Differences between smokers and nonsmokers in regional gray matter volumes and densities

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

Nicotine modulates prefrontal processing when tested with functional imaging. Previous studies on changes in regional brain volumes in small samples, reporting different life-time exposure to nicotine, identified reduced volume in smokers in prefrontal areas but reported controversial results for other areas. We investigated the association of cigarette smoking and regional gray and white matter volume by using voxel-based morphometry (VBM) for T1-weighted high-resolution magnetic resonance imaging in 315 current-smokers and 659 never-smokers from the representative Study of Health in Pomerania (SHIP). Our study showed that in current-smokers smoking is significantly associated with gray matter volume loss in the prefrontal cortex, the anterior cingulate cortex, the insula, and the olfactory gyrus. White matter volumes were not relevantly reduced in current-smokers. In current-smokers, we found associations of gray matter loss and smoking exposure (pack-years) in the prefrontal cortex, the anterior and middle cingulate cortex, and the superior temporal and angular gyrus, which however did not stand corrections for multiple testing. We confirmed associations between smoking and gray matter differences in the prefrontal cortex, the anterior cingulate cortex and the insula in the general population of Pomerania (Germany). For the first time, we identified differences in brain volumes in the olfactory gyrus. Other cerebral regions did not show significant differences when correcting for multiple comparisons within the whole brain. The regions of structural deficits might be involved in addictive behavior and withdrawal symptoms, whereas further investigations have to show if the observed atrophies were caused by smoking itself or are preexisting differences between smoking and non-smoking individuals.

Genetic, psychosocial and clinical factors associated with hippocampal volume in the general population

The hippocampus--crucial for memory formation, recall and mood regulation--is involved in the pathophysiology of dementia and depressive disorders. Recent genome-wide association studies (GWAS) have identified five genetic loci associated with hippocampal volume (HV). Previous studies have described psychosocial and clinical factors (for example, smoking, type 2 diabetes and hypertension) to have an impact on HV. However, the interplay between genetic, psychosocial and clinical factors on the HV remains unclear. Still, it is likely that genetic variants and clinical or psychosocial factors jointly act in modifying HV; it might be possible they even interact. Knowledge of these factors might help to quantify ones individual risk of or rather resilience against HV loss. We investigated subjects (N=2463; 55.7% women; mean age 53 years) from the Study of Health in Pomerania (SHIP-2; SHIP-TREND-0) who underwent whole-body magnetic resonance imaging (MRI) and genotyping. HVs were estimated with FreeSurfer. For optimal nonlinear model fitting, we used regression analyses with restricted cubic splines. Genetic variants and associated psychosocial or clinical factors were jointly assessed for potential two-way interactions. We observed associations between HV and gender (P<0.0001), age (P<0.0001), body height (P<0.0001), education (P=0.0053), smoking (P=0.0058), diastolic blood pressure (P=0.0211), rs7294919 (P=0.0065), rs17178006 (P=0.0002), rs6581612 (P=0.0036), rs6741949 (P=0.0112) and rs7852872 (P=0.0451). In addition, we found three significant interactions: between rs7294919 and smoking (P=0.0473), rs7294919 and diastolic blood pressure (P=0.0447) and between rs7852872 and rs6581612 (P=0.0114). We suggest that these factors might have a role in the individual susceptibility to hippocampus-associated disorders.

Adolescent brain maturation and smoking: what we know and where we're headed

Smoking is a leading cause of mortality and morbidity worldwide. Smoking initiation often occurs during adolescence. This paper reviews and synthesizes adolescent development and nicotine dependence literatures to provide an account of adolescent smoking from onset to compulsive use. We extend neurobiological models of adolescent risk-taking, that focus on the interplay between incentive processing and cognitive control brain systems, through incorporating psychosocial and contextual factors specific to smoking, to suggest that adolescents are more vulnerable than adults to cigarette use generally, but that individual differences exist placing some adolescents at increased risk for smoking. Upon smoking, adolescents are more likely to continue smoking due to the increased positive effects induced by nicotine during this period. Continued use during adolescence, may be best understood as reflecting drug-related changes to neural systems underlying incentive processing and cognitive control, resulting in decision-making that is biased towards continued smoking. Persistent changes following nicotine exposure that may underlie continued dependence are described. We highlight ways that interventions may benefit from a consideration of cognitive-neuroscience findings.

Dual role of nicotine in addiction and cognition: a review of neuroimaging studies in humans

Substantial evidence demonstrates both nicotine's addiction liability and its cognition-enhancing effects. However, the neurobiological mechanisms underlying nicotine's impact on brain function and behavior remain incompletely understood. Elucidation of these mechanisms is of high clinical importance and may lead to improved therapeutics for smoking cessation as well as for a number of cognitive disorders such as schizophrenia. Neuroimaging techniques such as positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI), which make it possible to study the actions of nicotine in the human brain in vivo, play an increasingly important role in identifying these dual mechanisms of action. In this review, we summarize the current state of knowledge and discuss outstanding questions and future directions in human neuroimaging research on nicotine and tobacco. This research spans from receptor-level PET and SPECT studies demonstrating nicotine occupancy at nicotinic acetylcholine receptors (nAChRs) and upregulation of nAChRs induced by chronic smoking; through nicotine's interactions with the mesocorticolimbic dopamine system believed to mediate nicotine's reinforcing effects leading to dependence; to functional activity and connectivity fMRI studies documenting nicotine's complex behavioral and cognitive effects manifest by its actions on large-scale brain networks engaged both during task performance and at rest. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.

Mood, mood regulation, and frontal systems functioning in current smokers, long-term abstinent ex-smokers, and never-smokers

Indices of mood, mood regulation, and executive functioning were examined in 61 current smokers who have smoked daily for at least one year, 36 ex-smokers who had not smoked a cigarette for at least one year, and 86 never-smokers. All participants completed the following measures online: Depression Anxiety Stress Scales (DASS-21), the Negative Mood Regulation (NMR) scale, the Frontal Systems Behavior Scale (FrSBe), the Fagerström Test for Cigarette Dependence (FTCD), and the Alcohol Use Disorders Identification Test (AUDIT). Multivariate analysis of variance (MANOVA) followed by Tukey post-hoc tests revealed significant differences (p < .01) such that current smokers indicated worse functioning than both ex-smokers and never-smokers on DASS, NMR, and FrSBe, as well as heavier drinking as measured by AUDIT. These differences remained significant even after controlling for AUDIT scores. Results most plausibly reflect a return to pre-smoking baseline brain function in long-term abstinent ex-smokers.

The effects of chronic cigarette smoking on gray matter volume: influence of sex

Cigarette smoke contains nicotine and toxic chemicals and may cause significant neurochemical and anatomical brain changes. Voxel-based morphometry studies have examined the effects of smoking on the brain by comparing gray matter volume (GMV) in nicotine dependent individuals (NDs) to nonsmoking individuals with inconsistent results. Although sex differences in neural and behavioral features of nicotine dependence are reported, sex differences in regional GMV remain unknown. The current study examined sex differences in GMV in a large sample of 80 NDs (41 males) and 80 healthy controls (41 males) using voxel-based morphometry. Within NDs, we explored whether GMV was correlated with measures of cigarette use and nicotine dependence. High-resolution T1 structural scans were obtained from all participants. Segmentation and registration were performed in SPM8 using the optimized DARTEL approach. Covariates included age and an estimate of total global GMV. Differences were considered significant at p≤0.001, with a whole brain FWE-corrected cluster probability of p<0.025. Among NDs compared to Controls less GMV was observed in the thalamus and bilateral cerebellum and greater GMV was observed in the bilateral putamen and right parahippocampus. Lower thalamic GMV was observed in both female and male NDs compared to Controls. Female NDs also had lower GMV in the left cerebellum and in the ventral medial and orbitofrontal cortices with no areas of greater GMV. Male NDs had lower GMV in bilateral cerebellum and greater GMV in bilateral parahippocampus and left putamen. Within male NDs, GMV in the left putamen was correlated with number of pack years. This study, conducted in a large cohort, contributes to our knowledge of brain morphology in nicotine addiction and provides additional evidence of sex-specific effects on GMV in NDs. Identifying brain vulnerabilities with respect to sex provides a methodological framework for personalized therapies to improve relapse rates for both sexes.

The neural mechanisms underlying the acute effect of cigarette smoking on chronic smokers

Although previous research had related structural changes and impaired cognition to chronic cigarette smoking, recent neuroimaging studies have associated nicotine, which is a main chemical substance in cigarettes, with improvements in cognitive functions (e.g. improved attention performance). However, information about the alterations of whole-brain functional connectivity after acute cigarette smoking is limited. In this study, 22 smokers underwent resting-state functional magnetic resonance imaging (rs-fMRI) after abstaining from smoking for 12 hours (state of abstinence, SOA). Subsequently, the smokers were allowed to smoke two cigarettes (state of satisfaction, SOS) before they underwent a second rs-fMRI. Twenty non-smokers were also recruited to undergo rs-fMRI. In addition, high-resolution 3D T1-weighted images were acquired using the same magnetic resonance imaging(fMRI)scanner for all participants. The results showed that smokers had structural changes in insula, thalamus, medial frontal cortex and several regions of the default mode network (DMN) compared with non-smokers. Voxel-wise group comparisons of newly developed global brain connectivity (GBC) showed that smokers in the SOA condition had higher GBC in the insula and superior frontal gyrus compared with non-smokers. However, smokers in the SOS condition demonstrated significantly lower GBC in several regions of the DMN, as compared with smokers in the SOA condition. These results suggest that structural integrity combined with dysfunction of the DMN might be involved in relapses after a short period of time among smokers.

Pretreatment measures of brain structure and reward-processing brain function in cannabis dependence: an exploratory study of relationships with abstinence during behavioral treatment

BACKGROUND

Cannabis is widely abused, and efficacies of therapeutics for cannabis dependence remain suboptimal. Magnetic resonance imaging (MRI) may aid in the identification of biological markers for successful treatment outcomes (i.e., abstinence).

METHODS

Twenty men with cannabis dependence and twenty non-substance-using healthy comparison (HC) men underwent MRI scanning. Cannabis-dependent individuals then participated in a 12-week randomized clinical trial of behavioral treatments (contingency management (CM), cognitive behavioral therapy (CBT) or both). Pretreatment functional and structural data were compared between the cannabis-dependent and HC participants. In addition, individuals with cannabis dependence were subdivided based on the successful achievement of 21 days of consecutive abstinence during treatment to assess whether abstinent versus non-abstinent cannabis-dependent participants displayed different pretreatment functional and structural characteristics when compared to HC participants.

RESULTS

In comparison to HC participants, cannabis-dependent participants demonstrated greater ventral striatal activation during the receipt of losing outcomes and smaller putamenal volumes. Cannabis-dependent participants who did not subsequently achieve 21 days of consecutive abstinence had increased activity within the striatum during the receipt of losing outcomes, relative to HC participants. Cannabis-dependent participants who did not achieve 21 days of abstinence had decreased bilateral putamen volumes prior to treatment, relative to HC participants.

CONCLUSIONS

Individual differences in pretreatment striatal function and structure may relate to individual differences in treatment responses for cannabis dependence. While mechanisms underlying these associations require further exploration, the striatum might mediate treatment responses via its role in associative reward-learning (e.g., through skills training in CBT or reinforcement of abstinence in CM).

Cigarette exposure, dependence, and craving are related to insula thickness in young adult smokers

The age period spanning late adolescence to emergent adulthood is associated with the highest prevalence of cigarette smoking in the United States, and is also a time of continued brain development. Nonetheless, although prior research has shown group differences in brain structure associated with smoking status in adults, few studies have examined how smoking and associated behavioral states relate to brain structure in this age group. Neuroimaging and lesion studies have suggested that the insula, a cortical region that integrates heterogeneous signals about internal states and contributes to executive functions, plays an important role in cigarette smoking behavior. Using high-resolution structural magnetic resonance imaging, we therefore measured cortical thickness of the insula in 18 smokers and 24 nonsmokers between the ages of 16 and 21 years. There were no group differences in insula thickness, but cigarette exposure (pack-years) was negatively associated with thickness in right insula. Cigarette dependence and the urge to smoke were negatively related to cortical thickness in the right ventral anterior insula. Although the results do not demonstrate causation, they do suggest that there are effects of cigarette exposure on brain structure in young smokers, with a relatively short smoking history. It is possible that changes in the brain due to prolonged exposure or to the progression of dependence lead to more extensive structural changes, manifested in the reported group differences between adult smokers and nonsmokers. Structural integrity of the insula may have implications for predicting long-term cigarette smoking and problems with other substance abuse in this population.

Machine learning classification of resting state functional connectivity predicts smoking status

Machine learning-based approaches are now able to examine functional magnetic resonance imaging data in a multivariate manner and extract features predictive of group membership. We applied support vector machine (SVM)-based classification to resting state functional connectivity (rsFC) data from nicotine-dependent smokers and healthy controls to identify brain-based features predictive of nicotine dependence. By employing a network-centered approach, we observed that within-network functional connectivity measures offered maximal information for predicting smoking status, as opposed to between-network connectivity, or the representativeness of each individual node with respect to its parent network. Further, our analysis suggests that connectivity measures within the executive control and frontoparietal networks are particularly informative in predicting smoking status. Our findings suggest that machine learning-based approaches to classifying rsFC data offer a valuable alternative technique to understanding large-scale differences in addiction-related neurobiology.

Smoking and increased Alzheimer's disease risk: a review of potential mechanisms

BACKGROUND

Cigarette smoking has been linked with both increased and decreased risk for Alzheimer's disease (AD). This is relevant for the US military because the prevalence of smoking in the military is approximately 11% higher than in civilians.

METHODS

A systematic review of published studies on the association between smoking and increased risk for AD and preclinical and human literature on the relationships between smoking, nicotine exposure, and AD-related neuropathology was conducted. Original data from comparisons of smoking and never-smoking cognitively normal elders on in vivo amyloid imaging are also presented.

RESULTS

Overall, literature indicates that former/active smoking is related to a significantly increased risk for AD. Cigarette smoke/smoking is associated with AD neuropathology in preclinical models and humans. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathology and increased risk for AD.

CONCLUSIONS

A reduction in the incidence of smoking will likely reduce the future prevalence of AD.

Vorinostat positively regulates synaptic plasticity genes expression and spine density in HIV infected neurons: role of nicotine in progression of HIV-associated neurocognitive disorder

Background

HIV-associated neurocognitive disorder (HAND) is characterized by development of cognitive, behavioral and motor abnormalities, and occurs in approximately 50% of HIV infected individuals. In the United States, the prevalence of cigarette smoking ranges from 35-70% in HIV-infected individuals compared to 20% in general population. Cognitive impairment in heavy cigarette smokers has been well reported. However, the synergistic effects of nicotine and HIV infection and the underlying mechanisms in the development of HAND are unknown.

Results

In this study, we explored the role of nicotine in the progression of HAND using SK-N-MC, a neuronal cell line. SK-N-MC cells were infected with HIV-1 in the presence or absence of nicotine for 7 days. We observed significant increase in HIV infectivity in SK-N-MC treated with nicotine compared to untreated HIV-infected neuronal cells. HIV and nicotine synergize to significantly dysregulate the expression of synaptic plasticity genes and spine density; with a concomitant increase of HDAC2 levels in SK-N-MC cells. In addition, inhibition of HDAC2 up-regulation with the use of vorinostat resulted in HIV latency breakdown and recovery of synaptic plasticity genes expression and spine density in nicotine/HIV alone and in co-treated SK-N-MC cells. Furthermore, increased eIF2 alpha phosphorylation, which negatively regulates eukaryotic translational process, was observed in HIV alone and in co-treatment with nicotine compared to untreated control and nicotine alone treated SK-N-MC cells.

Conclusions

These results suggest that nicotine and HIV synergize to negatively regulate the synaptic plasticity gene expression and spine density and this may contribute to the increased risk of HAND in HIV infected smokers. Apart from disrupting latency, vorinostat may be a useful therapeutic to inhibit the negative regulatory effects on synaptic plasticity in HIV infected nicotine abusers.

The cerebellum and addiction: insights gained from neuroimaging research

Although cerebellar alterations have been consistently noted in the addiction literature, the pathophysiology of this link remains unclear. The cerebellum is commonly classified as a motor structure, but human functional neuroimaging along with clinical observations in cerebellar stroke patients and anatomical tract tracing in non-human primates suggests its involvement in cognitive and affective processing. A comprehensive literature search on the role of the cerebellum in addiction was performed. This review article (1) considers the potential role of the cerebellum in addiction; (2) summarizes the cerebellar structural alterations linked to addiction; (3) presents the functional neuroimaging evidence linking the cerebellum with addiction; and (4) proposes a model for addiction that underscores the role of the cerebellum. The data implicate the cerebellum as an intermediary between motor and reward, motivation and cognitive control systems, as all are relevant etiologic factors in addiction. Furthermore, consideration of these findings could contribute to deeper and more sophisticated insights into normal reward and motivational function. The goal of this review is to spread awareness of cerebellar involvement in addictive processes, and to suggest a preliminary model for its potential role.

Postural stability in cigarette smokers and during abstinence from alcohol

BACKGROUND

Static postural instability is common in alcohol-dependent individuals (ALC). Chronic alcohol consumption has deleterious effects on the neural and perceptual systems subserving postural stability. However, little is known about the effects of chronic cigarette smoking on postural stability and its changes during abstinence from alcohol.

METHODS

A modified Fregly ataxia battery was administered to a total of 115 smoking (sALC) and nonsmoking ALC (nsALC) and to 71 smoking (sCON) and nonsmoking light/nondrinking controls (nsCON). Subgroups of abstinent ALC were assessed at 3 time points (TPs; approximately 1, 5, 34 weeks of abstinence from alcohol); a subset of nsCON was retested at 40 weeks. We tested whether cigarette smoking affects postural stability in CON and in ALC during extended abstinence from alcohol, and we used linear mixed effects modeling to measure change across TPs within ALC.

RESULTS

Chronic smoking was associated with reduced performance on the Sharpened Romberg eyes-closed task in abstinent ALC at all 3 TPs and in CON. The test performance of nsALC increased significantly between 1 and 32 weeks of abstinence, whereas the corresponding increases for sALC between 1 and 35 weeks were nonsignificant. With long-term abstinence from alcohol, nsALC recovered into the range of nsCON and sALC recovered into the range of sCON. Static postural stability decreased with age and correlated with smoking variables but not with drinking measures.

CONCLUSIONS

Chronic smoking was associated with reduced static postural stability with eyes closed and with lower increases of postural stability during abstinence from alcohol. Smoking cessation in alcohol dependence treatment may facilitate recovery from static postural instability during abstinence.

Intellectual, neurocognitive, and academic achievement in abstinent adolescents with cannabis use disorder

RATIONALE

The active component of cannabis, delta-9 tetrahydrocannabinol (THC), has a long half-life and widespread neurocognitive effects. There are inconsistent reports of neurocognitive deficits in adults and adolescents with cannabis use disorders (CUD), particularly after a period of abstinence.

OBJECTIVES

This study aims to examine neurocognitive measures (IQ, academic achievement, attention, memory, executive functions) in abstinent adolescents with CUD, while controlling for demographic, psychopathology, and poly-substance confounders.

METHODS

We investigated neurocognitive performance in three groups: adolescents with CUD after successful first treatment and in full remission (n = 33); controls with psychiatric disorders without substance use disorder history (n = 37); and healthy adolescents (n = 43).

RESULTS

Adolescents with psychiatric disorders, regardless of CUD status, performed significantly worse than the healthy adolescents in academic achievement. No group differences were seen in IQ, attention, memory, or executive functions. Lower academic achievement was positively associated with younger age of CUD onset, regular cannabis use, and maximum daily use. In the CUD group, lifetime nicotine use episodes were negatively associated with IQ. Lower overall neurocognitive function was associated with younger age of onset of regular cannabis use and relapse within the 1 year follow-up.

CONCLUSIONS

Verifiably, abstinent adolescents with CUD history did not differ from the two comparison groups, suggesting that previously reported neurocognitive deficits may be related to other factors, including residual drug effects, preexisting cognitive deficits, concurrent use of other substances (e.g., nicotine), or psychopathology. Adolescents with CUD may not be vulnerable to THC neuropsychological deficits once they achieve remission from all drugs for at least 30 days.

Chronic alcohol consumption and its effect on nodes of frontocerebellar and limbic circuitry: comparison of effects in France and the United States

Alcohol use disorders present a significant public health problem in France and the United States (U.S.), but whether the untoward effect of alcohol on the brain results in similar damage in both countries remains unknown. Accordingly, we conducted a retrospective collaborative investigation between two French sites (Caen and Orsay) and a U.S. laboratory (SRI/Stanford University) with T1-weighted, structural MRI data collected on a common imaging platform (1.5T, General Electric) on 288 normal controls (NC), 165 uncomplicated alcoholics (ALC), and 26 patients with alcoholic Korsakoff's syndrome (KS) diagnosed at all sites with a common interview instrument. Data from the two countries were pooled, then preprocessed and analyzed together at the U.S. site using atlas-based parcellation. National differences indicated that thalamic volumes were smaller in ALC in France than the U.S. despite similar alcohol consumption levels in both countries. By contrast, volumes of the hippocampus, amygdala, and cerebellar vermis were smaller in KS in the U.S. than France. Estimated amount of alcohol consumed over a lifetime, duration of alcoholism, and length of sobriety were significant predictors of selective regional brain volumes in France and in the U.S. The common analysis of MRI data enabled identification of discrepancies in brain volume deficits in France and the U.S. that may reflect fundamental differences in the consequences of alcoholism on brain structure between the two countries, possibly related to genetic or environmental differences.

Smoking status as a potential confounder in the study of brain structure in schizophrenia

Several but not all MRI studies have reported volume reductions in the hippocampus and dorsolateral prefrontal cortex (DLPFC) in patients with schizophrenia. Given the high prevalence of smoking among schizophrenia patients and the fact that smoking has also been associated with alterations in brain morphology, this study evaluated whether a proportion of the known gray matter reductions in key brain regions may be attributed to smoking rather than to schizophrenia alone. We examined structural MRI data of 112 schizophrenia patients (53 smokers and 59 non-smokers) and 77 healthy non-smoker controls collected by the MCIC study of schizophrenia. An automated atlas based probabilistic method was used to generate volumetric measures of the hippocampus and DLPFC. The two patient groups were matched with respect to demographic and clinical variables. Smoker schizophrenia patients showed significantly lower hippocampal and DLPFC volumes than non-smoker schizophrenia patients. Gray matter volume reductions associated with smoking status ranged between 2.2% and 2.8%. Furthermore, we found significant volume differences between smoker patients and healthy controls in the hippocampus and DLPFC, but not between non-smoker patients and healthy controls. Our data suggest that a proportion of the volume reduction seen in the hippocampus and DLPFC in schizophrenia is associated with smoking rather than with the diagnosis of schizophrenia. These results may have important implications for brain imaging studies comparing schizophrenia patients and other groups with a lower smoking prevalence.

Cannabis-related working memory deficits and associated subcortical morphological differences in healthy individuals and schizophrenia subjects

Cannabis use is associated with working memory (WM) impairments; however, the relationship between cannabis use and WM neural circuitry is unclear. We examined whether a cannabis use disorder (CUD) was associated with differences in brain morphology between control subjects with and without a CUD and between schizophrenia subjects with and without a CUD, and whether these differences related to WM and CUD history. Subjects group-matched on demographics included 44 healthy controls, 10 subjects with a CUD history, 28 schizophrenia subjects with no history of substance use disorders, and 15 schizophrenia subjects with a CUD history. Large-deformation high-dimensional brain mapping with magnetic resonance imaging was used to obtain surface-based representations of the striatum, globus pallidus, and thalamus, compared across groups, and correlated with WM and CUD history. Surface maps were generated to visualize morphological differences. There were significant cannabis-related parametric decreases in WM across groups. Similar cannabis-related shape differences were observed in the striatum, globus pallidus, and thalamus in controls and schizophrenia subjects. Cannabis-related striatal and thalamic shape differences correlated with poorer WM and younger age of CUD onset in both groups. Schizophrenia subjects demonstrated cannabis-related neuroanatomical differences that were consistent and exaggerated compared with cannabis-related differences found in controls. The cross-sectional results suggest that both CUD groups were characterized by WM deficits and subcortical neuroanatomical differences. Future longitudinal studies could help determine whether cannabis use contributes to these observed shape differences or whether they are biomarkers of a vulnerability to the effects of cannabis that predate its misuse.

Abnormal white matter integrity in the corpus callosum among smokers: tract-based spatial statistics

In the present study, we aimed to investigate the difference in white matter between smokers and nonsmokers. In addition, we examined relationships between white matter integrity and nicotine dependence parameters in smoking subjects. Nineteen male smokers were enrolled in this study. Eighteen age-matched non-smokers with no current or past psychiatric history were included as controls. Diffusion tensor imaging scans were performed, and the analysis was conducted using a tract-based special statistics approach. Compared with nonsmokers, smokers exhibited a significant decrease in fractional anisotropy (FA) throughout the whole corpus callosum. There were no significant differences in radial diffusivity or axial diffusivity between the two groups. There was a significant negative correlation between FA in the whole corpus callosum and the amount of tobacco use (cigarettes/day; R = - 0.580, p = 0.023). These results suggest that the corpus callosum may be one of the key areas influenced by chronic smoking.

Neuropathology of cigarette smoking

It is well established that cigarette smoking is hazardous to health and is a risk factor for many chronic diseases. However, its impact on the brain, whether it be from prenatal exposure to maternal cigarette smoking, cerebrovascular disease, Alzheimer's disease (AD) or Parkinson's disease, is still not very clear. Neuroimaging and neuropathological investigations suggest that there are heterogeneous effects of cigarette smoking on the brain. On the one hand, it is quite clear that cigarette smoking causes damage to endothelial cells, resulting in increased risk of cerebrovascular disease. On the other hand, it seems to be associated with different Alzheimer's pathologies in post-mortem brains and experimental models, despite the fact that epidemiological studies clearly indicate a positive correlation between cigarette smoking and increased risk for AD. Interestingly, cigarette smoking appears to be associated with reduced Parkinson's pathology in post-mortem brains. However, although nicotine in cigarettes may have some neuroprotective actions, the effects of all the other toxic compounds in cigarettes cannot be ignored. It is, therefore, our aim to summarize what is known about the neuropathology of cigarette smoking and, in particular, its implications for neurodegenerative diseases.

Interactive effects of chronic cigarette smoking and age on brain volumes in controls and alcohol-dependent individuals in early abstinence

Chronic alcohol-use disorders (AUDs) have been shown to interact with normal age-related volume loss to exacerbate brain atrophy with increasing age. However, chronic cigarette smoking, a highly co-morbid condition in AUD and its influence on age-related brain atrophy have not been evaluated. We performed 1.5 T quantitative magnetic resonance imaging in non-smoking controls [non-smoking light drinking controls (nsCONs); n = 54], smoking light drinking controls (sCONs, n = 34), and one-week abstinent, treatment-seeking alcohol-dependent (ALC) non-smokers (nsALCs, n = 35) and smokers (sALCs, n = 43), to evaluate the independent and interactive effects of alcohol dependence and chronic smoking on regional cortical and subcortical brain volumes, emphasizing the brain reward/executive oversight system (BREOS). The nsCONs and sALCs showed greater age-related volume losses than the nsALCs in the dorsal prefrontal cortex (DPFC), total cortical BREOS, superior parietal lobule and putamen. The nsALCs and sALCs demonstrated smaller volumes than the nsCONs in most cortical region of interests (ROIs). The sCONs had smaller volumes than the nsCONs in the DPFC, insula, inferior parietal lobule, temporal pole/parahippocampal region and all global cortical measures. The nsALCs and sALCs had smaller volumes than the sCONs in the DPFC, superior temporal gyrus, inferior and superior parietal lobules, precuneus and all global cortical measures. Volume differences between the nsALCs and sALCs were observed only in the putamen. Alcohol consumption measures were not related to volumes in any ROI for ALC; smoking severity measures were related to corpus callosum volume in the sCONs and sALCs. The findings indicate that consideration of smoking status is necessary for a better understanding of the factors contributing to regional brain atrophy in AUD.

The efficiency of functional brain networks does not differ between smokers and non-smokers

Acute nicotine consumption in smokers impacts on functional brain network topology indicating an increase in the efficiency of information transfer and attentional task performance. The effects of chronic nicotine consumption on functional brain network topology are unknown. We here investigated the effects of chronic smoking-behaviour on functional brain network topology. Minimally-deprived smokers (N=18) and non-smokers (N=17) were measured within an fMRI scanner during a resting state condition. Graph-theoretical metrics of functional network integration (global efficiency and clustering) that have been shown to be affected by acute nicotine administration were compared between both groups. Our results revealed that smoking status did not significantly change functional network integration. Additional tests for non-inferiority confirmed the similarity of regional or nodal network properties. Brain regions such as the left insular and middle frontal gyrus, in which acute nicotine consumption affected network topology, did not reveal any decrease in functional network efficiency following chronic nicotine consumption. Within the limitation of the investigated sample size, our data suggest that the integration of functional brain networks is not altered in minimally-deprived smokers. Our findings are of relevance for clinical studies showing changes in network topology between psychiatric patients with high prevalence of smoking and healthy control subjects.

Interactive effects of chronic cigarette smoking and age on hippocampal volumes

BACKGROUND

Previous cross-sectional MRI studies with healthy, young-to-middle-aged adults reported no significant differences between smokers and non-smokers on total hippocampal volume. However, these studies did not specifically test for greater age-related volume loss in the total hippocampus or hippocampal subregions in smokers, and did they did not examine relationships between hippocampal and subfield volumes and episodic learning and memory performance.

METHODS

Healthy, young-to-middle-aged (45 ± 12 years of age) smokers (n=39) and non-smokers (n=43) were compared on total hippocampal and subfield volumes derived from high-resolution 4 Tesla MRI, emphasizing testing for greater age-related volume losses in smokers. Associations between hippocampal volumes and measures of episodic learning and memory were examined.

RESULTS

Smokers showed significantly smaller volumes, as well as greater volume loss with increasing age than non-smokers in the bilateral total hippocampus and multiple subfields. In smokers, greater pack-years were associated with smaller volumes of the total hippocampus, presubiculum, and subiculum. In the entire cohort, performance on measures of learning and memory was related to larger total hippocampal and several subfield volumes, predominately in the left hemisphere.

CONCLUSIONS

Chronic cigarette smoking in this young-to-middle aged cohort was associated with smaller total hippocampal and subfield volumes, which were exacerbated by advancing age. Findings also indicated an adverse smoking dose/duration response (i.e., pack-years) with total hippocampal and select subfield volumes. These hippocampal volume abnormalities in smokers may be related to the deficiencies in episodic learning and memory in young-to-middle-aged smokers reported in previous studies.

Mood, mood regulation expectancies and frontal systems functioning in current smokers versus never-smokers in China and Australia

Indices of mood, mood regulation expectancies and everyday executive functioning were examined in adult current smokers and never-smokers of both genders in Australia (N = 97), where anti-smoking campaigns have dramatically reduced smoking prevalence and acceptability, and in China (N = 222), where smoking prevalence and public acceptance of smoking remain high. Dependent measures included the Depression Anxiety Stress Scales (DASS-21), the Negative Mood Regulation (NMR) expectancies scale, the Frontal Systems Behavior Scale (FrSBe), the Fagerström Test for Nicotine Dependence (FTND) and the Alcohol Use Disorders Identification Test (AUDIT). Multivariate analyses of covariance (MANCOVAs) controlling for demographic and recruitment related variables revealed highly significant differences between current smokers and never-smokers in both countries such that smokers indicated worse moods and poorer functioning than never-smokers on all dependent measures. Chinese smokers scored significantly worse on all dependent measures than Australian smokers whereas Chinese and Australian never-smokers did not differ on any of the same measures. Although nicotine dependence level as measured by FTND was significantly higher in Chinese than Australian smokers and was significantly correlated with all other dependent measures, inclusion of FTND scores as another covariate in MANCOVA did not eliminate the highly significant differences between Chinese and Australian smokers. Results are interpreted in light of the relative ease of taking up and continuing smoking in China compared to Australia today.

Readiness to change and brain damage in patients with chronic alcoholism

High motivation to change is a crucial triggering factor to patients' engagement in clinical treatment. This study investigates whether the low readiness to change observed in some alcoholic inpatients at treatment entry could, at least partially, be linked with macrostructural gray matter abnormalities in critical brain regions. Participants comprised 31 alcoholic patients and 27 controls, who underwent 1.5-T magnetic resonance imaging. The Readiness to Change Questionnaire, designed to assess three stages of motivation to change (precontemplation, contemplation and action stages), was completed by all patients, who were then divided into "Action" (i.e., patients in action stage) and "PreAction" (i.e., patients in precontemplation or in contemplation stage) subgroups. The PreAction subgroup, but not the Action subgroup, had gray matter volume deficits compared with controls. Unlike the patients in the Action subgroup, the PreAction patients had gray matter abnormalities in the cerebellum (Crus I), fusiform gyri and frontal cortex. The low level of motivation to modify drinking behavior observed in some alcoholic patients at treatment entry may be related to macrostructural brain abnormalities in regions subtending cognitive, emotional and social abilities. These brain volume deficits may result in impairment of critical abilities such as decision making, executive functions and social cognition skills. Those abilities may be needed to resolve ambivalence toward alcohol addiction and to apply "processes of change", which are essential for activating the desire to change problematic behavior.

Progressive levels of physical dependence to tobacco coincide with changes in the anterior cingulum bundle microstructure

BACKGROUND

The tobacco withdrawal syndrome indicates the development of neurophysiologic dependence. Clinical evidence indicates that neurophysiologic dependence develops through a set sequence of symptom presentation that can be assessed with a new 3-item survey measure of wanting, craving, and needing tobacco, the Level of Physical Dependence (PD). This study sought to determine if advancing neurophysiologic dependence as measured by the Level of PD correlates with characteristics of white matter structure measured by Fractional Anisotropy (FA).

METHODS

Diffusion-MRI based FA and diffusion tensor imaging probabilistic tractography were used to evaluate 11 smokers and 10 nonsmokers. FA was also examined in relation to two additional measures of dependence severity, the Hooked on Nicotine Checklist (HONC), and the Fagerström Test for Nicotine Dependence (FTND).

RESULTS

Among smokers, FA in the left anterior cingulate bundle (ACb) correlated negatively with the Level of PD (r = -0.68, p = 0.02) and HONC scores (r = -0.65, p = 0.03), but the correlation for the FTND did not reach statistical significance (r = -49, p = 0.12). With advancing Levels of PD, the density of streamlines between the ACb and precuneus increased (r = -0.67, p<0.05) and those between the ACb and white matter projecting to the superior-frontal cortex (r = -0.86, p = 0.0006) decreased significantly.

CONCLUSIONS

The correlations between neural structure and both the clinical Level of PD survey measure and the HONC suggest that the Level of PD and the HONC may reflect the microstructural integrity of white matter, as influenced by tobacco abuse. Given that the Level of PD is measuring a sequence of symptoms of neurophysiologic dependence that develops over time, the correlation between the Level of PD and neural structure suggests that these features might represent neuroplastic changes that develop over time to support the development of neurophysiologic dependence.

Reward, interrupted: Inhibitory control and its relevance to addictions

There are broad individual differences in the ability to voluntarily and effortfully suppress motivated, reward-seeking behaviors, and this review presents the hypothesis that these individual differences are relevant to addictive disorders. On one hand, cumulative experience with drug abuse appears to alter the molecular, cellular and circuit mechanisms that mediate inhibitory abilities, leading to increasingly uncontrolled patterns of drug-seeking and -taking. On the other, native inter-individual differences in inhibitory control are apparently a risk factor for aspects of drug-reinforced responding and substance use disorders. In both cases, the behavioral manifestation of poor inhibitory abilities is linked to relatively low striatal dopamine D2-like receptor availability, and evidence is accumulating for a more direct contribution of striatopallidal neurons to cognitive control processes. Mechanistic research is now identifying genes upstream of dopamine transmission that mediate these relationships, as well as the involvement of other neurotransmitter systems, acting alone and in concert with dopamine. The reviewed research stands poised to identify new mechanisms that can be targeted by pharmacotherapies and/or by behavioral interventions that are designed to prevent or treat addictive behaviors and associated behavioral pathology. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

How cigarette smoking may increase the risk of anxiety symptoms and anxiety disorders: a critical review of biological pathways

Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis.

Heavy smokers show abnormal microstructural integrity in the anterior corpus callosum: a diffusion tensor imaging study with tract-based spatial statistics

BACKGROUND

Abnormal macrostructural brain abnormalities in both gray matter and white matter have been reported in cigarette smokers. However, less is known about white matter microstructure in heavy cigarette smokers. In this study, we used diffusion tensor imaging (DTI) to investigate the integrity of the white matter microstructure in heavy smokers.

METHODS

Thirty-four heavy smokers and 34 non-smokers participated in this study. Whole brain analysis of fractional anisotropy (FA) was performed using tract-based spatial statistics (TBSS) to detect abnormal white matter regions between groups. Volume-of-interest (VOI) analysis was used to investigate changes in diffusivity indices in the regions showing FA abnormalities. Multiple regression analysis was applied to assess the relationships between diffusion indices and smoking-related variables in heavy smokers.

RESULTS

Compared with non-smokers, heavy smokers had lower FA in the left anterior (i.e., the genu and rostral body) corpus callosum while exhibiting no areas of higher FA. In the affected region, FA reduction was accompanied by a significantly decreased axial diffusivity and increased radial diffusivity, which suggests that axonal damage and disrupted myelin integrity may be associated with the degraded white matter integrity in heavy smokers. Moreover, significant positive correlations were found between both radial diffusivity and mean diffusivity and the duration of regular smoking.

CONCLUSIONS

Our findings suggest that heavy smokers demonstrate abnormal integrity of the white matter microstructure in the anterior corpus callosum, which is related to the duration of regular smoking. In addition, our study may increase the understanding of the neurobiological basis of chronic cigarette smoking.

Chronic cigarette smoking in alcohol dependence: associations with cortical thickness and N-acetylaspartate levels in the extended brain reward system

Chronic smoking in alcohol dependence is associated with abnormalities in brain morphology and metabolite levels in large lobar regions (e.g. frontal lobe). Here, we evaluated if these abnormalities are specifically apparent in several cortical and select subcortical components of the extended brain reward system (BRS), a network that is critically involved in the development and maintenance of all forms of addictive disorders. We studied 33 non-smoking and 43 smoking alcohol-dependent individuals (ALC) with 1 week of abstinence and 42 non-smoking Controls. At 1.5 Tesla, we obtained regional measures of cortical thickness and N-acetylaspartate (NAA; a surrogate marker of neuronal integrity) concentration in major components of the BRS as well as the corresponding measures throughout the cortex. Smoking ALC and non-smoking ALC demonstrated decreased thickness compared with Controls in the dorsolateral prefrontal cortex (DLPFC), insula, orbitofrontal cortex (OFC), the total BRS, total frontal cortex and global cortex. Smoking ALC had significantly decreased thickness compared to non-smoking ALC in the ACC, insula, the total BRS and total frontal cortex. Smoking ALC had also lower NAA concentrations than both non-smoking ALC and Controls in the DLPFC, insula, superior corona radiata and the total BRS. Alcohol consumption and common medical and psychiatric co-morbidities did not mediate differences between smoking and non-smoking ALC. This dual modality magnetic resonance (MR) study indicated that chronic smoking in ALC was associated with significant cortical thinning and NAA abnormalities in anterior brain regions that are implicated in the development and maintenance of addictive disorders.

Correlation between pulmonary function and brain volume in healthy elderly subjects

INTRODUCTION

Cigarette smoking decreases brain regional gray matter volume and is related to chronic obstructive lung disease (COPD). COPD leads to decreased pulmonary function, which is represented by forced expiratory volume in one second percentage (FEV1.0 %); however, it is unclear if decreased pulmonary function is directly related to brain gray matter volume decline. Because there is a link between COPD and cognitive decline, revealing a direct relationship between pulmonary function and brain structure is important to better understand how pulmonary function affects brain structure and cognitive function. Therefore, the purpose of this study was to analyze whether there were significant correlations between FEV1.0 % and brain regional gray and white matter volumes using brain magnetic resonance (MR) image data from 109 community-dwelling healthy elderly individuals.

METHODS

Brain MR images were processed with voxel-based morphometry using a custom template by applying diffeomorphic anatomical registration using the exponentiated lie algebra procedure.

RESULTS

We found a significant positive correlation between the regional white matter volume of the cerebellum and FEV1.0 % after adjusting for age, sex, and intracranial volume.

CONCLUSION

Our results suggest that elderly individuals who have a lower FEV1.0 % have decreased regional white matter volume in the cerebellum. Therefore, preventing decreased pulmonary function is important for cerebellar white matter volume in the healthy elderly population.

Neuroadaptive changes associated with smoking: structural and functional neural changes in nicotine dependence

Tobacco smoking is the most frequent form of substance abuse. We provide a review of the neuroadaptive changes evidenced in human smokers with regard to the current neurobiological models of addiction. Addiction is thought to result from an interplay between positive and negative reinforcement. Positive reinforcing effects of the drugs are mediated by striatal dopamine release, while negative reinforcement involves the relief of withdrawal symptoms and neurobiological stress systems. In addition, drug-related stimuli are attributed with excessive motivational value and are thought to exert a control on the behavior. This mechanism plays a central role in drug maintenance and relapse. Further neuroadaptive changes associated with chronic use of the drug consist of reduced responses to natural rewards and in the activation of an antireward system, related to neurobiological stress systems. Reduced inhibitory cognitive control is believed to support the development and the maintenance of addiction. The findings observed in human nicotine dependence are generally in line with these models. The current state of the research indicates specific neuroadaptive changes associated with nicotine addiction that need to be further elucidated with regard to their role in the treatment of nicotine dependence.

Free and nanoencapsulated curcumin prevents cigarette smoke-induced cognitive impairment and redox imbalance

Cigarette smoke-exposure promotes neurobiological changes associated with neurocognitive abnormalities. Curcumin, a natural polyphenol, have shown to be able to prevent cigarette smoke-induced cognitive impairment. Here, we investigated possible mechanisms involved in curcumin protection against cigarette smoke-induced cognitive impairment and, due to its poor bioavailability, we investigated the potential of using curcumin-loaded lipid-core nanocapsules (C-LNC) suspension. Rats were treated with curcumin and cigarette smoke, once a day, 5 days each week, for 30 days. Animals were divided into ten groups: I, control (vehicle/corn oil); II, curcumin 12.5mg/kg; III, curcumin 25mg/kg; IV, curcumin 50mg/kg; V, C-LNC 4 mg/kg; VI, tobacco exposed; VII, curcumin 12.5mg/kg along with tobacco exposure; VIII, curcumin 25mg/kg along with tobacco exposure; IX, curcumin 50mg/kg along with tobacco exposure; X, C-LNC 4 mg/kg along with tobacco exposure. Cigarette smoke-exposure impaired object recognition memory (P<0.001), indicated by the low recognition index, increased biomarkers of oxidative/nitrosative stress such as TBARS (P<0.05) and NOx (P<0.01), decreased antioxidant defenses such as NPSH content (P<0.01) and SOD activity (P<0.01) and inhibited the activities of enzymes involved in ion homeostasis such as Na(+),K(+)-ATPase and Ca(2+)-ATPase. Both curcumin formulations (free and nanoencapsulated) prevented the memory impairment, the redox imbalance and the alterations observed in the ATPases activities. Maintenance of ion homeostasis and redox balance is involved in the protective mechanism of curcumin against tobacco-induced cognitive impairment. Our results suggest that curcumin is a potential therapeutic agent for neurocognition and that C-LNC may be an alternative to its poor bioavailability.

Frontoparietal attentional network activation differs between smokers and nonsmokers during affective cognition

Smoking withdrawal-induced disruption of affect and cognition is associated with dysregulated prefrontal brain function, although little is known regarding the neural foci of smoker-nonsmoker differences during affective cognition. Thus, the current study used functional magnetic resonance imaging (fMRI) to identify smoker-nonsmoker differences in affective cognition. Thirty-four healthy volunteers (17 smokers, 17 nonsmokers) underwent fMRI during an affective Stroop task (aST). The aST includes emotional cue-reactivity trials, and response selection trials that contain either neutral or negative emotional distractors. Smokers had less activation during negative cue-reactivity trials in regions subserving emotional awareness (i.e., posterior cingulate), inhibitory control (i.e., inferior frontal gyrus) and conflict resolution (i.e., anterior cingulate); during response-selection trials with negative emotional distractors, smokers had greater activation in a frontoparietal attentional network (i.e., middle frontal and supramarginal gyri). Exploratory analyses revealed that task accuracy was positively correlated with anterior cingulate cortex and inferior frontal gyrus response on fMRI. These findings suggests that chronic nicotine use may reduce inhibitory control and conflict resolution of emotional distraction, and result in recruiting additional attentional resources during emotional interference on cognition.

Transcranial direct current stimulation reduces negative affect but not cigarette craving in overnight abstinent smokers

Transcranial direct current stimulation (tDCS) can enhance cognitive control functions including attention and top-down regulation over negative affect and substance craving in both healthy and clinical populations, including early abstinent (∼1.5 h) smokers. The aim of this study was to assess whether tDCS modulates negative affect, cigarette craving, and attention of overnight abstinent tobacco dependent smokers. In this study, 24 smokers received a real and a sham session of tDCS after overnight abstinence from smoking on two different days. We applied anode to the left dorsolateral prefrontal cortex and cathode to the right supra-orbital area for 20 min with a current of 2.0 mA. We used self-report questionnaires Profile of Mood States (POMS) to assess negative affect and Urge to Smoke (UTS) Scale to assess craving for cigarette smoking, and a computerized visual target identification task to assess attention immediately before and after each tDCS. Smokers reported significantly greater reductions in POMS scores of total mood disturbance and scores of tension-anxiety, depression-dejection, and confusion-bewilderment subscales after real relative to sham tDCS. Furthermore, this reduction in negative affect positively correlated with the level of nicotine dependence as assessed by Fagerström scale. However, reductions in cigarette craving after real vs. sham tDCS did not differ, nor were there differences in reaction time or hit rate change on the visual task. Smokers did not report significant side effects of tDCS. This study demonstrates the safety of tDCS and its promising effect in ameliorating negative affect in overnight abstinent smokers. Its efficacy in treating tobacco dependence deserves further investigation.

Insula-specific H magnetic resonance spectroscopy reactions in heavy smokers under acute nicotine withdrawal and after oral nicotine substitution

The aim of this study was to clarify whether addiction-specific neurometabolic reaction patterns occur in the insular cortex during acute nicotine withdrawal in tobacco smokers in comparison to nonsmokers. Fourteen male smokers and 10 male nonsmokers were included. Neurometabolites of the right and the left insular cortices were quantified by magnetic resonance spectroscopy (MRS) on a 3-Tesla scanner. Three separate MRS measurements were performed in each subject: among the smokers, the first measurement was done during normal smoking behavior, the second measurement during acute withdrawal (after 24 h of smoking abstinence), and the third shortly after administration of an oral nicotine substitute. Simultaneously, craving, withdrawal symptoms, and CO levels in exhaled air were determined during the three phases. The participants in the control group underwent the same MR protocol. In the smokers, during withdrawal, the insular cortex showed a significant increase in glutamine (Gln; p = 0.023) as well as a slight increase not reaching significance for glutamine/glutamate (Glx; p = 0.085) and a nonsignificant drop in myoinositol (mI; p = 0.381). These values tended to normalize after oral nicotine substitution treatment, even though differences were not significant: Gln (p = 0.225), Glx (p = 0.107) and mI (p = 0.810). Overall, the nonsmokers (control group) did not show any metabolic changes over all three phases (p > 0.05). In smokers, acute nicotine withdrawal produces a neurometabolic reaction pattern that is partly reversed by the administration of an oral nicotine substitute. The results are consistent with the expression of an addiction-specific neurometabolic shift in the brain and confirm the fact that the insular cortex seems to play a possible role in nicotine dependence.

Yoga meditation practitioners exhibit greater gray matter volume and fewer reported cognitive failures: results of a preliminary voxel-based morphometric analysis

Hatha yoga techniques, including physical postures (asanas), breathing exercises (pranayama), and meditation, involve the practice of mindfulness. In turn, yoga meditation practices may induce the state of mindfulness, which, when evoked recurrently through repeated practice, may accrue into trait or dispositional mindfulness. Putatively, these changes may be mediated by experience-dependent neuroplastic changes. Though prior studies have identified differences in gray matter volume (GMV) between long-term mindfulness practitioners and controls, no studies to date have reported on whether yoga meditation is associated with GMV differences. The present study investigated GMV differences between yoga meditation practitioners (YMP) and a matched control group (CG). The YMP group exhibited greater GM volume in frontal, limbic, temporal, occipital, and cerebellar regions; whereas the CG had no greater regional greater GMV. In addition, the YMP group reported significantly fewer cognitive failures on the Cognitive Failures Questionnaire (CFQ), the magnitude of which was positively correlated with GMV in numerous regions identified in the primary analysis. Lastly, GMV was positively correlated with the duration of yoga practice. Results from this preliminary study suggest that hatha yoga practice may be associated with the promotion of neuroplastic changes in executive brain systems, which may confer therapeutic benefits that accrue with repeated practice.

Chronic smoking and brain gray matter changes: evidence from meta-analysis of voxel-based morphometry studies

Structural neuroimaging studies on chronic smokers using voxel-based morphometry (VBM) had provided cumulative evidence of gray matter (GM) changes relative to nonsmokers. However, not all the studies reported entirely consistent findings. Here, we aimed at identifying consistent GM anomalies in chronic smokers by performing a meta-analysis, and a systematic search of VBM studies on chronic smokers and nonsmokers published in PubMed and Embase database from 2000 to April 2012. Meta-analysis was performed using a newly improved voxel-based meta-analytic tool, namely effect size signed differential mapping, to quantitatively explore the GM abnormalities between chronic smokers and nonsmokers. A total of 7 eligible VBM studies involving 213 chronic smokers and 205 nonsmokers met the inclusion criteria. A considerable regional GM volume decrease was detected in the anterior cingulate cortex (ACC) (BA 24) extending to BA32 in chronic smokers. The findings remain largely unchanged in the entire brain jackknife sensitivity analyses. The results of the present meta-analysis provide evidence of GM changes in ACC in chronic smokers which may be an important potential therapeutic neuro-target for nicotine dependence.

Differences between smokers and non-smokers in regional gray matter volumes: a voxel-based morphometry study

Magnetic resonance imaging (MRI) studies showed a link between chronic smoking and structural brain abnormalities. To date, little is known about the long-term effects of smoking on gray matter deficiencies. MRI study was carried for 44 smokers and 44 matched non-smokers to assess gray matter volume differences between the two groups. Decreased gray matter volumes were found in left thalamus, medial frontal cortex and anterior cingulate of smokers in comparison to controls. This voxel-based morphometry study is showing reduction of regional gray matter volume in smokers, which might better guide future research into the pathogenesis of chronic smoking.

Greater regional brain atrophy rate in healthy elderly subjects with a history of cigarette smoking

BACKGROUND

Little is known about the effects of cigarette smoking on longitudinal brain morphological changes in the elderly. This study investigated the effects of a history of cigarette smoking on changes in regional brain volumes over 2 years in healthy, cognitively intact elderly individuals. We predicted that individuals with a history of cigarette smoking, compared with never smokers, demonstrate greater rate of atrophy over 2 years in regions that manifest morphological abnormalities in the early stages of Alzheimer's disease (AD), as well as in the extended brain reward/executive oversight system (BREOS), which is implicated in the development and maintenance of substance use disorders.

METHODS

Participants were healthy, cognitively normal elderly control subjects (75.9 ± 4.8 years of age) with any lifetime history of cigarette smoking (n = 68) or no history of smoking (n = 118). Data were obtained through the Alzheimer Disease Neuroimaging Initiative from 2005 to 2010. Participants completed four magnetic resonance scans over 2 years. A standardized protocol using high-resolution three-dimensional T1-weighted sequences at 1.5 T was used for structural imaging and regional brain volumetric analyses.

RESULTS

Smokers demonstrated a significantly greater atrophy rate over 2 years than nonsmokers in multiple brain regions associated with the early stages of AD, as well as in the BREOS system. Groups did not differ on the rate of global cortical atrophy.

CONCLUSIONS

A history of cigarette smoking in this healthy elderly cohort was associated with decreased structural integrity of multiple brain regions, which manifested as a greater rate of atrophy over 2 years in regions specifically affected by incipient AD as well as chronic substance abuse.

Striatal volume increases in active methamphetamine-dependent individuals and correlation with cognitive performance

The effect of methamphetamine (MA) dependence on the structure of the human brain has not been extensively studied, especially in active users. Previous studies reported cortical deficits and striatal gains in grey matter (GM) volume of abstinent MA abusers compared with control participants. This study aimed to investigate structural GM changes in the brains of 17 active MA-dependent participants compared with 20 control participants aged 18-46 years using voxel-based morphometry and region of interest volumetric analysis of structural magnetic resonance imaging data, and whether these changes might be associated with cognitive performance. Significant volume increases were observed in the right and left putamen and left nucleus accumbens of MA-dependent compared to control participants. The volumetric gain in the right putamen remained significant after Bonferroni correction, and was inversely correlated with the number of errors (standardised z-scores) on the Go/No-go task. MA-dependent participants exhibited cortical GM deficits in the left superior frontal and precentral gyri in comparison to control participants, although these findings did not survive correction for multiple comparisons. In conclusion, consistent with findings from previous studies of abstinent users, active chronic MA-dependent participants showed significant striatal enlargement which was associated with improved performance on the Go/No-go, a cognitive task of response inhibition and impulsivity. Striatal enlargement may reflect the involvement of neurotrophic effects, inflammation or microgliosis. However, since it was associated with improved cognitive function, it is likely to reflect a compensatory response to MA-induced neurotoxicity in the striatum, in order to maintain cognitive function. Follow-up studies are recommended to ascertain whether this effect continues to be present following abstinence. Several factors may have contributed to the lack of more substantial cortical and subcortical GM changes amongst MA-dependent participants, including variability in MA exposure variables and difference in abstinence status from previous studies.

Neuroadaptation in nicotine addiction: update on the sensitization-homeostasis model

The role of neuronal plasticity in supporting the addictive state has generated much research and some conceptual theories. One such theory, the sensitization-homeostasis (SH) model, postulates that nicotine suppresses craving circuits, and this triggers the development of homeostatic adaptations that autonomously support craving. Based on clinical studies, the SH model predicts the existence of three distinct forms of neuroplasticity that are responsible for withdrawal, tolerance and the resolution of withdrawal. Over the past decade, many controversial aspects of the SH model have become well established by the literature, while some details have been disproven. Here we update the model based on new studies showing that nicotine dependence develops through a set sequence of symptoms in all smokers, and that the latency to withdrawal, the time it takes for withdrawal symptoms to appear during abstinence, is initially very long but shortens by several orders of magnitude over time. We conclude by outlining directions for future research based on the updated model, and commenting on how new experimental studies can gain from the framework put forth in the SH model.

Gray-matter volume in methamphetamine dependence: cigarette smoking and changes with abstinence from methamphetamine

BACKGROUND

Group differences in brain structure between methamphetamine-dependent and healthy research participants have been reported, but findings in the literature present discrepancies. Although most methamphetamine-abusing individuals also smoke cigarettes, the effects of smoking on brain structure have not been distinguished from those of methamphetamine. Changes with abstinence from methamphetamine have also been relatively unexplored. This study, therefore, attempted to account for effects of smoking and brief abstinence from methamphetamine on gray-matter measures in methamphetamine-dependent research participants.

METHODS

Gray matter was measured using voxel-based morphometry in three groups: 18 control nonsmokers, 25 control smokers, and 39 methamphetamine-dependent smokers (methamphetamine-abstinent 4-7 days). Subgroups of methamphetamine-dependent and control participants (n=12/group) were scanned twice to determine change in gray matter over the first month of methamphetamine abstinence.

RESULTS

Compared with Control Nonsmokers, Control Smokers and Methamphetamine-dependent Smokers had smaller gray-matter volume in the orbitofrontal cortex and caudate nucleus. Methamphetamine-dependent Smokers also had smaller gray-matter volumes in frontal, parietal and temporal cortices than Control Nonsmokers or Smokers, and smaller gray-matter volume in insula than control nonsmokers. Longitudinal assessment revealed gray matter increases in cortical regions (inferior frontal, angular, and superior temporal gyri, precuneus, insula, occipital pole) in methamphetamine-dependent but not control participants; the cerebellum showed a decrease.

CONCLUSIONS

Gray-matter volume deficits in the orbitofrontal cortex and caudate of methamphetamine-dependent individuals may be in part attributable to cigarette smoking or pre-morbid conditions. Increase in gray matter with methamphetamine abstinence suggests that some gray-matter deficits are partially attributable to methamphetamine abuse.

Functional and structural brain changes associated with methamphetamine abuse

Methamphetamine (MA) is a potent psychostimulant drug whose abuse has become a global epidemic in recent years. Firstly, this review article briefly discusses the epidemiology and clinical pharmacology of methamphetamine dependence. Secondly, the article reviews relevant animal literature modeling methamphetamine dependence and discusses possible mechanisms of methamphetamine-induced neurotoxicity. Thirdly, it provides a critical review of functional and structural neuroimaging studies in human MA abusers; including positron emission tomography (PET) and functional and structural magnetic resonance imaging (MRI). The effect of abstinence from methamphetamine, both short- and long-term within the context of these studies is also reviewed.

Confounders of excessive brain volume loss in schizophrenia

There is convincing evidence that schizophrenia is characterised by progressive brain volume changes during the course of the illness. In a large longitudinal study it was shown that different age-related trajectories of brain tissue loss are present in patients compared to healthy subjects, suggesting that brain maturation that occurs in the third and fourth decade of life is abnormal in schizophrenia. However, studies show that medication intake and cannabis use are important confounding factors when interpreting brain volume (change) abnormalities. Indeed, continues use of cannabis, but not cigarette smoking, is associated to a more pronounced loss of grey matter in the anterior cingulated and the prefrontal cortex. Atypical antipsychotics have been found to be related to smaller decreases in tissue loss. Moreover, independent of antipsychotic medication intake, the brain volume abnormalities appear associated to the outcome of the illness.

Cigarette smoking as a risk factor for other substance misuse: 10-year study of individuals with and without attention-deficit hyperactivity disorder

BACKGROUND

We previously documented that cigarette smoking is a risk factor for subsequent alcohol and drug misuse and dependence in adolescent girls with attention-deficit hyperactivity disorder (ADHD).

AIMS

To revisit this hypothesis with a large longitudinal sample of both genders followed up for 10 years into young adulthood.

METHOD

We used data from two identically designed, longitudinal, case-control family studies of boys and girls with and without ADHD ascertained from psychiatric and paediatric sources. We studied 165 individuals with ADHD and 374 controls followed up longitudinally and masked for 10 years. We assessed ADHD, smoking and substance use status using structured diagnostic interviews. We tested the association between cigarette smoking and subsequent substance use outcomes using Cox proportional hazard regression models.

RESULTS

Youth with ADHD who smoked cigarettes (n = 27) were significantly more likely to subsequently develop drug misuse and dependence compared with youth with ADHD who did not smoke (n = 138, P<0.05).

CONCLUSIONS

These results confirm that cigarette smoking increases the risk for subsequent drug and alcohol use disorders among individuals with ADHD. These findings have important public health implications, and underscore the already pressing need to prevent smoking in children with ADHD.