Electrophysiological Alterations During Hypnosis for Ego-Enhancement: A Preliminary Investigation

American Journal of Clinical Hypnosis, Apr 2004 by Stevens, Larry, Brady, Brian, Goon, Angela, Adams, Deanna, Et al

Theta is a very interesting brainwave frequency because it has previously been associated with visual imagery, problem solving, perceptual processing, attentive performance in cognitive tasks, creativity, and dissociative states (Crawford & Gruzelier, 1992; Schacter, 1977; Vogel & Broverman, 1964). Animal models suggest that the increased focusing of attention on environmental cues or task acquisition is associated with the activation of theta generators lying deep within the hippocampus and that midline frontal theta EEGs may well index a fronto-limbic-hippocampal attentional system through the anterior cingulate cortex (Crawford & Gruzelier, 1992). Similarly, the high-frequency, low-amplitude 40 Hz (actually ~36-44 Hz) EEG signal has been suggested as the physiological marker of focused arousal and is thought to result from activation of the rostral brainstem reticular formation producing increased cortical excitability (DePascalis, 1999; Sheer, 1976, 1984, 1989). These two brainwave frequencies capture quite well several of the phenomenologica! characteristics of deep hypnosis, that is, highly focused, selectively attentive, and cognitively aroused, yet dissociated from irrelevant cues, creative, and visually imaginai states of consciousness.

Although the number of studies examining the relationships between electrophyiological events and hypnotic trance is rather sizable and spans over five decades of laboratory research (see Crawford & Gruzelier, 1992, for an excellent review), the recording of ncuroelectrical changes occurring during the process of clinical hypnotic induction, deepening, and suggestion has been much less frequent. Indeed, most studies have been conducted within a laboratory setting, utilizing very brief, non-clinical, usually tape-recorded hypnotic inductions, often employing challenges and hypnotizability tests as a part of the induction process (e.g., DePascalis, et al., 1998; Graffin, et al. 1995; Sabourin, et al., 1990; Ulett, et al., 1971). In fact, a review of this literature revealed no studies that recorded EEGs during the process of a live clinical hypnotic induction, deepening, and suggestion procedure. Until such studies are conducted, the external validity of the existing research in this area will remain wanting. This deficit is quite understandable, as the process of attaching EEG electrodes and configuring equipment during a psychotherapy session, particularly during the days of collodion-applied electrodes and cumbersome tube amplifiers, could be most intrusive and damaging to the therapeutic process. However, with more contemporary laptop-based EEG systems and electrode application technologies, EEGs can be recorded from selected sites with a minimum of interference. Additionally, as indicated above, this literature has been controversial, with only recently two relatively reliable correlates of hypnosis (theta and 40 Hz gamma) emerging from over five decades of research, and this literature is still in its developmental stages. Clearly these studies need to be replicated and extended into the clinical milieu, the hypnotic trance signature needs to be elaborated and refined, if possible, into other EEG frequencies and derivations, and potential variations for different stages and depths of hypnosis need to be investigated. The present study represents the beginning of a line of research designed to accomplish this objective of elaborating the EEG signature of hypnosis into a more ecologically valid venue.