Current smoking and reduced gray matter volume-a voxel-based morphometry study

Characterizing the Structural Pattern of Heavy Smokers Using Multivoxel Pattern Analysis

Background: Smoking addiction is a major public health issue which causes a series of chronic diseases and mortalities worldwide. We aimed to explore the most discriminative gray matter regions between heavy smokers and healthy controls with a data-driven multivoxel pattern analysis technique, and to explore the methodological differences between multivoxel pattern analysis and voxel-based morphometry. Methods: Traditional voxel-based morphometry has continuously contributed to finding smoking addiction-related regions on structural magnetic resonance imaging. However, voxel-based morphometry has its inherent limitations. In this study, a multivoxel pattern analysis using a searchlight algorithm and support vector machine was applied on structural magnetic resonance imaging to identify the spatial pattern of gray matter volume in heavy smokers. Results: Our proposed method yielded a voxel-wise accuracy of at least 81% for classifying heavy smokers from healthy controls. The identified regions were primarily located at the temporal cortex and prefrontal cortex, occipital cortex, thalamus (bilateral), insula (left), anterior and median cingulate gyri, and precuneus (left). Conclusions: Our results suggested that several regions, which were seldomly reported in voxel-based morphometry analysis, might be latently correlated with smoking addiction. Such findings might provide insights for understanding the mechanism of chronic smoking and the creation of effective cessation treatment. Multivoxel pattern analysis can be efficient in locating brain discriminative regions which were neglected by voxel-based morphometry.

Effects of Smoking on Regional Homogeneity in Mild Cognitive Impairment: A Resting-State Functional MRI Study

Background

Smoking is a modifiable risk factor for Alzheimer’s disease (AD). However, smoking-related effects on intrinsic brain activity in high-risk AD population are still unclear.

Objective

We aimed to explore differences in smoking effects on brain function between healthy elderly and amnestic mild cognitive impairment (aMCI) patients using ReHo mapping.

Methods

We identified 64 healthy elderly controls and 116 aMCI patients, including 98 non-smoking and 18 smoking aMCI. Each subject underwent structural and resting-state functional MRI scanning and neuropsychological evaluations. Regional homogeneity (ReHo) mapping was used to assess regional brain synchronization. After correction for age, gender, education, and gray matter volume, we explored the difference of ReHo among groups in a voxel-wise way based on analysis of covariance (ANCOVA), followed by post hoc two-sample analyses (p < 0.05, corrected). Further, we correlated the mean ReHo with neuropsychological scales.

Results

Three groups were well-matched in age, gender, and education. Significant ReHo differences were found among three groups, located in the left supramarginal gyrus (SMG) and left angular gyrus (AG). Specifically, non-smoking aMCI had lower ReHo in SMG and AG than smoking aMCI and controls. By contrast, smoking aMCI had greater AG ReHo than healthy controls (p < 0.05). Across groups, correlation analyses showed that left AG ReHo correlated with MMSE (r = 0.18, p = 0.015), clock drawing test (r = 0.20, p = 0.007), immediate recall (r = 0.36, p < 0.001), delayed recall (r = 0.34, p < 0.001), and auditory verbal learning test (r = 0.20, p = 0.007).

Conclusion

Smoking might pose compensatory or protective effects on intrinsic brain activity in aMCI patients.

VBM sensitivity to localization and extent of mouse brain lesions: A simulation approach

BACKGROUND AND OBJECTIVES

Voxel-based morphometry (VBM) is a popular neuroimaging technique, used to detect and quantify morphological differences in brain tissues between groups. Widely used in human studies, VBM approaches have tremendous potential for neuroimaging studies in animal models. A significant challenge for applying VBM to small animal studies is the poor understanding of how the design of preprocessing pipelines impacts quantitative results. This is important because the large differences in size, resolution, and imaging parameters implies that human imaging preprocessing pipelines cannot be uncritically applied to small animal studies. In this work, we assessed and validated the performance of different VBM pipelines for the study of the mouse brain.

METHODS

We applied two pipelines -namely DARTEL VBM and Optimized VBM- by varying spatial normalization used during preprocessing. Using an automatic method, we simulated varying levels of volumetric gray matter (GM) loss and sizes of tissue atrophy on specific areas of the mouse brain. We evaluated the performance of each pipeline by comparing location and extent of the differences detected by them with the simulated ones. Finally, we applied both pipelines on magnetic resonance (MR) images of the brain derived from an experimental model of growth restriction on mice.

RESULTS

Our results demonstrated that some subtle atrophies were detected by the Optimized workflow but not by the DARTEL VBM workflow. Detection of less subtle atrophies was similar for the two workflows, but DARTEL VBM performed better at estimating their size and anatomical location. Both VBM pipelines had difficulties at finding atrophies with a very small level of volumetric loss and, in general, they underestimated the magnitudes of difference between groups. These results also varied across brain regions, with better performance on brain cortex than other regions such as the cerebellum.

CONCLUSIONS

The analysis and quantification of VBM pipelines on different areas of the mouse brain allows a better understanding of the advantages and limitations of their results. We performed a controlled and quantitative analysis of the method providing robust evidence to interpret changes in real contexts.

Independent and Combined Effects of Nicotine or Chronic Tobacco Smoking and HIV on the Brain: A Review of Preclinical and Clinical Studies

Tobacco smoking is highly prevalent among HIV-infected individuals. Chronic smokers with HIV showed greater cognitive deficits and impulsivity, and had more psychopathological symptoms and greater neuroinflammation than HIV non-smokers or smokers without HIV infection. However, preclinical studies that evaluated the combined effects of HIV-infection and tobacco smoking are scare. The preclinical models typically used cell cultures or animal models that involved specific HIV viral proteins or the administration of nicotine to rodents. These preclinical models consistently demonstrated that nicotine had neuroprotective and anti-inflammatory effects, leading to cognitive enhancement. Although the major addictive ingredient in tobacco smoking is nicotine, chronic smoking does not lead to improved cognitive function in humans. Therefore, preclinical studies designed to unravel the interactive effects of chronic tobacco smoking and HIV infection are needed. In this review, we summarized the preclinical studies that demonstrated the neuroprotective effects of nicotine, the neurotoxic effects of the HIV viral proteins, and the scant literature on nicotine or tobacco smoke in HIV transgenic rat models. We also reviewed the clinical studies that evaluated the neurotoxic effects of tobacco smoking, HIV infection and their combined effects on the brain, including studies that evaluated the cognitive and behavioral assessments, as well as neuroimaging measures. Lastly, we compared the different approaches between preclinical and clinical studies, identified some gaps and proposed some future directions. Graphical abstract Independent and combined effects of HIV and tobacco/nicotine. Left top and bottom panels: Both clinical studies of HIV infected persons and preclinical studies using viral proteins in vitro or in vivo in animal models showed that HIV infection could lead to neurotoxicity and neuroinflammation. Right top and bottom panels: While clinical studies of tobacco smoking consistently showed deleterious effects of smoking, clinical and preclinical studies that used nicotine show mild cognitive enhancement, neuroprotective and possibly anti-inflammatory effects. In the developing brain, however, nicotine is neurotoxic. Middle overlapping panels: Clinical studies of persons with HIV who were smokers typically showed additive deleterious effects of HIV and tobacco smoking. However, in the preclinical studies, when nicotine was administered to the HIV-1 Tg rats, the neurotoxic effects of HIV were attenuated, but tobacco smoke worsened the inflammatory cascade.

Short Bouts of Physical Activity Are Associated with Reduced Smoking Withdrawal Symptoms, but Perceptions of Intensity May Be the Key

The primary aim of this study was to assess the effectiveness of a short bout (10 min) of moderate-intensity exercise to reduce withdrawal symptomatology, craving and negative affect; while the secondary aim was to assess how the effectiveness of a short bout of moderate exercise can be modulated by the perception of intensity in physically active and low-activity smokers. Fifty low-activity and physically active smokers were recruited (24 male and 26 female) and randomized in three different conditions. Prescribed (objective) moderate intensity (OBJ) and perceived moderate intensity (PER), and passive waiting (PW). After the intervention (T3), smokers reported less desire to smoke in the PER (p < 0.001) and OBJ (p < 0.001) conditions, relative to the PW condition. At T3 smokers in the PER condition reported less negative affect than smokers in the PW condition relative to the baseline (T1) (p < 0.007). Further, smokers in the PER condition reported less negative affect than smokers in the PW condition (p < 0.048). Physically active (PA) smokers perceived less exertion than low-activity (LA) smokers, and the effects were stronger in the PER condition relative to OBJ. Generally, our results suggest that a short bout of moderate exercise helps both LA and PA smokers. These findings provided a novel insight into the psychological mechanisms that affect the efficacy of the exercise in smoking cessation and suggest that exercise should be tailored according to individual perception of intensity.

Meta-analysis of brain gray matter changes in chronic smokers

BACKGROUND

Previous studies based on voxel-based morphometry (VBM) had revealed brain gray matter (GM) changes in chronic smokers relative to nonsmokers. However, not all studies reported entirely consistent findings, or even opposite. The aim of this study was to conduct a quantitative meta-analysis of VBM studies of chronic smokers.

METHOD

A systematic database search was conducted in PubMed and Web of Knowledge from January 1, 2000 to January 31, 2020 to identify eligible VBM studies. Meta-analysis was performed with the Seed-based d Mapping software package to compare alternations between chronic cigarette smokers and nonsmokers. In addition, meta-regression analysis were performed to examine the influences of cigarette per day, smoking history and FTND.

RESULTS

A total of 17 VBM studies including 905 smokers and 1344 nonsmokers met the inclusion criteria. The results of this meta-analysis showed that the chronic smokers showed a robust GM volume decrease in bilateral prefrontal cortex and left insular and a GM increase in the right lingual cortex and left occipital cortex. Moreover, meta-regression analysis showed that cigarette per day, smoking history and FTND were partly associated with GM changes in chronic smokers.

CONCLUSIONS

This meta-analysis indicated that chronic cigarette smokers had significant and robust brain GM alternations compared with nonsmokers. Longitudinal studies should be performed in the future to explore whether these brain regions could be used as potential therapeutic neuro-target for nicotine dependence.

Cortical atrophy mediates the accumulating effects of vascular risk factors on cognitive decline in the Alzheimer's disease spectrum

There are increasing concerns regarding the association of vascular risk factors (VRFs) and cognitive decline in the Alzheimer's disease (AD) spectrum. Currently, we investigated whether the accumulating effects of VRFs influenced gray matter volumes and subsequently led to cognitive decline in the AD spectrum. Mediation analysis was used to explore the association among VRFs, cortical atrophy, and cognition in the AD spectrum. 123 AD spectrum were recruited and VRF scores were constructed. Multivariate linear regression analysis revealed that higher VRF scores were correlated with lower Mini-Mental State Examination scores and higher Alzheimer's Disease Assessment Scale-Cognitive Subscale scores, indicating higher VRF scores lead to severer cognitive decline in the AD spectrum. In addition, subjects with higher VRF scores suffered severe cortical atrophy, especially in medial prefrontal cortex and medial temporal lobe. More importantly, common circuits of VRFs- and cognitive decline associated with gray matter atrophy were identified. Further, using mediation analysis, we demonstrated that cortical atrophy regions significantly mediated the relationship between VRF scores and cognitive decline in the AD spectrum. These findings highlight the importance of accumulating risk in the vascular contribution to AD spectrum, and targeting VRFs may provide new strategies for the therapeutic and prevention of AD.

Cigarette smoking history is associated with poorer recovery in multiple neurocognitive domains following treatment for an alcohol use disorder

Cigarette smoking is associated with neurocognitive dysfunction in various populations, including those seeking treatment for an alcohol use disorder (AUD). This study compared the rate and extent of recovery on measures of processing speed, executive functions, general intelligence, visuospatial skills and working memory in treatment-seeking alcohol dependent individuals (ALC) who were never-smokers (nvsALC), former-smoker (fsALC), and active smokers (asALC), over approximately 8 months of abstinence from alcohol. Methods: ALC participants were evaluated at approximately 1 month of abstinence (AP1; n = 132) and reassessed after 8 months of sobriety (AP2; n = 54). Never-smoking controls (CON; n = 33) completed a baseline and follow-up (n = 19) assessment approximately 9 months later. Domains evaluated were executive functions, general intelligence, processing speed, visuospatial skills and working memory; a domain composite was formed from the arithmetic average of the foregoing domains. nvsALC showed greater improvement than fsALC, asALC and CON on most domains over the AP1-AP2 interval. fsALC demonstrated greater recovery than asALC on all domains except visuospatial skills; fsALC also showed greater improvements than CON on general intelligence, working memory and domain composite. asALC did not show significant improvement on any domain over the AP1-AP2 interval. At 8 months of abstinence, asALC were inferior to CON and nvsALC on multiple domains, fsALC performed worse than nvsALC on several domains, but nvsALC were not different from CON on any domain. Our results provide robust evidence that smoking status influenced the rate and extent of neurocognitive recovery between 1 and 8 months of abstinence in this ALC cohort. Chronic smoking in AUD likely contributes to the considerable heterogeneity observed in neurocognitive recovery during extended abstinence. The findings provide additional strong support for the benefits of smoking cessation and the increasing clinical movement to offer smoking cessation resources concurrent with treatment for AUD.

Sex/gender differences in brain function and structure in alcohol use: A narrative review of neuroimaging findings over the last 10 years

Over the last 10 years, rates of alcohol use disorder (AUD) have increased in women by 84% relative to a 35% increase in men. Rates of alcohol use and high-risk drinking have also increased in women by 16% and 58% relative to a 7% and 16% increase in men, respectively, over the last decade. This robust increase in drinking among women highlights the critical need to identify the underlying neural mechanisms that may contribute to problematic alcohol consumption across sex/gender (SG), especially given that many neuroimaging studies are underpowered to detect main or interactive effects of SG on imaging outcomes. This narrative review aims to explore the recent neuroimaging literature on SG differences in brain function and structure as it pertains to alcohol across positron emission tomography, magnetic resonance imaging, and functional magnetic resonance imaging modalities in humans. Additional work using magnetic resonance spectroscopy, diffusion tensor imaging, and event-related potentials to examine SG differences in AUD will be covered. Overall, current research on the neuroimaging of AUD, alcohol consumption, or risk of AUD is limited, and findings are mixed regarding the effect of SG on neurochemical, structural, and functional mechanisms associated with AUD. We address SG disparities in the neuroimaging of AUD and propose a call to action to include women in brain imaging research. Future studies are crucial to our understanding of the neurobiological underpinnings of AUD across neural systems and the vulnerability for AUD among women and men.

12-h abstinence-induced functional connectivity density changes and craving in young smokers: a resting-state study

Studying the neural correlates of craving to smoke is of great importance to improve treatment outcomes in smoking addiction. According to previous studies, the critical roles of striatum and frontal brain regions had been revealed in addiction. However, few studies focused on the hub of brain regions in the 12 h abstinence induced craving in young smokers. Thirty-one young male smokers were enrolled in the present study. A within-subject experiment design was carried out to compare functional connectivity density between 12-h smoking abstinence and smoking satiety conditions during resting state in young adult smokers by using functional connectivity density mapping (FCDM). Then, the functional connectivity density changes during smoking abstinence versus satiety were further used to examine correlations with abstinence-induced changes in subjective craving. We found young adult smokers in abstinence state (vs satiety) had higher local functional connectivity density (lFCD) and global functional connectivity density (gFCD) in brain regions including striatal subregions (i.e., bilateral caudate and putamen), frontal regions (i.e., anterior cingulate cortex (ACC) and orbital frontal cortex (OFC)) and bilateral insula. We also found higher lFCD during smoking abstinence (vs satiety) in bilateral thalamus. Additionally, the lFCD changes of the left ACC, bilateral caudate and right OFC were positively correlated with the changes in craving induced by abstinence (i.e., abstinence minus satiety) in young adult smokers. The present findings improve the understanding of the effects of acute smoking abstinence on the hubs of brain gray matter in the abstinence-induces craving and may contribute new insights into the neural mechanism of abstinence-induced craving in young smokers in smoking addiction.

Evaluating the Changes of White Matter Microstructures in Tobacco Addicts Based on Diffusion Tensor Imaging

BACKGROUND The tract-based spatial statistics (TBSS) method was used to investigate the changes of white matter microstructure in tobacco addicts, and to analyze its correlation with smoking index, smoking years, and daily smoking amount. MATERIAL AND METHODS Routine magnetic resonance imaging (excluding intracranial lesions) and diffusion tensor imaging (DTI) sequence scanning were performed in 156 nicotine addicts (nicotine dependence group) and 81 non-nicotine addicts (control group) recruited from the study group. TBSS method was used to preprocess DTI data, and age and education level were taken as covariables to statistically analyze relevant parameters between nicotine dependence group and control group, such as fractional anisotropy (FA) value and smoking index. Spearman correlation analysis was performed on smoking status and FA values in brain regions with significant differences between nicotine dependent group and control group, and the test level alpha was 0.05. RESULTS Compared with control group, FA values of white matter in part of the posterior limb of the right inner capsule (r=-0.428, P=0.003), the right superior radiating crown (r=-0.136, P=0.004), the right posterior radiating crown (r=-0.229, P=0.003), the right superior longitudinal bundle (r=-0.474, P=0.002), the right inferior longitudinal bundle (r=-0.354, P=0.003) and the inferior frontal occipital bundle (r=-0.310, P=0.002) were decreased, which were negatively correlated with smoking index (P<0.05). CONCLUSIONS Nicotine can damage the microstructure of white matter in specific brain regions and damage neurons, with cumulative effects.

Dissociable Effects of Theta-Burst Repeated Transcranial Magnetic Stimulation to the Inferior Frontal Gyrus on Inhibitory Control in Nicotine Addiction

Nicotine addiction, like other substance use disorders (SUD's), is associated with deficits in prefrontal mediated inhibitory control. The strength of inhibitory control task-based functional connectivity (tbFC) between the right inferior frontal gyrus (r.IFG) and thalamus (corticothalamic circuit) mediates the association between successful inhibition and smoking relapse vulnerability. However, the potential efficacy of theta burst stimulation (TBS) to the r.IFG, a treatment known to alter clinical symptoms among neuropsychiatric patients, has not been reported in a SUD population. This study utilized fMRI guided neuronavigation to examine the effects of TBS on inhibitory control among nicotine dependent individuals. Participants (N=12) were scanned while performing an inhibitory control task known to elicit inhibition-related activity in the r.IFG. Using a randomized, counterbalanced cross-over design, participants then received TBS over two visits: excitatory (iTBS) on one visit and inhibitory (cTBS) TBS on the other visit. The effects of each TBS condition on subsequent inhibitory control task performance were examined. A significant condition x time interaction was identified on trials requiring inhibitory control (F (1,10) = 7.27, p = .022, D = 1.63). iTBS improved inhibitory control, whereas cTBS impaired inhibitory control. Brain stimulation did not influence performance in control conditions including novelty detection and response execution. This is the first study to demonstrate that non-invasive neural stimulation using iTBS to the r.IFG enhances baseline inhibitory control among individuals with a SUD. Further research is needed to directly examine the potential parametric effects of TBS on corticothalamic tbFC in individuals with a SUD.

Cerebellar Morphometry and Cognition in the Context of Chronic Alcohol Consumption and Cigarette Smoking

BACKGROUND

Cerebellar atrophy (especially involving the superior-anterior cerebellar vermis) is among the most salient and clinically significant effects of chronic hazardous alcohol consumption on brain structure. Smaller cerebellar volumes are also associated with chronic cigarette smoking. The present study investigated effects of both chronic alcohol consumption and cigarette smoking on cerebellar structure and its relation to performance on select cognitive/behavioral tasks.

METHODS

Using T1-weighted Magnetic Resonance Images (MRIs), the Cerebellar Analysis Tool Kit segmented the cerebellum into bilateral hemispheres and 3 vermis parcels from 4 participant groups: smoking (s) and nonsmoking (ns) abstinent alcohol-dependent treatment seekers (ALC) and controls (CON) (i.e., sALC, nsALC, sCON, and nsCON). Cognitive and behavioral data were also obtained.

RESULTS

We found detrimental effects of chronic drinking on all cerebellar structural measures in ALC participants, with largest reductions seen in vermis areas. Furthermore, both smoking groups had smaller volumes of cerebellar hemispheres but not vermis areas compared to their nonsmoking counterparts. In exploratory analyses, smaller cerebellar volumes were related to lower measures of intelligence. In sCON, but not sALC, greater smoking severity was related to smaller cerebellar volume and smaller superior-anterior vermis area. In sALC, greater abstinence duration was associated with larger cerebellar and superior-anterior vermis areas, suggesting some recovery with abstinence.

CONCLUSIONS

Our results show that both smoking and alcohol status are associated with smaller cerebellar structural measurements, with vermal areas more vulnerable to chronic alcohol consumption and less affected by chronic smoking. These morphometric cerebellar deficits were also associated with lower intelligence and related to duration of abstinence in sALC only.

Associations of Regional Brain Structural Differences With Aging, Modifiable Risk Factors for Dementia, and Cognitive Performance

IMPORTANCE

Identifying brain regions associated with risk factors for dementia could guide mechanistic understanding of risk factors associated with Alzheimer disease (AD).

OBJECTIVES

To characterize volume changes in brain regions associated with aging and modifiable risk factors for dementia (MRFD) and to test whether volume differences in these regions are associated with cognitive performance.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study used data from UK Biobank participants who underwent T1-weighted structural brain imaging from August 5, 2014, to October 14, 2016. A voxelwise linear model was applied to test for regional gray matter volume differences associated with aging and MRFD (ie, hypertension, diabetes, obesity, and frequent alcohol use). The potential clinical relevance of these associations was explored by comparing their neuroanatomical distributions with the regional brain atrophy found with AD. Mediation models for risk factors, brain volume differences, and cognitive measures were tested. The primary hypothesis was that common, overlapping regions would be found. Primary analysis was conducted on April 1, 2018.

MAIN OUTCOMES AND MEASURES

Gray matter regions that showed relative atrophy associated with AD, aging, and greater numbers of MRFD.

RESULTS

Among 8312 participants (mean [SD] age, 62.4 [7.4] years; 3959 [47.1%] men), aging and 4 major MRFD (ie, hypertension, diabetes, obesity, and frequent alcohol use) had independent negative associations with specific gray matter volumes. These regions overlapped neuroanatomically with those showing lower volumes in participants with AD, including the posterior cingulate cortex, the thalamus, the hippocampus, and the orbitofrontal cortex. Associations between these MRFD and spatial memory were mediated by differences in posterior cingulate cortex volume (β = 0.0014; SE = 0.0006; P = .02).

CONCLUSIONS AND RELEVANCE

This cross-sectional study identified differences in localized brain gray matter volume associated with aging and MRFD, suggesting regional vulnerabilities. These differences appeared relevant to cognitive performance even among people considered cognitively healthy.

Preliminary evidence of altered gray matter volume in subjects with internet gaming disorder: associations with history of childhood attention-deficit/hyperactivity disorder symptoms

Attention-deficit/hyperactivity disorder (ADHD) is commonly comorbid with Internet gaming disorder (IGD). Although childhood ADHD symptoms may decline during late brain maturation, structural alterations in some brain areas may persist into adulthood. This study investigated whether young adults with IGD and a history of childhood ADHD symptoms had gray matter volume (GMV) alterations that were distinct from subjects without a history of childhood ADHD. As an exploratory investigation, we conducted a whole-brain voxel-based morphometry with the diffeomorphic anatomical registration using an exponentiated Lie algebra algorithm and applied an uncorrected threshold at the voxel level for multiple comparisons. GMVs of IGD subjects with a history of childhood ADHD (IGD_ADHD+ group; n = 20; 24.5 ± 2.5 years) were compared to those of subjects without a history of childhood ADHD (IGD_ADHD- group; n = 20; 23.9 ± 2.5 years) and controls (n = 20; 22.7 ± 2.4 years). Compared with controls, both IGD groups had a smaller GMV in the right anterior cingulate cortex, the left inferior frontal gyrus, and the left insula, yet had a larger GMV in the right angular gyrus. The IGD_ADHD+ group had a larger GMV in the right precuneus than the IGD_ADHD- group and controls. When controlling for other comorbid psychiatric symptoms, the IGD_ADHD+ group also had a smaller GMV in the right inferior frontal gyrus. In conclusion, we found that young adults with IGD and a history of childhood ADHD symptoms had characteristic GMV alterations, which may be linked with their manifestation of childhood ADHD.

Implications of insular cortex laterality for treatment of nicotine addiction

BACKGROUND

Damage to the insula disrupts nicotine-induced cravings and is associated with greater odds of cessation. The role of laterality in regulating these changes is unclear. Neuroimaging studies in cigarette smokers show left hemispheric activation during a period of forced withdrawal and right hemispheric activation after having just smoked. Among current smokers hospitalized for stroke involving their insula, we compared left versus right insular damage and its effect on smoking outcomes.

METHODS

A total of 37 smokers hospitalized with unilateral insular strokes (14 right, 23 left) were administered questionnaires to assess urge (Questionnaire on Smoking Urges) before (retrospectively) and during hospitalization and 3 months post-stroke, withdrawal during hospitalization (Wisconsin Smoking Withdrawal Scale), and prolonged abstinence at 3 months post-stroke. Crude and adjusted linear regression models were performed controlling for baseline covariates.

RESULTS

Right and left insular-damaged smokers experienced a significant decrease in urge from baseline to hospitalization and three-month follow-up (p < 0.01). Smokers with left-sided insular infarcts relative to right-sided experienced a larger decrease in acute urge (adjusted β=-1.16, 95% CI: -2.59, 0.27, p = 0.11) but not chronically (adjusted β=-0.06, 95% CI: -1.53, 1.40, p = 0.93). Left-sided insular damage was also associated with significantly fewer and less severe withdrawal symptoms during hospitalization (adjusted β=-3.52, 95% CI: -7.01, -0.04, p = 0.05). No differences were noted between groups for prolonged abstinence (p = 0.50).

CONCLUSIONS

Left insular adaptations are suggestive to have an impact on acute changes in urge and withdrawal more so than the right insula, however lateral asymmetries did not exist for long-term changes.

Region-Specific Changes of Insular Cortical Thickness in Heavy Smokers

Insula plays an essential role in maintaining the addiction to cigarette smoking and smoking-related alterations on the insular volume and density have been reported in smokers. However, less is known about the effects of chronic cigarette smoking on the insular cortical thickness. In this study, we explored the region-specific changes of insular cortical thickness in heavy smokers and their relations with smoking-related variables. 37 heavy smokers (29 males, mean age 47.19 ± 7.22 years) and 37 non-smoking healthy controls (29 males, mean age 46.95 ± 8.45 years) participated in the study. Subregional insular cortical thickness was evaluated and compared between the two groups. Correlation analysis was performed to investigate relationships between the insular cortical thickness and clinical characteristics in heavy smokers. There was no statistical difference on the cortical thickness in the left insula (p = 0.536) between the two groups while heavy smokers had a slightly thinner cortical thickness in the right insula (p = 0.048). In addition, heavy smokers showed a greater cortical thinning in the anterior (p = 0.0084) and superior (p = 0.0054) segment of the circular sulcus of the right insula as well as the inferior (p = 0.012) segment of the circular sulcus of the left insula. Moreover, the cortical thickness of the superior segment of the circular sulcus of the left insula was correlated negatively with nicotine severity (r = −0.423; p = 0.009) and the longer cigarette exposure was associated with the cortical thinning in the long insular gyrus and central sulcus of the right insula (r = −0.475; p = 0.003). Our findings indicate that chronic cigarette use is associated with region-specific insular thinning, which has the potential to improve our understanding of the specific roles of insular subregions in nicotine addiction.

The Insula: A Brain Stimulation Target for the Treatment of Addiction

Substance use disorders (SUDs) are a growing public health concern with only a limited number of approved treatments. However, even approved treatments are subject to limited efficacy with high long-term relapse rates. Current treatment approaches are typically a combination of pharmacotherapies and behavioral counselling. Growing evidence and technological advances suggest the potential of brain stimulation techniques for the treatment of SUDs. There are three main brain stimulation techniques that are outlined in this review: transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS). The insula, a region of the cerebral cortex, is known to be involved in critical aspects underlying SUDs, such as interoception, decision making, anxiety, pain perception, cognition, mood, threat recognition, and conscious urges. This review focuses on both the preclinical and clinical evidence demonstrating the role of the insula in addiction, thereby demonstrating its promise as a target for brain stimulation. Future research should evaluate the optimal parameters for brain stimulation of the insula, through the use of relevant biomarkers and clinical outcomes for SUDs.

Cigarette smoking and cerebral blood flow in a cohort of middle-aged adults

Cigarette smoking is often associated with dementia. This association is thought to be mediated by hypoperfusion; however, how smoking behavior relates to cerebral blood flow (CBF) remains unclear. Using data from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort (mean age = 50; n = 522), we examined the association between smoking behavior (status, cumulative pack-years, age at smoking initiation, and years since cessation) and CBF (arterial spin labeling) in brain lobes and regions linked to dementia. We used adjusted linear regression models and tested whether associations differed between current and former-smokers. Compared to never-smokers, former-smokers had lower CBF in the parietal and occipital lobes, cuneus, precuneus, putamen, and insula; in contrast, current-smokers did not have lower CBF. The relationship between pack-years and CBF was different between current and former-smokers (p for interaction < 0.05): Among current-smokers, higher pack-years were associated with higher occipital, temporal, cuneus, putamen, insula, hippocampus, and caudate CBF; former-smokers had lower caudate CBF with increasing pack-years. Results show links between smoking and CBF at middle-age in regions implicated in cognitive and compulsive/addictive processes. Differences between current and former smoking suggest that distinct pathological and/or compensatory mechanisms may be involved depending on the timing and history of smoking exposure.

The 20-Year Voyage Aboard the Journal of Alzheimer's Disease: Docking at 'Type 3 Diabetes', Environmental/Exposure Factors, Pathogenic Mechanisms, and Potential Treatments

The Journal of Alzheimer’s Disease (JAD), founded in 1998, played a pivotal role in broadening the field of research on Alzheimer’s disease (AD) by publishing a diverse range of clinical, pathological, molecular, biochemical, epidemiological, experimental, and review articles from its birth. This article recounts my own journey as an author who contributed articles to JAD over the 20 years of the journal’s existence. In retrospect, it seems remarkable that a considerable body of work that originated from our group marks a trail that began with studies of vascular, stress, and mitochondrial factors in AD pathogenesis, exploded into the concept of ‘Type 3 Diabetes’, and continued with the characterization of how environmental, exposure, and lifestyle factors promote neurodegeneration and which therapeutic strategies could reverse the neurodegeneration cascade.

Low Smoking Exposure, the Adolescent Brain, and the Modulating Role of CHRNA5 Polymorphisms

BACKGROUND

Studying the neural consequences of tobacco smoking during adolescence, including those associated with early light use, may help expose the mechanisms that underlie the transition from initial use to nicotine dependence in adulthood. However, only a few studies in adolescents exist, and they include small samples. In addition, the neural mechanism, if one exists, that links nicotinic receptor genes to smoking behavior in adolescents is still unknown.

METHODS

Structural and diffusion tensor magnetic resonance imaging data were acquired from a large sample of 14-year-old adolescents who completed an extensive battery of neuropsychological, clinical, personality, and drug-use assessments. Additional assessments were conducted at 16 years of age.

RESULTS

Exposure to smoking in adolescents, even at low doses, is linked to volume changes in the ventromedial prefrontal cortex and to altered neuronal connectivity in the corpus callosum. The longitudinal analyses strongly suggest that these effects are not preexisting conditions in those who progress to smoking. There was a genetic contribution wherein the volume reduction effects were magnified in smokers who were carriers of the high-risk genotype of the alpha 5 nicotinic receptor subunit gene, rs16969968.

CONCLUSIONS

These findings give insight into a mechanism involving genes, brain structure, and connectivity underlying why some adolescents find nicotine especially addictive.

Cigarette smoking and gray matter brain volumes in middle age adults: the CARDIA Brain MRI sub-study

Cigarette smoking has been associated with dementia and dementia-related brain changes, notably gray matter (GM) volume atrophy. These associations are thought to reflect the co-morbidity of smoking and vascular, respiratory, and substance use/psychological conditions. However, the extent and localization of the smoking-GM relationship and the degree to which vascular, respiratory, and substance use/psychological factors influence this relationship remain unclear. In the Coronary Artery Risk Development in Young Adults CARDIA cohort (n = 698; 52% women; 40% black participants; age = 50.3 (SD = 3.5)), we examined the associations of smoking status with total GM volume and GM volume of brain regions linked to neurocognitive and addiction disorders. Linear regression models were used to adjust for vascular, respiratory, and substance use/psychological factors and to examine whether they modify the smoking-GM relationship. Compared to never-smokers, current smokers had smaller total GM volume (-8.86 cm³ (95%CI = -13.44, -4.29). Adjustment for substance use/psychological - but not vascular or respiratory - factors substantially attenuated this association (coefficients = -5.54 (95% CI = -10.32, -0.76); -8.33 (95% CI = -12.94, -3.72); -7.69 (95% CI = -6.95, -4.21), respectively). There was an interaction between smoking and alcohol use such that among alcohol non-users, smoking was not related to GM volumes and among alcohol users, those who currently smoked had -12 cm³ smaller total GM, specifically in the frontal and temporal lobes, amygdala, cingulate, and insula. Results suggest a large-magnitude association between smoking and smaller GM volume at middle age, accounting for vascular, respiratory, and substance use/psychological factors, and that the association was strongest in alcohol users. Regions suggested to be most vulnerable are those where cognition and addiction processes overlap.

Methamphetamine use and cognitive function: A systematic review of neuroimaging research

BACKGROUND

Long-term use of MA has been associated with cognitive dysfunction in several domains. Neuroimaging studies have also reported structural, metabolic, and functional changes in MA users. However, no systematic review has been conducted on those studies in MA users that combined neuroimaging and cognitive tasks.

METHODS

This article systematically reviews correlation between brain imaging measures and cognitive performance in subjects with current and previous history of MA use. Findings are categorized based on cognitive domain.

RESULTS

MA users performed more poorly than controls in all cognitive domains (psychomotor, working memory, attention, cognitive control, and decision- making) and a positive correlation has been repeatedly observed between performance and brain measures (regional volume/density, blood flow, glucose metabolism, FA value, NAA level, and activation) in MA users. Performance in cognitive control was consistently reported to show relationship with brain measures in the PFC and ACC, while decision- making consistently showed correlation with brain measures in the PFC, ACC, and striatum.

CONCLUSIONS

There is solid evidence for brain- behavior relationship in cognitive functioning in MA users, particularly in cognitive control and decision-making. More research with correlation analysis between brain-behavior and MA use parameters is strongly encouraged.

Brain Function Network and Young Adult Smokers: A Graph Theory Analysis Study

Cigarette smoking is associated with abnormalities in the widespread inter-regional functional connectivity of the brain. However, few studies focused on the abnormalities in the topological organization of brain functional networks in young smokers. In the current study, resting-state functional magnetic resonance images were acquired from 30 young male smokers and 32 age-, gender-, and education-matched healthy male nonsmokers. A functional network was constructed by calculating the Pearson correlation coefficients among 246 subregions in the human Brainnetome Atlas. The topological parameters were compared between smokers and nonsmokers. The results showed that the functional network of both young smokers and nonsmokers had small-world topology. Compared to nonsmokers, young smokers exhibited a decreased clustering coefficient (C_p) and local network efficiency (E_local). C_p and E_local were negatively correlated with the duration of cigarette use. In addition, increased nodal efficiency (E_nodal) was mainly located in the prefrontal cortex (PFC), cingulate gyrus, insula, and caudate. Decreased connectivities among the PFC, cingulate gyrus, insula, basal ganglia (of specific node), and thalamus were also observed. In sum, we revealed the abnormal topological organization of brain functional networks in young smokers, which may improve our understanding of the neural mechanism of young smokers from a brain functional network topological organization perspective.

Polygenic risk for schizophrenia and associated brain structural changes: A systematic review

BACKGROUND

Genome wide association studies (GWAS) of schizophrenia allow the generation of Polygenic Risk Scores (PRS). PRS can be used to determine the contribution to altered brain structures in this disorder, which have been well described. However, findings from studies using PRS to predict brain structural changes in schizophrenia have been inconsistent. We therefore performed a systematic review to determine the association between schizophrenia PRS and brain structure.

METHODS

Following PRISMA systematic review guidelines, databases were searched for literature using key search terms. Inclusion criteria for the discovery sample required case-control schizophrenia GWAS summary statistics from European populations. The target sample was required to be of European ancestry, and have brain structure and genotype information. Quality assessment of the publications was conducted using the Mixed Methods Appraisal Tool for quantitative non-randomised studies.

MAIN FINDINGS

A total of seven studies were found to be eligible for review. Five studies found no significant association and two studies found a significant association of schizophrenia PRS with total brain, reduced white matter volume, and globus pallidus volume. However, the latter studies were conducted using smaller discovery (n_cases = 9394 n_controls = 12,462) and target samples compared to the studies with substantially larger discovery (n_cases = 33,636 n_controls = 43,008) and target samples where no association was observed. Taken together, the results suggest that schizophrenia PRS are not significantly associated with brain structural changes in this disorder.

CONCLUSIONS

The lack of significant association between schizophrenia PRS and brain structural changes may indicate that intermediate phenotypes other than brain structure should be the focus of future work. Alternatively, however, the lack of association found here may point to limitations of the current evidence-base, and so point to the need for future better powered studies.

Interactions between monoamine oxidase A rs1137070 and smoking on brain structure and function in male smokers

The monoamine oxidase A (MAOA) enzyme metabolizes monoamine neurotransmitters such as dopamine, serotonin and norepinephrine, and its genetic polymorphism (rs1137070) influences its activity level and is associated with smoking behaviors. However, the underlying neural mechanisms of the gene × environment interactions remain largely unknown. In this study, we aimed to explore the interactive effects of the rs1137070 and cigarette smoking on gray matter volume (GMV) and functional connectivity strength (FCS). A total of 81 smokers and 42 nonsmokers were enrolled in the present study. Voxel-based morphometry analysis showed a significant rs1137070 genotype × smoking effect on the GMV of the left orbitofrontal cortex (OFC), such that individuals with risk allele had greater GMV among nonsmokers but not smokers. Meanwhile, rs1137070 variant and nicotine dependence interactively altered the FCS of the right hippocampus, the left inferior parietal lobule (IPL), the left dorsolateral prefrontal cortex and bilateral OFC. In addition, the FCS in the left IPL was correlated with smoking initiation and smoking years in smokers with the risk allele. These findings suggest that MAOA rs1137070 contributes to the susceptibility to nicotine dependence through its influence on brain circuits involved in reward and attention, and interacts with smoking in the progression.

Physically active life style is associated with increased grey matter brain volume in a medial parieto-frontal network

To examine the association between the amount of sports activity performed during leisure time and gray matter volume (GMV) of the brain we investigated differences in GMV in a large cohort study of community-dwelling older adults. 967 individuals indicated their average weekly sports activity via a questionnaire, and underwent high resolution T1-weighted structural imaging of the brain. We used voxel based morphometry (CAT 12) in a region of interest approach for (1) comparing participants with higher versus lower sports activity (median split) and (2) calculating a linear regression on GMV and sports activity. We carefully corrected for other factors known to have an impact on GMV (sex, age, total brain volume, education, cigarettes and alcohol consumption, body mass index) and excluded pathology (history of psychiatric or neurological disease; visual inspection of brain scans). Those participants who spend more time performing sports activity per week (median split with > 1 h/week) showed higher GMV in the dorsomedial frontal lobe, the superior parietal lobe, and the precuneus/cuneus area. When splitting participants by their median (55.5 years) into two groups we found a stronger protective effect of sports against age related GMV decline for the older part of the cohort. Overall, a more active lifestyle was associated with increased GMV in areas associated with self-awareness and working memory. These cohort data support data on the protective role of sports activity for the GMV.

Chronotype differences in cortical thickness: grey matter reflects when you go to bed

Based on individual circadian cycles and associated cognitive rhythms, humans can be classified via standardised self-reports as being early (EC), late (LC) and intermediate (IC) chronotypes. Alterations in neural cortical structure underlying these chronotype differences have rarely been investigated and are the scope of this study. 16 healthy male ECs, 16 ICs and 16 LCs were measured with a 3 T MAGNETOM TIM TRIO (Siemens, Erlangen) scanner using a magnetization prepared rapid gradient echo sequence. Data were analysed by applying voxel-based morphometry (VBM) and vertex-wise cortical thickness (CTh) analysis. VBM analysis revealed that ECs showed significantly lower grey matter volumes bilateral in the lateral occipital cortex and the precuneus as compared to LCs, and in the right lingual gyrus, occipital fusiform gyrus and the occipital pole as compared to ICs. CTh findings showed lower grey matter volumes for ECs in the left anterior insula, precuneus, inferior parietal cortex, and right pars triangularis than for LCs, and in the right superior parietal gyrus than for ICs. These findings reveal that chronotype differences are associated with specific neural substrates of cortical thickness, surface areas, and folding. We conclude that this might be the basis for chronotype differences in behaviour and brain function. Furthermore, our results speak for the necessity of considering "chronotype" as a potentially modulating factor in all kinds of structural brain-imaging experiments.

Brain Structure Alterations in Respect to Tobacco Consumption and Nicotine Dependence: A Comparative Voxel-Based Morphometry Study

The main purpose of this study is to examine the lifetime tobacco consumption and the degree of nicotine dependence related gray matter (GM) and white matter (WM) volume alterations in young adult-male smokers. Fifty-three long-term male smokers and 53 well-matched male healthy non-smokers participated in the study, and the smokers were respectively categorized into light and heavy tobacco consumption subgroups by pack-years and into moderate and severe nicotine dependence subgroups using the Fagerström Test for Nicotine Dependence (FTND). Voxel-based morphometry analysis was then performed, and ANCOVA analysis combined with subsequent post hoc test were used to explore the between-group brain volume abnormalities related to the smoking amount and nicotine dependence. Light and heavy smokers displayed smaller GM and WM volumes than non-smokers, while heavy smokers were found with more significant brain atrophy than light smokers in GM areas of precuneus, inferior and middle frontal gyrus, superior temporal gyrus, cerebellum anterior lobe and insula, and in WM areas of cerebellum anterior lobe. However, the contrary trend was observed regarding alterations associated with severity of nicotine dependence. Severe nicotine dependence smokers rather demonstrated less atrophy levels compared to moderate nicotine dependence smokers, especially in GM areas of precuneus, superior and middle temporal gyrus, middle occipital gyrus, posterior cingulate and insula, and in WM areas of precuneus, posterior cingulate, cerebellum anterior lobe and midbrain. The results reveal that the nicotine dependence displays a dissimilar effect on the brain volume in comparison to the cigarette consumption. Our study could provide new evidences to understand the adverse effects of smoking on the brain structure, which is helpful for further treatment of smokers.

Lifestyle-dependent brain change: a longitudinal cohort MRI study

We investigated both independent and interconnected effects of 3 lifestyle factors on brain volume, measuring yearly changes using large-scale longitudinal magnetic resonance imaging, in middle-aged to older adults. We measured brain volumes in a cohort (n = 984, 49-79 years) from the Korean Genome and Epidemiology Study group, using baseline and follow-up estimates after 4 years. In our analysis, the accelerated brain atrophy in normal aging was observed across regions (e.g., brain tissue: -0.098 ± 0.01 mL/y, p < 0.001). An independent lifestyle-specific trend of brain atrophy across time was also evident in men, where smoking (p = 0.012) and physical activity (p = 0.014) showed the strongest association with the atrophy rate. Linear regression analysis of the interconnected effect revealed that brain atrophy is mitigated by intense physical activity in smoking males. Lifestyle factors did not show any significant effect on brain volume in women. These results provide important information regarding lifestyle factors that affect brain aging in mid-to-late adulthood. Our findings may aid in the identification of preventive measures against dementia.

Additive Effect of Cigarette Smoking on Gray Matter Abnormalities in Schizophrenia

It is widely known that there is a high prevalence of cigarette smoking in schizophrenia. One of the explanations is the self-medication hypothesis. Based on this hypothesis, it has been suggested that nicotine has procognitive effect or even neuroprotective effect in schizophrenia. However, cigarettes contain numerous neurotoxic substances, making the net effect of cigarette smoking on brain function and structure complex. Indeed, recent studies have called into question the self-medication hypothesis. We aimed to test whether there is an interaction between diagnosis and smoking status in gray matter volume, ie, whether smoking has specific effects on gray matter or whether main effects of these 2 variables additively affect common brain regions. Magnetic resonance imaging (MRI) images were obtained from 4 groups: (1) normal controls with no smoking history, (2) normal controls currently smoking and/or with a past history of smoking, (3) schizophrenia patients with no smoking history, and (4) schizophrenia patients currently smoking and/or with a past history of smoking. We used voxel-based morphometry to compare gray matter volumes among the 4 groups. We did not find any interaction between diagnosis and smoking, but we did find negative additive effects of schizophrenia diagnosis and smoking status in the left prefrontal cortex. The decrease in left prefrontal volume was associated with greater numbers of cigarette pack years and severe positive and negative symptoms. The current findings do not support the neuroprotective effect of smoking on gross brain structure in schizophrenia, emphasizing the necessity of longitudinal studies to test causal relationships among these variables.

Association of smoking but not HLA-DRB1*15:01, APOE or body mass index with brain atrophy in early multiple sclerosis

BACKGROUND

The course of multiple sclerosis (MS) shows substantial inter-individual variability. The underlying determinants of disease severity likely involve genetic and environmental factors.

OBJECTIVE

The aim of this study was to assess the impact of APOE and HLA polymorphisms as well as smoking and body mass index (BMI) in the very early MS course.

METHODS

Untreated patients ( n = 263) with a recent diagnosis of relapsing-remitting (RR) MS or clinically isolated syndrome underwent standardized magnetic resonance imaging (MRI). Genotyping was performed for single-nucleotide polymorphisms (SNPs) rs3135388 tagging the HLA-DRB1*15:01 haplotype and rs7412 (Ɛ2) and rs429358 (Ɛ4) in APOE. Linear regression analyses were applied based on the three SNPs, smoking and BMI as exposures and MRI surrogate markers for disease severity as outcomes.

RESULTS

Current smoking was associated with reduced gray matter fraction, lower brain parenchymal fraction and increased cerebrospinal fluid fraction in comparison to non-smoking, whereas no effect was observed on white matter fraction. BMI and the SNPs in HLA and APOE were not associated with structural MRI parameters.

CONCLUSIONS

Smoking may have an unfavorable effect on the gray matter fraction as a potential measure of MS severity already in early MS. These findings may impact patients' counseling upon initial diagnosis of MS.

Longitudinal assessment of gray matter volumes and white matter integrity in patients with medication-overuse headache

Background Medication-overuse headache is a common clinical entity, but neuroimaging studies investigating volumetric and microstructural alterations of the brain in medication-overuse headache are rare. Therefore, in the current longitidunal study we evaluated gray matter volume and white matter integrity in patients with medication-overuse headache before and after drug withdrawal. Methods A prospective study evaluated 27 patients with medication-overuse headache and 27 age-, sex-, and education-matched healthy adults. High-resolution T1-weighted magnetic resonance imaging and diffusion tensor imaging were obtained from the control group and medication-overuse headache patients before and six months after drug withdrawal. Tract-based spatial statistics of multiple diffusivity indices and voxel-based morphometry were employed to investigate white and gray matter abnormalities. Results No correlation was found between age, gender, education and smoking status in both groups. The most commonly overused medications were simple analgesics (96.3%) and combined analgesics (3.7%). The mean duration of the history of medication overuse and headaches was 56.7 ± 63.5 months. White matter diffusional and gray matter morphological alterations including volume, fractional anisotropy, radial diffusivity, and axial diffusivity analyses showed no significant relationship in the patients before and six months after withdrawal of analgesics. Also no difference was observed between the patients versus controls. Conclusion Our data demonstrated no structural alterations within the brain in medication-overuse headache.

Altered function but not structure of the amygdala in nicotine-dependent individuals

Tobacco use disorder is frequently comorbid with emotional disorders, each exerting reciprocal influence on the other. As an important hub for emotional processing, amygdala may also play a critical role in tobacco addiction. Therefore, we aimed to investigate the volume and spontaneous activity of the amygdala in nicotine-dependent individuals and their relationships with cigarette use. A total of 84 smokers (aged 22-54 years) and 41 nonsmokers (aged 26-56 years) were enrolled in the present study. 3D-T1 weighted images and resting-state fMRI images were acquired from all participants. We used ROI-wise volume, fractional amplitude of low frequency fluctuation (fALFF) and resting-state functional connectivity (FC) to assess structural and functional changes of the amygdala in the smokers. There was no significant difference between smokers and nonsmokers on amygdala volume (p > 0.05). When compared to nonsmokers, increased fALFF in the right amygdala was observed in smokers (p = 0.024). In addition, increased FC between the left amygdala and the right precuneus and decreased FC between the right amygdala and the right orbitofrontal cortex (OFC) was found in smokers. In smokers, these amygdala measures did not correlate with any measures of cigarette use. The results revealed that the amygdala function but not volume was affected in nicotine addiction. When considering the fALFF and FC results, we propose that the OFC top-down control may regulate the amygdala activity in nicotine addicts. The pattern of amygdala-based FC in smokers revealed in our study may provide new information about the brain circuitry of tobacco dependence.

Resting-State Functional Connectivity of the Basal Nucleus of Meynert in Cigarette Smokers: Dependence Level and Gender Differences

Introduction

Numerous studies have characterized impaired cerebral functioning in nicotine-addicted individuals. Whereas nicotine interacts with multiple neurotransmitters in cortical and subcortical circuits, it directly targets the cholinergic system, sourced primarily from the basal nucleus of Meynert (BNM). However, no studies have examined how this cholinergic system is influenced by cigarette smoking. Here, we addressed this gap of research.

Methods

Using a dataset from the Functional Connectome Projects, we investigated this issue by contrasting seed-based BNM connectivity of 40 current smokers and 170 age- and gender-matched nonsmokers. We followed our data analytic routines in recent work and examined differences between smokers and nonsmokers in men and women combined as well as separately.

Results

Compared to nonsmokers, female but not male smokers demonstrated greater positive BNM connectivity to the supplementary motor area, bilateral anterior insula, and right superior temporal/supramarginal gyri as well as greater negative connectivity to the posterior cingulate cortex and precuneus. Further, BNM connectivity to the supplementary motor area is negatively correlated to the Fagerström Test for Nicotine Dependence score in male but not female smokers.

Conclusions

Along with a previous report of upregulated nicotinic acetylcholine receptor in male but not female smokers, these new findings highlight functional changes of the cholinergic systems in cigarette smokers. The results suggest sex-specific differences in cholinergic dysregulation and a need for multiple imaging modalities to capture the neural markers of nicotine addiction.

Implications

Nicotine influences cognition via cholinergic projections of the basal forebrain to the cerebral cortex. This study examined changes in resting-state whole-brain functional connectivity of the BNM in cigarette smokers. The new findings elucidate for the first time sex differences in BNM-cerebral connectivity in cigarette smoking.

Altered White Matter Integrity in Smokers Is Associated with Smoking Cessation Outcomes

Smoking is a significant cause of preventable mortality worldwide. Understanding the neural mechanisms of nicotine addiction and smoking cessation may provide effective targets for developing treatment strategies. In the present study, we explored whether smokers have white matter alterations and whether these alterations are related to cessation outcomes and smoking behaviors. Sixty-six smokers and thirty-seven healthy non-smokers were enrolled. The participants underwent magnetic resonance imaging scans and smoking-related behavioral assessments. After a 12-week treatment with varenicline, 28 smokers succeeded in quitting smoking and 38 failed. Diffusion parameter maps were compared among the non-smokers, future quitters, and relapsers to identify white matter differences. We found that the future relapsers had significantly lower fractional anisotropy (FA) in the orbitofrontal area than non-smokers, and higher FA in the cerebellum than non-smokers and future quitters. The future quitters had significantly lower FA in the postcentral gyrus compared to non-smokers and future relapsers. Compared to non-smokers, pooled smokers had lower FA in bilateral orbitofrontal gyrus and left superior frontal gyrus. In addition, regression analysis showed that the left orbitofrontal FA was correlated with smoking-relevant behaviors. These results suggest that white matter alterations in smokers may contribute to the formation of aberrant brain circuits underlying smoking behaviors and are associated with future smoking cessation outcomes.

Smoking and olfactory dysfunction: A systematic literature review and meta-analysis

OBJECTIVES/HYPOTHESIS

A systematic review and meta-analysis of the literature was undertaken, examining the association between tobacco smoking and olfactory function in humans, utilizing PubMed and Web of Science (1970-2015) as data sources.

STUDY DESIGN

Systematic literature review and meta-analysis.

METHODS

This database review of studies of smoking and olfaction, with a focus on identifying high-quality studies (based on modified versions of the Newcastle-Ottawa Scale), used validated olfactory tests among the generally healthy population.

RESULTS

We identified 11 studies meeting inclusion criteria. Of 10 cross-sectional studies, two were excluded from meta-analysis because the cohorts they studied were included in another article in the review. In meta-analysis, current smokers had substantially higher odds of olfactory dysfunction compared to never smokers (odds ratio [OR] = 1.59, 95% confidence interval [CI] = 1.37-1.85). In contrast, former smokers were found to have no difference in risk of impaired olfaction compared to never smokers (OR = 1.05, 95% CI = 0.91-1.21). The single longitudinal study reviewed found a trend toward increased risk of olfactory decline over time in ever smokers; this trend was stronger in current as compared to former smokers.

CONCLUSIONS

Current smoking, but not former smoking, is associated with significantly increased risk of olfactory dysfunction, suggesting that the effects of smoking on olfaction may be reversible. Future studies that prospectively evaluate the impact of smoking cessation on improvement in olfactory function are warranted.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 127:1753-1761, 2017.

Difference in the functional connectivity of the dorsolateral prefrontal cortex between smokers with nicotine dependence and individuals with internet gaming disorder

Background

It has been reported that internet gaming disorder (IGD) and smokers with nicotine dependence (SND) share clinical characteristics, such as over-engagement despite negative consequences and cravings. This study is to investigate the alterations in the resting-state functional connectivity (rsFC) of the dorsolateral prefrontal cortex (DLPFC) observed in SND and IGD. In this study, 27 IGD, 29 SND, and 33 healthy controls (HC) underwent a resting-state functional magnetic resonance imaging (rs-fMRI) scan. DLPFC connectivity was determined in all participates by investigating the synchronized low-frequency fMRI signal fluctuations using a temporal seed-based correlation method.

Results

Compared with the HC group, the IGD and SND groups showed decreased rsFC with DLPFC in the right insula and left inferior frontal gyrus with DLPFC. Compared with SND group, the IGD subjects exhibited increased rsFC in the left inferior temporal gyrus and right inferior orbital frontal gyrus and decreased rsFC in the right middle occipital gyrus, supramarginal gyrus, and cuneus with DLPFC.

Conclusion

Our results confirmed that SND and IGD share similar neural mechanisms related to craving and impulsive inhibitions. The significant difference in rsFC with DLPFC between the IGD and SND subjects may be attributed to the visual and auditory stimulation generated by long-term internet gaming.

Effects of abstinence and chronic cigarette smoking on white matter microstructure in alcohol dependence: Diffusion tensor imaging at 4T

BACKGROUND

We previously reported widespread microstructural deficits of brain white matter in alcohol-dependent individuals (ALC) compared to light drinkers in a small 1.5T diffusion tensor imaging study employing tract-based spatial statistics. Using a larger dataset acquired at 4T, the present study is an extension that investigated the effects of alcohol consumption, abstinence from alcohol, and comorbid cigarette smoking on white matter microstructure.

METHODS

Tract-based spatial statistics were performed on 20 1-week-abstinent ALC, 52 1-month-abstinent ALC, and 30 controls. Regional measures of fractional anisotropy (FA) and mean diffusivity (MD) in the significant clusters were compared by Analysis of Covariance. The metrics were correlated with substance use history and behavioral measures.

RESULTS

1-week-abstinent ALC showed lower FA than controls in the corpus callosum, right cingulum, external capsule, and hippocampus. At 1 month of abstinence, only the FA in the body of the corpus callosum of ALC remained significantly different from controls. Some regional FA deficits correlated with more severe measures of drinking and smoking histories but only weakly with mood and impulsivity measures.

CONCLUSION

White matter microstructure is abnormal during early abstinence in alcohol dependent treatment seekers and recovers into the normal range within about four weeks. The compromised white matter was related to substance use severity, mood, and impulsivity. Our findings suggest that ALC may benefit from interventions that facilitate normalization of DTI metrics to maintain abstinence, via smoking cessation, cognitive-based therapy, and perhaps pharmacology to support remyelination.

Decreased Central Nervous System Grey Matter Volume (GMV) in Smokers Affects Cognitive Abilities: A Systematic Review

Although cigarette smoking is a leading cause of preventable mortality, tobacco is consumed by approximately 22% of the adult population worldwide. Smoking is also a risk factor for cardiovascular disease, affects brain processing, and is a recognized risk factor for Alzheimer disease (AD). Tobacco toxins (e.g., nicotine at high levels) inhaled in smoke may cause disorders resulting in preclinical brain changes. Researchers suggest that there are differences in brain volume between smokers and non-smokers. This review examines these differences in brain grey matter volume (GMV). In March/April 2015, MedLine, Embase, and PsycINFO were searched using the terms: "grey matter" AND "voxel-based" AND "smoking" AND "cigarette". The 4 studies analyzed found brain GMV decreases in smokers compared to non-smokers. Furthermore, sex-specific differences were found; while the thalamus and cerebellum were affected in both sexes, decreased GMV in the olfactory gyrus was found only in male smokers. Age-group differences were also found, and these may suggest pre-existing abnormalities that lead to nicotine dependence in younger individuals. Only 1 study found a positive correlation between number of pack-years smoked and GMV. Smoking decreases GMV in most brain areas. This decrease may be responsible for the cognitive impairment and difficulties with emotional regulation found in smokers compared with non-smokers.

Association Between Baseline Corticothalamic-Mediated Inhibitory Control and Smoking Relapse Vulnerability

IMPORTANCE

Tobacco use disorder is associated with dysregulated neurocognitive function in the right inferior frontal gyrus (IFG)-one node in a corticothalamic inhibitory control (IC) network.

OBJECTIVE

To examine associations between IC neural circuitry structure and function and lapse/relapse vulnerability in 2 independent studies of adult smokers.

DESIGN, SETTING, AND PARTICIPANTS

In study 1, treatment-seeking smokers (n = 81) completed an IC task during functional magnetic resonance imaging (fMRI) before making a quit attempt and then were followed up for 10 weeks after their quit date. In study 2, a separate group of smokers (n = 26) performed the same IC task during fMRI, followed by completing a laboratory-based smoking relapse analog task. Study 1 was performed at Duke University Medical Center between 2008 and 2012; study 2 was conducted at the Medical University of South Carolina between 2013 and 2016.

MAIN OUTCOMES AND MEASURES

Associations between corticothalamic-mediated IC, gray-matter volume, and smoking lapse/relapse.

RESULTS

Of the 81 study participants in study 1 (cessation study), 45 were women (56%), with mean (SD) age, 38.4 (10.2) years. In study 1, smoking relapse was associated with less gray-matter volume (F1,74 = 28.32; familywise error P threshold = 0.03), greater IC task-related blood oxygenation level-dependent (BOLD) response in the right IFG (F1,78 = 14.87) and thalamus (F1,78 = 14.97) (P < .05), and weaker corticothalamic task-based functional connectivity (tbFC) (F1,77 = 5.87; P = .02). Of the 26 participants in study 2 (laboratory study), 15 were women (58%), with mean (SD) age, 34.9 (10.3). Similar to study 1, in study 2, greater IC-BOLD response in the right IFG (t23 = -2.49; β = -0.47; P = .02), and weaker corticothalamic tbFC (t22 = 5.62; β = 0.79; P < .001) were associated with smoking sooner during the smoking relapse-analog task. In both studies, corticothalamic tbFC mediated the association between IC performance and smoking outcomes.

CONCLUSIONS AND RELEVANCE

In these 2 studies, baseline differences in corticothalamic circuitry function were associated with mediated IC and smoking relapse vulnerability. These findings warrant further examination of interventions for augmenting corticothalamic neurotransmission and enhancing IC during the course of tobacco use disorder treatment.

Structural Neuroimaging in Polysubstance Users

The simultaneous and/or concurrent use of licit and illicit substances (polysubstance use, PSU) is most common today. Structural magnetic resonance imaging (MRI) has been applied extensively to study individuals ostensibly using a single substance. These studies have produced a picture of regional gray matter and white matter alterations with each substance or class of substances. Very few studies measured regional brain morphometry in today's polysubstance users. This limited data suggest morphometric alterations with PSU that are not simply additive but often different from those of monosubstance users. Specifically, subcortical volume enlargements are observed that may be tied to mechanisms that also oppose volume reductions in cortical brain regions, thereby underestimating actual cortical atrophy. The complex actions of polysubstance use on brain structure and function need greater scrutiny with strong methodological approaches to inform more efficient treatment of polysubstance users.

Laterality of Brain Activation for Risk Factors of Addiction

Background:

Laterality of brain activation is reported for tests of risk factors of addiction - impulsivity and craving - but authors rarely address the potential significance of those asymmetries.

Objective:

The purpose of this study is to demonstrate this laterality and discuss its relevance to cognitive and neurophysiological asymmetries associated with drug abuse vulnerability in order to provide new insights for future research in drug abuse.

Method:

From published reports, brain areas of activation for two tests of response inhibition or craving for drugs of abuse were compiled from fMRI activation peaks and were tabulated for eight sections (octants) in each hemisphere. Percent asymmetries were calculated (R-L/R+L) across studies for each area.

Results:

For impulsivity, most activation peaks favored the right hemisphere. Overall, the percent difference was 32% (Χ² = 16.026; p < 0.0001) with the greater asymmetry for anterior peaks (46.8%; Χ² = 17.329; p < 0.0001). The asymmetries for cue-induced craving were opposite, favoring the left hemisphere by 6.7% (Χ² = 4.028; p < 0.05). The consistency of left asymmetry was found for almost all drugs. For nicotine, studies where subjects were not allowed to smoke (deprived) prior to measurement had the same left hemisphere activation but those who smoked (satiated) before the fMRI measure showed right asymmetry.

Conclusion:

Brain activation studies demonstrate different left/right hemispheric contributions for impulsivity versus craving - factors related to addiction. Failure to take laterality into consideration is a missed opportunity in designing studies and gaining insight into the etiology of drug abuse and pathways for treatment.

Behavioral impulsivity mediates the relationship between decreased frontal gray matter volume and harmful alcohol drinking: A voxel-based morphometry study

Alcohol use disorder (AUD) with harmful drinking patterns is on the one hand characterized by impulsive behavior and is on the other hand known to involve structural brain alterations with lower gray matter volume (GMV), especially in the prefrontal cortex (PFC). So far it is unclear whether frontal brain volumes are associated to harmful alcohol drinking and impulsivity, while controlling simultaneously for a wide array of important confounding factors, which are related to alcohol consumption. We used voxel-based morphometry in 99 adults ranging within a continuum of normal to harmful drinking behavior and alcohol dependence, measured by the 'Alcohol Use Disorders Identification Test', to examine whether the severity of harmful drinking is correlated with structural markers, in particular in the PFC and whether such markers are linked to self-reported impulsivity. We included alcohol and nicotine lifetime exposure, age, education, and BMI as covariates to control that GMV decreases were not related to those factors. Harmful drinking was associated with lower GMV in the right frontal pole, left inferior frontal gyrus, and bilateral inferior parietal lobe. GMV loss in the PFC regions was correlated with increased impulsivity. Follow-up mediation analyses showed that the relationship between GMV in the frontal pole and harmful drinking was mediated by impulsivity. Our findings show that PFC reductions are associated with harmful drinking and impulsivity. Our data suggest that reduced frontal pole GM, independent of a number of alcohol drinking associated covariates, e.g. lifetime alcohol consumption, is related to impaired top-down control of alcohol drinking behavior.

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration

BACKGROUND

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking.

OBJECTIVE

This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins.

METHODS

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs.

RESULTS

CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling.

CONCLUSION

Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

The search for imaging biomarkers in psychiatric disorders

The field of medicine is moving toward the use of biomarkers for the optimization of individualized care. This is a particular challenge for the field of psychiatry, in which diagnosis is based on a descriptive collection of behaviors without the availability of any objective test to stratify patients. Neuroimaging techniques such as molecular imaging with positron-emission tomography (PET) or structural and functional magnetic resonance imaging (MRI) provide an opportunity to bring psychiatry from an era of subjective descriptive classification into objective and tangible brain-based measures. Here we provide steps toward the development of robust, reliable and valid biomarkers. The success of such development is crucial because it will enable the field of psychiatry to move forward into the era of modern medicine.

Functional Connectivity Abnormalities of Brain Regions with Structural Deficits in Young Adult Male Smokers

Smoking is one of the most prevalent dependence disorders. Previous studies have detected structural and functional deficits in smokers. However, few studies focused on the changes of resting state functional connectivity (RSFC) of the brain regions with structural deficits in young adult smokers. Twenty-six young adult smokers and 26 well-matched healthy non-smokers participated in our study. Voxel-based morphometry (VBM) and RSFC were employed to investigate the structural and functional changes in young adult smokers. Compared with healthy non-smokers, young smokers showed increased gray matter (GM) volume in the left putamen and decreased GM volume in the left anterior cingulate cortex (ACC). Moreover, GM volume in the left ACC has a negative correlation trend with pack-years and GM volume in the left putamen was positively correlated with pack-years. The left ACC and putamen with abnormal volumes were chosen as the regions of interest (ROIs) for the RSFC analysis. We found that smokers showed increased RSFC between the left ACC and right amygdala and between the left putamen and right anterior insula. We revealed structural and functional deficits within the frontostriatal circuits in young smokers, which may shed new insights into the neural mechanisms of smoking.

A Bidirectional Relationship between Executive Function and Health Behavior: Evidence, Implications, and Future Directions

Physically active lifestyles and other health-enhancing behaviors play an important role in preserving executive function into old age. Conversely, emerging research suggests that executive functions facilitate participation in a broad range of healthy behaviors including physical activity and reduced fatty food, tobacco, and alcohol consumption. They do this by supporting the volition, planning, performance monitoring, and inhibition necessary to enact intentions and override urges to engage in health damaging behavior. Here, we focus firstly on evidence suggesting that health-enhancing behaviors can induce improvements in executive function. We then switch our focus to findings linking executive function to the consistent performance of health-promoting behaviors and the avoidance of health risk behaviors. We suggest that executive function, health behavior, and disease processes are interdependent. In particular, we argue that a positive feedback loop may exist whereby health behavior-induced changes in executive function foster subsequent health-enhancing behaviors, which in turn help sustain efficient executive functions and good health. We conclude by outlining the implications of this reciprocal relationship for intervention strategies, the design of research studies, and the study of healthy aging.