The fear-avoidance model advances fear of pain as a key factor in the origins of chronic pain disability. Initial evidence in those with chronic back pain reveals that exposure therapy reduces fear levels, disability, and pain. Despite the success of exposure in the clinic, fundamental research about its underlying mechanisms lags behind. Using a conditioning paradigm with movements as conditioned stimuli (CS) and a painful shock as unconditioned stimuli (US), we investigated the extinction of experimental fear of movement-related pain and pain-related anxiety (respectively induced by predictable and unpredictable pain). Dependent measures were self-reported fear and eyeblink startle. During acquisition, all groups received both predictable and unpredictable training. In the predictable context, one movement (CS+) was consistently followed by the shock-US, but another movement was not (CS-). In the unpredictable context, joystick movements never signaled the shock-US; shock-US were delivered during the intertrial interval (ITI). During extinction, the extinction group continued training in the predictable context but the CS+ movement was no longer reinforced; the context exposure group continued training in the unpredictable context but ITI shock-US were omitted. The control group continued training after the acquisition reinforcement scheme. Results revealed that fear ratings for the CS+ were extinguished in the extinction group but not in the control group. Interestingly, omitting the ITI shocks not only reduced ITI startle responses in the context exposure group compared with the control group, but also reduced the fear ratings and startle responses elicited by the unpredictable CS. The clinical implications of these findings are discussed.
Copyright © 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.