Combat veterans show normal discrimination during differential trace eyeblink conditioning, but increased responsivity to the conditioned and unconditioned stimulus

The question addressed in the present study was whether post-traumatic stress disorder (PTSD) results in associative learning impairments. To answer this question, differential trace eyeblink (EB) conditioning was studied in combat veterans with PTSD, combat veterans without PTSD, and non-combat veterans without PTSD. Veterans with PTSD showed normal EB discrimination, suggesting that associative learning is not impaired by PTSD. Veterans with PTSD also showed normal extinction. However, subjects with PTSD showed more EB conditioned responses (CRs), as well as increased CR amplitude. Increased response amplitude to the airpuff unconditioned stimulus presented alone (viz. the unconditioned response), as well as to the airpuff on CS+ trials during conditioning also occurred in the subjects with PTSD. These findings suggest increased reactivity in combat veterans with PTSD, compared to those without PTSD, but such heightened reactivity does not affect somatomotor associative learning. (C) 2006 Elsevier Ltd. All rights reserved.