Eysenck proposed a 'trait theory' of personality, the dimensions of which encompass numerous individual qualities. Whilst the influence of neuroticism on the brain processing of pain is well described, the role of extraversion, to date, has not been systematically investigated. Our aim was to address this knowledge gap using functional magnetic resonance imaging (fMRI).Extraversion was measured in 33 healthy volunteers (17 males, mean age 29. years [range 20-53]) using the Eysenck Personality Questionnaire. fMRI data were acquired using a 3T MRI scanner during rest, pain anticipation, and painful oesophageal balloon distention. The effect of extraversion on fMRI responses was determined.Extraversion scores varied (range 6-22) and did not influence pain threshold or rating. High extraversion was associated with significantly greater activity in the left cuneus during rest (p≤. 0.001), and the right insula during both anticipation (p≤. 0.0002) and pain (p≤. 0.0008). Low extraversion was associated with significantly greater brain activity in the bilateral precuneus, bilateral lingual gyrus, right inferior temporal gyrus, left fusiform gyrus and left superior parietal lobule during pain anticipation (all p≤. 0.0001).These results suggest that extraversion is associated with differences in the brain processing of visceral pain. Future studies of visceral pain, using fMRI, should control for extraversion.
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