Why Do We Freeze When Startled? New Study in Flies Points to Serotonin

Videos of flies using FlyWalker, a program that enables scientists to label and track the position of each of the fly’s footfalls, thereby building a high-resolution picture of it’s walking gait. Top: normal fly walking at around 25 mm/s. Bottom: fly with its VNC serotonin neurons stimulated, which slows its speed to 15 mm/s. A Columbia University study in fruit flies has identified serotonin as a chemical that triggers the body’s startle response, the automatic deer-in-the-headlights reflex that freezes t