Chaotic brain activity.

As demonstrated by this example fairy-tales long ago expressed what we refer to today as sensitive dependence on initial conditions. If we observe such a sensitive dependency in any given, deterministic system, we will call it 'chaos'. While the classical definition of chaos means absence of order and unpredictability, the scientific definition ofchaos is based on nonlinear mathematics.Although its principles were already established during the late 19th century by Poincare, they were not mathematically accessible until the work of Lorenz (1963). Today, chaos is defined as 'stochastic behaviour in a deterministic system', or more colloquially: Chaos is apparently lawless behaviour totally ruled by (deterministic) laws. An irregular motion is illustrated in Fig.1, in which two traces of brain activity in this case MEG are superimposed. The two traces were selected such that a large cross-correlation exists at the onset of activity. Both traces are based on the same generators, and the conditions during the two observations are very much the same. Neverthe-