Fig. 4

Hypothetical schematic illustration of the resting state functional connectivity modulated by acupuncture and its relevance to pain relief. Note that this diagram does not exhaustively describe all networks and brain regions involved in acupuncture analgesia but only summarizes the mechanisms likely relevant for the current study. Red indicates increased activation/connectivity; blue indicates decreased activation/connectivity. Verum acupuncture needle stimulation activated the operculum/insula, as suggested by the functional MRI analysis. The insula/operculum processes information about both the sensory component of pain (posterior insula), as well as cognitive-emotional aspects of pain (anterior insula) [101]. In its capacity as a nociceptive salience detection, affective and pain decision-making hub [102], it might (1) increase functional connectivity between the attention, cognitive control and appraisal networks (rFPN, ECN) and the rACC/MPFC, which is a key brain region for attention and descending pain modulation with a direct connection to the PAG [75], further inhibiting noxious input; (2) decrease functional connectivity between the SMN and dACC, representing reduced interaction between the sensory and affective components of pain processing, providing further relief from pain