The two sides of pain communication: effects of pain expressiveness on vicarious brain responses revealed in chronic back pain patients

Abstract

The dominant socioaffective model of empathy has emphasized the overlap between brain mechanisms involved in the encoding and the decoding of internal states. The role of dispositional empathy has been extensively studied in this research, but several other individual factors fundamental to communication processes have been largely ignored. We studied the effects of dispositional expressiveness in chronic back pain patients to determine if the decoding of communicative and noncommunicative information signaling pain in others would be enhanced in individuals displaying a spontaneous propensity to consistently express more pain during a behavioral-observational naturalistic standardized lifting task performed on 2 separate occasions. Blood oxygenation level-dependent signal change was measured in response to pictures showing facial pain expressions and hands/feet in pain-evoking situations in chronic back pain patients and healthy controls. Vicarious brain responses to others' pain were comparable between groups. However, more expressive patients rated others' pain higher and showed stronger vicarious pain responses in the right ventral part of the inferior frontal gyrus, the right insula, and the midbrain. Activity in the right insula correlated positively with both the patients' expressiveness (encoding) and the intensity of the pain perceived in the images (decoding), suggesting that this structure linked the dispositional expressiveness with vicarious pain perception. Importantly, these effects were independent from dispositional empathy and were found with both communicative (facial expression) and noncommunicative (hand and foot) cues. These results suggest that dispositional expressiveness is a self-related factor that facilitates vicarious pain processing and might reflect individual tendencies to rely on social coping strategies.

Perspective: This article shows that pain expressivity in chronic pain patients increased the vicarious brain responses and the sensibility to others' pain. These results may help provide empirical support for better defining models of pain communication in chronic pain patients.

Keywords: Pain communication; chronic back pain; empathy; functional magnetic resonance imaging; pain expressiveness.