Brain Sensory Network Activity Underlies Reduced Nociceptive-Initiated and Nociplastic Pain via Acupuncture in Fibromyalgia.

Chronic pain may arise from overlapping pain pathways, including nociceptive pain driven by peripheral tissue damage and nociplastic pain arising from central nervous system dysregulation, as seen in fibromyalgia. This study investigated how electroacupuncture (EA) produces analgesia by modulating these pain mechanisms via changes in brain activation and functional connectivity (FC). Following 4-weeks of EA, reductions in widespread pain, a marker of central nociplastic pain, were associated with increased pressure-pain tolerance to peripheral nociceptive stimuli. This nociplastic-nociceptive relationship was mediated by increased somatosensory activation (S1) and S1-insula FC, suggesting that EA operates through a "bottom-up" mechanism of action: afferent input from the needle modulates central sensory networks to reduce nociplastic pain. In contrast, the sham group reduced widespread pain via a "top-down" centrally inhibiting mechanism, characterized by decreased precuneus activation and reduced precuneus-insula FC. These findings elucidate contributions of bottom-up versus top-down circuits in mediating pain relief.