One cup or two faces? What we believe we see in one of the most famous optical illusions changes in a split second; and so does the path that the information takes in the brain. In a new theoretical study, scientists of the Max Planck Institute for Dynamics and Self-Organization, the Bernstein Center Göttingen and the German Primate Center now show how this is possible without changing the cellular links of the network. The direction of information flow changes, depending on the time pattern of communication between brain areas. This reorganisation can be triggered even by a slight stimulus, such as a scent or sound, at the right time.