Northwestern University neuroscientists now can read the mind of a fly. They have developed a clever new tool that lights up active conversations between neurons during a behavior or sensory experience, such as smelling a banana. Mapping the pattern of individual neural connections could provide insights into the computational processes that underlie the workings of the human brain. In a study focused on three of the fruit fly’s sensory systems, the researchers used fluorescent molecules of different colors to tag neurons in the brain to see which connections were active during a sensory experience that happened hours earlier.