Yawns Rewire Brain Fluids, Boost Blood Flow in Surprising Way

In a 22-volunteer MRI study, yawning moved cerebrospinal fluid outward toward the spinal column and carried venous blood with it, freeing space for a surge of arterial blood—over a third more than during deep breathing. The researchers also found a unique yawning signature tied to tongue movement. They suggest yawning may be a brain-maintenance process supporting temperature regulation and waste clearance.