The blood that flows into our heads is obviously important for it provides nutrients and oxygen to that most energetically demanding of organs - the brain. But for neuroscientists, blood flow in the brain has a special significance; many have used it to measure brain activity using a technique called functional magnetic resonance imaging, or fMRI.
This scanning technology has become a common feature of modern neuroscience studies, where it's used to follow firing neurons and to identify parts of the brain that are active during common mental tasks. Its use rests on the assumption that the flow of blood ("haemodynamics" to those in the know) is a decent enough stand-in for the firing of neurons - the latter creates a shortage of nutrients and oxygen that is corrected by the former.
But Yevgeniy Sirotin and Aniruddha Das from Columbia University have found that this assumption might not be entirely ...
