Invited Symposium: Neural Bases of Hypnosis
Discussion and Conclusion
The results presented are preliminary and await data collection of additional control participants to balance the number of PTSD and controls. Although the results presented are tentative at this point, they are consistent with proposals that PTSD patients exhibit a greater disposition than non-patient controls to dissociate in everyday life and in response to trauma-related stimuli. Nonetheless, neither these nor other data previously collected address directly the question of whether a tendency to dissociate, at least among PTSD individuals, is a consequence of exposure to trauma, precedes such exposure and becomes manifest only in conjunction with PTSD symptoms, or it intensifies after exposure to trauma. The finding that, retrospectively, PTSD patients endorse greater dissociation around the time of trauma suggests that, at the very least, trauma enhances dissociation.
The greater hypnotizability of PTSD patients is consistent with their tendency to dissociate in everyday life (what Pierre Janet might have called “spontaneous somnambulism”). Responsiveness to hypnotic suggestions seems to be mediated by three different mechanisms: a tendency to have amnesia and other episodes of dissociation, a tendency to fantasize and have vivid imagery, and high motivation and intelligence among individuals lacking in a strong tendency to dissociate or fantasize (Barber, 1998). It is likely that the higher hypnotizability of some PTSD patients is attained through dissociative processes, but further research is needed to clarify this matter.
The preliminary observation that PTSD patients seem to exhibit reduced amplitude for early ERP components may provide an electrocortical parallel to dissociative experience. Although dissociation is a concept with considerable baggage (cf. Cardeña, 1994), in a descriptive sense dissociation can be characterized as a “degraded” or “reduced” form of perception, in which incoming information about the self or the world is experienced as unreal or dreamlike. Lower early ERP amplitude would be consistent with this modality of experiencing. On the other hand, an enhanced P3 to traumatic stimuli may be the counterpart to the hyperarousal of patients once the traumatic event has impinged on conscious awareness.
If confirmed, these studies might help understand the alternating numbing and avoidance responses found in PTSD (e.g., Horowitz, 1986). Buchsbaum and Silverman (1968) hypothesized that a cortical reduction pattern protects the individual from excessive stimulation. Low cortisol levels in PTSD patients seem to minimize the intensity of distressing stimuli and may be associated with denial and emotional blunting (Brown, 1994) or, dissociation.
Although preliminary, the results of this study corroborate previous studies about the disposition of PTSD patients to dissociate and to be highly hypnotizable. Furthermore, preliminary observations suggest that dissociative experience may be generally reflected in lowered cortical arousal to stimuli. If corroborated, this relationship might help us understand the cognitive and physiological processes underlying pathological dissociation. A possible integration of findings on cortisol, cortical activity and experience in PTSD seem to be now within reach.
The integration of psychophysiology and the study of subjective experience promises to yield important data about dissociation and trauma. As Brown (1994) has stated, "an approach that integrates psychological and biological models offers the best opportunity to understand the nature of dissociation." (p. 94).
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|Cardena, E; (1998). Hypnotizability, Cognitive Processing and Electrocortical Activity in PTSD. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/woody/cardena0862/index.html|
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