How Optogenetics Lets Researchers Flip Individual Neurons On and Off

For decades, neuroscientists built a partial map of the brain the hard way: find a gene active in a particular neuron population, use it to delete those cells, then watch what goes wrong. The trouble is that the brain adapts. Remove a set of cells and remaining circuits can rewire; lose them early in development and the neurons they would have connected to may develop differently. As a result, it is often hard to say whether a behavior changed because of the missing cells or because of everything that shifted around them.

The 2026 Nobel Prize in Physiology or Medicine went to Karl Deisseroth, Peter Hegemann and Georg Nagel, whose work pointed to a better option: instead of deleting neurons, activate and silence them in an otherwise intact brain. The raw material came from single-celled algae that are attracted to light. From those studies grew optogenetics — using light to alter the behavior of nerve cells identified by the activity of individual genes.