What was this year’s medicine prize about? This year's Nobel Prize in Physiology or Medicine concerns the groundbreaking technique of optogenetics, which enables researchers to control individual nerve cells using light to switch them on or off. The method is used in laboratories around the world to investigate how nerve cells shape memories, emotions and behaviour in the living brain. For laureate Peter Hegemann, it all began with the question of how the green alga Chlamydomonas can detect light and move towards it. The algae sense the light with an eyespot that contains a light-capturing molecule, retinal. Hegemann discovered electrical signals in the eyespot that occurred just half a millisecond after illumination. He proposed that a single protein could both detect light and function as an ion channel, an idea that was initially met with scepticism. After several years of research, Hegemann and his colleague Georg Nagel demonstrated that the hypothesis was correct. They discovered proteins that open in response to light and published their findings in 2003. They also suggested that the protein channelrhodopsin-2 could be used to generate electrical impulses in cells using light. The baton was then taken up by the third laureate Karl Deisseroth. During his psychiatric training, Deisseroth realised that a deeper understanding of the brain’s neurons was essential for understanding the illnesses he encountered in his patients. When Deisseroth gained access to the DNA encoding channelrhodopsin-2, his research group introduced it into rat neurons. When the cells were exposed to blue light, they responded immediately, transmitting nerve signals to other neurons. Deisseroth’s research group published their discovery in 2005. The year after, this new method was given the name optogenetics. One year later, Deisseroth successfully activated nerve cells in the brains of living mice. Today optogenetics continues to unravel one of humanity’s greatest mysteries: how the brain works. Read more: nobelprize.org/prizes/medici…