New research sheds light on how the brain combines external information and internal memory to build a sense of touch. The research could help scientists understand how to better treat strokes and autism spectrum disorder. When you touch something, whether stepping onto a sandy beach or stroking the back of a dog, sensations fly into your brain. You feel the coarse grain of the sand under your feet, the fluffiness of the fur on your hand. But you also bring a bit of yourself into the feeling: Along with the external stimulation from the beach or pup, there’s the memory of past moments—toweling sand from your toes during a summer vacation, snuggling with a much-missed family pet. We all agree that something feels abrasive or soft, but interpret that sensation slightly differently. “When we perceive our environment, we’re actually doing two things,” says Boston University neurobiologist Jerry Chen, an expert on …