Changes in complexities and power spectrum of rat electroencephalogram under various anesthesia depth

The algorithmic complexity, the approximate entropy and the power spectrum of rat electroencephalogram (EEG) under different stages of anesthesia were calculated and analyzed. For synchronous EEGs, both complexity values decreased significantly with the development of anesthesia depth from light to deep. Although powers of synchronous EEG in high frequency bands of theta, alpha and beta gradually decreased, its total power and its power in delta band did not decrease until the deepest anesthesia. For de-synchronous EEGs, the complexity values did not change much with the development of anesthesia depth, and after the anesthesia was deep enough the de-synchronous EEGs would not appear any more, which indicated that the activities in the midbrain reticular formation had been inhibited. Powers of desynchronous EEG in high frequency bands of alpha and beta decreased gradually from light anesthesia stages. These findings suggest that more EEG features can be revealed by applying both methods of the complexity measures and the power spectral analysis.