Electrophysiology of Combat-Related PTSD zy JOHN KOUNIOS?‘ BRETT LITZ! DANNY KALOUPEK,’ DAVID RIGGS,’ zyx JEFF KNIGHT! TERENCE KEANE’ zyxw ‘Department of Psychology University of Pennsylvania 381 5 Walnut St. Philadelphia, Pennsylvania 191 zyxw 04-61 96 ’National Center for PTSD Boston Veterans Affairs Medical Center (1 16B-2) 150 S. Huntington Ave. Boston, Massachusetts 021 30 FRANK WEATHERS: JANE E. ANDERSON,’ AND One technique that has been applied to the study of posttraumatic stress disorder (PTSD) is the measurement of event-related brain potentials (ERPs).’ ERPs are measured by scalp-electrode recordings of a subject’s electroencephalogram during performance of a task involving discrete stimulus andor response events. Segments of the electroencephalogram following presentations of members of a class of stimuli are averaged, yielding a wave depicting the brain’s average electrical response to that stimulus class. Analyzing the temporal information given by the positive and negative deflections of such a wave and the spatial information provided by an array of electrodes distributed across the scalp yields valuable neurophysiological and functional-anatomical information.2 We explored the neurophysiology of PTSD by measuring ERPs while patients and control subjects viewed threatening and relatively nonthreatening words. In particular, we examined differences between patients and controls that could elucidate whether PTSD is best characterized as an exaggerated neural response specifically to trauma-related stimuli or a general disorder characterized by aberrant brain re- sponses to all stimuli. Sixteen male, right-handed, native English-speaking, Vietnam-era combat veter- ans participated. Eight were diagnosed with PTSD; the others were well-adjusted veterans (WAV). ERPs were measured with zyxw 64 tin electrodes mounted in an elastic cap (referenced to the left mastoid). The stimuli were a sequence of words displayed on a monitor. There were three blocks of words, each consisting of zy 45 “trauma” words (related to combat experiences in Vietnam, e.g., grenade), 45 comparatively neutral “nontrauma” words (related to school experiences, e.g., pencil), and 18 ‘Address for correspondence: John Kounios, Ph.D., Department of Psychology, University of Pennsylvania, 3815 Walnut St., Philadelphia, PA 19104-6196 (tel: (215)573-5767; e-mail: jkounios @cattell.psych.upenn.edu). 504