Neurophenomenology of near-death experience memory in hypnotic recall: a within-subject EEG study

Abstract

The neurobiological basis of near-death experiences (NDEs) is unknown, but a few studies attempted to investigate it by reproducing in laboratory settings phenomenological experiences that seem to closely resemble NDEs. So far, no study has induced NDE-like features via hypnotic modulation while simultaneously measuring changes in brain activity using high-density EEG. Five volunteers who previously had experienced a pleasant NDE were invited to re-experience the NDE memory and another pleasant autobiographical memory (dating to the same time period), in normal consciousness and with hypnosis. We compared the hypnosis-induced subjective experience with the one of the genuine experience memory. Continuous high-density EEG was recorded throughout. At a phenomenological level, we succeeded in recreating NDE-like features without any adverse effects. Absorption and dissociation levels were reported as higher during all hypnosis conditions as compared to normal consciousness conditions, suggesting that our hypnosis-based protocol increased the felt subjective experience in the recall of both memories. The recall of a NDE phenomenology was related to an increase of alpha activity in frontal and posterior regions. This study provides a proof-of-concept methodology for studying the phenomenon, enabling to prospectively explore the NDE-like features and associated EEG changes in controlled settings.

Figure 1

Participants’ Visual Analogic Scales (VAS) scores (and median, dashed lines) relating to level of similarity, absorption, and dissociation in normal consciousness (blue) and hypnotic state (red) for the autobiographical event (AUTOBIO) condition (A) and for the near-death experience (NDE) condition (B). *p < 0.05.

Figure 2

Effects of near-death experience (NDE) condition on spectral power (irrespective of whether this was in a hypnosis or normal consciousness experimental session). (A) The figure shows the power at a central frontal channel (left) and a central posterior channel (right), across all frequencies between 0 and 25 Hz. There are clear peaks at both channels at the low, delta frequencies, and around the alpha frequency which are then further examined. (B) The top panel shows the spectral power across all channels at selected frequency bands: delta (0.5–3.5 Hz), theta (7–8 Hz) and alpha (10–11 Hz) and “specific” alpha (alpha - theta band). The bottom panel shows the contrast between the EEG activity when participants described their NDE versus when they experienced another autobiographical event as T-values (i.e., mean difference normalized by variance). Regions in yellow indicate increased spectral power in the NDE condition (irrespective of whether this was in a hypnosis or normal consciousness experimental session). Significantly different channels are marked by white spots.

Figure 3

Spectral power of alpha activity for two selected channels with peak significant differences between near-death experience (NDE) and recollection of another autobiographical event (AUTOBIO) (highlighted in the bottom right of Fig. 3). The left graph shows the right-of-midline posterior channel also split by hypnosis (HY) and normal consciousness (NC) as well as recall of out-of-body experience (OBE)/kinaesthetic sensation (KS) (light coloured) or peacefulness (PE) (darker coloured). Here, the highest spectral power in NDE versus AUTOBIO is reflected in the NC condition, and only in the PE condition under hypnosis. The right graph shows the slightly left-of-centre frontal peak channel. At the frontal channel, the NDE condition has slightly higher spectral power during HY, but only for the PE condition during NC.

Figure 4

Procedure of the experimental session.