In optogenetics, scientists control neurons by stimulating them with light—potentially unlocking breakthroughs for conditions such as dementia, depression and blindness.

Three scientists won the Nobel Prize in medicine on Monday for their work in the field: U.S. neurologist Karl Deisseroth and German scientists Peter Hegemann and Georg Nagel.

"Being able to manipulate cells with a combination of light and genetics has been transformational across the biological sciences," said Simon Schultz, neurotechnology professor at Imperial College London.

Here are some key facts about optogenetics and its uses.

Protein discovery
In a type of green algae, Hegemann and Nagel discovered a light-sensitive protein that they dubbed channelrhodopsin.

Deisseroth introduced it genetically into a cell and stimulated it with light, which triggered a nerve signal in rats and mice.

By controlling the light, scientists can switch a neuron's signal on or off with minute precision.

By turning off some neurons and observing others, they can track which areas affect certain functions.

Introducing the prize, Nobel medicine committee member and neuroscientist Abdel El Manira said the discovery shed light on functions "from parental behavior and aggression to anxiety and fear, as well as fundamental physiological drives such as thirst and water intake."

Memory
Schultz said his own teams had used optogenetics "as a closed-loop treatment for memory disorders" by lengthening the pulses that help the brain store memories.

"The next step is to demonstrate that we can improve learning and memory in complex tasks," he said in comments released by the college...