The brain is considered as a complex, physical, and open system that exhibits spatiotemporal behavior at various time and length scales. A necessary condition for this pattern forming character of the brain is a nonlinear dynamics and a spatial interconnection of its elements, the neurons. The functional behavior of the brain is encoded in these spatiotemporal structures and can, at least partly, be extracted from the dynamics of the macroscopic quantities measured by the EEG and MEG. According to synergetics [1], this extraction contains all the relevant information about the spatiotemporal behavior of the brain and has, in general, a small number of degrees of freedom. This idea has been formalized to the order parameter conceptbased on circular causality: The order parameters are determined and created by the cooperation of microscopic quantities, but at the same time the order parameters govern the behavior of the whole system. Based on this approach phenomenological models were set up in the past for different experiments in order to find evolution equations that describe the experimentally observed macroscopic dynamics [2].