Nonlinear Dynamics Evaluation of Electroencephalogram Signals during Meditation

Electroencephalogram (EEG) is a reliable reflection of many physiological factors modulating the brain. The aim of this study is to evaluate nonlinear dynamics of electroencephalogram signals during meditation. For this purpose، we collected EEG signals of seven female meditators in two states: before meditation and during meditation. Correlation Dimension، Hurst Exponent and the maximum Lyapunov Exponents were calculated. The results of this study show that the Correlation Dimension was significantly lower during meditation، as well as the maximum Lyapunov Exponents. This reduction indicates that the number of parallel functional processes active in the brain is less and the brain goes to a more relaxed state. Besides that، the Hurst Exponent is increased during meditation. The finite values of Correlation Dimension and positive values of Lyapunov Exponents suggest that all of EEG signals have low dimensional chaos، and the complexity of signals are decreased during meditation.