Professor Karl Deisseroth is an emergency psychiatry physician. He's been responsible for some breakthrough scientific discoveries in optogenetics in which he developed ways to allow turning specific brain cells on or off, with light. This week he joins Robin to talk about that process and his new book on mental health and human empathy, Connections. Please note due to a couple of technical hitches, and last minute schedule changes, this week's episode is a little shorter than normal and Josie was unable to join us. Back to normal next week! Support the podcast and get all sorts of bonus goodies at patreon.com/bookshambles