Non-linear EEG dynamic changes and their probable relation to voluntary movement organization

This study was undertaken to analyze systematically the non-linear dynamic changes of EEG activity accompanying slow goal-directed voluntary movements, using three non-linear characteristics (NC): point-wise correlation dimension, Kolmogorov entropy and largest Lyapunov exponents as functions of time. NC indicated transitions with non-linear properties (NT). A significant difference between times of appearance of the NT with respect to the electrode position was established: before the movement onset, NT appeared first in contralateral and midline areas including frontal, sensorimotor and parietal cortices. Before target reaching, NT appeared first in the contralateral sensorimotor area, and evolved ipsilaterally. The results suggest that the NT could be regarded as precursors of higher functional coupling between cortical areas involved in voluntary movement organization.