Wade Morton posted an update 5 days, 22 hours ago
Thus, the present study applied a recently developed GBC method that could identify specific nodes or hubs influenced by smoking. Moreover, whether the regions influenced by acute cigarette smoking are related to structural change remains unknown. Although previous studies have used VBM based on the analysis of regions of interest to explore the changes caused by chronic cigarette smoking to some extent, this method excludes some key regions. Therefore, a whole-brain analysis without an ROI-based hypothesis could be conducted to comprehensively investigate the structural brain changes in TWS119 cost smokers and their relation to acute cigarette smoking. To examine the effect of acute cigarette smoking on brain function and its relation to the regions that show structural changes, this study compared the GBC of smokers when they abstained from smoking for 12 hours and after acute cigarette smoking and the GMV between smokers and non-smokers. On the basis of previous studies, we developed two a priori hypotheses. First, we hypothesized that smokers would display structural changes in prefrontal cortex and brain regions in DMN. Then, we hypothesized that the regional GBC of the DMN would be suppressed after acute cigarette smoking. Lastly, the regions of GBC changes caused by acute cigarette smoking would be associated with structural changes in chronic smokers, which would be expressed by increased or decreased GMV.A total of 42 participants aged 19 to 28 years-old were recruited through advertisements. All the participants recruited were undergraduates or graduates of Southwest University. After registration, potential participants were screened using semistructured interview to assess their psychiatric condition, medication use, medical condition, history of substance use, history of claustrophobia, and the presence of metal implants in their body. Cigarette smokers who smoked at least eight cigarettes per day without a period of abstinence longer than a week in the past year and met the DSM-IV criteria for nicotine dependence were considered suitable for this study. All the non-smokers in this study had no history of smoking in any case. All the participants were right-handed native Chinese speakers. The following exclusion criteria for smokers and non-smokers were used: acute physical illness, claustrophobia, history of head injury with skull fracture, presence of metal dentures, history of alcohol or drug abuse or dependence, history of central nervous system diseases or conditions, history of medical conditions with significant effects on the central nervous system, history of mental illness, and family history of psychopathic disorders. Participants were fully informed of the measurement methods and magnetic resonance imaging scanning. All participants gave their written informed consent. The local ethics committee of Southwest University approved this consent procedure and the experimental procedure, which were both in accordance with the standards of the Declaration of Helsinki. All participants were given appropriate compensation after completing this study. First, a specific template was computed using the average tissue probability maps from all the participants, and each participant’s maps were warped into the specific template. This procedure was repeated until the best study-specific template was generated to improve the alignment and achieve a more accurate inter-participant registration. Second, further modulation was conducted to preserve the volume of GM/WM. This step involves multiplying the spatially normalized GM/WM by its relative volume. Inference was made on the measures of volume rather than tissue concentration when using modulated images for performing subsequent group comparisons. Finally, a 10 mm full-width at half-maximum Gaussian kernel was applied to smooth the modulated GM/WM images. Based on the general linear model, voxel-based comparisons of GMV were performed between groups of smokers and nonsmokers using two-sample t-test. Age, education, and the whole brain volume were used as covariates to control for possible confounding variables in the whole-brain analysis. The significance of group differences was set at a 0.05 significance level using the AlphaSim criterion as the threshold to correct for multiple comparisons. In addition, we investigated the relationship between changed regions and smoking history. We performed an exploratory correlation analysis between the GMV of changed regions and the smoking history of each smoker. First, we created five ROI volumes based on a threshold significant peak of GMV to compare smokers and nonsmokers. We then extracted the GMV of each ROI for each smoker and correlated this value with years of smoking. In the present study, we observed the structural changes among smokers in the insula, medial frontal gyrus, and several DMN regions, such as the angular gyrus and the inferior parietal lobule. In addition, under the SOA condition, smokers demonstrated higher GBC in the insula and superior frontal cortex. After acute cigarette smoking, however, smokers showed lower GBC in the DMN, including the middle frontal cortex, precuneus, bilateral angular gyrus, and bilateral inferior parietal lobule, which are a group of brain areas important in goal-directed cognitive performance.