“John is one of five people who have volunteered to have their brains probed as part of a clinical trial. At the start of 2020, he had a total of 14 electrodes implanted across his brain. For nine days, he stayed in a hospital with protruding cables wrapped around his head, while neuroscientists monitored how his brain activity correlated with his mood. The researchers behind the trial say they have developed a ‘mood decoder’—a way of being able to work out how someone is feeling just by looking at brain activity. Using the decoder, the scientists hope to be able to measure how severe a person’s depression is, and target more precisely where the electrodes are placed to optimize the effect on the patient’s mood.” MIT Tech Review: Neuroscientists have created a mood decoder that can measure depression.