Suggested deafness during hypnosis and simulation of hypnosis compared to a distraction and control condition: A study on subjective experience and cortical brain responses

Abstract

Hypnosis is a powerful tool to affect the processing and perception of stimuli. Here, we investigated the effects of hypnosis on the processing of auditory stimuli, the time course of event-related-potentials (ERP; N1 and P3b amplitudes) and the activity of cortical sources of the P3b component. Forty-eight participants completed an auditory oddball paradigm composed of standard, distractor, and target stimuli during a hypnosis (HYP), a simulation of hypnosis (SIM), a distraction (DIS), and a control (CON) condition. During HYP, participants were suggested that an earplug would obstruct the perception of tones and during SIM they should pretend being hypnotized and obstructed to hear the tones. During DIS, participants’ attention was withdrawn from the tones by focusing participants’ attention onto a film. In each condition, subjects were asked to press a key whenever a target stimulus was presented. Behavioral data show that target hit rates and response time became significantly reduced during HYP and SIM and loudness ratings of tones were only reduced during HYP. Distraction from stimuli by the film was less effective in reducing target hit rate and tone loudness. Although, the N1 amplitude was not affected by the experimental conditions, the P3b amplitude was significantly reduced in HYP and SIM compared to CON and DIS. In addition, source localization results indicate that only a small number of neural sources organize the differences of tone processing between the control condition and the distraction, hypnosis, and simulation of hypnosis conditions. These sources belong to brain areas that control the focus of attention, the discrimination of auditory stimuli, and the organization of behavioral responses to targets. Our data confirm that deafness suggestions significantly change auditory processing and perception but complete deafness is hard to achieve during HYP. Therefore, the term ‘deafness’ may be misleading and should better be replaced by ‘hypoacusis’.

Hypnotic suggestions of safety reduce neuronal signals of delay discounting

“…Participants. In previous hypnosis studies conducted in our laboratory, the within-subjects effect size for event-related EEG potentials was d = 0.7 33,34 . With a power level of 0.95 and an alpha level of 0.05, 24 participants are required according to G*power 35 .…”

Segregated brain state during hypnosis

“…She gave informed written consent to take part in the study and received a small fee for participation. She has been extensively evaluated in previous studies ( Kallio et al 1999 ; Fingelkurts et al 2007 ; Kallio et al 2011 ; Kallio and Koivisto 2016 ). She rates at maximum in the Stanford suggestibility scale (C, Weitzenhoffer and Hilgard 1962 ) designed to assess individual suggestibility, and is considered a model example of a somnambulic or ‘hypnotic virtuoso’ individual.…”

“…the outcome of the hypnotic suggestion (e.g. Scheibe et al 1968 ; Franz et al 2020 ). We think this approach has merits, but it would not have worked in this study.…”

Neural dynamics of illusory tactile pulling sensations

“…However, we also wanted to check if there were any differences between the 'Neutral oddball' condition and the other two oddball conditions, for which we needed to use a partitioned error approach (random effects analysis), combined with two separate 2x2 within-subject's ANOVAs with factors of oddball condition (Neutral oddball vs Opposite pull oddball or Pull oddball after neutral) and stimulus type (oddball vs common). For these analyses image files (SPM maps; NIFTI) were transformed into four sets of differential effects (overall effect, main effect of condition, main effect of type, condition x type interaction) for each participant (1 st level contrasts), which were then entered into four separate one-sample t-tests (2 nd level contrasts; for details see Franz et al, 2020). Of these contrasts, only the condition x type interaction was of interest because this contrast showed the effect of the oddball condition, whilst controlling for the common stimulus.…”