate Francis Crick proposed using light as a tool to manipulate neurons, as nerve signals develop too rapidly for most other methods.

In the early 1990s, Hegemann investigated how Chlamydomonas detects light using a light-sensitive "eye spot." He measured the electrical response of this system, which occurred just 0.5 milliseconds after exposure to light — about 20 times faster than human vision.

Hegemann hypothesized that there was a single protein in the cell that both recognized light and functioned as an ion channel. At the time, this idea seemed controversial, as such functions were typically associated with different molecular mechanisms.

Later, Hegemann teamed up with Nagel, who utilized frog eggs as a model to study proteins. He introduced the genes from Chlamydomonas into the cells, causing them to produce unknown proteins on their surfaces.

Integration of Chlamydomonas genes into frog embryos. Source: The Nobel Prize.

This collaboration led to the identification of channelrhodopsin-1 and channelrhodopsin-2, light-sensitive ion channels that opened in response to light within 0.2 milliseconds, allowing positively charged ions to flow and generating an electrical impulse.

In 2003, the researchers published their findings, indicating that channelrhodopsin-2 could serve as a tool for generating electrical signals in cells using light.

The next significant advancement came from Deisseroth, who was working at the intersection of psychiatry and neurobiology. He needed a way to selectively activate specific neurons to analyze the mechanisms of mental disorders at the level of individual cell types and circuits, rather than broader brain regions.

After learning about Hegemann and Nagel's work, he requested the DNA of channelrhodopsin-2 and introduced this gene into rat neurons in a petri dish. Under blue light, the cells began to generate nerve signals.

Integration of channelrhodopsin into rat neurons. Source: The Nobel Prize.

The results were deemed groundbreaking by the Nobel Committee in 2005, establishing channelrhodopsin as a light switch for nerve cells.

In 2007, Deisseroth introduced the channelrhodopsin-2 gene into the motor cortex neurons of live mice and illuminated them through implanted optical fibers, controlling the movement of the animals' whiskers.

The same year, a group demonstrated light activation of neurons associated with wakefulness, effectively waking sleeping mice. These experiments provided early evidence that optogenetics could be used for direct control over neural circuits in a living brain.

In 2012, Deisseroth, along with Susumu Tonegawa, activated an engram — a memory trace — in mice, eliciting a fear response without a real threat.

Activation of nerve endings in mice using channelrhodopsin. Source: The Nobel Prize.

This method allowed researchers to sequentially turn on and off specific cell types, mapping circuits responsible for pain, social behavior, thirst, feeding, attention, circadian rhythms, and parenting. They also investigated mechanisms related to depression, anxiety, schizophrenia, Alzheimer's disease, and Parkinson's disease.

Applications

In clinical medicine, optogenetics is already being explored as a means to restore vision in individuals with impairments. Clinical trials have shown promise in helping patients with retinitis pigmentosa regain some sight.

Future applications are anticipated for enhancing cochlear implants. Per Svenningsson, the chair of the Nobel Committee for Physiology or Medicine, stated that optogenetics has opened up possibilities for mapping the brain that were previously only dreamed of.

Additionally, it is worth noting that in March, the Turing Award was presented for the first time for achievements in quantum informatics, awarded to Gilles Brassard and Charles Bennett for 2025.

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