Human fear conditioning and extinction: Timing is everything ... or is it?

A differential fear conditioning paradigm was used with 107 healthy undergraduate participants to evaluate the effect of conditioned stimulus (CS) temporal properties on fear acquisition and extinction. Two minute duration CSs were used for Day 1 fear acquisition. Participants were randomized to receive either 1, 2, or 4 min CS durations during Day 2 extinction. Extinction re-test was examined on Day 3 using the original acquisition CS duration (2 mm). Findings indicated that participants who were aware of the CS+/unconditioned stimulus (US) contingency (n = 52) develop a temporal expectation about when the unconditioned stimulus will be delivered. Although the shorter duration CS resulted in greater fear reduction during extinction, cessation of fear responding at re-test was the same for CS extinction durations ranging from half the CS acquisition duration to twice the CS acquisition duration. Thus, extinction performance did not predict extinction at re-test, which could have important implications for optimizing exposure therapy for anxiety disorders. (C) 2012 Elsevier B.V. All rights reserved.