Complexity Analysis of Sleep EEG Signal

The complexity of the EEG time series during sleeping is investigated. The relationships between these sleep states and the complexities of the EEG are assessed. Lempel-Ziv complexity is used as a novel index for quantifying the complexity of the EEG time series during different sleep states. Experimental results show that the Lempel-Ziv (LZ)complexity of the EEG time series during active (REM, rapid eye movement) sleep tends to be higher than during quiet (NREM, non rapid eye movement) sleep, and the complexity during wake is higher than during sleep. The Lempel-Ziv complexity can effectively distinguish the sleep states of the brain.