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The aim of the study was to investigate the possible association of hypnotizability and deep sleep (N3) duration, and whether the interoceptive sensibility influences this association. This was motivated by the proneness of highly hypnotizable individuals to easily change their psychophysiological state, i.e., from wakefulness to hypnosis and sleep, and by the positive association observed between hypnotizability and interoceptive sensibility. Forty-seven healthy participants previously enrolled in a polysomnographic night sleep study completed the questionnaire for Multidimensional Assessment of Interoceptive Awareness (MAIA) and underwent hypnotic assessment through the Stanford Hypnotic Susceptibility Scale, form A (SHSS,A). Results showed that N3 duration is not linearly correlated with hypnotizability. Controlling for a few MAIA scales did not modify the relation between hypnotizability and deep sleep. A polynomial relation indicates that N3 duration and N3 percentage of the total sleep time increase with hypnotizability in the low-to-medium range of hypnotizability and decrease in the medium-to-high range. In conclusion, hypnotic assessment predicts N3 duration and their association is not modified by interoceptive awareness/sensitivity.

Blink rate (BR), which is considered an index of the dopaminergic tone, has been studied in 41 subjects with high (highs), medium (mediums) and low (lows) hypnotisability scores in resting conditions. It has been found higher in highs; relaxation (indicated by skin conductance), anxiety and the proneness to absorption in tasks (assessed by questionnaires) were not responsible for the observed difference. In contrast, the BR difference did not survive controlling for mind wandering (MW questionnaire) whose variability could account for contrasting earlier reports, although no significant hypnotisability-related difference has been observed in MW scores. Findings do not allow to exclude that mechanisms other than dopaminergic ones may be involved in the observed difference in BR. In particular, we suggest that one of the mechanisms possibly sustaining the highs' higher BR may be a reduced cerebellar inhibition. In fact, cerebellar impairment is associated with higher BR and several studies of sensorimotor integration indicate different cerebellar controls in the highs' and lows' behavior.

The cognitive trait of hypnotizability modulates sensorimotor integration and mental imagery. In particular, earlier results show that visual recognition of 'nonmeaningful', unfamiliar objects bimanually explored is faster and more accurate in subjects with high (Highs) than with low hypnotizability (Lows). The present study was aimed at investigating whether Highs exhibit a similar advantage after unimanual exploration. Recognition frequency (RF) and Recognition time (RT) of correct recognitions of the explored objects were recorded. The results showed the absence of any hypnotizability-related difference in recognition frequencies. In addition, RF of the right and left hand was comparable in Highs as in Lows, while slight differences were found in RT. We suggest that hemispheric co-operation played a key role in the better performance of Highs in the bimanual task previously studied. In the unimanual exploration, the task's characteristics (favoring the left hand), hypnotizability-related cerebral asymmetry (favoring the right hand in Highs) and the possible preferential verbal style of recognition in Lows (favoring the right hand in this group) antagonize each other and prevent the occurrence of major differences between the performance of Highs and Lows.

It has been shown that, in subjects with high hypnotizability (Highs), imagined somatosensory stimulation can involuntarily activate the neural circuits involved in the modulation of reflex action. In this vein, aim of the study was to investigate whether the imagery of nociceptive stimulation in one leg may produce both subjective experience of pain and congruent postural adjustments during normal upright stance. The displacement of the centre of pressure (CoP) was studied during imagery of leg pain (LP) and during the control conditions of imagery of tactile stimulation of the same leg and of throat pain (TP) in 12 Highs and 12 low hypnotizable subjects (Lows). The results showed that the vividness of imagery was higher in Highs than in Lows for all tasks and that only Highs reported actually feeling pain during LP and TP. Congruently, during LP only Highs displaced their CoP towards the leg opposite to the one that was the object of painful imagery and increased their CoP mean velocity and area of excursion. Since the Highs' postural changes were not accounted for only by vividness of imagery and perceived pain intensity, high hypnotizability is apparently responsible for part of the postural effects of pain imagery.

The study assessed differences between highly (Highs) and low hypnotizable (Lows) subjects in the blindfolded reproduction of paths connected at acute or obtuse angles. Reproduction attempts were made after path exploration performed by one finger, with or without concomitant cognitive activities (mental computation or imagery of exploring an angle larger than the explored one). The variables analyzed were: subjective experience (scores of the exploring effort, reproduction difficulty, perceived accuracy of reproduction, attention to mental computation and efficacy of imagery), exploration time, relative error in reproduction (under or overestimation) and the percentage of "successful" trials (absolute error <10°). The results showed that the subjective experience of exploration/reproduction and the exploration times are similar in Highs and Lows and that all subjects underestimate the explored angles and reproduce the acute angle more accurately than the obtuse one. Exploration of the acute angle concomitant with imagery of a larger one reduced its underestimation in both groups. Highs exhibited a larger number of successful trials after exploration of the obtuse angle, while Lows (males) decreased their relative error in the reproduction of the acute angle. In conclusion, in the more demanding condition of reproducing an obtuse angle, the Highs' reproduction was more accurate and more independent of cognitive load than that of the Lows.

Previous studies showed that highly hypnotizable persons imagining a specific sensory context behave according to the corresponding real stimulation and perceive their behaviour as involuntary. The aim of the study was to confirm the hypothesis of a translation of sensory imagery into real perception and, thus, of a true involuntary response. We studied the imagery-induced modulation of the vestibulospinal (VS) reflex earlier component in highly (Highs) and low hypnotizable subjects (Lows), as it is not affected by voluntary control, its amplitude depends on the stimulus intensity, and the plane of body sway depends on the position of the head with respect to the trunk. Results showed that the effects of the "obstructive" imagery of anaesthesia are different from those elicited by the "constructive" imagery of head rotation. Indeed, both Highs and Lows having their face forward and reporting high vividness of imagery experienced anaesthesia and reduced their VS reflex amplitude in the frontal plane, while only Highs changed the plane of body sway according to the imagined head rotation that is from the frontal to the sagittal one. These effects cannot be voluntary and should be attributed to translation of sensory imagery into the corresponding real perception.

Aim of the experiment was to study whether cognitive load affects postural control more in low (Lows) than in highly hypnotizable (Highs) subjects due to the latter's 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 difficult (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 differences were detected (reduction in the Highs' SD and increases in the Lows' LFS in the difficult postural condition). Thus, the hypnotizability-related postural differences observed in previous studies during sensory alteration could not be accounted mainly by attentional abilities.

The aim of the experiment was to investigate whether the peculiar attentional/imagery abilities associated with susceptibility to hypnosis might make postural control in highly hypnotizable subjects (Highs) that are less vulnerable to sensory alteration than in individuals with low hypnotic susceptibility (Lows). The movement of the centre of pression (CoP) was monitored in Highs and Lows during alteration of the visual and leg proprioceptive input. The two groups responded differently to eyes closure and to an unstable support and the CoP movement was generally larger and faster in Highs. The stabilogram diffusion analysis indicated a different set point in Highs and Lows and suggested that the former are more independent of specific sensory information than the latter, likely due to different abilities in sensory re-weighting and/or peculiar internal models of postural control. The results are discussed within the general perspective of high pervasiveness of the hypnotizability trait, which modulates cognitive, autonomic and somatic functions.

Postural control in subjects with high (Highs) and low (Lows) susceptibility to hypnosis is differentially affected by changes in visual and neck tactile/proprioceptive input. The aim of the present experiment was to investigate whether imagery of the visual and tactile sensory modalities also induces different modulation of postural control in Highs and Lows. Fourteen Highs and 16 Lows were included in the study; they were recorded while standing upright with eyes closed during visual and tactile imagery tasks and during mental computation. Their posture and movement were recorded with an Elite System and their experience was assessed after each task in a structured interview. Visual imagery was judged "easier" than tactile imagery by Lows, while Highs performed both tasks easily and judged the tactile imagery less effortful and more vivid than Lows. No difference was observed for the mental computation. The Highs' body sway was not affected by the cognitive tasks, while Lows showed a task-related modulation of body sway. The results are in line with the hypothesis of lower vulnerability of Highs to the effects of tasks interfering with postural control and of different sensory-motor integration in Highs and Lows.

The aim of the experiment was to study possible differences between the kinematic strategies for the "involuntary" arm lowering of hypnotized highly susceptible subjects (H-Highs) and for the voluntary movement of non-hypnotizable simulators (Sims) during suggestions of arm heaviness (Part I). In addition, a comparison between awake susceptible subjects (W-Highs) and H-Highs was carried out to clarify the specific role of the hypnotic state and hypnotizability (Part II). Subjects' absorption and attentional/imagery capabilities were evaluated through neuropsychological tests. Their arm movements were monitored three-dimensionally at hand, wrist and elbow level through a Polhemus Fastrack system. A final interview collected self-reports concerning the perception of movement involuntariness. Neuropsychological tests showed better "absorption" and imagery capabilities in Highs. In the interview, H-Highs perceived a higher involvement in the task and greater involuntariness and difficulties in contrasting the arm lowering than the Sims. Kinematic analysis showed significant differences between H-Highs and Sims for arm displacements along the vertical axis and on the horizontal plane. In fact, the former lowered the left arm earlier and to a greater degree than the right arm; on the horizontal plane, a forearm flexion was observed for H-Highs on the right side. On comparing W-Highs and H-Highs, hypnosis appeared to magnify the waking motor strategies, but also to induce specific changes, mainly concerning the horizontal plane. These results cannot be interpreted on the basis of "role playing" and socio-cognitive factors. They are believed to be due to a balance between the effectiveness of the frontal executive control towards the selection of behaviors and movement automaticity, which is in line with the neo-dissociation theory of hypnosis.