In the brain, the visual cortex processes visual information and passes it from lower to higher areas of the brain. However, information also flows in the opposite direction, e.g. to direct attention to particular stimuli. But how does the brain know which path the information should take? Researchers at the Ernst Strüngmann Institute (ESI) for Neuroscience in Frankfurt in Cooperation with Max Planck Society have now demonstrated that the visual cortex of human subjects uses different frequency channels depending on the direction in which information is being transported. Their findings were only possible thanks to previous research with macaque monkeys. They might help to understand the cause of psychiatric illnesses in which the two channels appear to be mixed up.