The acquisition and generalization of cued and contextual pain-related fear: an experimental study using a voluntary movement paradigm.

Recent evidence indicates that pain-related fear can be acquired through associative learning. In the clinic, however, spreading of fear and avoidance is observed beyond movements/activities that were associated with pain during the original pain episode. One mechanism accounting for this spreading of fear is stimulus generalization. In a voluntary movement-conditioning paradigm, healthy participants received predictable pain (ie, one movement predicts pain, another does not) in one context, and unpredictable pain in another context. The former procedure is known to induce cued pain-related fear to the painful movement, whereas the latter procedure generates contextual pain-related fear. In both experimental pain contexts, we subsequently tested fear generalization to novel movements (having either proprioceptive features in common with the original painful movement or nonpainful movement). Results indicated that in the predictable pain context, pain-related fear spreads selectively to novel movements proprioceptively related to the original painful movement, and not to those resembling the original nonpainful movement. In the unpredictable context, nondifferential fear generalization was observed, suggesting persistent contextual pain-related fear and poor safety learning. These data illustrate that spreading of pain-related fear is fostered by previously acquired movement-pain contingencies. Based on recent advances in anxiety research, we proposed an innovative approach conceptualizing predictable pain as a laboratory model for fear of movement in regional musculoskeletal pain, and unpredictable pain generating contextual pain-related fear as a prototype of widespread musculoskeletal pain. Consequently, fear generalization might play an important role in spreading of pain-related fear and avoidance behavior in regional and widespread musculoskeletal pain.