Staging of awake and sleep based on feature map

The staging of sleep EEG is executed by the decision by human observations, and is utilized in the diagnosis of insomnia or psychiatric diseases. On the other hand, the sleep EEG includes a large amount of data, and the automation of the sleep staging is considered to be desirable. However, there has not been established a method for staging the biological state based on the awake EEG. This paper proposes an automatic method of staging the biological state based on the hypothesis that the biological state is the same if the same kind of waveforms occur with the same ratio. The proposed method is composed of two procedures: the first is to estimate the standard pattern for the waveform from the individual EEG and the cluster the waveforms; and the second is to examine the kind and ratio of the waveforms appearing in a specified interval of time so that the type of EEG can be identified. The results of staging the sleep EEG is compared to the result of the decision by a doctor, and an agreement of 79 percent is obtained. Generally, it is considered that there can be a difference of some 20 percent in the sleep staging by different doctors. Consequently, it is estimated that the proposed method has a performance comparable to that of the doctor. The staging of the awake EEG also is attempted, and the result is consistent with the skin potential response or the behavior of the subject. Thus it is concluded that the proposed method will be useful in the staging of the biological state.