The interleaved pcCSF and cortical BOLD MRI technique achieves a combined temporal resolution of under 450 ms, enabling simultaneous measurement of cerebrospinal fluid flow and cortical hemodynamics with sufficient precision to detect sub-second coupling dynamics.

When a person breathes deeply and slowly, the chest creates a suction effect that pulls blood into the torso, lowering pressure inside the skull. This drop in pressure pulls cerebrospinal fluid into the brain. At the same time, the breathing changes carbon dioxide levels in the blood, causing blood vessels in the brain to expand. This expansion pushes fluid out of the brain, and when the vessels shrink again, fluid flows back in. These two processes — fluid movement from pressure changes and fluid movement from blood vessel swelling — happen at the same time and lock together, allowing both to be measured simultaneously with high precision.