An MRI Study Of Brain Structural Of Smokers

CHAPTER ONE:An analysis of the structural alterations in the brain of smokersObjectives:To investigate the alterations of brain structural in chronic cigarette smokers and how these changes are associated with smoking behaviors.Methods:Thirty-five smokers and35nonsmokers underwent high-resolution anatomical magnetic resonance imaging (MRI) scanning and Diffusion Tensor Imaging (DTI) MRI scanning. Voxel-based morphometry (VBM) and Voxel-based analysis (VBA) were conducted to assess the differences of GM volume and WM integrity as measured by the fractional anisotropy (FA) between smoker vs. nonsmoker groups. Using marsbar0.42software to extract the regions of interest (ROIs), namely the mean GM volume and FA of the brain regions which had significant difference between the two groups, then using pearson correlation analysis methods to assess the correlation between the ROIs and smoking-related behavioral data.Results:Four chronic smokers and two non-smokers did not meet the inclusion criteria, there were31chronic smokers and33non-smokers in the final GM study. We found a decrease in GM volume in the bilateral cerebellum posterior lobe, right fusiform gyrus, right thalamus and right postcentral gyrus of smokers in comparison to non-smokers (voxels>50, p<0.001). No increase in the volume of GM areas in the chronic smoking group was found. Positive association between the smoking years and increased left cerebellum posterior lobe GM volume was found in chronic smokers. The other ROIs did not show significant correlation with the smoking-related behavioral data including smoking years, daily smoking amount, smoking index and Fagerstrom Test of Nicotine Dependence (FTND) scores.There were33chronic smokers and24non-smokers included in the final WM study. We found smokers had higher FA than healthy non-smokers in right frontal lobe. FA differences were not seen in other areas. No significant correlation between the FA and smoking-related behavioral data was found in chronic smokers.Conclusions:Smoking had a certain degree of influence on the brain structures including the GM and WM. It might provide a further basis of the mechanism of smoking addiction. CHAPTER Two:An analysis of the association between brain structure (GM and WM) and smoking cessation outcomesObjectives:In the present analysis we sought to explore whether there existed baseline brain structure predictors for smoking cessation treatment outcomes in smokers.Methods:Smokers underwent high-resolution anatomical MRI scanning and Diffusion Tensor Imaging (DTI) MRI scanning prior to a smoking cessation treatment. The GM volume and WM FA differences between relapser vs. quitter groups were compared using two independent sample t tests (p<0.001).Results:Fifteen smokers achieved a4-week point prevalence abstinence in the total30smokers, the others failed. Compared to relapsers, quitters had significantly bigger GM volume in right middle frontal gyrus and left limbic lobe and higher (p<0.001). We also found quitters had higher FA than relapsers in left temporal lobe.Conclusions:These results suggest that maintaining smoking abstinence is associated with greater pre-quit brain GM volume of the prefrontal cortex which can regulate the cognitive function including attention, impulsive control, learning and memory, delay exciting, emotion and so on,and the limbic lobe (uncus) which plays a key role in rewarding processing. And the WM integrity of the left temporal lobe may also have a relationship with maintaining smoking abstinence. Maybe there are some brain structures can serve as clinically useful predictors of smoking cessation treatment outcome. But it still needs further large-scale studies.