Stabilizing posture through imagery

Postural effects of interoceptive imagery as a function of hypnotizability

The aim of the study was to investigate the effects of pleasant and unpleasant interoceptive imagery on postural control in participants with different hypnotizability, interoceptive sensibility and ability of imagery. Forty-one healthy individuals classified as high (highs), medium (mediums) and low hypnotizables (lows) according to the Stanford Hypnotic Susceptibility Scale, form A (SHSS, A) were characterized for Interoceptive Sensitivity (IS) through the Multisensory Assessment of Interoceptive Awareness (MAIA) and for organic mental imagery (ORG) through Betts' questionnaire. The experimental session included baseline closed eyes conditions preceding tasks of pleasant (P) and unpleasant imagery (U) and a neutral cognitive task (NT) while standing on a stabilometric platform. Subjective reports of vividness and pleasantness/unpleasantness of mental images were collected. Postural variables, ECG and pneumogram were acquired. Highs exhibited greater vividness of imagery than mediums/lows and larger Area of the Centre of Pressure (CoP), while mediums and lows decreased it during all tasks with respect to baseline conditions. Significant differences moderated by IS and ORG were found between highs and lows in the CoP Area. In all groups significant task related differences in the CoP Area were moderated only by IS. Cardiovascular variables were similar in the three groups, but differed among tasks and were influenced by IS and ORG. Our findings extend earlier observations on the role of hypnotisability in the postural correlates of sensorimotor imagery to interoceptive imagery, support the hypothesis that interoceptive sensibility moderates postural control and cardiorespiratory variables during interoceptive imagery, and confirm earlier reports of the absence of hypnotisability-related modulation of cardiorespiratory variables during emotional tasks.

Hypnotizability-Related Effects of Pain Expectation on the Later Modulation of Cortical Connectivity

This study examined hypnotizability-related modulation of the cortical network following expected and nonexpected nociceptive stimulation. The electroencephalogram (EEG) was recorded in 9 high (highs) and 8 low (lows) hypnotizable participants receiving nociceptive stimulation with (W1) and without (noW) a visual warning preceding the stimulation by 1 second. W1 and noW were compared to baseline conditions to assess the presence of any later effect and between each other to assess the effects of expectation. The studied EEG variables measured local and global features of the cortical connectivity. With respect to lows, highs exhibited scarce differences between experimental conditions. The hypnotizability-related differences in the later processing of nociceptive information could be relevant to the development of pain-related individual traits. Present findings suggest a lower impact of nociceptive stimulation in highs than in lows.

High Motor Cortex Excitability in Highly Hypnotizable Individuals: A Favourable Factor for Neuroplasticity?

Hypnotizability is a psychophysiological trait associated with morphofunctional brain peculiarities and with several cognitive, sensorimotor and cardiovascular correlates. Behavioral and EEG studies indicate stronger functional equivalence (FE) between motor imagery and action in the individuals with high hypnotizability scores (Highs). We hypothesized that stronger FE leading to greater proneness to ideomotor behavior could be due to greater cortical excitability of the motor cortex. The aim of the study was to evaluate the motor cortical excitability through measurements of the muscle potentials (MEPs) evoked in the left abductor pollicis brevis by transcranial magnetic stimulation (TMS) of the right motor cortex in 10 Highs, 10 medium (Mediums) and 10 low hypnotizable individuals (Lows) classified according to the Stanford Hypnotic Susceptibility Scale, form A (SHSS). They were studied in basal conditions (B) and during motor imagery (MI). Results showed significant, negative correlations (i) between hypnotizability and MEPs Resting Motor Threshold (RMT) in basal conditions, and (ii) between hypnotizability and both MEPs RMT and suprathreshold (I_1mv) stimulation intensities during MI. ANOVA revealed significantly lower stimulation intensities in Highs than in Lows, with Mediums exhibiting intermediate values. Thus, the Highs' greater cortical excitability could sustain their greater FE and proneness to ideomotor behavior. In cognitive neuroscience these findings are relevant to the physiological interpretation of the response to sensorimotor suggestions by participants in the ordinary state of consciousness. In the clinical field they can predict the efficacy of mental training based on motor imagery and, possibly, the degree of imagery-induced cortical plasticity.

RESPONDING TO SENSORIMOTOR SUGGESTIONS: From Endothelial Nitric Oxide to the Functional Equivalence Between Imagery and Perception

The reduced cerebellar gray matter (GM) volume observed in highly hypnotizable individuals (highs) is likely due to the excessive release of endothelial nitric oxide in the brain and could account for their behavioral (postural and visuomotor control) and physiological (paradoxical pain control after cerebellar anodal stimulation) characteristics. Reduced cerebellar GM can induce low inhibition of the cerebral cortex, thus stronger functional equivalence (FE) between imagery and perception and greater proneness to respond to sensorimotor suggestions. In fact, stronger FE suggested in highs by behavioral studies has been confirmed by topological data analysis of EEG signals recorded during sensorimotor and imagery tasks. The authors' hypothesis cannot be applied to obstructive suggestions likely sustained by mechanisms related to socio-cognitive factors, i.e., oxytocin availability.

Visuospatial imagery in healthy individuals with different hypnotizability levels

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