Motor intention as a trigger for fear of movement-related pain: An experimental cross-US reinstatement study

Using a voluntary joystick movement task with arm movements as conditioned stimuli (CSs) a and a painful electrocutaneous stimulus as an unconditioned stimulus (pain-US), we investigated whether 1) the intention to perform a painful movement would elicit pain-related fear in healthy participants, 2) a non-painful but aversive sound-US (i.e. human scream) could induce cross-US reinstatement. All groups (same-US/different-US/no-US) received acquisition and extinction with the pain-US. During reinstatement, the same-US group received two unsignaled pain-USs, the different-US group received two unsignaled sound-USs and the no-US group did not receive any stimulus presentations. Next, we tested the return of fear (fear and US-expectancy ratings and startle eyeblink responses) in all groups. Uncoupling motor intention and action led to successful inhibition of pain-related fear elicited by merely thinking about a painful movement as compared to previous study results in which motor intention was always coupled with motor action. The different-US group showed a differential cross-US reinstatement effect in the pain-US expectancy ratings. However, this effect failed to materialize in the fear ratings and startle responses. Taken together, we found partial support for the hypothesis that reinstatement experiences might foster the acquisition of new fears rather than reinstating old fears. (C) Copyright 2014 Textrum Ltd. All rights reserved.