An algae, three scientists and a new window to the brain

How do we know what neurons do in the brain? Observing that a region is activated when we remember, feel fear or move allows us to relate that activity to a function, but does not in itself prove that it causes it. To test what role a neural circuit plays, researchers need to activate or inhibit selected neurons and see what changes. The 2026 Nobel Prize in Physiology or Medicine recognizes the discoveries that made optogenetics possible, a technique that combines genetics and light to control the activity of specific neurons and study their effects on the brain.

The prize was awarded to the American Karl Deisseroth, professor of bioengineering and psychiatry at Stanford University; and the Germans Peter Hegemann and Georg Nagel, physiologists and biophysicists, linked to the Humboldt Universities of Berlin and Würzburg. The research that supported the discovery was also carried out at Max Planck Institutes in Germany.

The story began with a question: how does a tiny single-celled algae orient itself toward light? Hegemann and Nagel identified channelrhodopsin-2 (ChR2) in its membrane, a protein that, upon receiving blue light, opens an ion channel and generates an electrical signal. Deisseroth and his collaborators used a virus prepared to carry the gene that encodes that protein to mammalian neurons. By producing it, the neurons became sensitive to light. The method was tested first in neuronal cultures and then in live mouse brains. The convergence of biology, biophysics and genetic engineering allowed the use of an algae protein as a tool to investigate neuronal circuits.

In animal models, optogenetics has made it possible to study circuits associated with the evocation of memories and fear responses. It is also used to investigate aspects of depression through observable behaviors, such as reduced social interaction or reduced preference for rewards. By activating or inhibiting selected neurons and observing the changes, researchers can test the causal role of certain circuits. These experiments expand knowledge of mechanisms relevant to neurological and psychiatric disorders and could guide future therapeutic research.

Artificial intelligence can help analyze large volumes of neural activity; Optogenetics then allows us to test which circuits influence a behavior. There are already works that combine analysis of neuronal activity in real time and optogenetic stimulation.

Optogenetics is already a powerful tool for investigating the nervous system, and some of its possible clinical applications are being tested in patients. One of the most advanced seeks to partially restore vision in certain degenerative retinal diseases. Through gene therapy, the gene that encodes a light-sensitive protein is introduced into certain surviving retinal cells. By producing this protein, cells can respond to light stimuli. Initial clinical studies have recorded partial improvements in some visual functions in certain patients, but the safety and effectiveness of this strategy remain to be confirmed in larger, controlled trials.

The lesson that the Nobel Prize in Physiology or Medicine leaves us is how a basic question, born of curiosity, can open a new field of research when it has continuity and collaboration between disciplines. In order for questions arising in Peru to advance, scientific communities capable of sustaining lines of work are needed; training and retention of young researchers; first-class laboratories and shared infrastructure; and collaboration between disciplines and countries, with universities, institutes, hospitals and companies. These capabilities require multi-year competitive funds, allocated through rigorous evaluation and supported by sufficient, stable and predictable budgets. Ensuring these conditions is an obligation of the authorities responsible for the national science, technology and innovation system.