Chronic pain, often lacking diagnostic peripheral pathology, has been attributed to cerebral dysfunction from recent neuroimaging findings. Here we used functional magnetic resonance imaging (fMRI) to seek for dynamic alterations in cerebral networks between no-pain and phasic-pain conditions in chronic pain patients with various etiologies. Specifically, we made a comparison between chronic pain patients (CP) and healthy controls (HC) in  whole-brain functional connectivity (FC) during resting-state, and dynamic FC changes during offset analgesia (OA)/sham paradigms by thermal pain stimulus known to trigger endogenous pain modulation.The present findings imply that chronic pain involves:
Default mode network weakness; Emotional network hyperactivity; "Pain matrix" exaggeration; Descending pain modulatory and reward system dysfunction.

Functional connectivity modulations in resting state and offset analgesia in chronic pain patients: an fMRI study