A brainstem circuit discovered in mice may help explain how active movement impacts the way the brain processes sensory information, researchers report. The researchers focused on the brain's mesencephalic locomotor region (MLR), which has been shown to mediate running and other forms of activity in many species. They hypothesized that neural pathways originating in the MLR could serve a dual role -- sending a signal down to the spinal cord to initiate locomotion, and another up to the cortex to turn up the visual response.