Psychophysiologic assessment of aversive conditioning in posttraumatic stress disorder

Background: The objective of this study was to evaluate the acquisition, generalization, and extinction of conditioned physiologic responses to aversive stimuli in posttraumatic stress disorder (PTSD). Methods: Thirty-six PTSD patients, 20 individuals with past trauma and no current PTSD, and 30 mentally healthy individuals without exposure to major trauma underwent a differential aversive conditioning experiment. Bursts of 105 dB white noise were used as unconditioned stimuli (UCSs), and 35 x 24 mm slides of different colors served as either CS+ (paired) or CS- (unpaired) stimuli. Heart rate (HR) and nondominant palm skin conductance (SC) were measured at rest and between 1 and 4 sec following each CS presentation. Results: The PTSD group showed higher levels of resting SC and resting HR, larger SC responses to the initial presentation of unpaired CSs, larger HR responses following paired CS+ stimuli, larger SC responses to unpaired CS- during acquisition and extinction, and larger SC and HR responses to CS+ during extinction. The group differences in responses to CS+ during extinction remained statistically significant after controlling for age, resting physiologic levels, and initial responsivity. Conclusions: PTSD is associated with elevated autonomic responses to both innocuous and aversive stimuli, with larger responses to unpaired cues and with reduced extinction of conditioned responses. Copyright (C) 2000 Society of Biological Psychiatry.