Contingency learning deficits and generalization in chronic unilateral hand pain patients

Contingency learning, in particular the formation of danger beliefs, underpins conditioned fear and avoidance behavior, yet equally important is the formation of safety beliefs. That is, when threat beliefs and accompanying fear/avoidance spread to technically safe cues, it might cause disability. Indeed, such overgeneralization has been advanced as a transdiagnostic pathologic marker, but it has not been investigated in chronic pain. Using a novel hand pain scenario contingency learning task, we tested the hypotheses that chronic hand pain patients demonstrate less differential pain expectancy judgments because of poor safety learning and demonstrate broader generalization gradients than healthy controls. Participants viewed digitized 3-dimensional hands in different postures presented in random order (conditioned stimulus [CS]) and rated the likelihood that a fictive patient would feel pain when moving the hand into that posture. Subsequently, the outcome (pain/no pain) was presented on the screen. One hand posture was followed by pain (CS1), another was not (CS_). Generalization was tested using novel hand postures (generalization stimuli) that varied in how similar they were to the original conditioned stimuli. Patients, but not healthy controls, demonstrated a contingency learning deficit determined by impaired safety learning, but not by exaggerated pain expectancy toward the CS1. Patients showed flatter, asymmetric generalization gradients than the healthy controls did, with higher pain expectancy for novel postures that were more similar to the original CS_. The results clearly uphold our hypotheses and suggest that contingency learning deficits might be important in the development and maintenance of the chronic pain-related disability. Perspective: Chronic hand pain patients demonstrate 1) reduced differential contingency learning determined by a lack of safety belief formation, but not by exaggerated threat belief formation, and 2) flatter, asymmetric generalization gradients than the healthy controls.