ESA astronaut Samantha Cristoforetti conducts plethysmography and PFS (Pulmonary Function System) measurements with an EAP-based neck collar during Brain Drain experiment operations on ISS. On Earth, blood flows down from a person’s brain back toward the heart thanks in part to gravity, but very little is known about how this flow happens without gravity’s effects. Many crew members report headaches and other neurological symptoms in space, which may be related to the absence of gravity acting on blood flowing through the veins. Drain Brain uses a special neck collar to measure blood flow from the brain, to help researchers understand which physical processes in the body can compensate for the lack of gravity to ensure blood flows properly.