Physica A 257 (1998) 149–155 Tsallis entropy and cortical dynamics: the analysis of EEG signals A. Capurro a , L. Diambra b , D. Lorenzo a , O. Macadar a , M.T. Martin b , C. Mostaccio b , A. Plastino b; ∗ , E. Rofman c , M.E. Torres d , J. Velluti a a Instituto de Investigaciones Biol ogicas Clemente Estable, Av. Italia 3318, Montevideo, Uruguay b Physics Department, National University La Plata, C.C. 727, 1900 La Plata, Argentina c Institut National de Recherche en Informatique et en Automatique (INRIA), Paris, France d Universidad Nacional de Entre R os, Dpto. de Matem atica e Inform atica, C.C. 57- Suc.3, 3100 Paran a, Entre R os., Argentina Abstract We undertake the study of EEG-signals by recourse to a wavelet based multiresolution analysis as adapted to an information-measure-scenario. Dierent information measures are employed. It is shown that non-extensive ones seem to be of particular usefulness. c  1998 Elsevier Science B.V. All rights reserved. PACS: 05.90.-y; 05.90.+m; 87.10.+e; 87.59.Bh Keywords: Wavelet transform; Multiresolution analysis; Tsallis information measure; Nonlinear systems 1. Introduction The collective dynamical behavior of the brain’s cortical neurons can be assessed by means of electroencephalographic (EEG) recordings. One of the most important uses of the traditional visual interpretation of EEGs is the identication of transient events associated with epilepsy, where the background activity is interrupted by sharp waves or spikes [ 1 –3]. Sharp waves and spikes recorded during the periods between seizures (interictal activity) are of great importance for diagnosis purposes, since the morpho- logy and topography of these sharp transients have been correlated with dierent types of seizures [1–3]. We intend here to use a combination of (i) the multiresolution wavelet analysis [4] with (ii) the entropy concept, which will provide one with an able tool both for the analysis of nonstationary signals and for the detection and local- ization of transients in EEG signals. We will show that the so-called multiresolution * Corresponding author. Fax: 54 21 258138; e-mail: plastino@venus.sica.unlp.edu.ar. 0378-4371/98/$19.00 Copyright c  1998 Elsevier Science B.V. All rights reserved. PII: S0378-4371(98)00137-X