We studied the trends of EEG signals during waking and hypnosis, by using fractal analysis to define the physiological concomitants of hypnosis. The subjects in this study were 6 psychiatric outpatients who were in good medical condition. The hypnotist induced hypnosis using a modified version of the hypnotic induction profile (HIP) technique. EEG data were acquired by means of a Telefactor EEG monitoring device installed in the EEG recording room. Twenty-five sets of data were analyzed using detrended fluctuation analysis (DFA), which is a well-established fractal analysis technique. The following results were obtained. 1) All of the scaling exponents, which constitute the result of fractal analysis, were greater than 0.5 and less than 1.5 in both the waking and hypnotic conditions. In addition, significant differences in the scaling exponents were found between the waking and hypnotic condition in most of the channels (except, Fp1 and F4). 2) We analyzed the individual changes in the scaling exponents of each subject, resulting from a number of hypnotic trials. In all of the trials, the differences among the scaling exponents of each trial were statistically nonsignificant. 3) The examination of the right-left symmetries did not yield any statistically significant difference. In this research, the scaling exponents of fractal analysis are reduced nearly to the level of white noise during the hypnotic condition. Therefore, this technique can differentiate the hypnotic condition from the waking condition. Additionally, the findings of this study suggest that hypnosis comes from a change in organization of neural activity in the whole brain network, rather than being a “specific area” phenomenon.
Introduction
Methods and Materials
Results
Discussion
References