Harvard Medical School Jul 16 2025 All day long, our brains carry out complicated and energy-intensive tasks such as remembering, solving problems, and making decisions. To supply the energy these tasks require while conserving this precious fuel, the brain has evolved a system that allows it to quickly and efficiently send blood only to the areas that need it most in any given moment. This system is essential to brain function and overall health, yet how it works has remained somewhat of a