EEG concomitants of hypnotic susceptibility

Numerous historical attempts have been directed at understanding electrocortical concomitants of hypnosis. Today, with the availability of more sophisticated multichannel recording technologies and signal-processing approaches, it is possible to reconsider and update previous attempts. The most solid relationship between electrocortical activity and hypnotizability exists in the EEG theta frequency range. Given the stable electrocortical differences found in high and low susceptible individuals, the question arises whether we can use additional EEG measures to help understand the nature of these individual differences. One possible alternative is the pointwise or fractal dimension, which we examined during baseline conditions with high and low hypnotic susceptible individuals. The dimensionality measures suggest that high susceptible individuals display underlying brain patterns associated with imagery, whereas low susceptible individuals show patterns consistent with cognitive activity (i.e., mental math). This type of speculation is similar to that of Tellegen, who makes a distinction between imaginative versus realistic responding. Future research should address the exact nature of the underlying process (imagination, effortlessness, suggestibility, etc.) seen in high and low susceptible individuals.