Higher hypnotic suggestibility is associated with the lower EEG signal variability in theta, alpha, and beta frequency bands

PLoS One. 2020 Apr 9;15(4):e0230853. doi: 10.1371/journal.pone.0230853. eCollection 2020.

Abstract

Variation of information in the firing rate of neural population, as reflected in different frequency bands of electroencephalographic (EEG) time series, provides direct evidence for change in neural responses of the brain to hypnotic suggestibility. However, realization of an effective biomarker for spiking behaviour of neural population proves to be an elusive subject matter with its impact evident in highly contrasting results in the literature. In this article, we took an information-theoretic stance on analysis of the EEG time series of the brain activity during hypnotic suggestions, thereby capturing the variability in pattern of brain neural activity in terms of its information content. For this purpose, we utilized differential entropy (DE, i.e., the average information content in a continuous time series) of theta, alpha, and beta frequency bands of fourteen-channel EEG time series recordings that pertain to the brain neural responses of twelve carefully selected high and low hypnotically suggestible individuals. Our results show that the higher hypnotic suggestibility is associated with a significantly lower variability in information content of theta, alpha, and beta frequencies. Moreover, they indicate that such a lower variability is accompanied by a significantly higher functional connectivity (FC, a measure of spatiotemporal synchronization) in the parietal and the parieto-occipital regions in the case of theta and alpha frequency bands and a non-significantly lower FC in the central region's beta frequency band. Our results contribute to the field in two ways. First, they identify the applicability of DE as a unifying measure to reproduce the similar observations that are separately reported through adaptation of different hypnotic biomarkers in the literature. Second, they extend these previous findings that were based on neutral hypnosis (i.e., a hypnotic procedure that involves no specific suggestions other than those for becoming hypnotized) to the case of hypnotic suggestions, thereby identifying their presence as a potential signature of hypnotic experience.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Brain / physiology*
  • Electroencephalography*
  • Entropy
  • Female
  • Humans
  • Hypnosis*
  • Male
  • Signal Processing, Computer-Assisted*

Grants and funding

This research was supported by Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for JSPS Research Fellow, and Japan Science and Technology Agency (JST). S.K. was funded by JSPS, KAKENHI (JP19K20746) and JST, CREST (JPMJCR18A1). M.A. was funded by Grant-in-Aid for JSPS Research Fellow (15F15046) and JST, CREST (2014-PM11-07-01). M.S. was funded by JST, CREST (JPMJCR18A1). K.H. was funded by JST, CREST (2014-PM11-07-01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.