Does hypnotic assessment predict the functional equivalence between motor imagery and action?

Motor imagery is influenced by individual and contextual factors. We investigated whether the psychophysiological trait of hypnotisability modulates its subjective experience and cortical correlates similarly to what was previously shown for head postures mental images. EEG was acquired in 18 high (highs) and 15 low (lows) hypnotizable subjects (Stanford Hypnotic Susceptibility Scale, A). The experimental conditions were: baseline, a complex arm/hand movement, visual (1st person) and kinesthetic imagery of the movement. After each imagery condition, participants scored the vividness and easeness of their performance and their ability to mantain the requested modality of imagery. Subjective reports, chronometric visual/kinesthetic indices, absolute beta and fronto-central midline alpha powers were analyzed. Findings confirmed earlier reports of better kinestetic imagery ability in highs than in lows and better visual than kinesthetic imagery in lows, as well as smaller restructuring of the cortical activity in highs than in lows, during all tasks. Also, they show that hypnotisability accounts for most of the correlations between brain regions for both alpha and beta changes. Thus, imagined and actual movements were less demanding processes in highs at subjective and cortical levels. Finally, hypnotic assessment assists to plan personalized mental training for neuro-rehabilitation and sports and predict their efficacy.

Topology highlights mesoscopic functional equivalence between imagery and perception: The case of hypnotizability.

The functional equivalence (FE) between imagery and perception or motion has been proposed on the basis of neuroimaging evidence of large spatially overlapping activations between real and imagined sensori-motor conditions. However, similar local activation patterns do not imply the same mesoscopic integration of brain regions, which can be described by tools from Topological Data Analysis (TDA). On the basis of behavioral findings, stronger FE has been hypothesized in the individuals with high scores of hypnotizability scores (highs) with respect to low hypnotizable participants (lows) who differ between each other in the proneness to modify memory, perception and behavior according to specific imaginative suggestions. Here we present the first EEG evidence of stronger FE in highs. In fact, persistent homology shows that the highs EEG topological asset during real and imagined sensory conditions is significantly more similar than the lows. As a corollary finding, persistent homology shows lower restructuring of the EEG asset in highs than in lows during both sensory and imagery tasks with respect to basal conditions. Present findings support the view that greater embodiment of mental images may be responsible for the highs greater proneness to respond to sensori-motor suggestions and to report involuntariness in action. In addition, findings indicate hypnotizability-related sensory and cognitive information processing and suggest that the psycho-physiological trait of hypnotizability may modulate more than one aspect of the everyday life.

Spectral and topological analyses of the cortical representation of the head position: Does hypnotizability matter?

INTRODUCTION: The aim of this exploratory study was to assess the EEG correlates of head positions (which have never been studied in humans) in participants with different psychophysiological characteristics, as encoded by their hypnotizability scores. This choice is motivated by earlier studies suggesting different processing of vestibular/neck proprioceptive information in subjects with high (highs) and low (lows) hypnotizability scores maintaining their head rotated toward one side (RH). METHODS: We analyzed EEG signals recorded in 20 highs and 19 lows in basal conditions (head forward) and during RH using spectral analysis, which captures changes localized to specific recording sites, and topological data analysis (TDA), which instead describes large-scale differences in processing and representing sensorimotor information. RESULTS: Spectral analysis revealed significant differences related to head position for alpha 1, beta 2, beta 3, and gamma bands, but not to hypnotizability. TDA instead revealed global hypnotizability-related differences in the strengths of the correlations among recording sites during RH. Significant changes were observed in lows on the left parieto-occipital side and in highs in right frontoparietal region. Significant differences between the two groups were found in the occipital region, where changes were larger in lows than in highs. CONCLUSIONS: This study reports finding of the EEG correlates of changes in the head posture for the first time, indicating that hypnotizability is related to the head posture representation/processing on large-scale networks and that spectral and topological data analyses provide complementary results.

Hypnotizability influences the cortical representation of visually and kinaesthetically imagined head position.

The study investigates the cortical representation of the visual and kinesthetic image of a rotated position of the head in highly (highs) and low hypnotizable individuals (lows) of both gender. Participants were invited to imagine maintaining their head rotated toward one side by seeing their chin aligned with their right shoulder (V, visual imagery), and in a different condition, by feeling tension in their neck muscles (K, kinaesthetic imagery). Vividness of imagery and cognitive effort were reported after each task. Alpha and beta band absolute power was studied. Highs reported higher vividness than lows only for the kinaesthetic modality of imagery. The cortical desyncronization observed during visual and kinaesthetic imagery were different in high females (HM), low females (LF), high males (HM) and low males (LM). In fact, only HF and LM exhibited significant power changes during the kinaesthetic task, whereas visual imagery was associated with cortical desynchronization in all subgroups except HM. The study supports earlier findings of an advantage of highs in kinesthetic imagery, shows an intriguing interaction of hypnotizability and gender, and indicates topographical difference in the four subgroups of participants suggesting differences in underlying generators.