Combination of Linear and Nonlinear Methods on Electroencephalogram State Recognition

Electroencephalogram (EEG) reveals brain state, i.e. awake, sleep, rather than the content of thinking. We calculated fast/slow power spectrum ratio and approximate entropy on the EEG of three brain states, normal awake, sleep and coma. Based on the above EEG quantities, the EEG in different brain states can be clearly separated in the following way: (1) fast and complex for normal awake, (2) slow and complex for sleep and (3) slow and simple for coma