Touching the intangible: an exploratory resting-state EEG study of complex bodily hallucinations in the general population

Experiences such as sensing a presence, feeling as if insects were crawling under the skin and related phenomena have been described in psychiatric, neurological, and toxicological contexts. However, they also occur frequently in the general population. Previous research suggests that stable physiological traits may predispose individuals to complex bodily hallucinations. The present exploratory study therefore examined whether resting-state electrocortical oscillatory activity is associated with proneness to such experiences. Participants from the general population completed the Complex Bodily Hallucinatory Experiences Scale (CBHES) prior to undergoing a brief eyes-closed resting-state EEG recording. Correlation clusters between CBHES scores and oscillatory activity were analyzed across the entire scalp, without any a priori hypotheses regarding frequency bands or localization. Significant correlations were found only within three left-lateralized clusters in the delta frequency range: the middle insula, which is involved in interoceptive bodily awareness; the superior anterior temporal lobe, which is associated with representations of animate intentional agents; and the orbitofrontal cortex, which is involved in affective touch processing, self-referential cognition, and reality monitoring. Together, these findings suggest that complex bodily hallucinations involve at least these functional properties and engage multiple cognitive mechanisms. They further suggest that intrinsic oscillatory activity in resting-state EEG constitutes a candidate neurophysiological correlate of proneness to such experiences.