Fig 1.
(a) The experiment was conducted in five stages. There were two baseline recordings before and after hypnosis session. Hypnosis session included induction, suggestion, and awake phases. (b) Subjects experienced hypnotic instructions that were prepared according to Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A). (c) Fourteen electrodes placed on the frontal, temporal, central, parietal, and occipital areas in both left and right hemispheres (red circles) and the midline locations (i.e. green circles) recorded EEG signals during the experiment.
Fig 2.
The function H calculates the entropy of its input time series as per Eq (1). Xθ, Xα, and Xβ are the frequency components associated with EEG time series X. We used the resulting feature vector V = [H(Xθ), H(Xα), H(Xβ)] in our analyses.
Fig 3.
Descriptive statistics of theta, alpha, and beta frequencies of EEG time series of HIGH and LOW suggestible groups.
Subplots are organized based on EEG 10-20 system. Y-axis represents the differential entropy (DE) of these frequency bands. This axis is within 1-4 (bits, given b = 2 in Eq 1) range in all subplots. Asterisks mark the significant difference between the corresponding frequencies in HIGH and LOW suggestible groups (***: p <.001).
Table 1.
Paired Wilcoxon rank sum between LOW and HIGH suggestible subjects.
[67] is the effect size with N and W representing the sample size and the Wilcoxon statistics, respectively. ML, SDL, MH, and SDH are the mean and standard deviation of the DE values of a given frequency for LOW (i.e., subscript L) and HIGH (i.e., subscript H) suggestible groups.
Fig 4.
Grand-average FC of the participants using paired Pearson correlation between EEG channels in HIGH (left column: (a) theta (c) alpha (e) beta) and LOW (right column: (b) theta (d) alpha (f) beta) suggestible participants.
In case of HIGH suggestible group, we observed significantly higher FC in theta and alpha bands, mostly in left parietal (P3, theta and alpha) as well as occipital (Oz, alpha). On the other hand, we observed a non-significantly lower FC in the case of beta band, approximately around the left central (C3) region. These subplots identify an overall increase in strength of FC in theta and alpha bands that is accompanied by an overall weakening in beta FC in case of HIGH compared to LOW suggestible groups. (a) Hθ (b) Lθ (c) Hα (d) Lα (e) Hβ (f) Lβ.
Table 2.
Wilcoxon rank sum test of FC between LOW and HIGH suggestible subjects.
[67] is the effect size with N and W representing the sample size and the Wilcoxon statistics, respectively. ML, SDL, MH, and SDH are the mean and standard deviations of the given frequency for LOW (i.e., subscript L) and HIGH (i.e., subscript H) suggestible groups.
Fig 5.
Grand averages of the change in FC among EEG channels of HIGH and LOW suggestible subjects: (a) theta (b) alpha (c) beta frequency bands.
In these subplots, the left map is associated with HIGH and the right map corresponds to LOW groups. In case of HIGH suggestible group, we observed higher regional connection counts in theta and alpha bands along with a lower connection counts in their beta band. Substantially higher connectivity in case of HIGH suggestible group in theta and alpha bands is evident in these subplots. rFC refers to Pearson correlation coefficient based on which FC among channels was determined. (a) Theta (b) Alpha (c) Beta.
Table 3.
Wilcoxon rank sum of the connectivity maps between LOW and HIGH suggestible subjects.
[67] is the effect size with N and W representing the sample size and the Wilcoxon statistics, respectively. ML, SDL, MH, and SDH are the mean and standard deviations of the given frequency for LOW (i.e., subscript L) and HIGH (i.e., subscript H) suggestible groups.