Pain is a multidimensional sensory experience that varies among individuals. The multi-factorial nature of pain produces wide-ranging variability in subjective pain ratings and pain-intensity related brain activations. Pain associated brain activation can cause temporary and long lasting changes in brain morphology, raising the possibility that structural brain differences could be related to inter-individual differences in pain sensitivity. To investigate this relationship, structural MRI and psychophysical data from 10 previous fMRI studies were used. A voxel-based morphometric (VBM) analysis was employed using grey matter density across the whole brain and supra-threshold pain intensity ratings from 116 healthy volunteers (62 females, 54 males). Age, sex, unpleasantness ratings, scanner sequence, and sensory testing location were added to the VBM model as covariates. Psychophysical assessment and MRI scanning sessions occurred during 2 independent experimental sessions. Analysis of pain sensitivity with age, sex, and ethnicity yielded no significant relationships. VBM regression analysis of pain intensity ratings at 49°C and grey matter density revealed a significant inverse relationship between pain sensitivity and grey matter density in bilateral regions of the posterior cingulate cortex (p = 0.006, corrected), precuneus (p = 0.006, corrected), anterior intraparietal sulcus (p = 0.012, corrected), and inferior parietal lobule (p = 0.021, corrected). This inverse relationship was also found in unilateral regions of the left primary somatosensory cortex (p = 0.012, corrected). No regions displayed a positive relationship. Brain regions showing pain sensitivity-related structural variations are associated with the default mode network, attentional processes, and somatosensory processing. These findings highlight the potential influence of default mode thought and attention in the construction and modulation of pain and also indicate that brain structure may potentially be used as a predictor of pain sensitivity.
|State||Published - 2014|