Objective: Previous research has suggested that chronic pain patients might be particularly vulnerable to the effects of negative mood during information processing. However, there is little evidence for abnormal brain processing of affective and sensory pain-related information in chronic pain. Behavioral and brain responses, to pain descriptors and pleasant words, were examined in chronic pain patients and healthy controls during a self-endorsement task.
Methods: Eighteen patients with fibromyalgia (FM), 18 patients with chronic musculoskeletal pain due to identifiable physical injury (MSK), and 16 healthy controls were asked to decide whether word targets described their current or past experience of pain. The number of self-endorsed words, elapsed time to endorse the words, and event-related potentials (ERPs) elicited by words, were recorded.
Results: Data revealed that chronic pain patients used more affective and sensory pain descriptors, and were slower in responding to self-endorsed pain descriptors than to pleasant words. In addition, it was found that affective pain descriptors elicited significantly more enhanced positive ERP amplitudes than pleasant words in MSK pain patients; whereas sensory pain descriptors elicited greater positive ERP amplitudes than affective pain words in healthy controls.
Conclusions: These data support the notion of abnormal information processing in chronic pain patients, which might be characterized by a lack of dissociation between sensory and affective components of pain-related information, and by an exaggerated rumination over word meaning during the encoding of self-referent information about pain.