Pain perception, somatosensory event-related potentials and skin conductance responses to painful stimuli in high, mid, and low hypnotizable subjects: effects of differential pain reduction strategies

Perceived Pain in Athletes: A Comparison between Endurance Runners and Powerlifters through a Cold Experimental Stimulation and Two Sessions of Various Physical Activation

Few studies in the literature have illustrated cold hypoalgesia induced by strength training. Objectives of this contribution were to compare the ratings of perceived pain in endurance running (n = 22) and powerlifting (n = 22) male athletes and controls (n = 22) at baseline and after two bouts of 40 min aerobic/strength training respectively, using the Cold Pressor Test (CPT) and simultaneously monitoring changes in blood pressure (BP), heart rate (HR), and body temperature. A two-way repeated measures ANOVA was conducted to examine the effects of training sessions in endurance runners vs. powerlifting athletes vs. controls on the intensity of perceived pain at CPT. A statistically significant two-way interaction between the group and training resulted in p < 0.001, ηp2 = 0.513. A simple main effects analysis showed that as the participants went through the strength training session, pain perception at CPT was significantly lower in powerlifters compared to runners and controls. Considering the physiological parameters, powerlifters reported significantly higher values of BP and HR. This difference was present at baseline but after training as well, and before and after CPT, despite a slight hypotensive effect. The differences reported after CPT at baseline, but very significantly after the strength activation session in the powerlifters, provide interesting insights into the hypoalgesic effect of high-intensity strength training.

Electrodermal Orienting Response During Active-Alert Hypnosis: Do Verbal Suggestions Influence Automatic Attentional Processes?

This study explored the influence of suggestions on differences in electrodermal laterality of the skin conductance orienting response (SCR). Thirty-two participants were randomly assigned to either permitting or excluding suggestions. During the dream task in the permitting condition the suggestion was: "You are aware of your surroundings and any distractions that might disturb your dream," while in the excluding condition the wording was: "No outside stimulus will disturb your sleep." Participants were presented with 12 standards and 2 deviant computer-generated tones during active-alert hypnosis and musical control conditions in a mixed within-between design. High hypnotizables produced higher SCRs after permissive compared to excluding suggestions during hypnosis, while low hypnotizables did the same in the control condition. Study limitations include some loss of data due to equipment failure and relative homogeneity of sample, therefore results cannot be considered definitive.

Boosting the hypnotic experience. Inhibition of the dorsolateral prefrontal cortex alters hypnotizability and sense of agency. A randomized, double-blind and sham-controlled tDCS study

Hypnotizability refers to the individual responsiveness to hypnosis, and literature shows that the greater the hypnotizability, the more effective the hypnotic suggestions. So far, few studies attempted to enhance hypnotizability, and only two adopted brain stimulation with magnetic pulses. In the present study, we aimed to boost hypnotizability through transcranial direct current stimulation (tDCS). To this aim, bilateral tDCS was applied over the dorsolateral prefrontal cortex (DLPFC) with the target electrode providing negative current (cathodal stimulation) over the left hemisphere. Twenty-nine subjects participated in the study and they were randomly assigned to the sham or the active group in a double-blind design. The hypnotic experience was assessed before and after the stimulation through a phenomenological measure of consciousness (the PCI-HAP). The main findings revealed that a single tDCS session enhanced the hypnotic depth by 11% and reduced the volitional control by 30%, while no differences emerged in the sham group. This is the first study adopting the electrical neurostimulation to produce an alteration of hypnotizability and sense of agency, and confirmed the key-role of the DLPFC and executive control in the hypnotic phenomena. If confirmed, these findings could have relevant implications as enhanced hypnotizability could be translated into better outcomes for many hypnotic interventions.

Effectiveness of Hypnoanalgesia in Paediatric Dermatological Surgery

Background and objective. Stress in surgical settings has subtle psychological and physiological repercussions in children. The objective is to evaluate whether hypnosedation is effective in reducing the doses of sedation and analgesia required during the periprocedural period in children undergoing dermatological surgery, without negatively affecting pain and satisfaction. Patients and methods: A prospective, longitudinal, observational study where paediatric patients (aged 5–16 years) scheduled for dermatological surgery were analysed according to whether they received hypnosis or distraction during surgery (both common procedures at the centre). As outcome measurements we used sedation doses (propofol) during surgery and the need for analgesia; pain assessment post-surgery and at 24 h using a visual analogue scale (VAS) or revised face pain scale (FPS-r) (both 0–10) depending on age, as well as patient and guardian satisfaction (on a scale of 0–10). Results: Of the 68 patients eligible during the follow-up period, 65 were included. Of these, 33 were treated with hypnosis and 32 with distraction. Children who underwent hypnosis required less total propofol (45.5 ± 11.8 mg vs. 69.3 ± 16.8 mg; p < 0.001) and metamizole in the immediate postoperative period (34.4% vs. 65.6%; p = 0.018). After 24 h, they required less ibuprofen (9.1% vs. 28.1%; p = 0.048) and paracetamol (48.5% vs. 75.0%; p = 0.028). Mean pain according to VAS or FPS-r at 24 h was 3.1 with hypnosis vs. 4.3 with distraction (p < 0.001). Overall satisfaction was higher in the hypnosis group (8.7 ± 0.1 vs. 8.1 ± 0.2; p = 0.009). Conclusions: Hypnoanalgesia in children undergoing dermatological outpatient surgery could not only reduce sedation and analgesia requirements, but also improve child and guardian(s) satisfaction.

Spinal and supraspinal modulation of pain responses by hypnosis, suggestions, and distraction

The mechanisms underlying pain modulation by hypnosis and the contribution of hypnotic induction to the efficacy of suggestions being still under debate, our study aimed, (1) to assess the effects of identical hypoalgesia suggestions given with and without hypnotic induction, (2) to compare hypnotic hypoalgesia to distraction hypoalgesia and (3) to evaluate whether hypnotic suggestions of increased and decreased pain share common psychophysiological mechanisms. To this end, pain ratings, nociceptive flexion reflex amplitude, autonomic responses and electroencephalographic activity were measured in response to noxious electrical stimulation of the sural nerve in 20 healthy participants, who were subjected to four conditions: suggestions of hypoalgesia delivered with and without hypnosis induction (i.e. hypnotic-hypoalgesia and suggested-hypoalgesia), distraction by a mental calculation task and hypnotic suggestions of hyperalgesia. As a result, pain ratings decreased in distraction, suggested-hypoalgesia and hypnotic-hypoalgesia, while it increased in hypnotic-hyperalgesia. Nociceptive flexion reflex amplitude and autonomic activity decreased during suggested-hypoalgesia and hypnotic-hypoalgesia but increased during distraction and hypnotic-hyperalgesia. Hypnosis did not enhance the effects of suggestions significantly in any measurement. No somatosensory-evoked potential was modulated by the four conditions according to strict statistical criteria. The absence of a significant difference between the hypnotic hypoalgesia and hyperalgesia conditions suggests that brain processes as evidenced by evoked potentials are not invariably related to pain modulation. Time-frequency analysis of electroencephalographic activity showed a significant differentiation between distraction and hypnotic hypoalgesia in the theta domain. These results highlight the diversity of neurophysiological processes underlying pain modulation through different psychological interventions.

Dispositional Self-Construal Modulates the Empathy for Others' Pain: An ERP Study

Previous studies have shown that temporal self-construal priming can modulate the empathic neural responses to others' pain. However, little is known about the influences of the dispositional self-construal on empathic neural responses to others' pain. The present study aimed to investigate neural correlates that underlie the modulation effect of dispositional self-construal on perception of others' pain. Event-related potentials were recorded for pictures depicting the hands of strangers in painful or no-painful situations while subjects performed a pain judgment task. The regression analysis on behavioral data showed that the level of interdependent self-construal could positively predict behavioral ratings of perceived pain, but not the self-unpleasantness. The ERP results showed painful stimuli elicited decreased N2 amplitudes and larger P3 amplitudes than those by no-painful stimuli. Moreover, the level of interdependent self-construal (interdependence minus independence scores) could predict the amplitude differences on the P3 component (painful minus neutral stimulus conditions), but not the N2 component: the higher the level of the interdependent self-construal, the larger amplitude differences of P3 to painful stimuli (vs. no-painful stimuli). These findings extended previous studies by showing a clear modulation effect of the dispositional self-construal on empathic neural responses to others' pain, and that this modulation effect occurred at the late cognitive evaluation stage indexed by the P3 component.

Hypnosis-induced modulation of corticospinal excitability during motor imagery

Hypnosis can be considered an altered state of consciousness in which individuals produce movements under suggestion without apparent voluntary control. Despite its application in contexts implying motor control, evidence for the neurophysiological mechanisms underlying hypnosis is scarce. Inter-individual differences in hypnotic susceptibility suggest that sensorimotor strategies may manifest in a hypnotic state. We tested by means of transcranial magnetic stimulation applied over the primary motor cortex whether motor system activation during a motor imagery task differs in the awake and in the hypnotic state. To capture individual differences, 30 healthy volunteers were classified as high or low hypnotizable (Highs and Lows) according to ad-hoc validated scales measuring hypnotic susceptibility and personality questionnaires. Corticospinal activation during motor imagery in the hypnotic state was greater in the Highs than the Lows. Intrinsic motivation in task performance and level of persuasion modulated corticospinal activation in the Highs. Corticospinal system activation under hypnosis may have practical implications that merit research in areas where hypnosis can be applied to improve motor performance, such as loss of motor abilities and sports.

Trait phenomenological control predicts experience of mirror synaesthesia and the rubber hand illusion

In hypnotic responding, expectancies arising from imaginative suggestion drive striking experiential changes (e.g., hallucinations) - which are experienced as involuntary - according to a normally distributed and stable trait ability (hypnotisability). Such experiences can be triggered by implicit suggestion and occur outside the hypnotic context. In large sample studies (of 156, 404 and 353 participants), we report substantial relationships between hypnotisability and experimental measures of experiential change in mirror-sensory synaesthesia and the rubber hand illusion comparable to relationships between hypnotisability and individual hypnosis scale items. The control of phenomenology to meet expectancies arising from perceived task requirements can account for experiential change in psychological experiments.

Are Cognitive Load and Focus of Attention Differentially Involved in Pain Management: An Experimental Study Using a Cold Pressor Test and Virtual Reality

Objective

The aim of this study is to assess whether distraction (lack of attentional focus) and attention (cognitive load) are differentially involved in the analgesic effect of virtual reality (VR) immersions during a cold pressor test (CPT).

Methods

Thirty-one participants were randomly assigned to four experimental conditions (high and low cognitive load, attention with or without a reminder of the pain stimuli) and performed three CPTs. Pain was assessed based on the duration of the CPT (pain tolerance), a visual analog rating scale of perceived pain intensity during the CPT and the subjective pain scale of the Short form McGill Pain Questionnaire (SF-MPQ).

Results

The statistical analyses revealed that VR immersions were associated with less pain compared to the baseline (all p <0.001), but for the experimental manipulations, only the conditions where there was an increase in cognitive load (ie, from low cognitive load at Immersion 1 to high cognitive load at Immersion 2) were effective for increasing pain tolerance (significant Time X Conditions interaction). The interactions were not significant for pain intensity assessed with the VAS or the SF-MPQ.

Conclusion

The results suggest that increases in cognitive load play an important role in the analgesic effect of VR immersion, although the combination of attentional focus and cognitive load may be important. Suggestions are given for designing a replication study.

Pain Perception and Body Awareness Among Individuals With Borderline Personality Disorder

Studies indicate that individuals with borderline personality disorder (BPD) often demonstrate attenuated pain perception, termed hypoalgesia. This study examines the hypothesis that body awareness moderates the association between BPD and pain perception. Participants consisted of 46 women diagnosed with BPD and 47 healthy controls. Sensory testing included the measurement of heat-pain thresholds, ratings of suprathreshold stimuli, measurement of temperature evoking moderate pain, and temporal summation of noxious mechanical stimuli. Body awareness was assessed by a self-report questionnaire. As hypothesized, among subjects with low levels of body awareness, those with BPD demonstrated hypoalgesia as manifested in their lower suprathreshold pain ratings and moderate pain evoked by higher temperature, in comparison with the controls. Among those with high levels of body awareness, BPD subjects demonstrated increased reactivity to pain as manifested in their higher pain ratings and moderate pain evoked by lower temperature, in comparison with the controls.

Effects of a Hypnotic Induction and an Unpleasantness-Focused Analgesia Suggestion on Pain Catastrophizing to an Experimental Heat Stimulus: A Preliminary Study

Pain catastrophizing is associated with greater levels of pain. While many studies support the efficacy of hypnosis for pain, the effect on pain catastrophizing remains unclear. The present study evaluated the effect of hypnosis on pain catastrophizing using experimental heat stimulation. Twenty-two pain patients engaged in 3 conditions: baseline (no suggestion), hypnotic induction, and hypnotic induction plus analgesia suggestion. Participants with higher baseline pain showed a significant reduction in rumination following hypnotic induction plus analgesia suggestion and significant reductions in pain due to both the hypnotic induction alone and the hypnotic induction plus analgesia suggestion. The findings suggest that unpleasantness-focused hypnotic analgesia reduces pain via its effect on the rumination component of pain catastrophizing.

Pain rather than induced emotions and ICU sound increases skin conductance variability in healthy volunteers

BACKGROUND

Assessing pain in critically ill patients is difficult. Skin conductance variability (SCV), induced by the sympathetic response to pain, has been suggested as a method to identify pain in poorly communicating patients. However, SCV, a derivate of conventional skin conductance, could potentially also be sensitive to emotional stress. The purpose of the study was to investigate if pain and emotional stress can be distinguished with SCV.

METHODS

In a series of twelve 1-min sessions with SCV recording, 18 healthy volunteers were exposed to standardized electric pain stimulation during blocks of positive, negative, or neutral emotion, induced with pictures from the International Affective Picture System (IAPS). Additionally, authentic intensive care unit (ICU) sound was included in half of the sessions. All possible combinations of pain and sound occurred in each block of emotion, and blocks were presented in randomized order.

RESULTS

Pain stimulation resulted in increases in the number of skin conductance fluctuations (NSCF) in all but one participant. During pain-free baseline sessions, the median NSCF was 0.068 (interquartile range 0.013-0.089) and during pain stimulation median NSCF increased to 0.225 (interquartile range 0.146-0.3175). Only small increases in NSCF were found during negative emotions. Pain, assessed with the numeric rating scale, during the sessions with pain stimulation was not altered significantly by other ongoing sensory input.

CONCLUSION

In healthy volunteers, NSCF appears to reflect ongoing autonomous reactions mainly to pain and to a lesser extent, reactions to emotion induced with IAPS pictures or ICU sound.

Hypnotizability and Placebo Analgesia in Waking and Hypnosis as Modulators of Auditory Startle Responses in Healthy Women: An ERP Study

We evaluated the influence of hypnotizability, pain expectation, placebo analgesia in waking and hypnosis on tonic pain relief. We also investigated how placebo analgesia affects somatic responses (eye blink) and N100 and P200 waves of event-related potentials (ERPs) elicited by auditory startle probes. Although expectation plays an important role in placebo and hypnotic analgesia, the neural mechanisms underlying these treatments are still poorly understood. We used the cold cup test (CCT) to induce tonic pain in 53 healthy women. Placebo analgesia was initially produced by manipulation, in which the intensity of pain induced by the CCT was surreptitiously reduced after the administration of a sham analgesic cream. Participants were then tested in waking and hypnosis under three treatments: (1) resting (Baseline); (2) CCT-alone (Pain); and (3) CCT plus placebo cream for pain relief (Placebo). For each painful treatment, we assessed pain and distress ratings, eye blink responses, N100 and P200 amplitudes. We used LORETA analysis of N100 and P200 waves, as elicited by auditory startle, to identify cortical regions sensitive to pain reduction through placebo and hypnotic analgesia. Higher pain expectation was associated with higher pain reductions. In highly hypnotizable participants placebo treatment produced significant reductions of pain and distress perception in both waking and hypnosis condition. P200 wave, during placebo analgesia, was larger in the frontal left hemisphere while placebo analgesia, during hypnosis, involved the activity of the left hemisphere including the occipital region. These findings demonstrate that hypnosis and placebo analgesia are different processes of top-down regulation. Pain reduction was associated with larger EMG startle amplitudes, N100 and P200 responses, and enhanced activity within the frontal, parietal, and anterior and posterior cingulate gyres. LORETA results showed that placebo analgesia modulated pain-responsive areas known to reflect the ongoing pain experience.

Neural mechanisms of hypnosis and meditation

Hypnosis has been an elusive concept for science for a long time. However, the explosive advances in neuroscience in the last few decades have provided a "bridge of understanding" between classical neurophysiological studies and psychophysiological studies. These studies have shed new light on the neural basis of the hypnotic experience. Furthermore, an ambitious new area of research is focusing on mapping the core processes of psychotherapy and the neurobiology/underlying them. Hypnosis research offers powerful techniques to isolate psychological processes in ways that allow their neural bases to be mapped. The Hypnotic Brain can serve as a way to tap neurocognitive questions and our cognitive assays can in turn shed new light on the neural bases of hypnosis. This cross-talk should enhance research and clinical applications. An increasing body of evidence provides insight in the neural mechanisms of the Meditative Brain. Discrete meditative styles are likely to target different neurodynamic patterns. Recent findings emphasize increased attentional resources activating the attentional and salience networks with coherent perception. Cognitive and emotional equanimity gives rise to an eudaimonic state, made of calm, resilience and stability, readiness to express compassion and empathy, a main goal of Buddhist practices. Structural changes in gray matter of key areas of the brain involved in learning processes suggest that these skills can be learned through practice. Hypnosis and Meditation represent two important, historical and influential landmarks of Western and Eastern civilization and culture respectively. Neuroscience has beginning to provide a better understanding of the mechanisms of both Hypnotic and Meditative Brain, outlining similarities but also differences between the two states and processes. It is important not to view either the Eastern or the Western system as superior to the other. Cross-fertilization of the ancient Eastern meditation techniques presented with Western modern clinical hypnosis will hopefully result in each enriching the other.

Neurocognitive evidence for mental imagery-driven hypoalgesic and hyperalgesic pain regulation

Mental imagery has the potential to influence perception by directly altering sensory, cognitive, and affective brain activity associated with imagined content. While it is well established that mental imagery can both exacerbate and alleviate acute and chronic pain, it is currently unknown how imagery mechanisms regulate pain perception. For example, studies to date have been unable to determine whether imagery effects depend upon a general redirection of attention away from pain or focused attentional mechanisms. To address these issues, we recorded subjective, behavioral and ERP responses using 64-channel EEG while healthy human participants applied a mental imagery strategy to decrease or increase pain sensations. When imagining a glove covering the forearm, participants reported decreased perceived intensity and unpleasantness, classified fewer high-intensity stimuli as painful, and showed a more conservative response bias. In contrast, when imagining a lesion on the forearm, participants reported increased pain intensity and unpleasantness, classified more low-intensity stimuli as painful, and displayed a more liberal response bias. Using a mass-univariate approach, we further showed differential modulation of the N2 potentials across conditions, with inhibition and facilitation respectively increasing and decreasing N2 amplitudes between 122 and 180 ms. Within this time window, source localization associated inhibiting vs. facilitating pain with neural activity in cortical regions involved in cognitive inhibitory control and in the retrieval of semantic information (i.e., right inferior frontal and temporal regions). In contrast, the main sources of neural activity associated with facilitating vs. inhibiting pain were identified in cortical regions typically implicated in salience processing and emotion regulation (i.e., left insular, inferior-middle frontal, supplementary motor and precentral regions). Overall, these findings suggest that the content of a mental image directly alters pain-related decision and evaluative processing to flexibly produce hypoalgesic and hyperalgesic outcomes.

Pain modulation in waking and hypnosis in women: event-related potentials and sources of cortical activity

Using a strict subject selection procedure, we tested in High and Low Hypnotizable subjects (HHs and LHs) whether treatments of hypoalgesia and hyperalgesia, as compared to a relaxation-control, differentially affected subjective pain ratings and somatosensory event-related potentials (SERPs) during painful electric stimulation. Treatments were administered in waking and hypnosis conditions. LHs showed little differentiation in pain and distress ratings between hypoalgesia and hyperalgesia treatments, whereas HHs showed a greater spread in the instructed direction. HHs had larger prefrontal N140 and P200 waves of the SERPs during hypnotic hyperalgesia as compared to relaxation-control treatment. Importantly, HHs showed significant smaller frontocentral N140 and frontotemporal P200 waves during hypnotic hypoalgesia. LHs did not show significant differences for these SERP waves among treatments in both waking and hypnosis conditions. Source localization (sLORETA) method revealed significant activations of the bilateral primary somatosensory (BA3), middle frontal gyrus (BA6) and anterior cingulate cortices (BA24). Activity of these contralateral regions significantly correlated with subjective numerical pain scores for control treatment in waking condition. Moreover, multivariate regression analyses distinguished the contralateral BA3 as the only region reflecting a stable pattern of pain coding changes across all treatments in waking and hypnosis conditions. More direct testing showed that hypnosis reduced the strength of the association of pain modulation and brain activity changes at BA3. sLORETA in HHs revealed, for the N140 wave, that during hypnotic hyperalgesia, there was an increased activity within medial, supramarginal and superior frontal gyri, and cingulated gyrus (BA32), while for the P200 wave, activity was increased in the superior (BA22), middle (BA37), inferior temporal (BA19) gyri and superior parietal lobule (BA7). Hypnotic hypoalgesia in HHs, for N140 wave, showed reduced activity within medial and superior frontal gyri (BA9,8), paraippocampal gyrus (BA34), and postcentral gyrus (BA1), while for the P200, activity was reduced within middle and superior frontal gyri (BA9 and BA10), anterior cingulate (BA33), cuneus (BA19) and sub-lobar insula (BA13). These findings demonstrate that hypnotic suggestions can exert a top-down modulatory effect on attention/preconscious brain processes involved in pain perception.

Hypnotic relaxation results in elevated thresholds of sensory detection but not of pain detection

Background

Many studies show an effectiveness of hypnotic analgesia. It has been discussed whether the analgesic effect is mainly caused by the relaxation that is concomitant to hypnosis. This study was designed to evaluate the effects of hypnotic relaxation suggestion on different somatosensory detection and pain thresholds.

Methods

Quantitative sensory testing (QST) measurements were performed before and during hypnosis in twenty-three healthy subjects on the dorsum of the right hand. Paired t-test was used to compare threshold changes. The influence of hypnotic susceptibility was evaluated by calculating correlation coefficients for threshold changes and hypnotic susceptibility (Harvard group scale).

Results

During hypnosis significantly changed somatosensory thresholds (reduced function) were observed for the following sensory detection thresholds: Cold Detection Threshold (CDT), Warm Detection Threshold (WDT), Thermal Sensory Limen (TSL) and Mechanical Detection Threshold (MDT). The only unchanged sensory detection threshold was Vibration Detection Threshold (VDT). No significant changes were observed for the determined pain detection thresholds (Cold Pain Thresholds, Heat Pain Thresholds, Mechanical Pain Sensitivity, Dynamic Mechanical Allodynia, Wind-up Ratio and Pressure Pain Threshold). No correlation of hypnotic susceptibility and threshold changes were detected.

Conclusion

Hypnotic relaxation without a specific analgesic suggestion results in thermal and mechanical detection, but not pain threshold changes. We thus conclude that a relaxation suggestion has no genuine effect on sensory pain thresholds.

Trial Registration

ClinicalTrials.gov, Identifier: NCT02261155 (9^th October 2014).

Hypnotizability, hypnosis and prepulse inhibition of the startle reflex in healthy women: an ERP analysis

A working model of the neurophysiology of hypnosis suggests that highly hypnotizable individuals (HHs) have more effective frontal attentional systems implementing control, monitoring performance, and inhibiting unwanted stimuli from conscious awareness, than low hypnotizable individuals (LHs). Recent studies, using prepulse inhibition (PPI) of the auditory startle reflex (ASR), suggest that HHs, in the waking condition, may show reduced sensory gating although they may selectively attend and disattend different stimuli. Using a within subject design and a strict subject selection procedure, in waking and hypnosis conditions we tested whether HHs compared to LHs showed a significantly lower inhibition of the ASR and startle-related brain activity in both time and intracerebral source localization domains. HHs, as compared to LH participants, exhibited (a) longer latency of the eyeblink startle reflex, (b) reduced N100 responses to startle stimuli, and (c) higher PPI of eyeblink startle and of the P200 and P300 waves. Hypnosis yielded smaller N100 waves to startle stimuli and greater PPI of this component than in the waking condition. sLORETA analysis revealed that, for the N100 (107 msec) elicited during startle trials, HHs had a smaller activation in the left parietal lobe (BA2/40) than LHs. Auditory pulses of pulse-with prepulse trials in HHs yielded less activity of the P300 (280 msec) wave than LHs, in the cingulate and posterior cingulate gyrus (BA23/31). The present results, on the whole, are in the opposite direction to PPI findings on hypnotizability previously reported in the literature. These results provide support to the neuropsychophysiological model that HHs have more effective sensory integration and gating (or filtering) of irrelevant stimuli than LHs.

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.

Response expectancy versus response hope in predicting birth-related emotional distress and pain

Response expectancies and response hopes have been shown to be two distinct constructs with important implications for nonvolitional outcomes. More specifically, studies show that response expectancies: (1) are sufficient to cause nonvolitional outcomes, (2) are not mediated by other psychological variables, and (3) are self-confirming while seemingly automatic. A new programmatic research line has differentiated between people's response expectancies and their response hopes regarding nonvolitional outcomes and showed that even if response hope and response expectancy are separate constructs, they are not unrelated. These concepts have not yet been studied in pregnant women. Moreover, determining the causal factors that best explain the variance of emotional distress and pain in pregnancy is of great importance. Thus, the aim of this study was to investigate the interrelations between response expectancy and response hope in pregnant women with respect to (1) emotional distress prior to giving birth and (2) pain during giving birth. Additionally, self-reported labor hours were analyzed as a secondary outcome. Results show that response expectancy for pain directly predicts pain, and that the discrepancy between response hopes and response expectancies is a strong predictor of investigated outcomes. Thus, our results support the idea that preventive psychological interventions for pregnant women should emphasize adjusting response expectancies and response hopes regarding the pain and emotional distress associated with giving birth. We believe that the results have both theoretical and practical implications and the topic deserves further investigation.

Effect of hypnotic suggestion on fibromyalgic pain: Comparison between hypnosis and relaxation

The main aims of this experimental study are: (1) to compare the relative effects of analgesia suggestions and relaxation suggestions on clinical pain, and (2) to compare the relative effect of relaxation suggestions when they are presented as "hypnosis" and as "relaxation training". Forty-five patients with fibromyalgia were randomly assigned to one of the following experimental conditions: (a) hypnosis with relaxation suggestions; (b) hypnosis with analgesia suggestions; (c) relaxation. Before and after the experimental session, the pain intensity was measured using a visual analogue scale (VAS) and the sensory and affective dimensions were measured with the McGill Pain Questionnaire. The results showed: (1) that hypnosis followed by analgesia suggestions has a greater effect on the intensity of pain and on the sensory dimension of pain than hypnosis followed by relaxation suggestions; (2) that the effect of hypnosis followed by relaxation suggestions is not greater than relaxation. We discuss the implications of the study on our understanding of the importance of suggestions used in hypnosis and of the differences and similarities between hypnotic relaxation and relaxation training.

Effects of hypnotic focused analgesia on dental pain threshold

The rate, intensity, and selectivity of hypnotic focused analgesia (HFA) were tested with dental pulp stimulation. Thirty-one healthy subjects were hypnotized, and hypnotic suggestions were given for anesthesia of the right mandibular arch. A posthypnotic suggestion of persisting analgesia was also given. The pain threshold of the first premolar was bilaterally measured before, during, and after hypnosis using a pulp tester. During hypnosis, the pain threshold increased significantly (p < .0001) for both sides. The posthypnotic right pain threshold was also significantly (p < .0015) higher than in the basal condition.

Hypnotizability-related integration of perception and action

Hypnotizability is a cognitive trait able to modulate many behavioural/physiological processes and associated with peculiar functional characteristics of the frontal executive system. This review summarizes experimental results on hypnotizability-related differences in sensorimotor integration at a reflex and an integrated level (postural control) and suggests possible interpretations based on morpho-functional considerations. In particular, hypnotizability-related differences in spinal motoneurones excitability are described, and the role of attention and imagery in maintaining a stable upright stance when sensory information is reduced or altered and when attention is absorbed in cognitive tasks is discussed as a function of hypnotic susceptibility. The projections from prefrontal cortex to spinal motoneurones and the balance between the activation of the right and left cortical hemisphere are considered responsible for the hypnotizability-related modulation of reflex responses, while the differences in postural control between subjects with high (highs) and low (lows) hypnotic susceptibility are considered a possible consequence of the activity of the locus coeruleus, which is also involved in attention, and of the cerebellum, which might be responsible for different internal models of postural control. We suggest a highly pervasive role of hypnotic susceptibility in human behaviour through the modulation of the integration of perception and action, which could be relevant for neurorehabilitative treatments and for the adaptation to special environments.

Hypnosis and pain in children

The development of studies on neuroimaging applied to hypnosis and to the study of pain not only helps to validate the existence of a hypnotic state but also to ratify its therapeutic effects. These studies also enable us to understand how hypnosis is effective on the cortical level. It also helps us see, from another perspective, the mechanisms of pain leading perhaps to a different definition of pain. This article develops the latest knowledge in the domain of hypnosis and pain, and approaches the clinical practices and their applications in the management of pain in children.

Hypnotic analgesia

Hypnosis has been used for centuries to treat various types of pain problems. Anecdotal reports of its efficacy have been around since the early 1800 s, but only recently has sophisticated research advanced the field. This paper will summarize the theoretical and clinical foundations of hypnotic analgesia, as well as offer recommendations for increasing its efficacy and improving future research to advance the field.

Hypnosis and surgery: past, present, and future

Hypnosis has been defined as the induction of a subjective state in which alterations of perception or memory can be elicited by suggestion. Ever since the first public demonstrations of "animal magnetism" by Mesmer in the 18th century, the use of this psychological tool has fascinated the medical community and public alike. The application of hypnosis to alter pain perception and memory dates back centuries. Yet little progress has been made to fully comprehend or appreciate its potential compared to the pharmacologic advances in anesthesiology. Recently, hypnosis has aroused interest, as hypnosis seems to complement and possibly enhance conscious sedation. Contemporary clinical investigators claim that the combination of analgesia and hypnosis is superior to conventional pharmacologic anesthesia for minor surgical cases, with patients and surgeons responding favorably. Simultaneously, basic research of pain pathways involving the nociceptive flexion reflex and positron emission tomography has yielded objective data regarding the physiologic correlates of hypnosis. In this article I review the history, basic scientific and clinical studies, and modern practical considerations of one of the oldest therapeutical tools: the power of suggestion.

Focused hypnotic analgesia: Local and remote effects

Suggestion for hypnotic analgesia aimed at a specific body area is termed "focused hypnotic analgesia". It is not clear, however, whether this analgesia is limited to a specific body location or spread all over the body. Focused hypnotic analgesia was studied, in response to ascending electrical stimuli, when analgesia and stimulation were applied to the same area (local), and when analgesia was applied to one location and stimulation was delivered to a different area (remote). The face or leg served alternately as the local or remote areas, and the effect was tested in 12 high-hypnotizable (HH) and 13 low-hypnotizable (LH) subjects. Hypnotic analgesia in the local site produced a significant pain reduction compared to the remote site in HH subjects (P<0.0001) but not in LH subjects (P=0.68). As stimuli increased in intensity the reduction in pain as a result of hypnosis was larger both in HH and LH subjects (P<0.0001). Nevertheless, significant analgesia occurred in the 3 highest intensities in the local and remote location of HH subjects, but only in 2 highest intensities in the local and 1 in the remote of LH subjects. We conclude that in HH subjects focused hypnotic analgesia is mostly confined to the area aimed at, but some spread of analgesia to remote areas cannot be dismissed all together. Alternatively, this "spread" of analgesia could be due to a placebo effect in the remote area. Focused hypnotic analgesia requires increased attention to the body area aimed at, unlike analgesia achieved by distraction of attention.

Modulation of pain-induced endothelial dysfunction by hypnotisability

Mental stress induces endothelial dysfunction, that is a reduction of the post-occlusion brachial artery flow-mediated vasodilation (FMD). This does not occur in subjects highly susceptible to hypnosis (Highs) in either the waking or hypnotic state. The aim of the present experiment was to assess whether endothelial dysfunction is also induced by acute nociceptive stimulation and whether high hypnotisability and/or the specific instruction of analgesia prevent its occurrence in awake highly hypnotizable individuals. Thus, nine Highs and nine subjects with low susceptibility to hypnosis (Lows) underwent an experimental session including the administration of pressor pain and of pressor pain associated with the instruction of analgesia. Heart rate, basal artery diameters and brachial artery flow-mediated vasodilation were measured during stimulation and rest conditions. Heart rate exhibited slight changes not modulated by hypnotisability. During painful stimulation both Highs and Lows showed a decrease of FMD, but it was significantly less pronounced in Highs. During the administration of painful stimulation together with the instruction of analgesia, only Highs reported analgesia and their FMD no longer decreased. This study provides the first evidence of pain-related endothelial dysfunction and extends previous findings concerning a sort of natural protection of Highs against the vascular effects of mental stress to acute pain.

Pain reduction is related to hypnotizability but not to relaxation or to reduction in suffering: a preliminary investigation

The present study examined the facilitation of pain reduction through the use of a pain reduction protocol. The protocol emphasized converting pain sensations into visual and auditory representations, which then were manipulated through therapeutic suggestion. Hypnosis was not mentioned in the intervention, minimizing creation of expectancy effects related to hypnosis. At the conclusion of the study, the Stanford Clinical Hypnotic Scale was administered. Measures of relaxation and reduction of suffering were not related to hypnotizability. However, pain reduction was significantly related to hypnotizability (r = .55, P < .001). High hypnotizables had a greater reduction in pain than low hypnotizables, even though both had equivalent degrees of relaxation.

Whither spontaneous hypnosis: A Critical issue for practitioners and researchers

The critical aspects of recognizing that hypnotic responses are part of everyday life for those who are hypnotizable are considered. The failure of the American Psychological Association (APA) definition to include spontaneous hypnosis is discussed along with the resultant implications for misinforming clinicians, researchers and the public.

Pain perception, obstructive imagery and phase-ordered gamma oscillations

The neural mechanisms underlying pain perception and anti-nociceptive effects of mental imagery are not well understood. Using a measure of phase-ordered beta and gamma EEG oscillations in response to painful electric stimulation, we recently found that somatosensory event-related phase-ordered gamma oscillations (38-42 Hz), elicited by the onset of painful stimuli over Cz scalp site, were linearly related to pain perception. In the present study, 38 subjects were engaged in a painful stimulus detection task using an oddball paradigm. This task was performed under a condition in which subjects were required simply to count the number of target stimuli (pain condition) and under another condition in which subjects were required to produce an obstructive mental imagery of painful stimulus perception (obstructive imagery). Only EEG responses to standard stimuli were analyzed in this study. Correlation analysis of sweeps for each individual revealed brief intervals of phase ordering of EEG patterns in the beta and gamma bands. The frequencies of interest were the beta1 (26-30 Hz), beta2 (30-34 Hz), gamma1 (34-38 Hz), gamma2 (38-42 Hz) and gamma3 (42-46 Hz) bands. Obstructive imagery treatment, compared to pain condition, significantly reduced pain perception. This reduction was paralleled by significant decreases of evoked phase-ordered gamma2 and gamma3 patterns over Cz scalp site. Phase-ordered oscillations at Cz scalp site, for both gamma2 and gamma3 bands, significantly predicted pain ratings during pain condition. Phase-ordered oscillation scores, obtained for these gamma bands over parietal and frontal scalp sites, resulted the best predictor of pain ratings during obstructive imagery. This study provides evidence for the role of gamma oscillations in the subjective experience of pain. Further, it has provided support for the view that pain reduction during obstructive mental imagery is the product of an inhibitory process involving frontal and parietal cortical regions.

Perception and modulation of pain in waking and hypnosis: functional significance of phase-ordered gamma oscillations

Somatosensory event-related phase-ordered gamma oscillations (40-Hz) to electric painful standard stimuli under an odd-ball paradigm were analyzed in 13 high, 13 medium, and 12 low hypnotizable subjects during waking, hypnosis, and post-hypnosis conditions. During these conditions, subjects received a suggestion of Focused Analgesia to produce an obstructive hallucination of stimulus perception; a No-Analgesia treatment served as a control. After hypnosis, a post-hypnotic suggestion was given to draw waking subjects into a deep hypnosis with opened eyes. High hypnotizables, compared to medium and low ones, experienced significant pain and distress reductions for Focused Analgesia during hypnosis and, to a greater extent, during post-hypnosis condition. Correlational analysis of EEG sweeps of each individual revealed brief intervals of phase ordering of gamma patterns, preceding and following stimulus onset, lasting approximately six periods. High and medium hypnotizable subjects showed significant reductions in phase-ordered gamma patterns for Focused Analgesia during hypnosis and post-hypnosis conditions; this effect was found, however, more pronounced in high hypnotizable subjects. Phase-ordered gamma scores over central scalp site predicted subject pain ratings across Waking-Pain and Waking-Analgesia conditions, while phase-ordered gamma scores over frontal scalp site predicted pain ratings during post-hypnosis analgesia condition. During waking conditions, this relationship was present in high, low and medium hypnotizable subjects and was independent of stimulus intensity measures. This relationship was unchanged by hypnosis induction in the low hypnotizable subjects, but not present in the high and medium ones during hypnosis, suggesting that hypnosis interferes with phase-ordered gamma and pain relationship.

Focused analgesia and generalized relaxation produce differential hypnotic analgesia in response to ascending stimulus intensity

This study was designed in order to examine the effects of different types of hypnotic suggestion on hypnotic analgesia. Generalized relaxation and focused analgesia were induced in seven high-hypnotizable (HH) and eight low-hypnotizable (LH) subjects. Subjects were not aware to which group they belonged. The two groups did not differ in their expectation rates to achieve analgesia under hypnosis. Pain intensity and unpleasantness were rated on visual analogue scales in response to painful electrical stimuli, delivered in random order in five ascending intensities. Both focused analgesia and generalized relaxation decreased pain intensity significantly (P < 0.01). However, stimulus-intensity response curves differed under the two hypnotic conditions. As stimulus intensity became higher pain reduction was enhanced under focused analgesia, while a constant reduction occurred under generalized relaxation. The interaction between hypnotic state and stimulus intensity was significant for focused analgesia (P < 0.05) but not for generalized relaxation (P > 0.07), difference became more pronounced when analyzed for HH subjects only (P < 0.002 for analgesia, P > 0.10 for relaxation). Pain reduction was significantly higher in HH than in LH subjects under focused analgesia (P < 0.02) but not under generalized relaxation (P > 0.5). We conclude that by utilizing two modes of hypnotic suggestions in response to ascending stimuli, we were able to discover two components of hypnotic analgesia. One shows a parallel shift in the stimulus-response function, has features similar to placebo and bears no clear relationship to hypnotic susceptibility. The other shows a slope change in the stimulus-response curve and has a positive relationship to hypnotic susceptibility.

Hypnosis and clinical pain

Hypnosis has been demonstrated to reduce analogue pain, and studies on the mechanisms of laboratory pain reduction have provided useful applications to clinical populations. Studies showing central nervous system activity during hypnotic procedures offer preliminary information concerning possible physiological mechanisms of hypnotic analgesia. Randomized controlled studies with clinical populations indicate that hypnosis has a reliable and significant impact on acute procedural pain and chronic pain conditions. Methodological issues of this body of research are discussed, as are methods to better integrate hypnosis into comprehensive pain treatment.

Hypnosis modulates activity in brain structures involved in the regulation of consciousness

The notion of consciousness is at the core of an ongoing debate on the existence and nature of hypnotic states. Previously, we have described changes in brain activity associated with hypnosis (Rainville, Hofbauer, Paus, Duncan, Bushnell, & Price, 1999). Here, we replicate and extend those findings using positron emission tomography (PET) in 10 normal volunteers. Immediately after each of 8 PET scans performed before (4 scans) and after (4 scans) the induction of hypnosis, subjects rated their perceived level of "mental relaxation" and "mental absorption," two of the key dimensions describing the experience of being hypnotized. Regression analyses between regional cerebral blood flow (rCBF) and self-ratings confirm the hypothesized involvement of the anterior cingulate cortex (ACC), the thalamus, and the ponto-mesencephalic brainstem in the production of hypnotic states. Hypnotic relaxation further involved an increase in occipital rCBF that is consistent with our previous interpretation that hypnotic states are characterized by a decrease in cortical arousal and a reduction in cross-modality suppression (disinhibition). In contrast, increases in mental absorption during hypnosis were associated with rCBF increases in a distributed network of cortical and subcortical structures previously described as the brain's attentional system. These findings are discussed in support of a state theory of hypnosis in which the basic changes in phenomenal experience produced by hypnotic induction reflect, at least in part, the modulation of activity within brain areas critically involved in the regulation of consciousness.

Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: a review of recent studies

The investigation of weak (<500 microT), extremely low frequency (ELF, 0-300 Hz) magnetic field (MF) exposure upon human cognition and electrophysiology has yielded incomplete and contradictory evidence that MFs interact with human biology. This may be due to the small number of studies undertaken examining ELF MF effects upon the human electroencephalogram (EEG), and the associated analysis of evoked related potentials (ERPs). Relatively few studies have examined how MF exposure may affect cognitive and perceptual processing in human subjects. The introduction of this review considers some of the recent studies of ELF MF exposure upon the EEG, ERPs and cognitive and perceptual tasks. We also consider some of the confounding factors within current human MF studies and suggest some new strategies for further experimentation.