Alcohol affects brain functional connectivity and its coupling with behavior: greater effects in male heavy drinkers

Alcohol Expectancy and Cerebral Responses to Cue-Elicited Craving in Adult Nondependent Drinkers

BACKGROUND

Positive alcohol expectancy (AE) contributes to excessive drinking. Many imaging studies have examined cerebral responses to alcohol cues and how these regional processes related to problem drinking. However, it remains unclear how AE relates to cue response and whether AE mediates the relationship between cue response and problem drinking.

METHODS

A total of 61 nondependent drinkers were assessed with the Alcohol Expectancy Questionnaire and Alcohol Use Disorder Identification Test and underwent functional magnetic resonance imaging while exposed to alcohol and neutral cues. Imaging data were processed and analyzed with published routines, and mediation analyses were conducted to examine the interrelationships among global positive score of the Alcohol Expectancy Questionnaire, Alcohol Use Disorder Identification Test score, and regional responses to alcohol versus neutral cues.

RESULTS

Alcohol as compared with neutral cues engaged the occipital, retrosplenial, and medial orbitofrontal cortex as well as the left caudate head and red nucleus. The bilateral thalamus showed a significant correlation in cue response and in left superior frontal cortical connectivity with global positive score in a linear regression. Mediation analyses showed that global positive score completely mediated the relationship between thalamic cue activity as well as superior frontal cortical connectivity and Alcohol Use Disorder Identification Test score. The alternative models that AE contributed to problem drinking and, in turn, thalamic cue activity and connectivity were not supported.

CONCLUSIONS

The findings suggest an important role of the thalamic responses to alcohol cues in contributing to AE and at-risk drinking in nondependent drinkers. AEs may reflect a top-down modulation of the thalamic processing of alcohol cues, influencing the pattern of alcohol use.

Acute alcohol administration dampens central extended amygdala reactivity

Alcohol use is common, imposes a staggering burden on public health, and often resists treatment. The central extended amygdala (EAc)—including the bed nucleus of the stria terminalis (BST) and the central nucleus of the amygdala (Ce)—plays a key role in prominent neuroscientific models of alcohol drinking, but the relevance of these regions to acute alcohol consumption in humans remains poorly understood. Using a single-blind, randomized-groups design, multiband fMRI data were acquired from 49 social drinkers while they performed a well-established emotional faces paradigm after consuming either alcohol or placebo. Relative to placebo, alcohol significantly dampened reactivity to emotional faces in the BST. To rigorously assess potential regional differences in activation, data were extracted from unbiased, anatomically predefined regions of interest. Analyses revealed similar levels of dampening in the BST and Ce. In short, alcohol transiently reduces reactivity to emotional faces and it does so similarly across the two major divisions of the human EAc. These observations reinforce the translational relevance of addiction models derived from preclinical work in rodents and provide new insights into the neural systems most relevant to the consumption of alcohol and to the initial development of alcohol abuse in humans.

Problem Drinking, Alcohol Expectancy, and Thalamic Resting-State Functional Connectivity in Nondependent Adult Drinkers

Alcohol misuse is associated with thalamic dysfunction. The thalamus comprises subnuclei that relay and integrate information between cortical and subcortical structures. However, it is unclear how the subnuclei contribute to thalamic dysfunctions in problem drinking. We investigated resting-state functional connectivity (rsFC) of thalamic subregions in 107 nondependent drinkers (57 women), using masks delineated by white matter tractography. Thalamus was parceled into motor, somatosensory, visual, premotor, frontal association, parietal association, and temporal association subregions. Whole-brain linear regression, each against Alcohol Use Disorders Identification Test (AUDIT) and positive alcohol expectancy (AE) score with age as a covariate, was performed for each seed, for men and women combined, and separately. Overall, problem drinking was associated with increased thalamic connectivities, whereas AE was associated with a mixed pattern of increased and decreased connectivities. Motor, premotor, somatosensory, and frontal association thalamic connectivity with bilateral caudate head was positively correlated with AUDIT score in men and women combined. Connectivity of the right caudate head with frontal association and premotor thalamus was also positively correlated with AE score in men and women combined. In contrast, motor and premotor thalamic connectivity with a number of cortical and subcortical structures showed sex differences in the correlation each with AUDIT and AE score. In mediation analyses, AE score completely mediated the correlation between thalamic caudate connectivity and AUDIT score, whereas the model where AE contributed to problem drinking and, in turn, altered thalamic caudate connectivity was not supported. To conclude, thalamic subregional rsFCs showed both shared and distinct changes and sex differences in association with problem drinking and AE. Increased thalamic caudate connectivity may contribute to problem drinking via enhanced AE. The findings suggest the importance of examining thalamic subdivisions and sex in investigating the functional roles of thalamus in problem drinking.

Bariatric surgery in obese patients reduced resting connectivity of brain regions involved with self-referential processing

Obese individuals exhibit brain alterations of resting-state functional connectivity (RSFC) integrity of resting-state networks (RSNs) related to food intake. Bariatric surgery is currently the most effective treatment for combating morbid obesity. How bariatric surgery influences neurocircuitry is mostly unknown. Functional connectivity density (FCD) mapping was employed to calculate local (lFCD)/global (gFCD) voxelwise connectivity metrics in 22 obese participants who underwent functional magnetic resonance imaging before and 1 month after sleeve gastrectomy (SG), and in 19 obese controls (Ctr) without surgery but tested twice (baseline and 1-month later). Two factor (group, time) repeated measures ANOVA was used to assess main and interaction effects in lFCD/gFCD; regions of interest were identified for subsequent seed to voxel connectivity analyses to assess resting-state functional connectivity and to examine association with weight loss. Bariatric surgery significantly decreased lFCD in VMPFC, posterior cingulate cortex (PCC)/precuneus, and dorsal anterior cingulate cortex (dACC)/dorsomedial prefrontal cortex (DMPFC) and decreased gFCD in VMPFC, right dorsolateral prefrontal cortex (DLPFC) and right insula (p_FWE  < .05). lFCD decreased in VMPFC and PCC/precuneus correlated with reduction in BMI after surgery. Seed to voxel connectivity analyses showed the VMPFC had stronger connectivity with left DLPFC and weaker connectivity with hippocampus/parahippocampus, and PCC/precuneus had stronger connectivity with right caudate and left DLPFC after surgery. Bariatric surgery significantly decreased FCD in regions involved in self-referential processing (VMPFC, DMPFC, dACC, and precuneus), and interoception (insula), and changes in VMPFC/precuneus were associated with reduction in BMI suggesting a role in improving control of eating behaviors following surgery.

Alcohol Consumption and Subclinical Findings on Cognitive Function, Biochemical Indexes, and Cortical Anatomy in Cognitively Normal Aging Han Chinese Population

Background: Binge drinking of alcohol is associated with brain damage, but less is known about relationship of light-to-moderate alcohol consumption with cognitive function, biochemical indexes, and cortical anatomy. Previous findings have debated on whether light-to-moderate drinking has any health benefits. We investigated cortical thickness and its association with alcohol consumption and cognitive functions in a non-dementia aging Han Chinese population.

Methods: 940 non-dementia aging subjects were included in our study (alcohol n = 149; non-alcohol n = 791). Among them, 572 received blood biochemical tests including liver function and lipid metabolism (alcohol n = 100; non-alcohol n = 472) and 141 had brain magnetic resonance imaging (alcohol n = 27; non-alcohol n = 114). The Beijing version of the Montreal Cognitive Assessment and the Chinese version of the neuropsychological test battery were used to assess cognitive functions.

Results: There was no significant difference in cognitive functions between alcohol and non-alcohol groups in the overall database. Similarly, there was no significant difference in liver function and lipid metabolism between two groups in the sub-database. The left superiortemporal gyrus was one of age sensitive regions and alcohol consumption was significantly associated with thinner cortex of the left superiotemporal cluster in the sub-database.

Conclusion: Alcohol consumption was not significantly associated with better or worse cognitive function and biochemical indexes abnormality, however, significantly associated with thinner cortex of the left superiortemporal gyrus in cognitively normal aging Han Chinese population.

Presence and User Experience in a Virtual Environment under the Influence of Ethanol: An Explorative Study

Virtual Reality (VR) is used for a variety of applications ranging from entertainment to psychological medicine. VR has been demonstrated to influence higher order cognitive functions and cortical plasticity, with implications on phobia and stroke treatment. An integral part for successful VR is a high sense of presence - a feeling of 'being there' in the virtual scenario. The underlying cognitive and perceptive functions causing presence in VR scenarios are however not completely known. It is evident that the brain function is influenced by drugs, such as ethanol, potentially confounding cortical plasticity, also in VR. As ethanol is ubiquitous and forms part of daily life, understanding the effects of ethanol on presence and user experience, the attitudes and emotions about using VR applications, is important. This exploratory study aims at contributing towards an understanding of how low-dose ethanol intake influences presence, user experience and their relationship in a validated VR context. It was found that low-level ethanol consumption did influence presence and user experience, but on a minimal level. In contrast, correlations between presence and user experience were strongly influenced by low-dose ethanol. Ethanol consumption may consequently alter cognitive and perceptive functions related to the connections between presence and user experience.

Aberrant patterns of local and long-range functional connectivity densities in schizophrenia

Schizophrenia is a disorder of brain dysconnectivity, and both the connection strength and connection number are disrupted in patients with schizophrenia. The functional connectivity density (FCD) can reflect alterations in the connection number. Alterations in the global FCD (gFCD) in schizophrenia were previously demonstrated; however, alterations in two other indices of the pathological characteristics of the brain, local FCD (lFCD) and long-range FCD (lrFCD), have not been revealed. To investigate lFCD and lrFCD alterations in patients with schizophrenia, 95 patients and 93 matched healthy controls were examined using structural and resting-state functional magnetic resonance imaging scanning. lFCD and lrFCD were measured using FCD mapping, and differences were identified using a two-sample t-test in a voxel-wise manner, with age and gender considered to increase variability. Multiple comparisons were performed using a false discovery rate method with a corrected threshold of P<0.05. Our analysis showed that lFCD was primarily decreased in the postcentral gyrus, right calcarine sulcus, and inferior occipital gyrus lobule, but increased in the bilateral subcortical regions. The differences in lFCD were more pronounced and complicated than those in lrFCD. In summary, in contrast with previous studies that focused on the connection strength, our findings, from the perspective of connection number, indicate that schizophrenia is a disorder of brain dysconnectivity, particularly affecting the local functional connectivity network, and support the hypothesis that schizophrenia is associated with a widespread cortical functional connectivity/activity deficit, with hyper- and/or hypo-connectivity/activity coexisting in some cortical or subcortical regions.

An asymptotic theory for cross-correlation between auto-correlated sequences and its application on neuroimaging data

BACKGROUND

Functional connectivity is among the most important tools to study brain. The correlation coefficient, between time series of different brain areas, is the most popular method to quantify functional connectivity. Correlation coefficient in practical use assumes the data to be temporally independent. However, the time series data of brain can manifest significant temporal auto-correlation.

NEW METHOD

A widely applicable method is proposed for correcting temporal auto-correlation. We considered two types of time series models: (1) auto-regressive-moving-average model, (2) nonlinear dynamical system model with noisy fluctuations, and derived their respective asymptotic distributions of correlation coefficient. These two types of models are most commonly used in neuroscience studies. We show the respective asymptotic distributions share a unified expression.

RESULT

We have verified the validity of our method, and shown our method exhibited sufficient statistical power for detecting true correlation on numerical experiments. Employing our method on real dataset yields more robust functional network and higher classification accuracy than conventional methods.

COMPARISON WITH EXISTING METHODS

Our method robustly controls the type I error while maintaining sufficient statistical power for detecting true correlation in numerical experiments, where existing methods measuring association (linear and nonlinear) fail.

CONCLUSIONS

In this work, we proposed a widely applicable approach for correcting the effect of temporal auto-correlation on functional connectivity. Empirical results favor the use of our method in functional network analysis.

Earlier alcohol use onset prospectively predicts changes in functional connectivity

BACKGROUND

Half of all new alcohol initiates are between 12 and 17 years old. This is a period of intense neurodevelopment, including changes in functional connectivity patterns among higher-order function areas. It is crucial to understand how alcohol-related neurotoxicity may be influenced by drinking onset age.

DESIGN

This study prospectively examined the effects of age of first drink on frontoparietal context-dependent functional connectivity (cdFC) during a visual working memory task. Youth 13.5 years of age (SD = 1.2) underwent a neuropsychological and neuroimaging session before drinking initiation and at follow-up 6 years later. Hierarchical linear regressions examined if youth with earlier ages of onset for first and weekly alcohol use showed higher follow-up cdFC between the dorsolateral prefrontal cortex and posterior parietal cortex regions of interest and whole-brain exploratory regions, controlling for pre-drinking cdFC. Higher follow-up cdFC was hypothesized to be correlated with poorer performances in neuropsychological performance.

RESULTS

Exploratory whole-brain analyses showed that, as hypothesized, earlier ages of weekly drinking onset were associated with higher cdFC between the bilateral posterior cingulate and cortical and subcortical areas implicated in attentional processes, which was in turn associated with poorer performance on neuropsychological tasks of attention, ps < .05. No relationship between age of onset and cdFC between the two ROIs were found.

CONCLUSION

Earlier ages of weekly alcohol use initiation may adversely affect neurodevelopment by reducing developmentally appropriate integration of attentional circuits during a cognitive challenge. Delaying the onset of weekly alcohol use patterns well after early adolescence may reduce the risk for harm of alcohol use on the brain.

Adolescent alcohol exposure decreases frontostriatal resting-state functional connectivity in adulthood

Connectivity of the prefrontal cortex (PFC) matures through adolescence, coinciding with emergence of adult executive function and top-down inhibitory control over behavior. Alcohol exposure during this critical period of brain maturation may affect development of PFC and frontolimbic connectivity. Adult rats exposed to adolescent intermittent ethanol (AIE; 5 g/kg ethanol, 25 percent v/v in water, intragastrically, 2-day-on, 2-day-off, postnatal day 25-54) or water control underwent resting-state functional MRI to test the hypothesis that AIE induces persistent changes in frontolimbic functional connectivity under baseline and acute alcohol conditions (2 g/kg ethanol or saline, intraperitoneally administered during scanning). Data were acquired on a Bruker 9.4-T MR scanner with rats under dexmedetomidine sedation in combination with isoflurane. Frontolimbic network regions-of-interest for data analysis included PFC [prelimbic (PrL), infralimbic (IL), and orbitofrontal cortex (OFC) portions], nucleus accumbens (NAc), caudate putamen (CPu), dorsal hippocampus, ventral tegmental area, amygdala, and somatosensory forelimb used as a control region. AIE decreased baseline resting-state connectivity between PFC subregions (PrL-IL and IL-OFC) and between PFC-striatal regions (PrL-NAc, IL-CPu, IL-NAc, OFC-CPu, and OFC-NAc). Acute ethanol induced negative blood-oxygen-level-dependent changes within all regions of interest examined, along with significant increases in functional connectivity in control, but not AIE animals. Together, these data support the hypothesis that binge-like adolescent alcohol exposure causes persistent decreases in baseline frontolimbic (particularly frontostriatal) connectivity and alters sensitivity to acute ethanol-induced increases in functional connectivity in adulthood.

Effect of combined naltrexone and bupropion therapy on the brain's functional connectivity

Background

The control of food intake in environments with easy access to highly rewarding foods is challenging to most modern societies. The combination of sustained release (SR) naltrexone and SR bupropion (NB32) has been used in weight-loss and obesity management. However, the effects of NB32 on the brain circuits implicated in the regulation of food intake are unknown. Here we used functional connectivity density (FCD) mapping to evaluate the effects of NB32 on resting brain FC.

Methods

Thirty-six healthy women underwent magnetic resonance imaging (MRI) before and after 4-week treatment with NB32 (n = 16) or with placebo (n = 20). In each imaging visit, a 5-min resting-state functional MRI scan was conducted after 15 h of fasting. The FC of brain regions showing significant group effects on FCD were subsequently assessed using seed-voxel correlation analyses. We characterized the associations between FCD measures and craving control scores in the Control of Eating Questionnaire.

Results

After NB32 treatment, the group showed lower local and global FCD than the placebo group in the right superior parietal cortex and lower local FCD in the left middle frontal gyrus. Seed-voxel correlation analysis for the right superior parietal cortex seed demonstrated higher positive FC with the dorsal anterior cingulate gyrus (ACC), bilateral insula, and left superior parietal gyrus and stronger negative FC with right inferior frontal gyrus and right superior parietal cortices for the NB32 than the placebo group. Further, the NB32 group showed a significant correlation between local FCD change after treatment in left middle frontal gyrus and craving control scores (r = 0.519, p = 0.039).

Conclusions

NB32 treatment decreased local and global FCD in superior parietal cortex and increased its connectivity with ACC (involved with saliency attribution), insula (interoception), and decreased local FCD in the medial prefrontal cortex (craving), which might underlie NB32 improved control over eating behaviors. ClinicalTrails.gov: NCT00711.

Metabotropic glutamate receptor 5 binding in male patients with alcohol use disorder

Glutamate signaling plays a major role in addiction. Preclinical research strongly suggests an implication of G-protein-coupled metabotropic glutamate receptor subtype 5 (mGluR5) in nicotine addiction and alcohol use disorder. In humans, smoking is related to a global reduction in mGluR5 availability. In the present study, we investigated mGluR5 in vivo in patients with alcohol use disorder without the confounding effects of smoking. A total of 14 male subjects with alcohol use disorder and at least a 25-day abstinence and 14 matched male non-smoking healthy controls were included in the study. We employed positron emission tomography (PET) with the mGluR5-specific radiotracer [11C]ABP688, using a bolus/infusion protocol. We found increased mGluR5 DVR in several regions within the temporal lobe in patients, as compared to controls. The largest between-group difference was in the amygdala. There was a marked positive relation between mGluR5 DVR in the anterior cingulate and mGluR5 DVR in the orbitofrontal cortex in patients, but not in controls. In patients, lower temptation to drink was related to higher amygdala mGluR5 DVR. We did not find altered mGluR5 DVR in the basal ganglia of subjects recovering from alcohol use disorder. In conclusion, our study provides clinical evidence for altered mGluR5 signaling in the amygdala in alcohol use disorder. This alteration was associated with the temptation to drink. In addition, this study suggests abnormal mGluR5 signaling in a network underlying reward-related behavioral flexibility. These findings strengthen the case for pharmacological agents acting on mGluR5 as promising candidates for the treatment of alcohol use disorder.

Heavy alcohol use in adolescence is associated with altered cortical activity: a combined TMS-EEG study

Long-term alcohol use affects cognitive and neurophysiological functioning as well as structural brain development. Combining simultaneous electroencephalogram (EEG) recording with transcranial magnetic stimulation (TMS) enables direct, in vivo exploration of cortical excitability and assessment of effective and functional connectivity. In the central nervous system, the effects of alcohol are particularly mediated by alterations in gamma-aminobutyric acid (GABA)ergic neurotransmission, and TMS-evoked potentials (TEPs) N45 and N100 in EEG are known to reflect GABAergic function. However, no previous studies have examined the effects of long-term alcohol use in adolescence on TEPs. In this study, a total of 27 young adults with heavy alcohol use in adolescence and 25 age-matched, gender-matched and education-matched controls with little or no alcohol use participated in TMS-EEG measurements. The motor cortex (M1) was stimulated with an intensity of 90 percent of the resting motor threshold of the abductor pollicis brevis muscle. No significant differences were found in the resting motor threshold, TEP latencies or neuropsychological functioning between the groups. We observed an increase in the global mean field power in the time window of 54- to 75-millisecond post-TMS, as well as significant topographical differences in the P60 and N100 in those with a history of heavy drinking. Furthermore, there was a marked increase in the GABAergic N45 amplitude in alcohol users. These findings suggest that long-term alcohol use in adolescence, even when not meeting the diagnostic criteria for a disorder, is associated with changes in connectivity and cortical excitability.

Frequency-Specific Functional Connectivity Density as an Effective Biomarker for Adolescent Generalized Anxiety Disorder

Several neuropsychiatric diseases have been found to influence the frequency-specific spontaneous functional brain organization (SFBO) in resting state, demonstrating that the abnormal brain activities of different frequency bands are associated with various physiological and psychological dysfunctions. However, little is known about the frequency specificities of SFBO in adolescent generalized anxiety disorder (GAD). Here, a novel complete ensemble empirical mode decomposition with adaptive noise method was applied to decompose the time series of each voxel across all participants (31 adolescent patients with GAD and 28 matched healthy controls; HCs) into four frequency-specific bands with distinct intrinsic oscillation. The functional connectivity density (FCD) of different scales (short-range and long-range) was calculated to quantify the SFBO changes related to GAD within each above frequency-specific band and the conventional frequency band (0.01–0.08 Hz). Support vector machine classifier was further used to examine the discriminative ability of the frequency-specific FCD values. The results showed that adolescent GAD patients exhibited abnormal alterations of both short-range and long-range FCD (S-FCD and L-FCD) in widespread brain regions across three frequency-specific bands. Positive correlation between the State Anxiety Inventory (SAI) score and increased L-FCD in the fusiform gyrus in the conventional frequency band was found in adolescents with GAD. Both S-FCD and L-FCD in the insula in the lower frequency band (0.02–0.036 Hz) had the highest classification performance compared to all other brain regions with inter-group difference. Furthermore, a satisfactory classification performance was achieved by combining the discrepant S-FCD and L-FCD values in all frequency bands, with the area under the curve (AUC) value of 0.9414 and the corresponding sensitivity, specificity, and accuracy of 87.15, 92.92, and 89.83%, respectively. This study indicates that the alterations of SFBO in adolescent GAD are frequency dependence and the frequency-specific FCD can potentially serve as a valuable biomarker in discriminating GAD patients from HCs. These findings may provide new insights into the pathophysiological mechanisms of adolescent GAD.

Subcortical Local Functional Hyperconnectivity in Cannabis Dependence

BACKGROUND

Cannabis abuse (CA) has been associated with psychopathology, including negative emotionality and higher risk of psychosis, particularly with early age of initiation. However, the mechanisms underlying this association are poorly understood. Because aberrant dopamine signaling is implicated in cannabis-associated psychopathology, we hypothesized that regular CA would be associated with altered resting-state functional connectivity in dopamine midbrain-striatal circuits.

METHODS

We examined resting-state brain activity of subcortical regions in 441 young adults from the Human Connectome Project, including 30 subjects with CA meeting DSM-IV criteria for dependence and 30 control subjects matched on age, sex, education, body mass index, anxiety, depression, and alcohol and tobacco usage.

RESULTS

Across all subjects, local functional connectivity density hubs in subcortical regions were most prominent in ventral striatum, hippocampus, amygdala, dorsal midbrain, and posterior-ventral brainstem. As hypothesized, subjects with CA showed markedly increased local functional connectivity density relative to control subjects, not only in ventral striatum (where nucleus accumbens is located) and midbrain (where substantia nigra and ventral tegmental nuclei are located) but also in brainstem and lateral thalamus. These effects were observed in the absence of significant differences in subcortical volumes and were most pronounced in individuals who began cannabis use earliest in life and who reported high levels of negative emotionality.

CONCLUSIONS

Together, these findings suggest that chronic CA is associated with changes in resting-state brain function, particularly in dopaminergic nuclei implicated in psychosis but that are also critical for habit formation and reward processing. These results shed light on neurobiological differences that may be relevant to psychopathology associated with cannabis use.

Correlation between Traits of Emotion-Based Impulsivity and Intrinsic Default-Mode Network Activity

Negative urgency (NU) and positive urgency (PU) are implicated in several high-risk behaviors, such as eating disorders, substance use disorders, and nonsuicidal self-injury behavior. The current study aimed to explore the possible link between trait of urgency and brain activity at rest. We assessed the amplitude of low-frequency fluctuations (ALFF) of the resting-state functional magnetic resonance imaging (fMRI) signal in 85 healthy volunteers. Trait urgency measures were related to ALFF in the lateral orbitofrontal cortex, dorsolateral prefrontal cortex, ventral and dorsal medial frontal cortex, anterior cingulate, and posterior cingulate cortex/precuneus. In addition, trait urgency measures showed significant correlations with the functional connectivity of the posterior cingulate cortex/precuneus seed with the thalamus and midbrain region. These findings suggest an association between intrinsic brain activity and impulsive behaviors in healthy humans.

Temporal Evolution of Brain Functional Connectivity Metrics: Could 7 Min of Rest be Enough?

Unaccounted temporal dynamics of resting-state functional connectivity (FC) metrics challenges their potential as biomarkers for clinical applications in neuroscience. Here we studied the scan time required to reach stable values for various FC metrics including seed-voxel correlations and spatial independent component analyses (sICA), and for the local functional connectivity density (lFCD), a graph theory metric. By increasing the number of time points included in the analysis, we assessed the effects of scan time on convergence of accuracy, sensitivity, specificity, reproducibility, and reliability of these FC metrics. The necessary scan time to attenuate the effects of the temporal dynamics by 80% varied across connectivity metrics and was shorter for lFCD (7 min) than for FC (11 min) or for sICA (10 min). Findings suggest that the scan time required to achieve stable FC is metric-dependent, with lFCD being the most resilient metric to the effects of temporal dynamics. Thus, the lFCD metric could be particularly useful for pediatric and patient populations who may not tolerate long scans.

Sex differences in the interacting roles of impulsivity and positive alcohol expectancy in problem drinking: A structural brain imaging study

Alcohol expectancy and impulsivity are implicated in alcohol misuse. However, how these two risk factors interact to determine problem drinking and whether men and women differ in these risk processes remain unclear. In 158 social drinkers (86 women) assessed for Alcohol Use Disorder Identification Test (AUDIT), positive alcohol expectancy, and Barratt impulsivity, we examined sex differences in these risk processes. Further, with structural brain imaging, we examined the neural bases underlying the relationship between these risk factors and problem drinking. The results of general linear modeling showed that alcohol expectancy best predicted problem drinking in women, whereas in men as well as in the combined group alcohol expectancy and impulsivity interacted to best predict problem drinking. Alcohol expectancy was associated with decreased gray matter volume (GMV) of the right posterior insula in women and the interaction of alcohol expectancy and impulsivity was associated with decreased GMV of the left thalamus in women and men combined and in men alone, albeit less significantly. These risk factors mediated the correlation between GMV and problem drinking. Conversely, models where GMV resulted from problem drinking were not supported. These new findings reveal distinct psychological factors that dispose men and women to problem drinking. Although mediation analyses did not determine a causal link, GMV reduction in the insula and thalamus may represent neural phenotype of these risk processes rather than the consequence of alcohol consumption in non-dependent social drinkers. The results add to the alcohol imaging literature which has largely focused on dependent individuals and help elucidate alterations in brain structures that may contribute to the transition from social to habitual drinking.

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Alcohol expectancy (AE) and impulsivity are risk factors for problem drinking.

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AE mediates the correlation between right insula GMV and problem drinking in women.

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AE and impulsivity interacts to mediate left thalamus GMV and problem drinking in all.

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Models where changes in GMV as a result of problem drinking are not supported.

Brain structural and functional dissociated patterns in schizophrenia

BACKGROUND

Although previous studies found that aberrations in gray matter volume (GMV) and global functional connectivity density (gFCD) are important characteristics of schizophrenia, to the best of our knowledge no study to date has investigated the associations between the spatial distribution patterns of GMV and gFCD alterations. We investigated pattern changes in gFCD and GMV among patients with schizophrenia and their associated spatial distributions.

METHODS

Ninety-five patients with schizophrenia and 93 matched healthy controls underwent structural and resting-state functional MRI scanning to assess gFCD and GMV.

RESULTS

We found that gFCD increased in the subcortical regions (caudate, pallidum, putamen, and thalami) and limbic system (left hippocampus and parahippocampus), and decreased in the posterior parieto-occipito-temporal cortices (postcentral gyri, occipital cortex, temporo-occipital conjunction, and inferior parietal lobule), in patients with schizophrenia. By contrast, we found decreased GMV in brain regions including the frontal, parietal, temporal, occipital, cingulate cortices, and the insular, striatum, thalamus in these patients. Increased gFCD primarily occurred in subcortical regions including the basal ganglia and some regions of the limbic system. Decreased gFCD appeared primarily in the cortical regions. There were no statistically significant correlations between changes in gFCD and GMV, and their spatial distribution patterns, in different regions.

CONCLUSIONS

Our findings indicate that gFCD and GMV are both perturbed in multiple brain regions in schizophrenia. gFCD and GMV consistently decreased in the cortical regions, with the exception of the Supplementary Motor Area (SMA). However, in the sub-cortical regions, the alterations of gFCD and GMV showed the opposite pattern, with increased gFCD and decreased GMV simultaneously observed in these regions. Overall, our findings suggest that structural and functional alterations appear to contribute independently to the neurobiology of schizophrenia.

Treating Addiction: Perspectives from EEG and Imaging Studies on Psychedelics

Despite reports of apparent benefits, social and political pressure beginning in the late 1960s effectively banned scientific inquiry into psychedelic substances. Covert examination of psychedelics persisted through the 1990s; the turn of the century and especially the past 10 years, however, has seen a resurgent interest in psychedelic substances (eg, LSD, ayahuasca, psilocybin). This chapter outlines relevant EEG and brain imaging studies evaluating the effects of psychedelics on the brain. This chapter also reviews evidence of the use of psychedelics as adjunct therapy for a number of psychiatric and addictive disorders. In particular, psychedelics appear to have efficacy in treating depression and alcohol-use disorders.