Brain Activity Analysis of Rat Based on Electroencephalogram Complexity Under General Anesthesia

In order to estimate the change of brain activity under general anesthesia, the Lempel-Ziv complexity (C(n)) of electroencephalogram (EEG) of SD rat was studied in this paper. The C(n)s of EEG from different channels under different depth of anesthesia were measured and the relationship between C(n) and the depth of anesthesia (DOA) was analyzed. The result shows that the C(n) variations of EEG of different channels with DOA are similar, and predicates that the activities of every part of brain change similarly. Therefore, it is enough to detect DOA by only one channel EEG. The C(n) of EEG will decrease while the depth of anesthesia increasing and vice versa. Two thresholds of C(n) are defined, one distinguishes awake and light anesthesia state, the other distinguishes light and deep anesthesia state. Besides EEG complexity analysis, the complexity variations of four rhythms of EEG (delta, theta, alpha and beta) are also analyzed. The study shows the dynamic change of complexity of delta rhythm leads to that of EEG, so the delta rhythm is the dominant rhythm during anesthesia for rat.