Call it neuroscience on the go. Scientists have developed a backpack that tracks and stimulates brain activity as people go about their daily lives. The advance could allow researchers to get a sense of how the brain works outside of a laboratory—and how to monitor diseases such as Parkinson’s and post-traumatic stress disorder in real-world settings. The technology is “an inspiring demonstration of what’s possible” with portable neuroscience equipment, says Timothy Spellman, a neurobiologist at Weill Cornell Medicine who was not involved with the work. The backpack and its vast suite of tools, he says, could broaden the landscape for...