关键词: abstinence, brain, functional connectivity, heroin addiction

Abstract: Objective: Addiction is a reward deficit and stress surfeit disorder. By using resting-state function-al connectivity MRI (rs-fcMRI), the aim of this study is to investigate the pattern of aberrant brain networks in heroin addiction, and whether addiction-related brain abnormalities would be persistent or recovered after long periods of abstinence. Methods: Rs-fcMRI analysis was performed on groups of recently abstinent (no more than 3 months) heroin-dependent (HD) subjects, long-term abstinent (more than 3 years) HD subjects, and non-addicted control (CN) subjects. The left and right nucleus accumbens (NAc) were defined as the seed regions of interest (ROIs), a brain region implicated in relapse-related processes, including craving and reactivity to stress following acute and protracted withdrawal from heroin. For each subject, correlation maps were created by calculat-ing Pearson’s correlation coefficients between the time series of the seed ROIs and that of each voxel in the brain. These correlation maps were converted to Z-value maps using Fisher’s r-to-z transformation. Two-sample t-test was performed between different groups, to identify possible addiction-related NAc functional connectivity changes. The relationship between the duration of abstinence and the altered NAc functional connectivity in the heroin group was also examined. Re-sults: Compared to the CN group, the recently abstinent HD group showed significantly increased functional connectivity between the NAc and the reward network (caudate, amygdala, thalamus and ventral medial prefrontal cortex), whereas decreased functional connectivity between the NAc and the executive control network (frontal-parietal regions). The long-term abstinent HD group also showed imbalanced functional link between the reward and executive control networks. However, with longer abstinence time, the strength of some NAc functional connectivity gradually restored to near-normal levels. Conclusion: Our results suggest that the imbalanced functional link between large-scale brain networks could serve as system-level neural underpinnings of persistent drug ad-diction and potential for relapse, which can at least partly be recovered after long periods of absti-nence.

Key words: abstinence, brain, functional connectivity, heroin addiction