Hyper-connectivity between the left motor cortex and prefrontal cortex is associated with the severity of dysfunction of the descending pain modulatory system in fibromyalgia

The impaired cortical function likely plays a critical role in chronic pain maintenance and fibromyalgia symptoms. Functional connectivity (FC), as assessed by functional near-infrared spectroscopy (fNIRS), is a promising approach that evaluates cortical activation through hemodynamic response estimation. This study compared the FC of bilateral motor and prefrontal cortices between responders and nonresponders to the conditioned pain modulation test (CPM-test) induced by hand immersion in cold water (0–1°C). We included 37 women with fibromyalgia according to the American College of Rheumatology diagnoses criteria (n = 23 responders to CPM-test and n = 14 nonresponders). After the adjustment for multiple comparisons, we found that nonresponders relative to responders showed higher FC between the left motor cortex (LMC) with the left prefrontal cortex (LPFC) and right prefrontal cortex (RPFC). The psychiatric diagnoses were also positively associated with a higher FC in LMC–LPFC and LMC–RPFC. These results indicate that the increased connectivity between the left motor and bilateral prefrontal cortex might be a neural marker of DPMS dysfunction and an intermediate in the interplay between fibromyalgia and psychiatric disorders.