Alike, But Not Quite: Comparing the Generalization of Pain-Related Fear and Pain-Related Avoidance

• Published in: The journal of pain Vol. 23; no. 9; pp. 1616 - 1628
• Main Authors: Glogan, Eveliina, Meulders, Michel, Pfeiffer, Leon, Vlaeyen, Johan W.S., Meulders, Ann
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2022
• Subjects: Avoidance behavior; avoidance generalization; chronic pain; fear generalization; generalization gradient; operant conditioning; chronic pain; fear generalization; generalization gradient; operant conditioning; avoidance generalization; Avoidance behavior
• ISSN: 1526-5900; 1528-8447
• DOI: 10.1016/j.jpain.2022.04.010

•Pain-related fear generalized, decreasing with increasing dissimilarity to a painful movement.•Avoidance did not show this pattern, suggesting that costs associated with avoidance, reduced it.•Pain-related avoidance, when unnecessary and costly, can dissociate from fear in pain-free people.•More research is needed on how fear and avoidance interact and diverge to culminate in disability. Pain-related fear and –avoidance crucially contribute to pain chronification. People with chronic pain may adopt costly avoidance strategies above and beyond what is necessary, aligning with experimental findings of excessive fear generalization to safe movements in these populations. Furthermore, recent evidence suggests that, when avoidance is costly, it can dissociate from fear. Here, we investigated whether concurrently measured pain-related fear and costly avoidance generalization correspond in one task. We also explored whether healthy participants avoid excessively despite associated costs, and if avoidance would decrease as a function of dissimilarity from a pain-associated movement. In a robotic arm-reaching task, participants could avoid a low-cost, pain-associated movement trajectory (T+), by choosing a high-cost non-painful movement trajectory (T-), at opposite ends of a movement plane. Subsequently, in the absence of pain, we introduced three movement trajectories (G1-3) between T+ and T-, and one movement trajectory on the side of T- opposite to T+ (G4), linearly increasing in costs from T+ to G4. Avoidance was operationalized as maximal deviation from T+, and as trajectory choice. Fear learning was measured using self-reported pain-expectancy, pain-related fear, and startle eye-blink electromyography. Self-reports generalized, both decreasing with increasing distance from T+. In contrast, all generalization trajectories were chosen equally, suggesting that avoidance-costs and previous pain balanced each other out. No effects emerged in the electromyography. These results add to a growing body of literature showing that (pain-related) avoidance, especially when costly, can dissociate from fear, calling for a better understanding of the factors motivating, and mitigating, disabling avoidance. This article presents a comparison of pain-related fear- and avoidance generalization, and an exploration of excessive avoidance in healthy participants. Our findings show that pain-related avoidance can dissociate from fear, especially when avoidance is costly, calling for a better understanding of the factors motivating and mitigating disabling avoidance.