The topographic mapping of EEG using the first positive Lyapunov exponent

The electroencephalogram (EEG) signal is known to be chaotic, and it has the characteristics of unpredictability. Dimensional analysis of a chaotic signal is an important index to quantify and qualify its dynamical characteristics. The first positive Lyapunov exponent is one of the dimensional analysis methods, and is a standard method of checking whether a time series is chaotic or not. Here, the authors present a new method to derive the topographic mapping of the EEG. Using the first positive Lyapunov exponent, the derived mapping shows the chaotic state at each site of the cerebral cortex which would be important for neurophysiologists and psychologists.