Neuroscientists have made an important advance in studying the human brain with functional magnetic resonance imaging (fMRI). This imaging technique is used in research to investigate the interactions between different brain regions – but indirectly: fMRI does not measure neuronal processes, but marks active brain areas on the basis of their blood flow. Now researchers have shown that interactions measured with fMRI indeed reflect correlated nerve cell activity, and in what form they do so. This will make the imaging method even more attractive for neuroscience research.