Over decades of research, scientists have built up a partial picture of what specialized cells within the brain and spinal cord do. By studying how the brain develops, they could identify genes that were active in different populations of neurons, and where in the brain those neurons resided. In some cases, these genes could then be used to genetically delete the neurons, allowing us to get some indication of what they might be doing, building on the information we’ve obtained from studies of brains with damaged regions.
But this approach has its limits. The brain is flexible enough to potentially adapt to the loss of some cells, and their loss early in development may alter the development of any neurons they would have normally formed connections with. It would be far more informative to activate and shut down the neurons in an otherwise intact brain.
Today’s Nobel Prize in Physiology or Medicine rewards three people—Karl Deisseroth, Peter Hegemann and Georg Nagel—who developed our ability to do precisely that. Starting from studies of single-celled algae that are attracted to light, these and many other researchers built an entire field of study that we now call optogenetics: using light to alter the behavior of nerve cells marked by the activity of individual genes. Nerve impulses are generated by proteins called ion channels, which sit in the membrane and allow charged atoms to cross it.
The nervous system uses a population of ion channels that are only active under specific circumstances, like when they sense a neurotransmitter or experience voltage changes. It’s this fine level of control that allows specialized nerve cells to send impulses only under specific circumstances, keeping the brain from descending into a haze of electrical noise.
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