Neural Correlates of the Relationship between Optimism and Pain Perception in a Conditioned Pain Modulation Paradigm

Abstract

Introduction: Pain is a pervasive public health problem in the United States. Despite its prevalence, the variables influencing pain processing remain poorly understood. It is now accepted that psychological factors such as optimism have the potential to influence both clinical and experimental pain outcomes. It has been suggested that people in high in optimism may modulate pain more effectively. However, the neural mechanisms of this relationship have not been explored. Method: Participants underwent psychophysical testing using a conditioned pain modulation (CPM) paradigm, a common measure of endogenous pain modulation. Participants rated a series of painful heat test stimuli alone and then again in the presence of a painful pressure conditioning stimulus.Participants typically rate the test stimuli as less painful in the presence of the conditioning stimulus, a phenomenon known as "pain inhibits pain” or CPM. Participants repeated the CPM paradigm in a separate session during a functional MRI scan. A measure of dispositional optimism was administered before the scan. Results: Imaging results showed that greater dispositional optimism was associated with increased heat-pain related brain activity in areas involved in sensory pain processing, including the somatosensory cortex, superior parietal lobe, and posterior insula. Optimism was also positively associated with activity in sensory brain areas during CPM stimulation, including in the superior parietal lobe, somatosensory cortex, and supramarginal gyrus. Additionally, during CPM stimulation, optimism was negatively associated with activity in brain areas implicated in gating attention to pain, including the dorsolateral prefrontal cortex. Conclusion: Optimism may modulate differences in pain perception via attention and sensory awareness, whereby greater attention to painful stimuli causes increased perception of pain intensity.