Cerebellar structural variations in subjects with different hypnotizability

Hypnotizability-the proneness to accept suggestions and behave accordingly-has a number of physiological and behavioral correlates (postural, visuomotor, and pain control) which suggest a possible involvement of cerebellar function and/or structure. The present study was aimed at investigating the association between cerebellar macro- or micro-structural variations (analyzed through a voxel-based morphometry and a diffusion tensor imaging approach) and hypnotic susceptibility. We also estimated morphometric variations of cerebral gray matter structures, to support current evidence of hypnotizability-related differences in some cerebral areas. High (highs, N = 12), and low (lows, N = 37) hypnotizable healthy participants (according to the Stanford Hypnotic Susceptibility Scale, form A) were submitted to a high field (3 T) magnetic resonance imaging protocol. In comparison to lows, highs showed smaller gray matter volumes in left cerebellar lobules IV/V and VI at uncorrected level, with the results in left lobule IV/V maintained also at corrected level. Highs showed also gray matter volumes smaller than lows in right inferior temporal gyrus, middle and superior orbitofrontal cortex, parahippocampal gyrus, and supramarginal parietal gyrus, as well as in left gyrus rectus, insula, and middle temporal cortex at uncorrected level. Results of right inferior temporal gyrus survived also at corrected level. Analyses on micro-structural data failed to reveal any significant association. The here found morphological variations allow to extend the traditional cortico-centric view of hypnotizability to the cerebellar regions, suggesting that cerebellar peculiarities may sustain hypnotizability-related differences in sensorimotor integration and emotional contro

Neurophysiologie de l’hypnose

We here review behavioral, neuroimaging and electrophysiological studies of hypnosis as a state, as well as hypnosis as a tool to modulate brain responses to painful stimulations. Studies have shown that hypnotic processes modify internal (self awareness) as well as external (environmental awareness) brain networks. Brain mechanisms underlying the modulation of pain perception under hypnotic conditions involve cortical as well as subcortical areas including anterior cingulate and prefrontal cortices, basal ganglia and thalami. Combined with local anesthesia and conscious sedation in patients undergoing surgery, hypnosis is associated with improved peri- and postoperative comfort of patients and surgeons. Finally, hypnosis can be considered as a useful analogue for simulating conversion and dissociation symptoms in healthy subjects, permitting better characterization of these challenging disorders by producing clinically similar experiences

Brain oscillations in highly hypnotisable participants during neutral hypnosis, hypnotic suggestions, and pre- and posthypnosis

Tavoitteet: Tämän tutkimuksen tavoitteena oli edistää yhtenäisen teorian muodostusta hypnoosista tutkimalla muutoksia aivosähkökäyrän (EEG:n) tehotiheysspektrissä, joita hypnoosi mahdollisesti aiheuttaa herkästi hypnotisoitaville tutkittaville. Aiemman kirjallisuuden nojalla tehon oletettiin kasvavan EEG:n theta-taajuuksilla (4–8 Hz) ja muuttuvan gamma-taajuuksilla (25–45 Hz) hypnoosin aikana. Menetelmät: Yhdeksän herkästi hypnotisoitavaa tutkittavaa (8 naista) osallistui kokeeseen. Jatkuvaa EEG:tä mitattiin kymmenellä elektrodilla neljässä koetilanteessa: ennen hypnoosia, neutraalissa hypnoosissa, hypnoottisessa suggestiotilanteessa, ja hypnoosin jälkeen. Tutkittavat katselivat monotonista videota kaikissa koetilanteissa sinimuotoisten äänimerkkien soidessa hiljaa taustalla oddball-paradigman mukaisesti. Tutkittavia ohjeistettiin jättämään äänimerkit huomiotta, ja suggestiotilanteessa tutkittaville annettiin suggestio kuulla kaikki äänet saman korkuisina. Analyysit toteutettiin jokaiselle määritellylle taajuuskaistalle erikseen yhteensä yhdeksällä toistettujen mittausten varianssianalyysillä. Lisäksi tutkimuskysymyksiä 2 ja 3 varten tutkittavat jaettiin kahteen ryhmään sen mukaan, toimiko hallusinatorinen suggestio heillä seulontavaiheessa. Tämän jälkeen analyysit suoritettiin uudelleen. Tulokset: Koetilanteiden välillä ei löydetty eroa theta-taajuuskaistalla, mutta gamma-taajuuskaistalla tehon havaittiin vähenevän hypnoosissa verrattuna hereillä oloon (hypnoosin jälkeen). Lisäksi todettiin joitakin tehotiheysmuutoksia, jotka riippuivat hallusinatorisen suggestion toimivuudesta tutkittavilla. Johtopäätökset: Tulokset tukevat hypoteesia muuttuneesta gamma-tehosta hypnoosin aikana, mutta eivät teoriaa kasvaneesta theta-tehosta yhtenä hypnoosin indikaattorina. Aiempien tutkimusten ja tämän tutkimuksen tulosten perusteella spekulatiivinen teoreettinen yhteys esitetään löytyvän vähentyneen perifeerisen tietoisuuden ja vähentyneen gamman välillä hypnoosin aikana.Objective: To contribute to the theory-building on hypnosis by studying the possible changes that hypnosis causes in the electroencephalographic (EEG) spectral power in highly hypnotisable individuals. In accordance with previous literature, hypnosis was hypothesised to cause an increase in theta (4–8 Hz) power and a change in gamma (25–45 Hz) power. Methods: Nine highly hypnotisable individuals (8 females) participated. Continuous EEG was recorded at ten electrodes during four conditions: prehypnosis, neutral hypnosis, hypnotic suggestion, and posthypnosis. During all conditions, the participants watched a monotonous video while sinusoidal tones following an oddball paradigm played silently in the background. The participants were instructed not to pay any attention to the tones, and in the suggestion-condition a suggestion to hear all tones as similar in pitch was given. Nine repeated-measures analyses of variance, one for each frequency range, were performed. For research questions 2 and 3, the participants were divided into two groups depending on their responsiveness to a hallucinatory suggestion in the screening phase, and the analyses were then run again. Results: No differences between conditions were found in the theta range, but a decrease was found in the gamma range during hypnosis compared with wakefulness (posthypnosis). Spectral power differences depending on responsiveness to the hallucinatory suggestion were also found. Conclusions: The findings support the hypothesis of changed gamma-frequency power during hypnosis, but not the theory of increased theta frequencies as a marker of hypnosis. A tentative theoretical connection between reduced peripheral awareness and reduced gamma power in hypnosis is presented

Alterations in The States and Contents of Consciousness: Empirical and Theoretical Aspects

The main purpose of the present doctoral thesis is to investigate subjective experiences and cognitive processes in four different types of altered states of consciousness: naturally occurring dreaming, cognitively induced hypnosis, pharmacologically induced sedation, and pathological psychosis. Both empirical and theoretical research is carried out, resulting in four empirical and four theoretical studies. The thesis begins with a review of the main concepts used in consciousness research, the most influential philosophical and neurobiological theories of subjective experience, the classification of altered states of consciousness, and the main empirical methods used to study consciousness alterations. Next, findings of the original studies are discussed, as follows. Phenomenal consciousness is found to be dissociable from responsiveness, as subjective experiences do occur in unresponsive states, including anaesthetic-induced sedation and natural sleep, as demonstrated by post-awakening subjective reports. Two new tools for the content analysis of subjective experiences and dreams are presented, focusing on the diversity, complexity and dynamics of phenomenal consciousness. In addition, a new experimental paradigm of serial awakenings from non-rapid eye movement sleep is introduced, which enables more rapid sampling of dream reports than has been available in previous studies. It is also suggested that lucid dreaming can be studied using transcranial brain stimulation techniques and systematic analysis of pre-lucid dreaming. For blind judges, dreams of psychotic patients appear to be indistinguishable from waking mentation reports collected from the same patients, which indicates a close resemblance of these states of mind. However, despite phenomenological similarities, dreaming should not be treated as a uniform research model of psychotic or intact consciousness. Contrary to this, there seems to be a multiplicity of routes of how different states of consciousness can be associated. For instance, seemingly identical time perception distortions in different alterations of consciousness may have diverse underlying causes for these distortions. It is also shown that altered states do not necessarily exhibit impaired cognitive processing compared to a baseline waking state of consciousness: a case study of time perception in a hypnotic virtuoso indicates a more consistent perceptual timing under hypnosis than in a waking state. The thesis ends with a brief discussion of the most promising new perspectives for the study of alterations of consciousness.Siirretty Doriast

Beyond imagination: Hypnotic visual hallucination induces greater lateralised brain activity than visual mental imagery

Hypnotic suggestions can produce a broad range of perceptual experiences, including hallucinations. Visual hypnotic hallucinations differ in many ways from regular mental images. For example, they are usually experienced as automatic, vivid, and real images, typically compromising the sense of reality. While both hypnotic hallucination and mental imagery are believed to mainly rely on the activation of the visual cortex via top-down mechanisms, it is unknown how they differ in the neural processes they engage. Here we used an adaptation paradigm to test and compare top-down processing between hypnotic hallucination, mental imagery, and visual perception in very highly hypnotisable individuals whose ability to hallucinate was assessed. By measuring the N170/VPP event-related complex and using multivariate decoding analysis, we found that hypnotic hallucination of faces involves greater top-down activation of sensory processing through lateralised neural mechanisms in the right hemisphere compared to mental imagery. Our findings suggest that the neural signatures that distinguish hypnotically hallucinated faces from imagined faces lie in the right brain hemisphere.Fil: Lanfranco, Renzo C.. University of Edinburgh; Reino Unido. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Rivera Rei, Álvaro. Universidad Adolfo Ibañez; ChileFil: Huepe, David. Universidad Adolfo Ibañez; ChileFil: Ibañez, Agustin Mariano. Universidad Adolfo Ibañez; Chile. Universidad de San Andrés. Departamento de Matemáticas y Ciencias; Argentina. University of California; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Canales Johnson, Andrés. University of Cambridge; Estados Unidos. Universidad Catolica de Maule; Chil

Linear and nonlinear quantitative EEG analysis during neutral hypnosis following an opened/closed eye paradigm

Hypnotic susceptibility is a major factor influencing the study of the neural correlates of hypnosis using EEG. In this context, while its effects on the response to hypnotic suggestions are undisputed, less attention has been paid to “neutral hypnosis” (i.e., the hypnotic condition in absence of suggestions). Furthermore, although an influence of opened and closed eye condition onto hypnotizability has been reported, a systematic investigation is still missing. Here, we analyzed EEG signals from 34 healthy subjects with low (LS), medium (MS), and (HS) hypnotic susceptibility using power spectral measures (i.e., TPSD, PSD) and Lempel-Ziv-Complexity (i.e., LZC, fLZC). Indeed, LZC was found to be more suitable than other complexity measures for EEG analysis, while it has been never used in the study of hypnosis. Accordingly, for each measure, we investigated within-group differences between rest and neutral hypnosis, and between opened-eye/closed-eye conditions under both rest and neutral hypnosis. Then, we evaluated between-group differences for each experimental condition. We observed that, while power estimates did not reveal notable differences between groups, LZC and fLZC were able to distinguish between HS, MS, and LS. In particular, we found a left frontal difference between HS and LS during closed-eye rest. Moreover, we observed a symmetric pattern distinguishing HS and LS during closed-eye hypnosis. Our results suggest that LZC is better capable of discriminating subjects with different hypnotic susceptibility, as compared to standard power analysis

Monitoring the Depth of Anaesthesia

One of the current challenges in medicine is monitoring the patients’ depth of general anaesthesia (DGA). Accurate assessment of the depth of anaesthesia contributes to tailoring drug administration to the individual patient, thus preventing awareness or excessive anaesthetic depth and improving patients’ outcomes. In the past decade, there has been a significant increase in the number of studies on the development, comparison and validation of commercial devices that estimate the DGA by analyzing electrical activity of the brain (i.e., evoked potentials or brain waves). In this paper we review the most frequently used sensors and mathematical methods for monitoring the DGA, their validation in clinical practice and discuss the central question of whether these approaches can, compared to other conventional methods, reduce the risk of patient awareness during surgical procedures

The effectiveness of hypnosis for pain relief: A systematic review and meta-analysis of 85 controlled experimental trials

The current meta-analysis aimed to quantify the effectiveness of hypnosis for reducing pain and identify factors that influence efficacy. Six major databases were systematically searched for trials comparing hypnotic inductions with no- intervention control conditions on pain ratings, threshold and tolerance using experimentally-evoked pain models in healthy participants. Eighty-five eligible studies (primarily crossover trials) were identified, consisting of 3632 participants (hypnosis n=2892, control n=2646). Random effects meta-analysis found analgesic effects of hypnosis for all pain outcomes (g=0.54-0.76, p’s<.001). Efficacy was strongly influenced by hypnotic suggestibility and use of direct analgesic suggestion. Specifically, optimal pain relief was obtained for hypnosis with direct analgesic suggestion administered to high and medium suggestibles, who respectively demonstrated 42% (p<.001) and 29% (p<.001) clinically meaningful reductions in pain. Minimal benefits were found for low suggestibles. These findings suggest that hypnotic intervention can deliver meaningful pain relief for most people and therefore may be an effective and safe alternative to pharmaceutical intervention. High quality clinical data is, however, needed to establish generalisability in chronic pain populations