Electroencephalographic signal analysis and desynchronization effect caused by two differing mental arithmetic skills

Using several electroencephalographic signal analysis methods, it is possible to detect activated cortical areas during cognitive processes. These methods are of interest for neuropsychological studies and in an attempt to develop neurophysiological methods that can be used in the clinic. We used two distinct methods to study two different mental arithmetic tasks. Our purpose was to test the hypothesis that there are different desynchronization effects during the two distinct cognitive processes and to compare the two methods used. The first method concerned EEG signal band reactivity changes. The bands were obtained using spectral analysis. The second method is a new one for estimation of the whole EEG signal complexity (ASE = Acceleration Spectrum Entropy). We estimated the EEG signal bands and the ASE changes during two arithmetical tasks in 24 subjects and compared them with the values of the resting state. The ASE method and the EEG band reactivity method could distinguish between the resting condition and the tasks thus demonstrating the usefulness of the ASE method to study cognitive processes. Furthermore, the two tasks affected differently the power spectrum values of the delta, theta and the alpha bands thus indicating the involvement of different brain mechanisms.