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Fear learning deficiencies might contribute to the development and maintenance of chronic pain disability. Fear is often not restricted to movements (conditioned stimulus [CS+]) originally associated with pain (unconditioned stimulus), but expands to similar movements (generalization stimuli [GSs]). This spreading of fear becomes dysfunctional when overgeneralization to safe stimuli occurs. More importantly, persistence of pain-related fear to GSs despite corrective feedback might even be more debilitating and maintain long-term chronic pain disability. Yet, research on this topic is lacking. Using a voluntary joystick movement paradigm, we examined (extinction of) pain-related fear generalization in fibromyalgia patients (FM) and healthy control participants (HC). During acquisition, one movement (CS+) predicted pain; another did not (CS-). We tested (extinction of) fear generalization to 5 GSs varying in similarity with the CS+ and CS-. Results revealed flatter pain expectancy generalization gradients in FM than in HC due to elevated responses to GSs more similar to the CS-; the fear generalization gradients did not differ. Although pain-related fear and expectancy to the GSs decreased during extinction, responses to the GSs remained higher for FM than HC, suggesting that extinction of generalization is impaired in chronic pain patients. Persistence of excessive protective responses may contribute to maintaining long-term chronic pain disability.Perspective: Pain-related fear and expectancy to movements-varying in similarity with the original painful and nonpainful movement-decrease during extinction in HC and FM. Yet, conditioned responses remain elevated in patients despite corrective feedback, indicating impaired extinction of generalization. Persistent excessive protective responses may contribute to preserving pain disability. [ABSTRACT FROM AUTHOR]

Recent experimental data show that associative learning processes are involved not only in the acquisition but also in the spreading of pain-related fear. Clinical studies suggest involvement of positive affect in resilience against chronic pain. Surprisingly, the role of positive affect in associative learning in general, and in fear generalization in particular, has received scant attention. In a voluntary movement paradigm, in which one arm movement (reinforced conditioned stimulus [CS+]) was followed by a painful stimulus and another was not (unreinforced conditioned stimulus [CS–]), we tested generalization of fear inhibition in response to 5 novel but related generalization movements (GSs; within-subjects) after either a positive affect induction or a control exercise (Group = between-subjects) in healthy participants (N = 50). The GSs' similarity with the original CS+ movement and CS– movement varied. Fear learning was assessed via verbal ratings. Results indicated that there was an interaction between the increase in positive affect and the linear generalization gradient. Stronger increases in positive affect were associated with steeper generalization curves because of relatively lower pain–unconditioned stimulus expectancy and less fear of stimuli more similar to the CS–. There was no Group by Stimulus interaction. Results thus suggest that positive affect may enhance safety learning through promoting generalization from known safe movements to novel yet related movements. Improved safety learning may be a central mechanism underlying the association between positive affect and increased resilience against chronic pain. Perspective We investigated the extent to which positive affect influences the generalization (ie, spreading) of pain-related fear inhibition in response to situations similar to the original, pain-eliciting situation. Results suggest that increasing positive affect in the acute pain stage may limit the spreading of pain-related fear, thereby potentially inhibiting transition to chronic pain conditions. [ABSTRACT FROM AUTHOR]

Anomalies in fear learning, such as failure to inhibit fear to safe stimuli, lead to sustained anxiety, which in turn may augment pain. In the same vein, stimulus generalization is adaptive as it enables individuals to extrapolate the predictive value of 1 stimulus to similar stimuli. However, when fear spreads in an unbridled way to novel technically safe stimuli, stimulus generalization becomes maladaptive and may lead to dysfunctional avoidance behaviors and culminate in severe pain disability. In a voluntary movement conditioning paradigm, we compared the acquisition and generalization of pain-related fear in patients with fibromyalgia (FM) and healthy controls. During acquisition, participants received predictable pain in 1 context (ie, 1 movement predicts pain, whereas another does not), and unpredictable pain in another (ie, pain never contingent upon movement). Fear generalization to novel movements (resembling the original painful or nonpainful movement) was tested in both contexts. Results indicated that the FM group showed slower differential acquisition of pain-related fear in the predictable context, and more contextual pain-related fear in the unpredictable context. Fear of movement-related pain spreads selectively to novel movements similar to the original painful movement, and not to those resembling the nonpainful movement in the healthy controls, but nondifferential fear generalization was observed in FM. As expected, in the unpredictable context, we also observed nondifferential fear generalization; this effect was more pronounced in FM. Given the status of overgeneralization as a plausible transdiagnostic pathogenic marker, we believe that this research might increase our knowledge about pathogenesis of musculoskeletal widespread pain. [ABSTRACT FROM AUTHOR]

Abstract: From a treatment perspective, it is highly relevant to pinpoint individual vulnerability factors for resistance to exposure treatment in highly fearful chronic pain patients. Previous fear conditioning research showed that healthy individuals scoring relatively high on trait anxiety display sustained fear to safety cues during extinction. In the context of fear of movement-related pain, this intriguing question has been largely neglected so far. Even more importantly, positive psychological traits such as trait positive affect may function as protective factors against the spreading of fear to safe movements and improve exposure treatment outcomes. In this study, healthy participants completed a trait anxiety and trait positive affect questionnaire and underwent acquisition and extinction of fear of movement-related pain using an experimental voluntary movement paradigm. During acquisition, one movement (CS+) was paired with a painful stimulus and another movement was not (CS−). During extinction, the CS+ was no longer reinforced. Results show failure of fear inhibition to the CS− during extinction in healthy individuals scoring relatively high on trait anxiety or relatively low on positive affect. These findings seem to suggest that safety learning is more vulnerable in healthy people with a high anxious disposition and/or relatively lower levels of positive affect. In addition, this is the first study to show that the negative impact of high trait anxiety on fear inhibition to safety cues during extinction can be countered by high levels of positive affect. These findings may have important clinical implications. Perspective: Both low positive affect and high trait anxiety are associated with impaired fear inhibition to nonpainful movements during fear extinction. Interestingly, high levels of positive affect buffer against the negative impact of trait anxiety. Increasing positive affect during exposure may counter the effects of trait vulnerabilities and improve treatment outcomes. [Copyright &y& Elsevier]

Abstract: Fresh empirical evidence supports the notion that fear of movement-related pain can be acquired through associative learning. In the context of these findings, 2 ideas are appealing, yet uninvestigated. The first is that merely the intention to perform a painful movement acts as a covert conditioned stimulus (CS) inducing defensive fear responses (ie, gaining excitatory properties following Pavlovian acquisition). The second idea is that after extinction, fear of movement-related pain can easily be reinstated after unexpected painful stimuli (ie, reinstatement). In a voluntary differential conditioning movement paradigm with movements as CSs and a painful electrocutaneous stimulus as the unconditioned stimulus (pain-US), 2 groups were included (Experimental/Control). One movement (CS+) was followed by the pain-US and another movement (CS−) was not during acquisition, while the CS+ was no longer reinforced during extinction. Next, the Experimental group received 2 reinstating pain-USs, whereas the Control group did not. The CS+ but not the CS− evoked fear of movement-related pain in self-reports and eye-blink startles. Intriguingly, the mere intention to perform the painful movement produced higher eye-blink startle responses than the intention to perform the nonpainful movement. We also demonstrated nondifferential reinstatement in the verbal fear ratings in the Experimental group only. Perspective: This study demonstrates that the mere intention to perform a painful movement prior to the actual painful movement itself can come to elicit conditioned fear responses. These results suggest that actual movement may not be necessary to elicit pain-related fear responses, maintaining chronic pain-related fear, avoidance, and disability. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]