Extinction of Fear Generalization: A Comparison Between Fibromyalgia Patients and Healthy Control Participants.

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.