Relativity of Dynamical Measures in Study of the Human Brain

The deterministic character of cortical processes in the human brain invites an assessment of nonlinear methods of analysis and exploration of their applicability. Because brain processes are frequently nonstationary, questions arise as to the validity of formal assumptions. Here we present a simple algorithm for estimation of the local divergence measure (Mayer-Kress 1994, Kowalik and Elbert 1994) based on the local Lyapunov exponent (Wolff, 1992) that can be used for nonstationary data.1