Embodied cognition: motor imagery, interoceptive accuracy and hypnotizability

Hypnotizability is a physiological and cognitive trait measured by standard scales. Different hypnotizability levels are associated with different degrees of equivalence between actual and imagined perception/action and of interoceptive accuracy (IA) – i.e. the ability to detect bodily signals - likely due to different grey matter volumes of the insula. Since the insula integrates interoceptive signals with several other inputs, including somesthesia, the study aimed to assess whether trait IA - measured by baseline heartbeat-evoked cortical potential (HEP) and by the Interoceptive Accuracy Scale (IAS) - partially sustains the chronometric, subjective and EEG correlates of motor imagery (MI). Thirty-two healthy right-handed participants classified as high (highs) or low (lows) hypnotizable according to the Stanford Hypnotic Susceptibility Scale, Form A (SHSS: A) were enrolled. EEG and ECG were recorded during baseline condition (B), actual movement (M), visual (V), and kinesthetic MI. MI performance was characterized by chronometry, self-reported efficacy of imagery, and modulation of alpha, low, and high beta power spectral density (PSD). All the studied frequency bands showed changes during actual and imagined movement. Both interoceptive accuracy and hypnotizability modulated cortical correlates of motor imagery. Highs' better imagery ability was partially masked by their lower interoceptive accuracy. The role of trait interoceptive accuracy in MI is here reported for the first time and accords with the theory of embodied cognition.