The awake background electroencephalogram (EEG) is the basic EEG for EEG interpretation, and it is important to represent its characteristics quantitatively. We have already proposed an EEG model consisting of sinusoidal waves with Markov process amplitude. This model can represent the characteristics of background EEGs appropriately, especially the αrhythm, which is the most important. However, slow waves(δandθwaves)have slightly different characteristics-both the amplitude and frequency fluctuate. Inthisstudy, an EEG model consisting of sinusoidal waves with fluctuating amplitude and frequency was proposed to represent the characteristics of slow waves accurately. The theoretical power spectrum of the model was derived and used for determining the model parameters in the frequency domain. The αandβ
waves were represented by sinusoidal waves with amplitude fluctuationonly, while the δandθwaves were represented by sinusoidal waves with fluctuation of both amplitude and frequency. The features of the time series of the constructed model were compared with those of the raw EEG and satisfactory results were obtained. Furthermore, the rhythmicity of slow waves was quantitatively represented using the proposed model.
