Washington University in St. Louis Jun 12 2026 In the split second after you hear a noise, your brain is already making a potentially life-or-death deduction: Did I do that, or did something else? Our nervous systems answer this question using something called corollary discharge, a copy of a motor command that tells sensory areas what to expect from our own actions. This mechanism is at the center of a new study by biologists at Washington University in St. Louis, published in Current Biology .