Life Scienas, Vol. 61, No. 14, pi. 1421-1434, 1997 Published by Elsevier Science Inc. Printed in the USA. All rights rcsered 0024-32n5p7 $17.00 + .oo PII SOO24-3205(97)006&l-7 COMBAT VETERANS WITH POSTTRAUMATIC STRESS DISORDER EXHIBIT DECREASED HABITUATION OF THE P 1 MIDLATENCY AUDITORY EVOKED POTENTIAL Gregory M. Gillette5,6, Robert D. Skinne?, Lisa M. Rasco’, Elliot M. Fielstein5,6, Doyle H. Davis’, James E. Pawelak’, Thomas W. Freeman’,3, Craig N. Kar~on’~~, Frederick A. Boop4, Edgar Garcia-Rill’ Eugene J. Towbin Health Care Center, John L. McClellan Memorial Veterans Hospital, N.Little Rock Division’, N.Little Rock AR; Departments of Anatomg, Psychiatry3, and Neurosurgery4, University of Arkansas for Medical Sciences, Little Rock AR; Vanderbilt University Medical Center Department of Psychiatry5 and Veterans Affairs Medical Center’, Nashville TN (Received in final zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP fom June 2.5,1997) zyxwvutsrqponmlkjihgfedcbaZYXWV Summary The current study used a paired stimulus paradigm to investigate the PI midlatency auditory evoked potential in Vietnam combat veterans with posttraumatic stress disorder (PTSD) and three comparison groups: alcohol dependents, combat-exposed normals, and combat-unexposed normals. Compared to each comparison group. PTSD subjects exhibited significantly diminished habituation of the Pl potential. Pl potential habituation within the PTSD group, correlated significantly with intensity of PTSD reexperiencing symptoms, such as trauma-related nightmares and flashbacks, These findings are discussed as consistent with a sensory gating defect at the brainstem level in PTSD, and are mother discussed in the context of other psychophysiological measures in PTSD and of Pl potential findings in psychiatric disorders other than PTSD. key WO&: posttraumatic stress disorder, midlatency auditory evoked potential, pedunculopontine nudeus, combat veterans, sleep disturbances Auditory evoked potentials have been classified in humans, according to the time of occurrence of the peak amplitude after a stimulus, as short-latency (O-10 msec), midlatency (lo-100 msec), and long- latency (>lOO msec). Long-latency auditory evoked potentials have been studied and results published for numerous psychiatric disorders (l), including PTSD (PTSD)(2,3), which was codified for the first time in the oficial nosology of the American Psychiatric Association in 1980 (4), with two revisions thereafter (56). Paige et al. (2), in a study of combat-related PTSD using a long- latency P2 auditory evoked potential augmentation-reduction paradigm, found that nine of twelve PTSD subjects exhibited reduced P2 evoked potential amplitudes as stimulus intensity increased, as contrasted with five of six combat-exposed normal controls, who exhibited augmented P2 potential amplitudes with increasing stimulus intensity. The authors stated that the results of their study are consistent with “hypotheses that PTSD represents a state of CNS sensitivity and that individuals with Correspondence to: Gregory M. Gillette, M.D., Psychiatry Service, VAMC, 13 10 24th Avenue South, Nashville TN 37212, Phone (615) 327-4751 X.5937, FAX (615) 321-6375, E-mail gillette.gregory@nashville.va.gov