Default mode network mechanisms of repeated transcranial magnetic stimulation in heroin addiction

Repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) has been shown to reduce cravings in heroin-dependent (HD) individuals, but the mechanisms underlying the anti-craving effects of rTMS are unknown. Abnormalities in the default mode network (DMN) are known to be consistent findings in HD individuals and are involved in cravings. We assessed the effect of rTMS on DMN activity and its relationship to the treatment response. Thirty HD individuals were included in this self-controlled study, and all HD participants received 10-Hz rTMS 7-session during a week. Data for cravings and withdrawal symptoms and resting-state functional magnetic resonance imaging data were collected before and after rTMS treatment. Thirty demographically matched healthy individuals who did not receive rTMS were included as controls. We focused on changes in coupling seeded from the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC), and bilateral inferior parietal lobe (IPL), which are the core regions of the DMN. The craving and withdrawal symptom score of HD individuals decreased significantly after rTMS treatment. The left IPL-left middle frontal gyrus coupling and the left IPL-right inferior occipital gyrus coupling decreased significantly, and the changes in the left IPL-left middle frontal gyrus coupling were positively correlated with changes in drug-cue induced cravings. rTMS could modulate the coupling between the DMN and executive control network (ECN). Alterations of the left IPL-left middle frontal gyrus coupling may play an important mechanistic role in reducing drug cue-induced cravings.