Complexity International      /vol05/watters/ © Copyright 1998     
Volume 05 Received: 
Accepted: 
19 001 1998
006 005 1998



Fractal Structure in the Electroencephalogram

P. A. Watters

Abstract
    

Many analyses of the EEG signal using frequency decomposition methods rest on the assumption that the fundamental signal-generating process has stochastic properties (i.e., no long-range temporal correlations, or temporal self-similarity). In this paper, the detrended fluctuation analysis (DFA) algorithm of Peng et al. (1992) was used to determine whether the locally-detrended EEG contained long-range correlations, indicating fractal structure, or whether it was best characterised as a stochastic random-walk process. If the EEG was generated by a random walk process, then an estimated scaling parameter was predicted to be =0.5, whereas the scaling parameter for a fractal process would lie in the range 0.5< 1.5. In this study, highly significant departures from =0.5 were observed from an ensemble of 32 EEG signals, ()=1.26, =0.06, indicating that the EEG samples could not have been generated by a random walk process. This result also suggests that the EEG is generated by a fractal process which contains long-range temporal correlations of the order 1/f1.52.

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