The Effect Of Smoking And Internet Addiction On Brain Structural And Functional Connectivity

Smoking is addictive and seriously endangers human health.Currently,the brain structural and functional changes in smokers had been revealed by using brain imaging techniques,which furthered our understanding of the neural mechanism of smoking addiction.However,the neural mechanism of smoking still remains unclear.Internet addiction(IA)bears a strong resemblance to smoking addiction in behaviors and has a serious impact on the adolescents’physical and mental health,academic study and daily life.Evidence showed that the adolescents with IA were more voruneble to addicted to smoking.Therefore,investigating the neural mechanism of IA seems important to the intervention and prevention of IA and smoking addiction.The present study investigated the brain structural connectivity and resting state functional connectivity(RSFC)abnormalities in smokers and IA adolescents by using magnetic resonance imaging technique.The main findings and innovations obtained in this paper are as follows:Firstly,the study of insula RSFC abnormalities in young smokers.The insula plays critical roles in cognitive control and interoceptive awareness of craving.RSFC abnormalities of both left and right anterior(AI)and posterior insula(PI)in young smokers were investigated.Pearson correlation analysis was applied to assess the relationship between the insula RSFC changes and the cognitive control behaviors as well as the smoking behaviors,such as craving.Compared with non-smokers,young smokers showed reduced RSFC between right AI and anterior cingulate cortex(ACC),ventromedial prefrontal cortex(VMPFC),amygdala,left dorsolateral prefrontal cortex(DLPFC)and dorsal striatum.Additionally,left AI showed reduced RSFC with ACC.Moreover,in young smokers,FTND and incongruent errors in Stroop task were negatively correlated with the RSFC between AI and ACC.Craving scores showed a significantly negative relationship with the RSFC strength between right AI and left VMPFC.These results provide a more thorough network-level understanding the role of insula in cigarette smoking.The findings provide new insights into the roles of AI-ACC circuit in cognitive control deficits and right AI-VMPFC circuit relevant to the craving of nicotine dependence for young smokers.Secondly,the study of 12h abstinence-induced insula RSFC changes in young smokers.The present study examined the effects of 12 h of abstinence from smoking on the RSFC of AI and PI in young smokers using a within-subject design.Multiple regression analysis was applied to investigate the possible relationships between the RSFC changes of insula(abstinence minus satiety)and the abstinence-induced craving changes.Smoking abstinence state(versus satiety)was associated with increased RSFC between right AI and right medial orbitofrontal cortex(OFC),VMPFC as well as ACC.The abstinence-induced RSFC changes between right AI and right lateral OFC was significantly correlated with the craving changes.These findings improve the understanding of the effects of short-term smoking abstinence on insula circuit connectivity and may contribute new insights into the neural basis of abstinence-induced craving to smoke.Thirdly,the study of white matter structural connectivity of the central executive network(CEN)correlates with enhanced brain reactivity to smoking cues in smokers.The attentional bias to smoking cues contributes to smoking cue reactivity and cognitive declines underlines smoking behaviors,which were probably associated with the CEN.The white matter structural connectivity of the CEN was quantified in smokers and non-smokers using the diffusion tensor imaging and deterministic fiber tractography methods.Then,multiple regression analysis were employed to assess the relationship between structural connectivity of the CEN and smoking cue reactivity as well as cognitive control impairments in smokers.Relative to non-smokers,smokers showed increased fractional anisotropy(FA)values of the bilateral CEN fiber tracts.The FA values of left CEN positively correlated with the smoking cue-induced activation of the DLPFC and right middle occipital cortex in smokers.Meanwhile,the FA values of left CEN positively correlated with the incongruent errors during Stroop task in smokers.Collectively,the present study highlighted the role of the structural connectivity of the CEN in smoking cue reactivity and cognitive control performance,which may underpin the attentional bias to smoking cues and cognitive deficits in smokers.The multimodal imaging method by forging links from brain structure to brain function extended the notion that structural connections can modulate the brain activity in specific projection target regions.Finally,the study of disrupted inter-hemispheric functional and structural coupling in IA adolescents.Previous studies reported that the IA were associated with changes in brain structure and function,relatively little is known about the changes of inter-hemispheric RSFC and structural connectivity in IA.In the current study,voxel-mirrored homotopic connectivity(VMHC)was used to examine inter-hemispheric RSFC in IA adolescents and controls.The integrity of the fibers connecting the regions,which showed aberrant inter-hemispheric functional connectivity,was assessed by fiber tractography analysis.In addition,the coupling of inter-hemispheric functional and structural connectivity was investigated.Relative to controls,IA adolescents showed decreased VMHC of DLPFC and reduced FA values in the genu of corpus callosum(CC).The decreased VMHC of DLPFC was significantly negative correlated with the duration of IA.Moreover,the VMHC of DLPFC showed significant correlations with the FA of CC in healthy controls,which was disrupted in IA.Our findings provided more scientific evidence for the involvement of DLPFC in IA.It is hoped that multimodal imaging methods can provide deeper insights into the IA effects on the brain.In summary,smoking and short-term abstinence related insula RSFC changes provided insights into the neural mechanism of cognitive control deficits and craving in smokers.White matter structural connectivity of central executive network could predict smoking cue-induced brain activation and cognitive control behaviors in smokers.Finally,the VMHC and structural connectivity abnormalities between bilateral DLPFC in IA adolescents furthered our understanding of the neural mechanism of IA.