Investigation of effective connectivity alteration during hypnosis induction using direct directed transfer function

Hypnosis therapy is a widely applied method for treating psychiatric disorders, pain relief, and sleep irregularity. Research findings have demonstrated that hypnosis therapy will be useful, mostly for high hypnotizable subjects. Another factor which makes hypnosis therapy efficient is the hypnotic depth. In this study, we were interested in relationship between hypnotic depth and its corresponding effective connectivity patterns. Furthermore, effective connectivity changes between different hypnotizable subjects was studied. Direct directed transfer function (dDTF) was used in order to estimate effective connectivity between EEG channels. Based on our result, in medium and high hypnotizable groups, as subjects reach to their final depth of hypnosis, effective connectivity patterns were significantly reduced in delta and theta frequency bands while for low hypnotizable group, reduction was only seen in delta band and effective connectivity among channels in theta, beta and gamma frequency bands remained unchanged.