Anticipatory haemodynamic signals in sensory cortex not predicted by local neuronal activity

Functional magnetic resonance imaging (fMRI) of brain activity relies on the assumption that increases in local blood flow in the brain are directly correlated with the neuronal activity in that brain region. Using simultaneous direct recording and fMRI in monkeys, Yevgeniy Sirotin and Aniruddha Das demonstrate that this is not the whole story; part of the fMRI signal is unrelated to actual brain activity. As well as the brain activity component, there is increased blood flow in less active regions of the brain in anticipation of their employment in the near future. These findings challenge to the current interpretation of functional brain imaging signals, and also point to a novel anticipatory mechanism in the brain.