Abnormal central pain processing is a leading etiology underlying fibromyalgia (FM) pain and is perceptually characterized with the psychophysical measure of temporal summation of pain (TSP). TSP is the perception of increasingly greater pain to repetitive or tonic noxious stimuli. Previous neuroimaging studies have used static (i.e. summary) measures to examine the fMRI correlates of TSP in FM. However, functional brain activity rapidly and dynamically reorganizes across time, and TSP is similarly a temporally evolving process. A full understanding of the neural circuitry supporting TSP in FM thus requires a dynamic measure that evolves over time.
We applied novel dynamic functional connectivity (dFC) methods to examine how TSP-associated fluctuations are linked to dynamic functional reconfigurations of the brain. We acquired high-temporal resolution fMRI data during a resting-state (REST) and during sustained cuff pressure pain applied to the leg (PAIN) in 84 FM patients and matched healthy controls (HCs).
FM patients experienced greater TSP than HCs (FM: 17.93 ± 19.24; HC: 9.47 ± 14.06; p = 0.028), but TSP varied substantially between patients. In the brain, the presence versus absence of TSP in FM was marked by more sustained enmeshment between sensorimotor and salience networks during PAIN. Furthermore, dynamic enmeshment was more isolated in FM patients with high TSP, as interactions with all other brain networks were dampened during PAIN.
This study elucidates the dynamic brain processes underlying facilitated central pain processing in FM, and enables future work investigating dynamic symptomatology in FM.