--- title: "Karl Deisseroth Still Sees His Patients: The Nobel Psychiatrist Who Turned Light Into a Switch for the Brain" description: Karl Deisseroth shares the 2026 Nobel Prize in Medicine for optogenetics. Why the psychiatrist still sees patients, and what his work teaches you about empathy. author: Dr Marina Nani (Editor-in-Chief) date: 2026-11-08T11:32:04.237Z updated: 2026-11-08T11:33:14.899Z canonical: https://thequantumoflight.com/article/karl-deisseroth-still-sees-his-patients-the-nobel-psychiatrist-who-turned-light-into-a-switch-for-th image: https://cdn.nanimediahouse.com/pexels-40292175.webp categories: Literary Culture content_type: Feature publication: The Quantum of Light schema_type: Article about: - type: Person name: Karl Deisseroth description: Of the Howard Hughes Medical Institute and Stanford University. He turned channelrhodopsin into a light-controlled switch for nerve cells and shares the 2026 Nobel Prize in Physiology or Medicine. --- When the call came from Stockholm, Karl Deisseroth had only just put down a paper he was writing late into the night. His children were asleep. He described himself as a night owl, and said he doubted he would sleep again for a while. A month later, the 2026 Nobel laureate in Physiology or Medicine is preparing for Stockholm, where the prizes are presented on 10th December. He shares the prize with [Peter Hegemann](https://thequantumoflight.com/article/peter-hegemann-asked-how-a-tiny-alga-finds-the-light-and-his-curiosity-won-a-nobel-prize) and [Georg Nagel](https://thequantumoflight.com/article/georg-nagel-kept-going-until-the-signal-came-the-persistence-behind-a-nobel-prize), 'for their discoveries concerning light-gated ion channels and optogenetics'. Of the three, Deisseroth is the one who turned a protein from pond algae into a tool that is changing how we understand the human mind. ## A Switch Made of Light Your brain holds billions of nerve cells, and for most of the last century scientists could only watch them from a distance. They could see which regions lit up during a task, but they could not prove which cells caused which feelings or behaviours. The Nobel Committee compared the old picture of the brain to a sketch map full of question marks. Hegemann and Nagel had found channelrhodopsin, a protein that opens a tiny channel when blue light falls on it, letting an electrical signal flow into the cell. Deisseroth put the gene for that protein into the nerve cells of rats. When he shone blue light on them, the cells fired. He published the breakthrough in 2005. Two years later, he made the same switch work in the brains of living mice. That method is called optogenetics. Scientists can now switch specific nerve cells on and off with light and watch what happens. It has revealed the circuits behind particular memories, feelings and behaviours, including some linked to neurological and psychiatric illness. In clinics, researchers are using it in attempts to restore sight to people with visual impairment. ## The Doctor in the Laboratory Deisseroth is a professor of bioengineering and of psychiatry at Stanford University and the Howard Hughes Medical Institute. He is also a practising psychiatrist, and he has never stopped seeing patients. In his first interview after the announcement, he explained why. Listening to people describe states of mind that are hard to put into words keeps him connected to what matters to those who most need help and are most misunderstood. That connection shapes the experiments he designs and the way he teaches his students. He also used the moment to speak about stigma. Every psychiatric disorder, in his view, exists to some extent on a spectrum, with roots deep in human evolution. His hope is that a wider understanding of the mind will increase empathy for people who are suffering and cannot find the words to explain it. ## What His Story Teaches You **Stay close to the people your work is for.** Deisseroth could have left the clinic for the laboratory. He kept both. If your work feels abstract, spend an hour this week with the person who uses what you make: a customer, a patient, a pupil, a reader. **Borrow from unexpected places.** The most important tool in modern neuroscience came from a single-celled alga that swims towards light. The answer to your problem may sit in a field you have never thought to look at. **Give your mind the same patience you give your body.** Nobody blames themselves for a broken wrist. A low mood, an anxious week or a racing mind are also states of a physical organ. If you are struggling, speak to someone, and if someone close to you is struggling, listen without judging. **Thank the people who helped you.** On the night of his prize, Deisseroth said his first thoughts were of the trainees, staff and collaborators around the world who had made the work possible. Before the year ends, write to one person who helped you reach where you are. ## The Brain Is Your Greatest Frontier Optogenetics has not yet cured a single psychiatric illness, and its pioneers are careful to say so. What it has done is turn the brain from a sketch map into a landscape that can be explored, one circuit at a time. The same is true of your own mind. You cannot switch your nerve cells on with blue light, but you can notice what lifts you and what drains you, and choose a little more of the first. Human potential begins in the most complex object we know, the three pounds of tissue behind your eyes, and this year's Nobel Prize in Medicine is a reminder of how much of it is still to be discovered.