Low Hypnotizable Participants Research Articles

Well-Being in Highly Hypnotizable Persons

ABSTRACT Both hypnotizability and well-being are relevant to health. This study aimed to investigate whether high hypnotizability was positively associated with well-being and whether the latter was related to the activity of the behavioral inhibition/approach system (BIS/BAS). ANOVA revealed significantly higher scores on the General Well-Being Index (PGWBI) in highly hypnotizable (highs, n = 31) compared with low hypnotizable participants (lows, n = 53), with medium hypnotizable participants (mediums, n = 41) exhibiting intermediate values. This finding was discussed in relation to other hypnotizability-related traits, such as morpho-functional brain characteristics, equivalence between imagery and perception, and interoceptive sensitivity. A secondary finding was a nonsignificant gender difference in scores on the PGWBI. The highs’ higher well-being could be considered a favorable prognostic factor for physical and mental health.

Systematic decrease of slow-wave sleep after a guided imagery designed to deepen sleep in low hypnotizable subjects.

Slow‐wave sleep is one of the most important restorative components of sleep and central for our health and cognitive functioning. Although the amount of slow‐wave sleep depends on sleep drive, age and other factors, also the pre‐sleep mental state might influence sleep depth. We had shown that a pre‐sleep hypnotic suggestion to sleep more deeply increased slow‐wave sleep duration in hypnotizable subjects. In contrast, low‐hypnotizable participants decreased sleep depth after this intervention. A possible reason might be an aversion to and active resistance against hypnosis. To overcome this potential opposition, we introduced the procedure as ‘guided imagery’. We replaced the hypnotic induction by a breathing relaxation. Importantly, the suggestion ‘to sleep more deeply’ remained identical. We expected that these changes would make it easier for low‐hypnotizable subjects to benefit from the suggestion. In contrast, young healthy low‐hypnotizable participants did not show positive effects. Similar to our previous studies, they exhibited a reduced slow‐wave sleep duration after the intervention. Additionally, the ratio between slow‐wave activity and beta band power decreased. Subjective sleep quality remained unaffected. Our results indicate that suggestions to sleep more deeply result in decreased sleep depth in low‐hypnotizable participants regardless of the mental technique (guided imagery versus hypnosis). Thus, the aversion against hypnosis per se cannot explain the detrimental effect of the intervention on slow‐wave sleep in low‐hypnotizable subjects. The results support the notion that our mental state before sleep can influence subsequent slow‐wave sleep. However, the mechanisms of the contradictory decrease in low‐hypnotizable subjects remain unknown.

Imagined and Actual Movements with and without Suggestions for anesthesia in Subjects with Different Hypnotizability

Background: Hypnotizability is a psychophysiological trait associated with several differences including the level of functional equivalence (FE) between imagery and perception - that is similarity of the cortical activations and network configurations associated with each of them. FE is stronger in the individuals with high hypnotisability (highs) with respect to low hypnotizable participants (lows). In this frame, the study investigates the EEG correlates of imagined arm/hand movements (MI) and of actual movements performed in the absence (M) and in the presence of suggestions of arm/hand anesthesia (MA) in highs and lows. Methods: The EEG alpha (8-12 Hz) and beta (13-25 Hz) absolute power, classically associated with movement preparation and execution were studied in 18 highs and 17 lows classified according to the Stanford Hypnotic Susceptibility Scale, form A. EEG was recorded during M, MI, MA. The subjective reports of imagery and the duration of movements were also studied. Results: The movements duration did not differ between highs and lows. Highs reported better imagery during MI, greater perceived influence of the suggestion of anaesthesia during MA, lower cognitive effort than lows for both tasks. In line with earlier studies, spectral analysis did not reveal significant restructuring of the cortical activity during tasks in highs, whereas lows showed cortical changes during MI and MA indicating that they were able to mentally simulate movements and to accept suggestions for anaesthesia during voluntary movement, despite their low hypnotizability scores. Conclusions: Findings suggest that peculiar psychophysiological characteristics could enable different individuals to respond to suggestions.

Topology highlights mesoscopic functional equivalence between imagery and perception: The case of hypnotizability

The functional equivalence (FE) between imagery and perception or motion has been proposed on the basis of neuroimaging evidence of large spatially overlapping activations between real and imagined sensori-motor conditions. However, similar local activation patterns do not imply the same mesoscopic integration of brain regions, which can be described by tools from Topological Data Analysis (TDA). On the basis of behavioral findings, stronger FE has been hypothesized in the individuals with high scores of hypnotizability scores (highs) with respect to low hypnotizable participants (lows) who differ between each other in the proneness to modify memory, perception and behavior according to specific imaginative suggestions. Here we present the first EEG evidence of stronger FE in highs. In fact, persistent homology shows that the highs EEG topological asset during real and imagined sensory conditions is significantly more similar than the lows. As a corollary finding, persistent homology shows lower restructuring of the EEG asset in highs than in lows during both sensory and imagery tasks with respect to basal conditions. Present findings support the view that greater embodiment of mental images may be responsible for the highs greater proneness to respond to sensori-motor suggestions and to report involuntariness in action. In addition, findings indicate hypnotizability-related sensory and cognitive information processing and suggest that the psycho-physiological trait of hypnotizability may modulate more than one aspect of the everyday life.

AUDITORY EVOKED POTENTIALS EVIDENCE FOR DIFFERENCES IN INFORMATION PROCESSING BETWEEN HIGH AND LOW HYPNOTIZABLE SUBJECTS

N100 and P300 auditory evoked potentials in 2-stimulus oddball paradigm were analyzed in high (HH, n = 18) and low (LH, n = 15) hypnotizable participants under waking condition. LH subjects committed more errors than HH subjects. HH subjects demonstrated shorter N100 latencies at frontal electrodes and significant N100 differences between target and nontarget stimuli (higher N100 amplitude and increased latency at parietal sites to targets vs. nontargets), whereas LH subjects failed to show any differences. The overall increase of P300 amplitude with frontal-central localization of P300 maximum was found in HH subjects compared to LH subjects. The obtained results support the psychophysiological model of HH individuals having more effective frontal attentional systems involved in detecting, integrating, and filtering relevant information.

BILATERAL ELECTRODERMAL ACTIVITY IN THE ACTIVE–ALERT HYPNOTIC INDUCTION

Shifts in hemispheric dominance were previously proposed to play a role in hypnosis. Participants (N = 32) were exposed to an active–alert hypnosis induction and a music-control condition while electrodermal activity was registered bilaterally, providing information on alterations in hemispheric dominance. The results suggest that highly hypnotizable participants show a shift to right-sided and low hypnotizable participants demonstrated a shift to left-sided electrodermal dominance in response to the induction, whereas no change in laterality is present in the control condition. Additionally, the authors found that self-reported hypnosis experiences were also associated with a shift in laterality. These results underline the importance of the shift to right hemispheric activity in hypnosis and underscore the importance of hemispheric changes in shaping subjective experience.

Attention or instruction: Do sustained attentional abilities really differ between high and low hypnotisable persons?

Previous research has suggested that highly hypnotisable participants (‘highs’) are more sensitive to the bistability of ambiguous figures—as evidenced by reporting more perspective changes of a Necker cube—than low hypnotisable participants (‘lows’). This finding has been interpreted as supporting the hypothesis that highs have more efficient sustained attentional abilities than lows. However, the higher report of perspective changes in highs in comparison to lows may reflect the implementation of different expectation-based strategies as a result of differently constructed demand characteristics according to one’s level of hypnotisability. Highs, but not lows, might interpret an instruction to report perspective changes as an instruction to report many changes. Using a Necker cube as our bistable stimulus, we manipulated demand characteristics by giving specific information to participants of different hypnotisability levels. Participants were told that previous research has shown that people with similar hypnotisability as theirs were either very good at switching or maintaining perspective versus no information. Our results show that highs, but neither lows nor mediums, were strongly influenced by the given information. However, highs were not better at maintaining the same perspective than participants with lower hypnotisability. Taken together, these findings favour the view that the higher sensitivity of highs in comparison to lows to the bistability of ambiguous figures reflect the implementation of different strategies.

Is Primary-Process Cognition a Feature of Hypnosis?

The division of cognition into primary and secondary processes is an important part of contemporary psychoanalytic metapsychology. Whereas primary processes are most characteristic of unconscious thought and loose associations, secondary processes generally govern conscious thought and logical reasoning. It has been theorized that an induction into hypnosis is accompanied by a predomination of primary-process cognition over secondary-process cognition. The authors hypothesized that highly hypnotizable individuals would demonstrate more primary-process cognition as measured by a recently developed cognitive-perceptual task. This hypothesis was not supported. In fact, low hypnotizable participants demonstrated higher levels of primary-process cognition. Exploratory analyses suggested a more specific effect: felt connectedness to the hypnotist seemed to promote secondary-process cognition among low hypnotizable participants.

Blink reflex in subjects with different hypnotizability: New findings for an old debate

Hypnotizability is associated with attentional characteristics whose neurophysiological bases are still under debate. Aim of the study was the assessment of possible hypnotizability-related differences in blink reflex (BR) which has a nociceptive component, is sensitive to attentional-emotional traits and states and is modulated by the brain dopamine content.In 10 high (highs) and 10 low hypnotizable participants (lows) BR was induced by electrical nociceptive stimulation of the right supraorbital nerve in the absence (noW) and in the presence of a visual cue preceding the electrical stimulation by 0.1ms (W01) and by 1ms (W1). The studied variables were: the amplitude of BR components (R1, R2, R3), the amplitude of the quick change (TO) of heart rate (“turbulence”) induced by stimulation and its recovery slope (TS), the role of the Behavioral Inhibition/Activation System (BIS/BAS) in the variability BR and cardiac turbulence.Repeated measures ANOVA did not show any significant difference between highs and lows in blink reflex. TO indicated stimulation related HR increase in highs and decrease in lows, TS was larger in highs. BIS and BAS accounted for the warning effects on the BR amplitude and modulated the hypnotizability and warning effects on TO and TS. Findings do not support dopamine based hypnotizability-related attentional abilities. In contrast, they indicate that hypnotizability modulates the short-lasting cardiac response to electrical nociceptive stimulation.

What makes your brain suggestible? Hypnotizability is associated with differential brain activity during attention outside hypnosis

Theoretical models of hypnosis have emphasized the importance of attentional processes in accounting for hypnotic phenomena but their exact nature and brain substrates remain unresolved. Individuals vary in their susceptibility to hypnosis, a variability often attributed to differences in attentional functioning such as greater ability to filter irrelevant information and inhibit prepotent responses. However, behavioral studies of attentional performance outside the hypnotic state have provided conflicting results. We used fMRI to investigate the recruitment of attentional networks during a modified flanker task in High and Low hypnotizable participants. The task was performed in a normal (no hypnotized) state. While behavioral performance did not reliably differ between groups, components of the fronto-parietal executive network implicated in monitoring (anterior cingulate cortex; ACC), adjustment (lateral prefrontal cortex; latPFC), and implementation of attentional control (intraparietal sulcus; IPS) were differently activated depending on the hypnotizability of the subjects: the right inferior frontal gyrus (rIFG) was more recruited, whereas IPS and ACC were less recruited by High susceptible individuals compared to Low. Our results demonstrate that susceptibility to hypnosis is associated with particular executive control capabilities allowing efficient attentional focusing, and point to specific neural substrates in right prefrontal cortex. Significance statementWe demonstrated that outside hypnosis, low hypnotizable subjects recruited more parietal cortex and anterior cingulate regions during selective attention conditions suggesting a better detection and implementation of conflict. However, outside hypnosis the right inferior frontal gyrus (rIFG) was more recruited by highly hypnotizable subjects during selective attention conditions suggesting a better control of conflict. Furthermore, in highly hypnotizable subjects this region was more connected to the default mode network suggesting a tight dialogue between internally and externally driven processes that may permit higher flexibility in attention and underlie a greater ability to dissociate.

Hypnotic ability and baseline attention: fMRI findings from Stroop interference.

A benchmark experimental conflict task, the Stroop interference effect, probes selective attention. Regarding individual differences, accounts from multiple independent research groups have shown that a specific suggestion to obviate word meaning can reduce the Stroop interference effect in high- but usually not low-hypnotizable participants. Here we report findings from functional magnetic resonance imaging (fMRI) showing that high-hypnotizable participants, compared with low-hypnotizables, may maintain a distinct baseline of attention even outside of hypnosis or suggestion. Although previous neuroimaging investigation of suggestion-induced Stroop reduction implicated a locus of brain regions prominently including the anterior cingulate cortex, here we observed suggestion-free group differences focal to the fusiform gyrus and pulvinar nucleus of the thalamus—regions associated with word reading and visual attention, respectively. We contextualize our findings in terms of earlier efforts that have attempted to link hypnotizability and baseline performance of attention.

Hypnotizability and Performance on a Prism Adaptation Test.

The susceptibility to hypnosis, which can be measured by scales, is not merely a cognitive trait. In fact, it is associated with a number of physiological correlates in the ordinary state of consciousness and in the absence of suggestions. The hypnotizability-related differences observed in sensorimotor integration suggested a major role of the cerebellum in the peculiar performance of healthy subjects with high scores of hypnotic susceptibility (highs). In order to provide behavioral evidence of this hypothesis, we submitted 20 highs and 21 low hypnotizable participants (lows) to the classical cerebellar Prism Adaptation Test (PAT). We found that the highs' performance was significantly less accurate and more variable than the lows' one, even though the two groups shared the same characteristics of adaptation to prismatic lenses. Although further studies are required to interpret these findings, they could account for earlier reports of hypnotizability-related differences in postural control and blink rate, as they indicate that hypnotizability influences the cerebellar control of sensorimotor integration.

Pain perception and EEG dynamics: Does hypnotizability account for the efficacy of the suggestions of analgesia?

We report novel findings concerning the role of hypnotizability, suggestions of analgesia and the activity of the Behavioral Inhibition/Activation System (BIS/BAS) in the modulation of the subjective experience of pain and of the associated EEG dynamics. The EEG of high (highs) and low hypnotizable participants (lows) who completed the BIS/BAS questionnaire was recorded during basal conditions, tonic nociceptive stimulation without (PAIN) and with suggestions for analgesia (AN). Participants scored the perceived pain intensity at the end of PAIN and AN. The EEG midline dynamics was characterized by indices indicating the signal predictability (Determinism) and complexity (Entropy) obtained through the Recurrence Quantification Analysis. The reduced pain intensity reported by highs during AN was partially accounted for by the activity of the Behavioral Activation System. The decreased midline cortical Determinism observed during nociceptive stimulation in both groups independently of suggestions remained significantly reduced only in lows after controlling for the activity of the Behavioral Activation System. Finally, controlling for the activity of the Behavioral Inhibition System abolished stimulation, suggestions and hypnotizability-related differences. Results indicate that the BIS/BAS activity may be more important than hypnotizability itself in pain modulation and in the associated EEG dynamics.

Using hypnosis to disrupt face processing: mirrored-self misidentification delusion and different visual media.

Mirrored-self misidentification delusion is the belief that one’s reflection in the mirror is not oneself. This experiment used hypnotic suggestion to impair normal face processing in healthy participants and recreate key aspects of the delusion in the laboratory. From a pool of 439 participants, 22 high hypnotisable participants (“highs”) and 20 low hypnotisable participants were selected on the basis of their extreme scores on two separately administered measures of hypnotisability. These participants received a hypnotic induction and a suggestion for either impaired (i) self-face recognition or (ii) impaired recognition of all faces. Participants were tested on their ability to recognize themselves in a mirror and other visual media – including a photograph, live video, and handheld mirror – and their ability to recognize other people, including the experimenter and famous faces. Both suggestions produced impaired self-face recognition and recreated key aspects of the delusion in highs. However, only the suggestion for impaired other-face recognition disrupted recognition of other faces, albeit in a minority of highs. The findings confirm that hypnotic suggestion can disrupt face processing and recreate features of mirrored-self misidentification. The variability seen in participants’ responses also corresponds to the heterogeneity seen in clinical patients. An important direction for future research will be to examine sources of this variability within both clinical patients and the hypnotic model.

Cognitive Modulation of Psychophysical, Respiratory and Autonomic Responses to Cold Pressor Test

In healthy subjects with high hypnotisability (highs) under hypnosis, subjectively effective suggestions for analgesia abolish the increases in blood pressure associated with cold pressor test (cpt) by reducing the peripheral vascular resistance. The aim of the present study was to investigate the effects of the suggestions of analgesia on the responses to cpt in healthy highs (n = 22) and in low hypnotisable participants (lows, n = 22) out of hypnosis. Cpt was administered without (CPT) and with suggestions for analgesia (CPT+AN). Psychophysical (pain intensity, pain threshold, cpt duration (time of immersion) and pain tolerance, defined as the difference between cpt duration and pain threshold), respiratory (amplitude and frequency) and autonomic variables (tonic skin conductance, mean RR interval (RR = 1/heart rate), blood pressure, skin blood flow) were studied. The suggestions for analgesia increased cpt duration and RR in both groups, but decreased pain intensity and enhanced pain threshold only in highs; in both groups they did not modulate systolic blood pressure, tonic skin conductance and skin blood flow; thus, increased parasympathetic activity appears responsible for the heart rate reduction induced by suggestions in both groups. In conclusion, our findings show that suggestions modulate pain experience differentially in highs and lows, and are partially effective also in lows. We hypothesize that the mechanisms responsible for the efficacy of suggestions in healthy lows may be involved also in their efficacy in chronic pain patients with low hypnotisability.

Hypnotic analogues of delusions: The role of delusion proneness and schizotypy

There is compelling evidence that hypnotic suggestions can be used to model clinical delusions in the laboratory. In two studies, we investigated the role that personality factors, delusion proneness and schizotypy, played in shaping such hypnotic models. In the first study, 398 participants were screened on measures of hypnotisability, delusion proneness, and schizotypy. Hypnotisability correlated with both delusion proneness and the cognitive–perceptual subscale of schizotypy. In the second study, 22 high and 20 low hypnotisable participants were given suggestions to model two content specific delusions: Frégoli (the belief that strangers are actually known people in disguise) and mirrored-self misidentification (the belief that one’s reflection in the mirror is a stranger). Whereas high delusion proneness predicted which high hypnotisable participants responded to the suggestion for Frégoli delusion, hypnotisability scores predicted which high hypnotisable participants responded to the suggestion for mirrored-self misidentification. No lows responded to either suggestion. We discuss the implications of these findings for hypnotic models of delusions.

Flexibility in Processing Visual Information: Effects of Mood and Hypnosis 1

This quasi-experiment using a real/simulator model investigated differences in cognitive flexibility in high and low hypnotizable participants. Using the variables of hypnotizability (low/high), consciousness (nonhypnotized/hypnotized), mood (happy/sad), and visual-information processing (global/local), reaction times and target detection paradigms of the subjects were evaluated during both nonhypnotic and hypnotic states. Flexibility in cognitive processing was operationalized as the ability to overcome the typical global precedence and answer quickly about the nonprevalent local features. It was observed that the low hypnotizable participants were not influenced in their preference for the global or local dimension by any manipulated variable, whereas the high hypnotizables were more flexible.

The Cognitive Demands of Hypnotic Response

This study tests the proposal that hypnotic responding is effortless. The authors compared the responses of high and low hypnotizable participants (N = 70) in and out of hypnosis on a dual-task paradigm in which they were required to maintain hypnotic blindness during presentation of visual stimuli of varying salience intensities while simultaneously completing a secondary task. Whereas high hypnotizable participants in both hypnosis and wake conditions reported comparable levels of conviction in the hallucination suggestion, hypnotized highs performed poorer on the secondary task when the stimulus was present. Performance on the secondary task deteriorated when the visual stimulus was intensified. These findings contradict the notion that hypnotic response is not demanding on cognitive resources and suggest that increased effort is required to resolve the extent of conflict between reality and suggestion.

Can Facilitation Imagery Alter the Effects of Semantic Priming?

This study examined if task motivational imagery suggestions could facilitate a semantic priming effect, relative to general relaxation suggestions and no specific suggestions; and if the participants’ hypnotizablity moderated the effects of the three types of instructions. Participants (n = 127) were assigned randomly in groups to one of the three instructional conditions (imagery, relaxation, or control) and two versions of a stimulus list for counterbalancing. A 3-way analysis of variance suggested that the semantic priming effect was found to be stronger for stimulus list version 2 than for version 1. A stronger semantic priming effect was found for the high, relative to the low and medium, hypnotizable groups. When medium hypnotizable participants were excluded, an instructional group X hypnotizability group interaction was found for list 1 suggesting that while the low hypnotizable participants benefited more from the relaxation suggestion, the high hypnotizables benefited more from the imagery instruction. The results suggest that imagery instructions may moderate automatic processes for highly hypnotizable individuals.

Hypnotic Illusions and Clinical Delusions: A Hypnotic Paradigm for Investigating Delusions of Misidentification

In 2 experiments, the authors created a hypnotic analogue of delusions of misidentification and explored their impact on autobiographical memory. In Experiment 1, to establish the paradigm, high and low hypnotizable participants were given a suggestion to become someone similar or dissimilar to themselves. In Experiment 2, to further test the paradigm and to examine autobiographical remembering, highs were given a suggestion to become a same-sex sibling, administered 2 challenges to the temporary delusion, and asked to generate autobiographical memories. For high hypnotizable participants, the suggested delusions of misidentification were compelling and resistant to challenge. During these temporary delusions, participants generated specific autobiographical memories that reflected previously experienced events viewed from the perspective of the suggested identity. These findings highlight the instrumental value of hypnosis to the investigation and understanding of delusions and autobiographical memory.