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 35x24 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.