Complex role of hypnotizability in the cognitive control of pain

This opinion article deals with the role of hypnotizability in the efficacy of the suggestions of analgesia for the cognitive control of pain and of its physiological correlates

New views of hypnotizability

Hypnotizability is much more than a cognitive trait enabling people to feel and behave according to suggestions reporting involuntariness in action. In fact, we have shown several hypnotizability-related differences in sensorimotor integration in the participants’ ordinary state of consciousness and in the absence of specific suggestions. This article deals with postural control during imagined sensory modulation in subjects with high and low hypnotizability. It reports evidence of automaticity in the imagery-triggered activation of neural circuits not controlled by expectancy and volition, and suggests that the perceived involuntariness in action associated with imagery of movements potentially controlled by volition/expectancy may be sustained by physiological mechanisms making it a real involuntariness. The described evidence suggests that part of the hypnotizability-related differences observed may depend on peculiar cerebellar activity/connectivity, proposes a possible role of the brain endothelial nitric oxide in hypnotic behavior, and, on the whole, brings the interpretation of hypnotic involuntariness beyond neo-dissociative and socio-cognitive perspectives

Attentional and emotional tasks: gender differences in heart rate variability detected by short-term detrended fluctuation analysis

In this study we analyzed the heart rate variability of 21 subjects, 12 females and 9 males performing a two-step task. The subjects were requested to watch a relaxing movie for 30 minutes and, in a different day, to watch a stressful movie again for 30 minutes. The electrocardiographic signal was recorded for all the duration of the sessions. The series of the beat-to-beat time intervals were analyzed by detrended fluctuation analysis. The short-term variability index clearly indicated a significant gender difference independently of the specific movie, while the long-term variability index did not reveal any significant difference of gender and task. This finding contrasts with the results of physical stimulation, which abolishes the gender differences observed in resting conditions. The discrepancy may depend on lower autonomic engagement in cognitive/affective than in physical tasks as well as on a possible different balance of the sympathetic and parasympathetic activities

Hypnotizability as a possible parameter to identify the attentional abilities of a pilot

The pilot might well be considered as the ultimate component of an aircraft, hence the importance of tailoring his training in order to optimise his performance. Hypnotizability is a psychophysiological trait quite popular owing to its role in the cognitive control of pain. It is measured by scales, which allow to classify the general population as highly (highs), medium (mediums) and low (lows) hypnotizable individuals, and is associated with differences in cortical activity/connectivity, sensorimotor integration and cardiovascular control, also in the absence of suggestions and in the ordinary state of consciousness. We suggest that few hypnotisability- related psychophysiological characteristics may be relevant to pilot selection. In fact, highs exhibit peculiar imagery abilities and proneness to experience bodily signals in an adaptive perspective. The former characteristic mainly consists of stronger Functional Equivalence (FE) between imagery and perception/action, as suggested by behavioural studies and supported by topological analysis of EEG during mental imagery. Stronger FE indicates greater ability to simulate actual sensorimotor information, which occurs likely through greater cortical excitability and allows to produce ideomotor behaviour responding to sensori-motor suggestions. The latter consists of greater ability to utilize bodily signals in the construction of the individual self, which occurs at high levels of the central nervous system owing to continuous monitoring of bodily information. Nonetheless, the highs’ greater sensibility to interoceptive signals is associated with lower accuracy in their detection, so that different modes of homeostatic responses to interoceptive stimulation could be suggested in participants with different hypnotisability levels. Highs could be more suitable to serve as pilots owing to their ability to substitute lacking actual information with imagined information and to adaptively interpret interoceptive changes associated with flights. Unfortunately, they represent only 15% of the population, which consists also of 70% of mediums and 15% of lows. Thus, our proposal is to submit low to medium hypnotizable pilots to mental training focused on sensorimotor images and on the re-appraisal of bodily informatio

Modulation of the postural effects of cognitive load by hypnotizability

Aim of the experiment was to study whether cognitive load aVects postural control more in low (Lows) than in highly hypnotizable (Highs) subjects due to the latter\u27s greater attentional abilities. Standing Highs and Lows underwent an experimental session (closed eyes) consisting of a basal condition and of mental computation in an easy (stable support) and a diYcult (unstable support) postural condition. Variability [standard deviation (SD)] and complexity [sample entropy (SampEn)] of the movement of the centre of pressure (CoP), its mean velocity (Velocity), the area swept by the CoP (Area) and the ratio between the CoP trajectory length and area [length for surface (LFS)] were measured. Few hypnotizability-related diVerences were detected (reduction in the Highs\u27 SD and increases in the Lows\u27 LFS in the diYcult postural condition). Thus, the hypnotizability-related postural diVerences observed in previous studies during sensory alteration could not be accounted mainly by attentional abilities

Is Hypnotic Induction Necessary to Experience Hypnosis and Responsible for Changes in Brain Activity?

The relevance of formal hypnotic induction to the experience of trance and its neural correlates is not clear, in that hypnotizability, beliefs and expectation of hypnosis may play a major role. The aim of the study was assessing the EEG brain activity of participants with high (highs) or low hypnotizability scores (lows), aware of their hypnotizability level and informed that the session will include simple relaxation, formal hypnotic induction and neutral hypnosis. A total of 16 highs and 15 lows (according to the Stanford Hypnotic Susceptibility Scale, form A) were enrolled. Their EEGs were recorded during consecutive conditions of open/closed-eyes relaxation, hypnotic induction, neutral hypnosis and post hypnosis not interrupted by interviews. The studied variables were theta, alpha and gamma power spectral density (PSD), and the Determinism (DET) and Entropy (ENT) of the EEG signal Multidimensional Recurrence Plot (mRP). Highs reported significantly greater changes in their state of consciousness than lows across the session. The theta, alpha and gamma PSD did not exhibit condition-related changes in both groups. The Alpha PSD was larger in highs than in lows on midline sites, and the different sides/regions’ theta and gamma PSD were observed in the two groups independently from conditions. ENT showed no correlation with hypnotizability, while DET positively correlated with hypnotizability during hypnosis. In conclusion, the relevance of formal hypnotic induction to the experience of trance may be scarce in highs, as they are aware of their hypnotizability scores and expecting hypnosis. Cognitive processing varies throughout the session depending on the hypnotizability level

Visuospatial imagery in healthy individuals with different hypnotizability levels

Hypnotizability is a psychophysiological trait associated with morpho-functional brain differences. Since also cerebellar peculiarities have been reported in individuals with different hypnotizability levels and the cerebellar function is relevant to spatial imagery, the present study was aimed at investigating possible hypnotizability-related differences in the ability of spatial imagery. Highly (highs, N=31), low (lows, N=17) and medium (mediums, N=16) hypnotizable participants (classified by Stanford Hypnotic Susceptibility Scale, form A) of both genders were submitted to a test of mental rotation, which requires the integrity of both executive and cerebellar structures. In order to disentangle the role of the cerebellum from that of executive circuits as much as possible, visuospatial and verbal working memory tests, which mainly reflect executive processes, were also performed. Healthy highs exhibited higher scores of mental rotation ability compared to mediums in the absence of significant differences in visual-spatial and verbal working memory. Lows reported intermediate scores not significantly different from both highs’ and mediums’. Different cognitive strategies were observed in the three groups as the correlations between mental rotation, visuospatial and verbal working memory were different in highs, mediums and lows. In conclusion, present findings represent the first report of hypnotizability-related differences in a mental rotation task, which is relevant to several cognitive functions