Harper DE, et al. - Researchers performed a cross-sectional study using a combination of behavioral Conditioned pain modulation (CPM) testing, voxel based morphometry (VBM), and resting state functional connectivity to identify neural correlates of CPM in healthy controls and fibromyalgia (FM) patients. In addition, they probed for differences that could explain the pain-facilitative CPM that was observed in their patient sample. As per findings, some of the normal variability in CPM could be explained by variation in the strength of the periaqueductal gray's (PAG) resting functional connectivity. Moreover, in FM patients, pain-facilitative CPM likely involved both attenuation of pain inhibitory and amplification of pain facilitative processes in the central nervous system.