The Nobel Prize in Physiology or Medicine has been awarded to US psychiatrist and neurologist Karl Deisseroth and his German colleagues Peter Hegemann and Georg Nagel for their work in optogenetics - a field whose name sounds like a rejected Depeche Mode album but is, in fact, the reason we now know which specific neurons are responsible for your 3 a.m. existential dread.

The Nobel Committee praised the trio for laying the foundation of a new era in neuroscience by revealing how to switch neural circuits on and off behind "specific memories, feelings, and behaviours relevant for neurological and psychiatric disorders." In other words, the thing that makes you you can now be operated with what is essentially a very fancy light switch.

The committee noted that optogenetics has "fundamentally altered our understanding of the brain," adding that "every day brings new discoveries, helping to solve one of humanity's great mysteries: how our incredible brain works." Which is reassuring, given that most of us are still using ours to forget where we left the keys.

The winners said it was "absolutely wonderful" to get the award and an honour to share the accolade with friends. The three men will also share the £900,000 (12 million Swedish kronor) prize money - a sum that, split three ways, might just cover a decent lab coffee machine and a round of drinks in Stockholm.

Per Svenningsson, chair of the Nobel Committee for Physiology or Medicine, explained: "Optogenetics provides opportunities for mapping the brain in a way that we could once only dream of." Before this work, the inner workings behind feelings, behaviours and bodily functions were more of a mystery - a situation many people still experience daily, usually around 3 p.m. on a Tuesday.

Optogenetics is a way to illuminate brain pathways, using a special protein borrowed from algae that scientists use to control cell electrical activity using light. In the early 2000s, Hegemann and Nagel discovered channelrhodopsin, the algal protein with unique properties. Deisseroth then worked out how to use this light-controlled protein to switch on nerve cells in the brains of mice, which presumably had no idea they were participating in a Nobel-winning breakthrough.

Researchers have since been able to study nerve cells and pathways in animals to see and discover more about what they do. The Nobel Committee said: "Using light, researchers are now able to switch individual neural circuits on or off in the brain. They can bring memories to life, create feelings, drive behaviours and study the types of neurons that are involved in various psychiatric and neurological disorders." That is providing important insights into how the nervous system interacts with various cells in other areas of the body, such as in the heart and gut - a finding that will delight anyone who has ever had a "gut feeling" and wondered if it was a medical condition.

Researchers have also taken "the first steps" towards using optogenetics as a medical treatment. In ongoing clinical trials, scientists have been working to restore vision in people who have become blind due to retinitis pigmentosa, a disease that destroys the eye's rods and cones. By inserting a special protein in the damaged region of the eye, the patient regained some vision when wearing special glasses emitting light. This switched on the therapeutic algae proteins - proving that sometimes the answer to a serious medical problem is, quite literally, to see the light.