[Analysis of effective connectivity in default mode network in male long-term smokers based on dynamic causal...

Objective: To investigate the alterations in effective connection of default mode network (DMN) in long-term male smokers and its correlation with clinical characteristics of smoking. Methods: A total of 131 subjects through WeChat platform and underwent resting-state functional magnetic resonance (rs-fMRI) examinations were recruited, including 76 long-term smokers [long-term smoking group, male, aged 20 to 55 (32.1±6.3) years] and 55 non-smokers [healthy controls, male, aged 20 to 55(32.3±7.4) years] from January 2014 to December 2018. Long-term smokers were defined as those who smoked at least 10 cigarettes per day for more than 2 years, and met the Diagnostic and Statistical Manual of Mental Disorders-Four Edition (DSM-Ⅳ) criteria for substance dependence. Four major nodes of DMN, including left inferior parietal lobule (LIPL), right inferior parietal lobule (RIPL), posterior cingulate cortex (PCC), medial prefrontal cortex (mPFC) were chosen as for the region of interest. The effective connectivity (EC) alterations of DMN between smoking group and healthy controls were compared using dynamic causal modeling (DCM). The correlation between EC with significant difference among the two groups and Nicotine Dependence Scale (FTND) score, pack-year score and smoking duration were evaluated. Results: Compared to the healthy controls, the EC of LIPL to PCC and PCC to mPFC were decreased in the smoking group (EC = -0.091, -0.174, respectively, Bayesian-PP>0.95), and the EC of RIPL to PCC was increased (EC = 0.136, Bayesian-PP>0.95). Besides, EC of LIPL to PCC showed negative correlation with pack-year scores(r=-0.282,P=0.017). No significant linear correlations were observed between EC with significant group difference and FTND score or smoking duration (r=-0.103、-0.089,all P>0.05). Conclusion: Long-term smokers showed multiple abnormalities in IPL-PCC-mPFC circuits, and associated with the pack-year scores.