Connections by Karl Deisseroth review – artful insights into the brain

The psychiatrist and neuroscientist exploits cutting-edge technology to illuminate emotions and mental illness in these vivid case studies

Karl Deisseroth’s book comes so richly garlanded with endorsements that I wanted to dislike it. A world-renowned psychiatrist and neuroscientist, Deisseroth is also a talented writer who, when the technology comes up short or the science is found wanting, always seems to have the perfect metaphor or line of poetry to hand. There are times when literature provides “a window on to the brain more informative than any microscope objective”, he writes, peppering each chapter with epigrams from Joyce, Milton and Millay.

Using optogenetics, a technology that renders individual, highly specific brain cells photosensitive and then activates those cells using flashes of light delivered through a fibreoptic wire, Deisseroth’s research focuses on the brain circuits behind everything from our sudden mood swings to behaviour, such as crying, which are unique to humans. Likening these complex axonal connections to “warp threads”, Deisseroth hopes that by using optogenetics to turn these circuits on and off, he can better understand the physiochemical basis of human behaviour and with it the “tapestry of the human story”, by which he means the evolutionary roots of mental illness and emotions such as joy, hope and anxiety.

At various points, Deisseroth hints that this is as much a journey into his psyche as those of his patients