Developmental Study on Measuring, Recording & Procession System of EEG during Working and Sleep

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The electrical activity of the human brain has been studied extensively since the discovery of the EEG(electroencephalogram). The EEG monitors the nerophysiological activity of the central nervous system and are sensitive to both organic and psychological changes. The awake and sleep EEG show the brain states in the working and resting, respectively. In order to find the detailed information from the EEG, doctors carefully investigate wave- forms of the EEG from every direct ions. It is desirable to estimate the states of the human brain in the working and the sleep. Thus, we tried to analyze the EEG waves in the detail to extract significant information from it. Sleep spindles and slow waves, aperiodic wave-forms found in sleep EEG, are distinctive parameters to judge the sleep stages by the standardized scoring manual of sleep. These waves are nonstationary and transient signals from the view of stochastic time series. The first purpose of this study is to present a computational procedure of Complex Demodulation in the time domain for the quantification of sleep spindles in sleep EEG. In this study, we developed a computational procedure of the repeated use of Complex Demodulation to resolve an important unsolved technique problem in the Complex Demodulation which is how to choose the demodulating frequency. Next, we propose a procedure of Complex Demodulation in the frequency domain by means of the fast Fourier transform for fast processing.