Study On Spontaneous Brain Activity Of Nicotine Addicts Based On Static And Dynamic Amplitude Of Low Frequency Fluctuation

Background and purposeTobacco use is still a major public health problem worldwide.Worldwide more than 5 million people per year die as a result of tobacco use,according to the tobacco epidemic report issued by the World health organization in 2018.Tobacco can not only cause multiple system diseases but also change structure and function of the brain.The previous studies have preliminarily evaluated nicotine effects on brain measured by rest state functional magnetic resonance imaging.Smoking is companied with altered intrinsic activity of the brain measured by amplitude of low-frequency fluctuation.Evidence has revealed that human brain activity is a highly dynamic and rapidly-changing system(high temporal resolution imaging techniques such as electroencephalography).How exactly cigarette smoking affect temporal dynamic intrinsic brain activity is not fully understood,nor is it clear how smoking severity influences spontaneous brain activity.Materials and methods1.The current study has recruited 93 subjects,including 63 male nicotine addicts and 30 healthy controls.Functional MRI data of all subjects was collected in Siemens 3.0 T magnetic resonance scanner.2.The rs-fMRI data were preprocessed by the Data Processing Assistant for Resting-State fMRI Analysis Toolkit(DPARSF).Amplitude of low-frequency fluctuation(ALFF)was computed in REST software.Dynamic ALFF variability was computed in DynamicBC software combined with sliding window technique.We further divided smokers into light and heavy smokers(including 33 light nicotine addicts and 30 heavy nicotine addicts).3.The temporal variability in intrinsic brain activity and static ALFF among there groups was compared(GRF corrected,voxel P<0.005,cluster P<0.05).Correlation analyses were also performed between dALFF in areas showing group differences and smoking behavior(P<0.05,uncorrected).ResultsNicotine addicts showed increasing static ALFF in left middle/inferior gyrus,right middle gyrus,bilateral precuneus and right cuneus(F=6.43,clusters≥57),compared with healthy controls.In comparison with healthy controls,Light nicotine addicts showed increased static ALFF in the left middle frontal gyrus and decreased static ALFF in the bilateral precuneus(t=2.92,clusters≥23).Compared with healthy controls,Our results found that heavy nicotine addicts exhibited increased static ALFF in the left superior frontal gyrus,left middle/inferior frontal gurus and decreased bilateral precuneus,right cuneus(t=2.92,clusters≥23).There no difference between heavy smokers and light smokers in static ALFF.In comparison with healthy controls,nicotine addicts showed significantly increased dALFF in left inferior/middle frontal gyrus,right orbitofrontal gyrus,right insular,left superior/medial frontal gyrus and Right middle frontal gyrus(F=6.41,clusters≥98).Compared to healthy controls,increased dALFF variability was found that light nicotine addicts had significance in right middle orbitofrontal gyrus and left superior frontal gyrus(t=2.92,clusters≥20)and heavy nicotine addicts showed increasing dALFF in left inferior frontal gyrus,right precentral gyrus,right middle orbitofrontal gyrus,right insula,right precentral/postcentral gyrus,left middle frontal gyrus,right middle frontal gyrus and left superior frontal gyrus(t=2.92,clusters≥20).Comparing heavy nicotine addicts with light nicotine addicts,we found increasing dALFF variability in right precentral/postcentral gyrus and left precentral gyrus(t=2.92,clusters≥20).Conclusion1.Nicotine can alters spontaneous brain activity in multiple brain regions.Combined,these results suggest that smokers increase stable and persistent spontaneous brain activity in prefrontal cortex,involved impaired gold-directed action and value-based decision-making.2.In addition,individuals with heavier nicotine addicts show increased perturbance on spontaneous brain activity of perception and sensorimotor,probably related to increased reliance.3.In addition,dALFF is more conducive to the discovery of differences in subtle brain activity changes between different levels of nicotine dependence.