A first paper on this subject discusses a neural complexity measure for EEG and was motivated by a method proposed by Tononi and Edelman.

M.J.A.M. van Putten and C.J. Stam. A neural complexity measure for multichannel EEG, Phys Lett A 281 (2001).

A paper discussing potential nonlinear structure in hypsarrhythmia appeared in 2001:
Is the EEG really chaotic in hypsarrhythmia, M.J.A.M. van Putten and C.J.  Stam, IEEE Engineering in Medicine and Bioloyg Magazine, 2001.

Another paper discusses changes in (phase) synchronization and introduces the concept of link rates. The method is applied to three different EEGs, a normal control, a patient suffering from generalized seizure activity and a patient with a severe postanoxic encephalopathy.

M.J.A.M. van Putten. Proposed link rates in the human brain, J Neurosci Methods 127 (2003) 1-10.