Hypnosis decouples cognitive control from conflict monitoring processes of the frontal lobe

Hypnosis can profoundly alter sensory awareness and cognitive processing. While the cognitive and behavioral phenomena associated with hypnosis have long been thought to relate to attentional processes, the neural mechanisms underlying susceptibility to hypnotic induction and the hypnotic condition are poorly understood. Here, we tested the proposal that highly hypnotizable individuals are particularly adept at focusing attention at baseline, but that their attentional control is compromised following hypnosis due to a decoupling between conflict monitoring and cognitive control processes of the frontal lobe. Employing event-related fMRI and EEG coherence measures, we compared conflict-related neural activity in the anterior cingulate cortex (ACC) and control-related activity in the lateral frontal cortex (LFC) during Stroop task performance between participants of low and high hypnotic susceptibility, at baseline and after hypnotic induction. The fMRI data revealed that conflict-related ACC activity interacted with hypnosis and hypnotic susceptibility, in that highly susceptible participants displayed increased conflict-related neural activity in the hypnosis condition compared to baseline, as well as with respect to subjects with low susceptibility. Cognitive-control-related LFC activity, on the other hand, did not differ between groups and conditions. These data were complemented by a decrease in functional connectivity (EEG gamma band coherence) between frontal midline and left lateral scalp sites in highly susceptible subjects after hypnosis. These results suggest that individual differences in hypnotic susceptibility are linked with the efficiency of the frontal attention system, and that the hypnotized condition is characterized by a functional dissociation of conflict monitoring and cognitive control processes.     

Frontal lobe contributions to hypnotic susceptibility: A neuropsychological screening of executive functioning

Current theory on the cognitive mechanisms of hypnotic experience suggests that hypnosis is mediated by a dissociation between contention-scheduling mechanisms and a supervisory attention system. This theory is based on neuropsychological research with frontal lobe dysfunction patients, who show performance deficits similar in executive functioning to hypnotized individuals. To test an extension of this theory, high hypnotically susceptible (n = 9) and low hypnotically susceptible (n = 7) participants were given four tests of executive functioning. In a baseline condition, high susceptible individuals performed significantly better on one of the four tests (the Wisconsin Card Sorting Test). The role of increased cognitive flexibility in hypnotic susceptibility is considered as a possible component of the dissociated control model of hypnosis.     

Frontal lobe contributions to hypnotic susceptibility: a neuropsychological screening of executive functioning

Current theory on the cognitive mechanisms of hypnotic experience suggests that hypnosis is mediated by a dissociation between contention-scheduling mechanisms and a supervisory attention system. This theory is based on neuropsychological research with frontal lobe dysfunction patients, who show performance deficits similar in executive functioning to hypnotized individuals. To test an extension of this theory, high hypnotically susceptible (n = 9) and low hypnotically susceptible (n = 7) participants were given four tests of executive functioning. In a baseline condition, high susceptible individuals performed significantly better on one of the four tests (the Wisconsin Card Sorting Test). The role of increased cognitive flexibility in hypnotic susceptibility is considered as a possible component of the dissociated control model of hypnosis.     

Differentiation of hypnosis and relaxation by analysis of narrow band theta and alpha frequencies

Narrow band theta and alpha activity were recorded over anterior and posterior sites before, during, and after hypnosis in high and low hypnotically susceptible subjects (N = 16). In theta, high susceptibles had greater activity posthypnosis, otherwise there were no group differences. These findings common to low and high susceptibles suggest that theta is an index of relaxation that continues after hypnosis in highs. In alpha in high susceptibles, posterior power increased from the prehypnosis to hypnosis conditions and decreased posthypnosis. Exactly the converse effects were seen in lows. Furthermore, highs had greater alpha power than lows during both prehypnosis and hypnosis conditions, demonstrating an association of alpha with hypnotic susceptibility. The results indicate that, whereas theta indexes relaxation, alpha indexes the hypnotic experience and susceptibility.     

Task structure as a limiting condition of the occurrence of the treatment effects of simulation instruction in application of the real-simulating model of hypnosis

The hypothesis tested was that lack of task structure facilitates the occurrence of the treatment effects of simulation instruction in application of the real-simulating model of hypnosis. Following appropriate instruction 10 susceptible and 10 insusceptible Ss were tested in 2 sessions by an E who wm blind to the hypnotic susceptibility of Ss. In Session I, Ss were tested on an unstructured (Rorschach) and a structured (Unusual Uses Test) task. In Session II, Ss were administered the same tests again but after hypnosis had been induced and terminated. It was predicted that after receiving instructions to simulate, insusceptible Ss, initially constricted in their response, would change their behavior in Session II in the direction of increased productivity of response, while hypnotic Ss would not, and that the change would be most apparent on the unstructured task. Data supported the hypothesis. In Session II, simulating Ss, but not hypnotic Ss, significantly increased responses on the Rorschach and not on the Uses test. Results suggested that task definition is a limiting condition of the occurrence of the treatment effects of faking instruction.     

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.     

EEG Correlates of Virtual Reality Hypnosis

The study investigated hypnosis-related electroencephalographic (EEG) coherence and power spectra changes in high and low hypnotizables (Stanford Hypnotic Clinical Scale) induced by a virtual reality hypnosis (VRH) induction system. In this study, the EEG from 17 participants (Mean age?=?21.35, SD?=?1.58) were compared based on their hypnotizability score. The EEG recording associated with a 2-minute, eyes-closed baseline state was compared to the EEG during a hypnosis-related state. This novel induction system was able to produce EEG findings consistent with previous hypnosis literature. Interactions of significance were found with EEG beta coherence. The high susceptibility group (n?=?7) showed decreased coherence, while the low susceptibility group (n?=?10) demonstrated an increase in coherence between medial frontal and lateral left prefrontal sites. Methodological and efficacy issues are discussed.     

Amnesia and Hypnosis

The present study explored the relative effects of 2 factors (3 levels of measured hypnotic susceptibility and 3 kinds of motivation procedures) on short-term memory for a paired associate learning task. 36 Ss were stratified, according to their HGSHS:A scores (Shor & E. Ome, 1962), into 3 groups (low, medium, and high susceptibility) of 12 Ss each. The Ss within each of the 3 groups were then evenly but randomly assigned to 3 treatment conditions, which differed in terms of the kind of motivational procedure (hypnotic, waking, or waking non motivational) in which suggestions of amnesia for a recently learned paired associate task were given. Generally, results did not directly support or were sometimes contrary to predictions derived from popular hypnosis theories, which assert that posthypnotic amnesia is a reliable behavioral criterion for the “hypnotic state”.     

Differentiation of hypnosis and relaxation by analysis of narrow band theta and alpha frequencies.

Narrow band theta and alpha activity were recorded over anterior and posterior sites before, during, and after hypnosis in high and low hypnotically susceptible subjects (N = 16). In theta, high susceptibles had greater activity posthypnosis, otherwise there were no group differences. These findings common to low and high susceptibles suggest that theta is an index of relaxation that continues after hypnosis in highs. In alpha in high susceptibles, posterior power increased from the prehypnosis to hypnosis conditions and decreased posthypnosis. Exactly the converse effects were seen in lows. Furthermore, highs had greater alpha power than lows during both prehypnosis and hypnosis conditions, demonstrating an association of alpha with hypnotic susceptibility. The results indicate that, whereas theta indexes relaxation, alpha indexes the hypnotic experience and susceptibility.     

A comparison of hypnotic and waking recall

This paper presents data from a programmatic series of studies that varied the range of conditions affecting potential increase of recall, memory distortions, and distortions of confidence during and following hypnosis. All the studies used a paradigm that exposed Ss to misleading information some time before memory was tested and applied procedures in the hypnotic setting to analyze memory performance in both recognition and free recall. Results from the program failed to demonstrate any increment in accurate memory due to hypnosis, and the accuracy of memory reports in hypnosis was at times significantly reduced. Further, hypnotic recall was distinctively distorted when false information was introduced after, rather than before hypnosis. Results were discussed in relation to the role hypnotic as opposed to contextual variables may play in explaining Ss' memory test performances, and some legal implications are drawn from the data.     

The Conceptual Space of Good and Poor Hypnotic Subjects: A Preliminary Exploration

A form of the Semantic Differential, containing eight concepts related to hypnosis and research, was administered to 12 deeply hypnotizable and 14 nonsusceptible Ss. The good hypnotic Ss evaluated all the concepts more favorably than did the poor hypnotic Ss, with the greatest differential between the two groups occurring on the concept hypnosis. Moreover, the susceptible Ss perceived hypnosis as closer in connotative meaning to such concepts as experiment and professor, then did the nonsusceptible Ss. All differences between the two groups of Ss were of small absolute magnitude, however. Therefore, while the results suggest a relationship between hypnotic susceptibility and attitude toward hypnosis, they appear to preclude the use of the Semantic Differential as a practical predictor of hypnotic susceptibility.     

PRERECORDED HYPNOTIC PERI-SURGICAL INTERVENTION TO ALLEVIATE RISK OF CHRONIC POSTSURGICAL PAIN IN TOTAL KNEE REPLACEMENT: A RANDOMIZED CONTROLLED PILOT STUDY

This pilot study evaluated the effect sizes associated with prerecorded hypnotic interventions provided during the perisurgical period for reducing risk factors associated with chronic postsurgical pain, including acute postsurgical pain, anxiety, depression, and pain catastrophizing. A total of 25 participants (N = –25) were randomly assigned to receive a hypnotic intervention (n = 8), minimal-effect treatment (n = 8), or treatment as usual (n = 9) during their hospital stay for total knee replacement (TKR). Participants were followed for 6 months after hospital discharge. Results indicate that prerecorded hypnotic intervention exerted medium effects for reducing acute postsurgical pain and large effects for reducing perisurgical anxiety and pain catastrophizing. The findings indicate that a fully powered clinical trial to evaluate the beneficial effects of prerecorded hypnosis to manage pain and psychological distress in patients undergoing TKR is warranted.     

Hypnotizability and task motivating suggestions: A further look at how they affect performance

An attempt was made to ferret out the separate effects on cognitive performance of hypnotic susceptibility, task motivating suggestions, and the hypnotic trance state. An equal number of susceptible and unsusceptible Ss were given 3 cognitive tasks, first to ascertain their baseline performances, and then again following either a traditional hypnotic induction, an alert trance induction or a short interview. All Ss were given task motivating suggestions prior to administering the alternate form of the 3 tasks. An additional control group of Ss was used to assess practice effects. Results indicated that task motivating suggestions were effective in enhancing performance for all groups on the digit symbol and abstract reasoning tasks but not on the memory task. Waking suggestion Ss performed as well as hypnotized Ss when both groups of Ss were given task motivating suggestions. It was concluded that when the experimental design of a study incorporates necessary controls, hypnosis does not facilitate performance.     

Perception of short time scale intervals in a hypnotic virtuoso

Previous studies showed that hypnotized individuals underestimate temporal intervals in the range of several seconds to tens of minutes. However, no previous work has investigated whether duration perception is equally disorderly when shorter time intervals are probed. In this study, duration perception of a hypnotic virtuoso was tested using repeated standard temporal generalization and duration estimation tasks. When compared to the baseline state, hypnosis affected perception of intervals spread around 600 ms in the temporal generalization task but did not alter perception of slightly longer intervals spread around 1000 ms. Furthermore, generalization of temporal intervals was more orderly under hypnosis than in the baseline state. In contrast, the hypnotic virtuoso showed a typical time underestimation effect when perception of longer supra-second intervals was tested in the duration estimation task, replicating results of the previous hypnosis studies.     

A single-treatment method to stop smoking using ancillary self-hypnosis: Final remarics in response to the discussants

The purpose of this study was to investigate the influence on suggested amnesia of 2 variables: hypnotic susceptibility and active versus passive learning. 36 chronic schizophrenic patients, 18 low in hypnotic susceptibility and 18 medium or high in hypnotic susceptibility, were randomly assigned to active or passive learning conditions. These Ss were first tested in a hypnosis condition (Day 1) and were retested in a nonhypnosis condition (Day 2) with the presence of waking suggestion. The results for the hypnosis condition indicated that (a) there were no differences between low susceptible and medium-high susceptible Ss on recall amnesia and reversibility (reversible amnesia); (b) recall amnesia and reversibility were significantly higher (p <.01) in passive than active learning conditions; and (c) in all conditions recall was consistently ordered. The results for the nonhypnosis condition were similar, except that reversibility was not significantly higher in passive than active learning conditions. A secondary analysis which partitioned high susceptible (scoring 8-12) from medium susceptible (scoring 5-7) Ss revealed that reversibility was significantly higher in the high susceptible Ss than in the low susceptible Ss; medium susceptible Ss did not differ from either high or low susceptible Ss. The data suggest that the chronic schizophrenics' failure to recall hypnotic events may involve different mechanisms from those which account for posthypnotic amnesia in normal Ss.     

Group Hypnotizability Of Inpatient Adolescents

This study investigated group hypnotizability in 167 adolescents (ages 13-17) in an inpatient behavioral healthcare setting through use of the Waterloo-Stanford Group Scale, Form C. It also investigated the influence of hypnotic inductions on group hypnotizability. Adolescents were randomly assigned to either a group session of hypnosis (n = 84) with a hypnotic induction or a comparison “no-induction” group (n = 83) that received identical suggestions without a hypnotic induction. Adolescents’ imaginative absorption and dissociation were measured to examine their influence on hypnotizability. A between-group comparison showed the induction condition had a significantly higher score than the no-induction group on both behavioral and subjective measures of hypnotizability.     

Motor Imagery in Hypnosis: Accuracy and Duration of Motor Imagery in Waking and Hypnotic States

This study assessed response times and accuracy of motor imagery in waking and hypnotic states and to related responses to hypnotic experiences. The Vividness of Motor Imagery Questionnaire (VMIQ) was administered to 47 participants. A mental walking task was then performed in the waking state. In hypnosis, the same task was included within an imaginary journey after a hypnotic induction. An interaction effect showed for condition (waking vs. hypnotic) and distances. The further the participants had to walk in imagination, the longer they took. For all combinations, participants took significantly longer in hypnosis (p < .001) and were significantly less accurate in hypnosis in reproducing the difference between the different distances (p < .001). Results appear to show a relationship between motor imagery and hypnotic responding and support a state-trait conception of imagery.     

An alternative approach to personality correlates of hypnotizability: Hypnosis-specific mediational attitudes

In an attempt to overcome the limitations of employing general personality traits to predict hypnotic performance, this study compared the predictive validity of 2 hypnosis-specific mediational attitudes with a general personality trait (internal-external locus of control). 2 new hypnosis-specific constructs were developed and termed “desirability of hypnosis” and “locus of control in hypnosis.” Desirability of hypnosis attitudes significantly predicted hypnotic susceptibility (p < .001). There was no relationship between susceptibility and either of the 2 locus of control variables. The results are discussed in relation to the social-learning approaches to personality and, in particular, with respect to hypnosis. Attitudes concerning the desirability of hypnosis are considered for modifying hypnotizability.     

Oxytocin and Cortisol in the Hypnotic Interaction1

Changes in oxytocin and cortisol levels were tested in healthy volunteers during hypnotic interactions in standardized laboratory sessions. Pre- to posthypnosis changes of oxytocin and cortisol were related to the hypnotic susceptibility of subjects and the relational experiences reposted by subjects and hypnotists on several paper-and-pencil tests. Results show that the changes in oxytocin are not related to hypnotic susceptibility but to relational experiences. After the hypnotic interaction, the subject's oxytocin level increased if perceived harmony with the hypnotist was high, whereas it increased in the hypnotist if the subject had memories of less warm emotional relationships with his or her parents. The results are interpreted within the social-psychobiological model of hypnosis.