Brain volumes in alcohol use disorder: Do females and males differ? A whole-brain magnetic resonance imaging mega-analysis

Brain structural alterations in vestibular schwannoma beyond tinnitus and hearing loss

Brain tumours alter brain structures and functions. However, morphometric alterations induced by unilateral vestibular schwannoma, a benign tumour of the vestibulocochlear nerve, have not been extensively explored. Recent studies have suggested that the tumour does not grow bigger following diagnosis in several patients, suggesting an avenue for conservative therapy. This study aims to comprehensively investigate brain structural re-organizations in vestibular schwannoma patients taking into account the effects of hearing loss and tinnitus-the most common symptoms. To this end, preoperative data from 48 vestibular schwannoma pathology-confirmed patients and a healthy control group of 30 volunteers were retrospectively included in this study. The clinical and imaging data from these participants were processed. General linear models were designed to identify tumour-related brain alterations in grey matter volume and cortical thickness, alongside three other surface measures: sulcal depth, gyrification index and fractal dimension. The differences obtained were further analysed for correlation with tumour size and pure tone audiometry. Interestingly, grey matter volume, cortical thickness and for the first time, fractal dimension measures were increased in vestibular schwannoma patients across key frontal regions (PFWE < 0.05). The precuneus, superior and inferior frontal gyrus had increased grey matter volumes and cortical thickening in patients compared to controls, among other changes (P FWE < 0.05). Meanwhile, the sulcal depth and gyrification index measures demonstrated no significant alterations. Furthermore, grey matter volume changes at the paracentral lobule and precuneus were positively correlated to the tumour size, while the fractal dimension at the superior frontal sulcus was negatively correlated. Finally, grey matter volume increase at the inferior frontal gyrus and cortical thickening at the supramarginal gyrus were negatively correlated to pure tone audiometry. These findings suggest that factors beyond hearing loss and tinnitus contribute to brain structural alterations in this tumour, a better understanding of which might pave the way for non-surgical symptomatic therapies.

Connectomics modeling of regional networks of white-matter fractional anisotropy to predict the severity of young adult drinking

Background

Alcohol use impacts brain structure, including white matter integrity, which can be quantified by fractional anisotropy (FA) in diffusion tensor imaging (DTI). This study explored the relationship between the severity of alcohol consumption and white matter FA changes, and its sex differences, in young adults, using data from the Human Connectome Project.

Methods

We analyzed DTI data from 949 participants (491 females) and used principal component analysis (PCA) of 15 drinking metrics to quantify drinking severity. Connectome-based predictive modeling (CPM) was employed to predict the principal component of drinking severity from network FA values in a matrix of 116×116 regions. Mediation analyses were conducted to explore the interrelationships among networks identified by CPM, drinking severity, and rule-breaking behavior.

Results

Significant correlations were found between drinking severity and network FA values. Both men and women showed significant correlations between negative network connectivity and drinking severity (men: r=0.15, P=0.001; women: r=0.30, P<0.001). Sex differences were observed in the brain regions contributing to drinking severity predictions. Mediation analyses revealed significant inter-relationships between network features, drinking severity, and rule-breaking behavior.

Conclusions

The connectomics of white matter FA can predict the severity of alcohol consumption, and by incorporating brain network pathways, identify sex differences. This approach provides new clues to the biological basis of alcohol abuse and evaluates how these regions interact in broader brain networks for understanding alcohol misuse and its comorbidities.

Remission from addiction: erasing the wrong circuits or making new ones?

Chronic relapse is a hallmark of substance-use disorders (SUDs), but many people with SUDs do recover and eventually enter remission. Many preclinical studies in this field aim to identify interventions that can precipitate recovery by reversing or erasing the neuronal circuit changes caused by chronic drug use. A better understanding of remission from SUDs can also come from preclinical studies that model factors known to influence recovery in humans, such as the negative consequences of drug use and positive environmental influences. In this Perspective we discuss human neuroimaging studies that have provided information about recovery from SUDs and highlight mechanisms identified in preclinical studies - such as the reconfiguration of neuronal circuits - that could contribute to remission. We also analyse how studies of memory and forgetting can provide insights into the mechanisms of remission. Overall, we propose that remission can be driven by the introduction of new neuronal changes (which outcompete those induced by drugs) as well as by the erasure of drug-induced changes.

The effects of alcohol use severity and polygenic risk on gray matter volumes in young adults

Genetic factors contribute to alcohol misuse. Chronic alcohol consumption is associated with decreases in gray matter volumes (GMVs) of the brain. However, it remains unclear whether or how genetic risks may alter GMVs independent of the effects of alcohol exposure. Here, we employed the Human Connectome Project data of neurotypical adults (n = 995; age 22-35; 618 women) and, with voxel-based morphometry analysis, computed the GMVs of 166 regions in the automated anatomical atlas 3. Alcohol use behaviors were assessed with the Semi-Structured Assessment for the Genetics of Alcoholism. Alcohol use severity was quantified by the first principal component (PC1) identified of principal component analysis of 15 drinking measures. Polygenic risk scores (PRS) for alcohol dependence were computed for all subjects using the Psychiatric Genomics Consortium study of alcohol dependence as the base sample. With age, sex, race, and total intracranial volume as covariates, we evaluated the relationships of regional GMVs with PC1 and PRS together in a linear regression. PC1 was negatively correlated with GMVs of right insula and Heschl's gyrus, and PRS was positively correlated with GMVs of left posterior orbitofrontal cortex, bilateral intralaminar nuclei of the thalamus and lingual gyri. These findings suggest distinct volumetric neural markers of drinking severity and genetic risks of alcohol misuse. Notably, in contrast to volumetric reduction, the genetic risks of dependent drinking may involve larger regional volumes in the reward, emotion, and saliency circuits.

Association of altered cortical gyrification and working memory in male early abstinent alcohol-dependent individuals

BACKGROUND

Alcohol dependence (AD) is an addictive disorder with multifaceted neurobiological features. Recent research on the pathophysiological mechanisms of AD has emphasized the important role of dysconnectivity. Cortical gyrification is known to be a reliable marker of neural connectivity. This study aimed to explore cortical gyrification using the local gyrification index (LGI) between alcohol-dependent patients and controls.

METHODS

Magnetic resonance images were collected from 60 early abstinent patients with AD (5-12 days after stopping alcohol consumption) and 59 controls and preprocessed using FreeSurfer, followed by surface-based morphometry (SBM) analysis to compare the LGI between the two groups. Cognitive performance was assessed using the Spatial Working Memory (SWM) test in the Cambridge Neuropsychological Test Automated Battery (CANTAB). The relationship between LGI, cognitive performance, and clinical variables was also explored in the patient group.

RESULTS

Compared with controls, patients with AD exhibited significantly decreased LGI in several regions, including the postcentral gyrus, precentral gyrus, middle frontal, superior temporal, middle temporal, insula, superior parietal, and inferior parietal cortex. AD patients did worse than controls in several SWM measures. Furthermore, decreased LGI in the left postcentral was negatively correlated with working memory performance after multiple comparison corrections in the patient group.

CONCLUSION

Alcohol-dependent individuals exhibit abnormal patterns of cortical gyrification, which may be underlying neurobiological markers of AD. Our findings further indicate that working memory deficits may be related to abnormalities in cortical gyrification in alcohol addiction.

Gray matter volume differences based on sex in first-episode drug-naive patients with major depressive disorder and its molecular analysis

This study analyzed whether gray matter volume (GMV) differences exist between the sexes in patients with major depressive disorder (MDD) and explored the relationships between these differences and neurotransmitter systems. This study enrolled 190 first-episode drug-naive patients with MDD and 293 healthy controls. All participants underwent T1-weighted high-resolution MRI. The interaction between the diagnosis (healthy controls vs. MDD) and sex (male vs. female) regarding GMV alterations was analyzed. The JuSpace toolbox, which covers a wide range of neurotransmitter systems, was used to identify the relationship between MDD-induced and sex-induced GMV alterations and specific receptor/transporter proteins in the brain. Sex-specific GMV differences were observed in the healthy controls but not in MDD patients. Male healthy controls had a larger GMV in the bilateral parahippocampal, lingual, inferior occipital, fusiform, cerebellar subregions, and left inferior temporal than female healthy controls, but several subregions of the thalamus had a larger GMV in female healthy controls than in male healthy controls. Sex-induced GMV alterations were associated with 5-hydroxytryptamine receptor subtype 1a, cannabinoid receptor, and dopamine receptor ( P  < 0.01, false discovery rate corrected). GMV differences were not detected in the main effect of diagnosis and the interaction of diagnosis and sex. Sex-specific GMV differences are associated with the spatial distribution of serotonin, dopamine, and cannabinoid neurotransmitter receptor systems. Sex-based physiological differences in the GMV may account for male and female susceptibility to and differences in the clinical symptoms of MDD.

Altered individual gray matter structural covariance networks in early abstinence patients with alcohol dependence

While alterations in cortical thickness have been widely observed in individuals with alcohol dependence, knowledge about cortical thickness-based structural covariance networks is limited. This study aimed to explore the topological disorganization of structural covariance networks based on cortical thickness at the single-subject level among patients with alcohol dependence. Structural imaging data were obtained from 61 patients with alcohol dependence during early abstinence and 59 healthy controls. The single-subject structural covariance networks were constructed based on cortical thickness data from 68 brain regions and were analyzed using graph theory. The relationships between network architecture and clinical characteristics were further investigated using partial correlation analysis. In the structural covariance networks, both patients with alcohol dependence and healthy controls displayed small-world topology. However, compared to controls, alcohol-dependent individuals exhibited significantly altered global network properties characterized by greater normalized shortest path length, greater shortest path length, and lower global efficiency. Patients exhibited lower degree centrality and nodal efficiency, primarily in the right precuneus. Additionally, scores on the Alcohol Use Disorder Identification Test were negatively correlated with the degree centrality and nodal efficiency of the left middle temporal gyrus. The results of this correlation analysis did not survive after multiple comparisons in the exploratory analysis. Our findings may reveal alterations in the topological organization of gray matter networks in alcoholism patients, which may contribute to understanding the mechanisms of alcohol addiction from a network perspective.

Sex differences in distributed error-related neural activation in problem-drinking young adults

BACKGROUND

Detecting and responding to errors is central to goal-directed behavior and cognitive control and is thought to be supported by a network of structures that includes the anterior cingulate cortex and anterior insula. Sex differences in the maturational timing of cognitive control systems create differential periods of vulnerability for psychiatric conditions, such as substance use disorders.

METHODS

We examined sex differences in error-related activation across an array of distributed brain regions during a Go/No-Go task in young adults with problem alcohol use (N=69; 34 females; M=19.4 years). Regions of interest previously linked to error-related activation, including anterior cingulate cortex, insula, and frontoparietal structures, were selected in a term-based meta-analysis. Individual differences in their responses to false alarm (FA) inhibitory errors relative to "go" trials (FA>GO) and correct rejections (FA>CR) were indexed using multivariate summary measures derived from principal components analysis.

RESULTS

FA>GO and FA>CR activation both revealed a first component that explained the majority of the variance across error-associated regions and displayed the strongest loadings on salience network structures. Compared to females, males exhibited significantly higher levels of the FA>GO component but not the FA>CR component.

CONCLUSIONS

Males exhibit greater salience network activation in response to inhibitory errors, which could be attributed to sex differences in error-monitoring processes or to other functions (e.g., novelty detection). The findings are relevant for the further characterization of sex differences in cognitive control and may have implications for understanding individual differences in those at risk for substance use or other cognitive control disorders.

The inter-related effects of alcohol use severity and sleep deficiency on semantic processing in young adults

BACKGROUND

Both alcohol misuse and sleep deficiency are associated with deficits in semantic processing. However, alcohol misuse and sleep deficiency are frequently comorbid and their inter-related effects on semantic processing as well as the underlying neural mechanisms remain to be investigated.

METHODS

We curated the Human Connectome Project data of 973 young adults (508 women) to examine the neural correlates of semantic processing in link with the severity of alcohol use and sleep deficiency. The latter were each evaluated using the first principal component (PC1) of principal component analysis of all drinking metrics and the Pittsburgh Sleep Quality Index (PSQI). We employed path modeling to elucidate the interplay among clinical, behavioral, and neural variables.

RESULTS

Among women, we observed a significant negative correlation between the left precentral gyrus (PCG) and PSQI scores. Mediation analysis revealed that the left PCG activity fully mediated the relationship between PSQI scores and word comprehension in language tasks. In women alone also, the right middle frontal gyrus (MFG) exhibited a significant negative correlation with PC1. The best path model illustrated the associations among PC1, PSQI scores, PCG activity, and MFG activation during semantic processing in women.

CONCLUSIONS

Alcohol misuse may lead to reduced MFG activation while sleep deficiency hinder semantic processing by suppressing PCG activity in women. The pathway model underscores the influence of sleep quality and alcohol consumption severity on semantic processing in women, suggesting that sex differences in these effects need to be further investigated.

Sex Differences in Alcohol Use: Is It All About Hormones?

Risky alcohol use and alcohol use disorders (AUD) are a rising problem in women, yet a major disparity in our understanding of what drives alcohol consumption in women remains. Historically biomedical research has focused on male subjects; however, recent increases in reporting of females, have highlighted major differences between the sexes. Here we review the current literature of the effect of gonadal steroid hormones (estrogens, androgens, and progestins), neurosteriods, and neurobiological factors on alcohol use in clinical and preclinical studies of both sexes. Further, we briefly discuss how fundamental sex differences in genetics, metabolism, neuroimmune, and stress responses may influence sex differences in alcohol intake. Comparing the sexes could aid in the discovery of novel therapeutics to treat AUD, and implementation of current treatment options in women.

Sex differences in dorsolateral prefrontal cortical and superior colliculus activities support the impact of alcohol use severity and sleep deficiency on two-back memory

Background

Working memory refers to a process of temporary storage and manipulation of information to support planning, decision-making, and action. Frequently comorbid alcohol misuse and sleep deficiency have both been associated with working memory deficits. However, how alcohol misuse and sleep deficiency interact to impact working memory remains unclear. In this study, we aim to investigate the neural processes inter-relating alcohol misuse, sleep deficiency and working memory.

Methods

We curated the Human Connectome Project (HCP) dataset and investigated the neural correlation of working memory in link with alcohol use severity and sleep deficiency in 991 young adults (521 women). The two were indexed by the first principal component (PC1) of principal component analysis of all drinking metrics and Pittsburgh Sleep Quality Index (PSQI) score, respectively. We processed the imaging data with published routines and evaluated the results with a corrected threshold. We used path model to characterize the inter-relationship between the clinical, behavioral, and neural measures, and explored sex differences in the findings.

Results

In whole-brain regression, we identified β estimates of dorsolateral prefrontal cortex response (DLPFC β) to 2- vs. 0-back in correlation with PC1. The DLPFC showed higher activation in positive correlation with PC1 across men and women (r=0.16, P<0.001). Path analyses showed the model PC1 → DLPFC β → differences in reaction time (2- minus 0-back; RT2-0) of correct trials → differences in critical success index (2- minus 0-back; CSI2-0) with the best fit. In women alone, in addition to the DLPFC, a cluster in the superior colliculus (SC) showed a significant negative correlation with the PSQI score (r=-0.23, P<0.001), and the path model showed the inter-relationship of PC1, PSQI score, DLPFC and SC β's, and CSI2-0 in women.

Conclusions

Alcohol misuse may involve higher DLPFC activation in functional compensation, whereas, in women only, sleep deficiency affects 2-back memory by depressing SC activity. In women only, path model suggests inter-related impact of drinking severity and sleep deficiency on 2-back memory. These findings suggest potential sex differences in the impact of drinking and sleep problems on working memory that need to be further investigated.

Novel insight into the lipid network of plasma extracellular vesicles reveal sex-based differences in the lipidomic profile of alcohol use disorder patients

BACKGROUND

Alcohol use disorder (AUD) is one of the most common psychiatric disorders, with the consumption of alcohol considered a leading cause of preventable deaths worldwide. Lipids play a crucial functional role in cell membranes; however, we know little about the role of lipids in extracellular vesicles (EVs) as regulatory molecules and disease biomarkers.

METHODS

We employed a sensitive lipidomic strategy to characterize lipid species from the plasma EVs of AUD patients to evaluate functional roles and enzymatic activity networks to improve the knowledge of lipid metabolism after alcohol consumption. We analyzed plasma EV lipids from AUD females and males and healthy individuals to highlight lipids with differential abundance and biologically interpreted lipidomics data using LINEX2, which evaluates enzymatic dysregulation using an enrichment algorithm.

RESULTS

Our results show, for the first time, that AUD females exhibited more significant substrate-product changes in lysophosphatidylcholine/phosphatidylcholine lipids and phospholipase/acyltransferase activity, which are potentially linked to cancer progression and neuroinflammation. Conversely, AUD males suffer from dysregulated ceramide and sphingomyelin lipids involving sphingomyelinase, sphingomyelin phosphodiesterase, and sphingomyelin synthase activity, which relates to hepatotoxicity. Notably, the analysis of plasma EVs from AUD females and males demonstrates enrichment of lipid ontology terms associated with "negative intrinsic curvature" and "positive intrinsic curvature", respectively.

CONCLUSIONS

Our methodological developments support an improved understanding of lipid metabolism and regulatory mechanisms, which contribute to the identification of novel lipid targets and the discovery of sex-specific clinical biomarkers in AUD.

Brain volumes in alcohol use disorder: Do females and males differ? A whole-brain magnetic resonance imaging mega-analysis

Emerging evidence suggests distinct neurobiological correlates of alcohol use disorder (AUD) between sexes, which however remain largely unexplored. This work from ENIGMA Addiction Working Group aimed to characterize the sex differences in gray matter (GM) and white matter (WM) correlates of AUD using a whole-brain, voxel-based, multi-tissue mega-analytic approach, thereby extending our recent surface-based region of interest findings on a nearly matching sample using a complementary methodological approach. T1-weighted magnetic resonance imaging (MRI) data from 653 people with AUD and 326 controls was analyzed using voxel-based morphometry. The effects of group, sex, group-by-sex, and substance use severity in AUD on brain volumes were assessed using General Linear Models. Individuals with AUD relative to controls had lower GM volume in striatal, thalamic, cerebellar, and widespread cortical clusters. Group-by-sex effects were found in cerebellar GM and WM volumes, which were more affected by AUD in females than males. Smaller group-by-sex effects were also found in frontotemporal WM tracts, which were more affected in AUD females, and in temporo-occipital and midcingulate GM volumes, which were more affected in AUD males. AUD females but not males showed a negative association between monthly drinks and precentral GM volume. Our results suggest that AUD is associated with both shared and distinct widespread effects on GM and WM volumes in females and males. This evidence advances our previous region of interest knowledge, supporting the usefulness of adopting an exploratory perspective and the need to include sex as a relevant moderator variable in AUD.