Pain in the default mode network: a voxel-based morphometry study on thermal pain sensitivity

During nociceptive processing of pain, activated regions, specified as the 'pain matrix', have been proven not selectively or preferentially tied to pain. Counterintuitively, the deactivated regions, especially the default mode network (DMN), are recently revealed to be simultaneously and functionally involved. In this study, we searched for pain-specific structural correlates among pain-free young adults using the voxel-based morphometry (VBM) approach within regions of interest comprising the pain matrix and DMN. Variances in confounding factors, namely the thermal detection threshold, thermal pain tolerance threshold and pain-related psychological traits, were statistically controlled to obtain pain-specific structural correlates. As a result, we found that less grey matter volume (GMV) of a critical DMN region, the precuneus, predicts enhanced thermal pain sensitivity (i.e., lower threshold). In contrast, this relationship is absent in all regions within the pain matrix. Such a dissociation between pain matrix and precuneus highlights the significance of precuneus in processing of pain, and is discussed with a conception taking pain as a salience detection system for the body, rather than as a nociceptive-specific system restricted within the so-called pain matrix.