Invited Symposium: Neural Bases of Hypnosis
Materials and Methods
Two matched groups of 13 diagnosed PTSD (mean age=37.4) and 8 non-PTSD Gulf War veterans (mean age=36.1) served as volunteers. Diagnosis was obtained through a comprehensive medical and psychiatric evaluation at Walter Reed Army Medical Center.
After informed consent was secured, volunteers were given a battery of tests evaluating medical and psychiatric symptomatology, dissociation, and hypnotizability. For the experimental session, they were exposed to a modified Stroop test with 4 lists of 10 words each (positive, negative, semantically related, and trauma-related). The words were presented in a computer monitor in random order, either in green or red, and the participants’ task was to press as rapidly as possible one button for words in red, and another button for words in green. Words were presented in balanced order (diagram square), while the individual’s ERP, reaction time and heart rate were monitored. ERP data were collected from 19 active channels and 1 artifact site (oculogram), referred to linked ears, at a rate of 256 Hz and a bandpass filter of .5-50 Hz, after being amplified 20K times , all of them usual parameters for this setting (cf. McFarlane et al., 1993). The stimuli were presented by a computer program that triggered the collection of ERPs and button presses. Statistical aggregation and analysis were made off-line.
At the end of each list, the PDEQ questionnaire for dissociative experiences (Marmar, Weiss & Metzler, 1998) was administered. Hypnotizability was measured through the Stanford Hypnotic Scale for Hypnotic Susceptibility, Form C (Weitzenhoffer & Hilgard, 1962). Dissociative trait was measured by the Dissociative Experiences Scale (DES-II;Carlson & Putnam, 1993), whereas dissociation and anxiety symptoms at the time of trauma was evaluated by the Stanford Acute Stress Reaction Questionnaire (SASRQ; see Cardeña, 1996). In this paper I will present preliminary analyses for hypnotizability, dissociation and ERPs.
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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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