Introduction Eysenck proposed ‘trait theory’ of personality, where the dimensions extraversion (degree of optimism and sociability) and neuroticism (degree of anxiety and fear) encompass numerous individual qualities. Whilst the influence of neuroticism on the brain processing of pain is well studied, the role of extraversion in pain processing remains to be investigated and thus this was the aim of our study using functional magnetic resonance imaging (fMRI).
Methods 33 healthy volunteers participated in the study, all of whom consented in writing (17 male; mean age 29, range 20–53, all right handed). Extraversion was measured using the Eysenck Personality Questionnaire. fMRI data was acquired using a 3T GE MRI scanner during rest, anticipation of pain, and painful distal oesophageal balloon distention. During fMRI, 480 T2* weighted images per slice (40 × 3 mm slices, 0.3 interslice gap, TE 30 ms, TR 2500 ms, flip angle 80°, matrix size 642, sum of images per scan = 19,200) were captured to illustrate blood oxygen level dependent (BOLD) contrast during the different experimental events. The effects of extraversion on fMRI response during these events were subsequently determined using ANOVA brain activation mapping analyses within XBAM, a statistical package of image processing and statistical inference.
Results There was a diversity of extraversion scores (range 6–22), which did not influence pain threshold or rating. High extraversion was associated with significantly greater activity in the left cuneus (Brodmann Area (BA) 18) during rest (p < 0.001) and the right insula (BA13) during both anticipation (p < 0.0002) and pain (p < 0.0008). Low extraversion was associated with significantly greater brain activity in numerous regions during pain anticipation, including the bilateral precuneus (BA31), bilateral lingual gyrus (BA18) and the right inferior temporal gyrus (p < 0.0001).
Conclusion Our results suggest that the brain processing of pain is influenced by the personality dimension of extraversion and therefore like other personality dimensions such as neuroticism, extraversion should be controlled for in brain imaging studies of pain in health and disease.
Disclosure of Interest None Declared.