The Study Of Brain Damage In Nicotine Dependent Subjects Based On Structural Covariance Network

ObjectiveSmoking is a huge public healthy problem in the world.According to the statistics,there are about 1 billion smokers in the world,and more than 300 million smokers in our country,accounting for about 1/3 of the total number of smokers in the world.Moreover,there are about 740 million non-smokers suffer from second-hand smoke.Although most smokers have tried to quit smoking,but only 3%-5% smokers have successfully quitted smoking on their own will,most of them will resume in a week.The difficulty in quitting smoking is mainly due to the production of highly addictive substances in tobacco combustion: nicotine,which can make smokers dependent.Smoking addicts need to smoke a cigarette for a certain time to keep the level of nicotine in the brain to a certain extent.Therefore,it is of great significance to study the mechanism of smoking addiction to guide the smoking cessation.In recent years,a large number of neuroimaging studies have found that the smokers' brain structure and function have changed,among brain networks the functional networks and anatomic networks are mostly studied,and less attention has been paid to structural networks.Previous imaging studies have shown that the effect of smoking on the brain is not a simple regional change,but through the reorganization of the cerebral cortical connection patterns.The structural covariant network analysis method based on voxel morphometry is a new method to study the synergistic change of gray matter volume between different cerebral cortex.The structural covariant network analysis which is based on voxel-based morphometry,is a new method to study the synergistic changes of gray matter volume in different brain regions.This study collected the 3D T1 structural images of 118 long-term smokers and 57 non-smokers,exploring the structural different brain regions caused by smoking and its related structural covariant network through two groups of comparisons.Materials and methodsIn this study,SIEMENS Skyro 3.0T magnetic resonance scanner was used to scan 118 long-term smokers and 57 non-smoking healthy controls.During the scan,the head of the volunteers was fully fixed with the sponge earplug,and the volunteers should keep their eyes closed,sober,relaxed,calm,and avoid excessive thinking.The volunteers were scanned by routine MRI sequence and 3D-T1 structural image sequence.The structural data of all volunteers were segmented by SPM8 on the Matlab software platform,and the two sample t-test was applied to the gray matter structure data between the smoking group and the control group.Then the smoking group was divided into two subgroups of the mild nicotine dependence group(FTND<6)(93 cases)and the severe nicotine dependence group(FTND > 6)(25 cases)according to FTND scores,which were 93 cases and 25 cases respectively.And we also divided the smoking group into mild smoking group and severe smoking group according to smoking index,which were 77 cases and 41 cases respectively.First,we compared the subgroups of smoking with the controls by ANOVA to find out the differential brain region,then the differential brain region was used as the region of interest to analyze the structural covariant network.Result1.Compared with the control group,the volume of the right thalamus,right precentral gyrus and left parietal lobe of the smoking group decreased(P< 0.001,cluster size >50voxels)in the smoking group,no increased region was found.2.According to FTND scores,the analysis of variance in mild nicotine dependent group,severe nicotine dependent group and control group showed that the difference between the three groups was located in the right thalamus and the left superior temporal gyrus.The multiple comparison between the mild nicotine dependence group and the control group showed that the volume of gray matter in the right thalamus decreased in the mild nicotine dependence group.The multiple comparison between the severe nicotine dependence group and the control group showed that the volume of gray matter in the left temporal gyrus was decreased.The multiple comparison between the severe nicotine dependence group and the mild nicotine dependence group showed the gray matter volume decreased in the left superior temporal gyrus.3.According to smoking index,the variance analysis of three groups in the mild smoking group,severe smoking group and the control group showed that the difference of brain area was located in the right thalamus.We found that the right thalamus(GMV)decreased of the mild smoking group was decreased than the control group and the severe smoking group.There was no difference between mild smoking group and severe smoking group.4.In the analysis of structural covariant network,we found that when using the thalamus as the seed point,the gray matter volume of the smoking group showed a rising covariance in the right thalamus with the left temporal gyrus,left temporal gyrus,left parietal lobe and right superior parietal lobe compared with the control group.But the trend of correlation with the thickness of the right inferior frontal gyrus(TRIAD),left thalamus,bilateral middle occipital gyrus,bilateral middle frontal gyrus and right central prefrontal cortex were decreased.When using the inferior parietal lobe as the seed point,the trend of the left top and lower parietal lobe in the left side of the temporal pole,bilateral temporal gyrus,left central posterior gyrus and right frontal gyrus was increased.But the trend of correlation with left medial upper frontal gyrus,right upper upper lobe,bilateral inferior temporal gyrus,left cingulate gyrus(central)and left cerebellar gray matter volume decreased.ConclusionLong term smokers have changes in the volume of gray matter in the brain,and the abnormalities of the structural covariant network associated with the thalamus and Inferior parietal lobe can provide a new way of thinking for the study of the mechanism of brain damage in nicotine dependent people.