, Volume 8, Issue 2, pp 127-136

Dynamic power and coherence analysis of ultra short-term cognitive processes — A methodical study

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This EEG mapping study was designed to explore ultra short-term cognitive processes in human thinking. The EEG was recorded while the subjects performed two tasks randomly mixed in time: category concept activation and pattern comparison. A novel approach is introduced to examine these tasks by means of band powers and coherence with high time and frequency resolution. This approach is based on general adaptive principles and the adaptive fit of a bivariate linear model (ARMA model) with time-varying parameters, and allows the estimation of band powers and coherences continuously in time. The application of mapping to these spectral parameter functions results in map sequences of band powers, and local band coherences. It was proved that these map sequences of the frequency band 13–20Hz reflect the dynamic behaviour of information processing in a characteristic topographical manner. Based on these dynamic topographical examinations, conceptual and imaginal representations are distinguishable.

We would like to thank G. Grieszbach of the Department of Biomedical Engineering and Informatics of the Technical University of Ilmenau and J. Bolten of the Institute of Medical Statistics, Computer Sciences and Documentation of the University of Jena for their extensive help in preparing the necessary software and for helpful discussions. The development of the mathematical approach of the first author was supported by the BMBF (01ZZ9104) and by the CEC BIOMEDI (ANDEE; BMH1-CT94-1129).