Neural processes of an indirect analog of risk taking in young nondependent adult alcohol drinkers-an FMRI study of the stop signal task

Statistical Nonparametric fMRI Maps in the Analysis of Response Inhibition in Abstinent Individuals with History of Alcohol Use Disorder

Inhibitory impairments may persist after abstinence in individuals with alcohol use disorder (AUD). Using traditional statistical parametric mapping (SPM) fMRI analysis, which requires data to satisfy parametric assumptions often difficult to satisfy in biophysical system as brain, studies have reported equivocal findings on brain areas responsible for response inhibition, and activation abnormalities during inhibition found in AUD persist after abstinence. Research is warranted using newer analysis approaches. fMRI scans were acquired during a Go/NoGo task from 30 abstinent male AUD and 30 healthy control participants with the objectives being (1) to characterize neuronal substrates associated with response inhibition using a rigorous nonparametric permutation-based fMRI analysis and (2) to determine whether these regions were differentially activated between abstinent AUD and control participants. A blood oxygen level dependent contrast analysis showed significant activation in several right cortical regions and deactivation in some left cortical regions during successful inhibition. The largest source of variance in activation level was due to group differences. The findings provide evidence of cortical substrates employed during response inhibition. The largest variance was explained by lower activation in inhibition as well as ventral attentional cortical networks in abstinent individuals with AUD, which were not found to be associated with length of abstinence, age, or impulsiveness.

Prefrontal activity during the emotional go/no-go task and computational markers of risk-based decision-making predict future relapse in alcohol use disorder

AIM

To longitudinally examine if the results of cognitive tasks or brain function during emotional or cognitive tasks can predict relapse in alcohol use disorder.

METHODS

We selected 41 patients with alcohol use disorder during hospitalization. Functional near-infrared spectroscopy (fNIRS) measured the relative change in oxygenated hemoglobin in the frontotemporal areas during an emotional go/no-go task and verbal fluency task (VFT). They performed the N-back and risk-based decision-making tasks for determining working memory or risk-based decision-making. The presence of relapse 6 months following discharge was the primary outcome.

RESULTS

Twenty-four patients (21 men, three women) remained abstinent, whereas 17 (14 men, three women) relapsed. Compared with the abstinent group, those with relapse displayed significantly decreased activation in the right frontotemporal region during the emotional go/no-go task, significantly shorter reaction time to non-emotional stimuli, and greater risk preference in the risk-based decision-making task. In the abstinent group, we observed a negative correlation between oxygenated hemoglobin and the craving scale. A logistic regression analysis demonstrated that the risk of relapse increased with smaller oxygenated hemoglobin in the right frontotemporal region (odds ratio = 0.161, p = 0.013) and with greater gambling thoughts (odds ratio = 7.04, p = 0.033).

CONCLUSION

Decreased activation in the right frontotemporal region in response to an emotional stimulus and risk preference could predict relapse in alcohol use disorder.

Addictions NeuroImaging Assessment (ANIA): Towards an integrative framework for alcohol use disorder

Alcohol misuse and addiction are major international public health issues. Addiction can be characterized as a disorder of aberrant neurocircuitry interacting with environmental, genetic and social factors. Neuroimaging in alcohol misuse can thus provide a critical window into underlying neural mechanisms, highlighting possible treatment targets and acting as clinical biomarkers for predicting risk and treatment outcomes. This neuroimaging review on alcohol misuse in humans follows the Addictions Neuroclinical Assessment (ANA) that proposes incorporating three functional neuroscience domains integral to the neurocircuitry of addiction: incentive salience and habits, negative emotional states, and executive function within the context of the addiction cycle. Here we review and integrate multiple imaging modalities focusing on underlying cognitive processes such as reward anticipation, negative emotionality, cue reactivity, impulsivity, compulsivity and executive function. We highlight limitations in the literature and propose a model forward in the use of neuroimaging as a tool to understanding underlying mechanisms and potential clinical applicability for phenotyping of heterogeneity and predicting risk and treatment outcomes.

"Free won't" after a beer or two: chronic and acute effects of alcohol on neural and behavioral indices of intentional inhibition

BACKGROUND

Response inhibition can be classified into stimulus-driven inhibition and intentional inhibition based on the degree of endogenous volition involved. In the past decades, abundant research efforts to study the effects of alcohol on inhibition have focused exclusively on stimulus-driven inhibition. The novel Chasing Memo task measures stimulus-driven and intentional inhibition within the same paradigm. Combined with the stop-signal task, we investigated how alcohol use affects behavioral and psychophysiological correlates of intentional inhibition, as well as stimulus-driven inhibition.

METHODS

Experiment I focused on intentional inhibition and stimulus-driven inhibition in relation to past-year alcohol use. The Chasing Memo task, the stop-signal task, and questionnaires related to substance use and impulsivity were administered to 60 undergraduate students (18-25 years old). Experiment II focused on behavioral and neural correlates acute alcohol use on performance on the Chasing Memo task by means of electroencephalography (EEG). Sixteen young male adults (21-28 years old) performed the Chasing Memo task once under placebo and once under the influence of alcohol (blood alcohol concentration around 0.05%), while EEG was recorded.

RESULTS

In experiment I, AUDIT (Alcohol Use Disorder Identification Test) total score did not significantly predict stimulus-driven inhibition or intentional inhibition performance. In experiment II, the placebo condition and the alcohol condition were comparable in terms of behavioral indices of stimulus-driven inhibition and intentional inhibition as well as task-related EEG patterns. Interestingly, a slow negative readiness potential (RP) was observed with an onset of about 1.2 s, exclusively before participants stopped intentionally.

CONCLUSIONS

These findings suggest that both past-year increases in risky alcohol consumption and moderate acute alcohol use have limited effects on stimulus-driven inhibition and intentional inhibition. These conclusions cannot be generalized to alcohol use disorder and high intoxication levels. The RP might reflect processes involved in the formation of an intention in general.

Isolating Proactive Slowing from Reactive Inhibitory Control in Heavy Drinkers

Background: Impaired inhibitory control is thought to contribute to alcohol (mis)use. However, current definitions of inhibitory control are over-simplified by a failure to distinguish reactive inhibitory control from proactive slowing. Objectives: To distinguish "reactive" inhibitory control and proactive slowing in heavy drinkers, and characterize associations between both constructs and individual differences in alcohol consumption. Methods: Sixty heavy drinkers completed self-reported measures of alcohol consumption, followed by two modified Stop-Signal tasks and an AX-continuous performance task in a laboratory setting. Results: Heavy drinkers demonstrated proactive slowing when inhibition was more likely but individual differences in proactive slowing and reactive stopping were unrelated to individual differences in alcohol consumption. Conclusions/Importance: Within a sample of heavy drinkers, individual differences in reactive inhibitory control and proactive slowing are unrelated to individual differences in alcohol consumption.

Young frequent binge drinkers show no behavioral deficits in inhibitory control and cognitive flexibility

Alcohol intoxication and abuse are well-known to cause impairments in executive functioning and control. Still, we know surprisingly little about individuals engaging in frequent binge drinking, even though they have an increased risk to develop an alcohol use disorder (AUD) later in life. As this risk has been suggested to be linked to (premorbid) executive deficits, we assessed changes in cognitive flexibility and inhibition with the help of a switching task and a stop-change task. Both paradigms had previously been shown to be modulated by alcohol, as well as by functional variations in dopaminergic and GABAergic neurotransmission. We employed an extreme group approach, where we compared pre-selected samples of frequent binge drinkers and non-frequent binge drinkers, all of which had stably pursued their respective consumption pattern for at least 3 years. In combination with Bayes analyses, our results showed that individuals engaging in frequent binge drinking showed no impairments of cognitive flexibility or inhibition, as compared to non-frequent binge drinkers. These observations suggest that frequent binge drinking alone is not associated with the cognitive control deficits commonly observed in AUD. Importantly, the investigated executive functions are known to be altered both during binge drinking and in individuals with AUD. It could hence be speculated that their intermittent consumption pattern prevents non-AUD frequent binge drinkers from the homeostatic counter-regulations of alcohol- and control-associated neurotransmitter systems that may be observed in AUD patients. Yet, this hypothesis still needs to be tested in future research, including studies that combine MR and molecular imaging.

Differential Activation of the Left and Right Cerebral Hemispheres of Individuals Who Use or are Dependent on Drugs of Abuse

Introduction:

The left and right cerebral hemispheres are not equivalent in performance of cognitive functions associated with risk factors of drug abuse, nor is their development equivalently affected by drugs of abuse. The question addressed here is whether drugs of abuse affect cognitive function as assessed by brain activation, in particular related to impulsivity, and/or whether weaker brain activation associated with impulsivity increases the risk of drug abuse.

Methodology:

Using PubMed and key words, articles were selected that addressed brain activation in individuals who used or abused one of the psychoactive drugs. Findings are summarized.

Results:

For each of the drugs, hypoactivation was found. In some cases this reduced activation was reported predominantly for the right or both hemispheres. There were fewer reports for the left hemisphere.

Discussion and Conclusion:

Rarely do authors focus on why only one or the other hemisphere is affected or why specific structures are affected. Neurobiological differences between the hemispheres and among various brain structures could provide clues to the specific effect of drugs. Increased attention to this gap in research will give additional insights into the etiology of drug abuse and provide direction for treatment.

Dynamic network dysfunction in cocaine dependence: Graph theoretical metrics and stop signal reaction time

Graphic theoretical metrics have become increasingly popular in characterizing functional connectivity of neural networks and how network connectivity is compromised in neuropsychiatric illnesses. Here, we add to this literature by describing dynamic network connectivities of 78 cocaine dependent (CD) and 85 non-drug using healthy control (HC) participants who underwent fMRI during performance of a stop signal task (SST). Compared to HC, CD showed prolonged stop signal reaction time (SSRT), consistent with deficits in response inhibition. In graph theoretical analysis of dynamic functional connectivity, we examined temporal flexibility and spatiotemporal diversity of 14 networks covering the whole brain. Temporal flexibility quantifies how frequently a brain region interacts with regions of other communities across time, with high temporal flexibility indicating that a region interacts predominantly with regions outside its own community. Spatiotemporal diversity quantifies how uniformly a brain region interacts with regions in other communities over time, with high spatiotemporal diversity indicating that the interactions are more evenly distributed across communities. Compared to HC, CD exhibited decreased temporal flexibility and increased spatiotemporal diversity in the great majority of neural networks. The graph metric measures of the default mode network negatively correlated with SSRT in CD but not HC. The findings are consistent with diminished temporal flexibility and a compensatory increase in spatiotemporal diversity, in association with impairment of a critical executive function, in cocaine addiction. More broadly, the findings suggest that graph theoretical metrics provide new insights for connectivity analyses to elucidate network dysfunction that may elude conventional measures.

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Cocaine addiction (CA) is associated with prolonged stop signal reaction time (SSRT).

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CA is associated with decreased temporal flexibility (TF) of neural networks.

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CA is associated with increased spatial temporal diversity (STD) of neural networks.

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The TF and STD of default mode network correlated negatively with SSRT in CA.

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Dynamic connectivity captures network dysfunction in link with inhibition deficits in CA.

Barratt Impulsivity in Healthy Adults Is Associated with Higher Gray Matter Concentration in the Parietal Occipital Cortex that Represents Peripheral Visual Field

Impulsivity is a personality trait of clinical importance. Extant research focuses on fronto-striatal mechanisms of impulsivity and how executive functions are compromised in impulsive individuals. Imaging studies employing voxel based morphometry highlighted impulsivity-related changes in gray matter concentrations in a wide array of cerebral structures. In particular, whereas prefrontal cortical areas appear to show structural alterations in individuals with a neuropsychiatric condition, the findings are less than consistent in the healthy population. Here, in a sample (n = 113) of young adults assessed for Barratt impulsivity, we controlled for age, gender and alcohol use, and showed that higher impulsivity score is associated with increased gray matter volume (GMV) in bilateral medial parietal and occipital cortices known to represent the peripheral visual field. When impulsivity components were assessed, we observed that this increase in parieto-occipital cortical volume is correlated with inattention and non-planning but not motor subscore. In a separate behavioral experiment of 10 young adults, we demonstrated that impulsive individuals are more vulnerable to the influence of a distractor on target detection in an attention task. If replicated, these findings together suggest aberrant visual attention as a neural correlate of an impulsive personality trait in neurotypical individuals and need to be reconciled with the literature that focuses on frontal dysfunctions.

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.

Error detection and behavioural inhibition in young heavy drinkers

BACKGROUND

Increases in inhibitory errors in heavy drinkers are established; less well-studied is whether heavy drinkers are aware of these errors in performance. Reductions in error detection and awareness limit the possibility for remedial action to be taken, and have implications for substance abusers seeking to control use: failure to monitor and/or adjust ongoing behaviour may be linked to using more or more often than intended, and failing to adjust behaviour after a slip. Here we report the first study of both inhibitory control and error awareness in young heavy drinkers, using behavioural and psychophysiological measures.

METHODS

Heavy drinkers (n=25) and light- or non-drinking controls (n=35) completed a difficult inhibitory task which required signaling the awareness of inhibitory errors on the subsequent trial, while brain electrical activity was recorded.

RESULTS

Heavy drinkers made more inhibitory errors than controls, but we observed no difference in error awareness, both via overt signaling and with equivalent amplitude of the error positivity (Pe), indexing conscious error detection. Similarly, controls and heavy drinkers showed no difference in amplitude or latency of the error-related negativity (ERN), indexing early pre-conscious error detection.

CONCLUSIONS

This research suggests no significant difference in detection of errors in heavy drinkers, even as they are more prone to make these errors, a result seen in dependent drinkers reported elsewhere. Future research with larger sample sizes, and a more difficult task producing sufficient errors, should determine whether heavy drinkers employ sufficient post-error remedial action.

Novelty Seeking, Harm Avoidance, and Cerebral Responses to Conflict Anticipation: An Exploratory Study

Proactive control allows us to maneuver a changing environment and individuals are distinct in how they anticipate and approach such changes. Here, we examined how individual differences in personality traits influence cerebral responses to conflict anticipation, a critical process of proactive control. We explored this issue in an fMRI study of the stop signal task, in which the probability of stop signal – p(Stop) – was computed trial by trial with a Bayesian model. Higher p(Stop) is associated with prolonged go trial reaction time, indicating conflict anticipation and proactive control of motor response. Regional brain activations to conflict anticipation were correlated to novelty seeking (NS), harm avoidance (HA), reward dependence, as assessed by the Tridimensional Personality Questionnaire, with age and gender as covariates, in a whole-brain linear regression. Results showed that increased anticipation of the stop signal is associated with activations in the bilateral inferior parietal lobules (IPL), right lateral orbitofrontal cortex (lOFC), middle frontal gyrus (MFG), anterior pre-supplementary motor area (pre-SMA), and bilateral thalamus, with men showing greater activation in the IPL than women. NS correlated negatively to activity in the anterior pre-SMA, right IPL, and MFG/lOFC, and HA correlated negatively to activity in the thalamus during conflict anticipation. In addition, the negative association between NS and MFG/lOFC activity was significant in men but not in women. Thus, NS and HA traits are associated with reduced mobilization of cognitive control circuits when enhanced behavioral control is necessary. The findings from this exploratory study characterize the influence of NS and HA on proactive control and provide preliminary evidence for gender differences in these associations.

Sex differences in the relationship between heavy alcohol use, inhibition and performance monitoring: Disconnect between behavioural and brain functional measures

Previous research has reported mixed evidence of sex differences in the relationship between heavy alcohol use and deficits in behavioural control. Here, we examine sex differences in behavioural and event-related potential (ERP) markers of deficient inhibition. Participants were 71 young adults aged 18-21, who either drank heavily regularly (i.e., four standard drinks on one occasion, at least once a month, n=33, 20 male) or drank heavily less often than this (including never, n=38, 21 male). They completed a stop-signal task while ERPs were recorded. Increases in stop-signal reaction time, the time required to stop a response, were related to heavy drinking only in female participants. P3 amplitude, ERN amplitude and ERN latency did not display a significant interaction between group and sex. Heavy drinkers, regardless of sex, displayed a marginally larger successful>failed effect for P3 amplitude, and a marginally smaller error-related negativity. An apparent disconnect exists in behavioural and psychophysiological measures of sex differences in the relationship between heavy alcohol consumption and inhibitory processing; male heavy drinkers display only psychophysiological but not behavioural deficits, while female heavy drinkers display both. Future research may determine whether sex differences are apparent for other substances besides alcohol.

Power spectrum scale invariance as a neural marker of cocaine misuse and altered cognitive control

BACKGROUND

Magnetic resonance imaging (MRI) has highlighted the effects of chronic cocaine exposure on cerebral structures and functions, and implicated the prefrontal cortices in deficits of cognitive control. Recent investigations suggest power spectrum scale invariance (PSSI) of cerebral blood oxygenation level dependent (BOLD) signals as a neural marker of cerebral activity. We examined here how PSSI is altered in association with cocaine misuse and impaired cognitive control.

METHODS

Eighty-eight healthy (HC) and seventy-five age and gender matched cocaine dependent (CD) adults participated in functional MRI of a stop signal task (SST). BOLD images were preprocessed using standard procedures in SPM, including detrending, band-pass filtering (0.01-0.25 Hz), and correction for head motions. Voxel-wise PSSI measures were estimated by a linear fit of the power spectrum with a log-log scale. In group analyses, we examined differences in PSSI between HC and CD, and its association with clinical and behavioral variables using a multiple regression. A critical component of cognitive control is post-signal behavioral adjustment, which is compromised in cocaine dependence. Therefore, we examined the PSSI changes in association with post-signal slowing (PSS) in the SST.

RESULTS

Compared to HC, CD showed decreased PSS and PSSI in multiple frontoparietal regions. PSSI was positively correlated with PSS in HC in multiple regions, including the left inferior frontal gyrus (IFG) and right supramarginal gyrus (SMG), which showed reduced PSSI in CD.

CONCLUSIONS

These findings suggest disrupted connectivity dynamics in the fronto-parietal areas in association with post-signal behavioral adjustment in cocaine addicts. These new findings support PSSI as a neural marker of impaired cognitive control in cocaine addiction.

Escalating risk and the moderating effect of resistance to peer influence on the P200 and feedback-related negativity

Young people frequently socialize together in contexts that encourage risky decision making, pointing to a need for research into how susceptibility to peer influence is related to individual differences in the neural processing of decisions during sequentially escalating risk. We applied a novel analytic approach to analyze EEG activity from college-going students while they completed the Balloon Analogue Risk Task (BART), a well-established risk-taking propensity assessment. By modeling outcome-processing-related changes in the P200 and feedback-related negativity (FRN) sequentially within each BART trial as a function of pump order as an index of increasing risk, our results suggest that analyzing the BART in a progressive fashion may provide valuable new insights into the temporal neurophysiological dynamics of risk taking. Our results showed that a P200, localized to the left caudate nucleus, and an FRN, localized to the left dACC, were positively correlated with the level of risk taking and reward. Furthermore, consistent with our hypotheses, the rate of change in the FRN was higher among college students with greater self-reported resistance to peer influence.

Association of Drinking Problems and Duration of Alcohol Use to Inhibitory Control in Nondependent Young Adult Social Drinkers

BACKGROUND

Deficits in inhibitory control have been widely implicated in alcohol misuse. However, the literature does not readily distinguish the effects of drinking problems and chronic alcohol use. Here, we examined how years of drinking and the Alcohol Use Disorders Identification Test (AUDIT) score each influences the cerebral responses to inhibitory control in nondependent drinkers.

METHODS

Fifty-seven adult drinkers and 57 age- and gender-matched nondrinkers participated in one 40-minute functional magnetic resonance imaging scan of the stop signal task. Data were preprocessed and modeled using SPM8. In a regression model, we contrasted stop and go success trials for individuals and examined activities of response inhibition each in link with the AUDIT score and years of alcohol use in group analyses. We specified the effects of duration of use by contrasting regional activations of drinkers and age-related changes in nondrinkers. In mediation analyses, we investigated how regional activities mediate the relationship between drinking problems and response inhibition.

RESULTS

Higher AUDIT score but not years of drinking was positively correlated with prolonged stop signal reaction time (SSRT) and diminished responses in the cerebellum, thalamus, frontal and parietal regions, independent of years of alcohol use. Further, activity of the thalamus, anterior cingulate cortex, and presupplementary motor area significantly mediates the association, bidirectionally, between the AUDIT score and SSRT. The duration of alcohol use was associated with decreased activation in the right inferior frontal gyrus extending to superior temporal gyrus, which was not observed for age-related changes in nondrinkers.

CONCLUSIONS

The results distinguished the association of drinking problems and years of alcohol use to inhibitory control in young adult nondependent drinkers. These new findings extend the imaging literature of alcohol misuse and may have implications for treatment to prevent the escalation from social to dependent drinking. More research is needed to confirm age-independent neural correlates of years of alcohol use.

Rapid-response impulsivity: definitions, measurement issues, and clinical implications

Impulsivity is a multifaceted construct that is a core feature of multiple psychiatric conditions and personality disorders. However, progress in understanding and treating impulsivity is limited by a lack of precision and consistency in its definition and assessment. Rapid-response impulsivity (RRI) represents a tendency toward immediate action that occurs with diminished forethought and is out of context with the present demands of the environment. Experts from the International Society for Research on Impulsivity (InSRI) met to discuss and evaluate RRI measures in terms of reliability, sensitivity, and validity, with the goal of helping researchers and clinicians make informed decisions about the use and interpretation of findings from RRI measures. Their recommendations are described in this article. Commonly used clinical and preclinical RRI tasks are described, and considerations are provided to guide task selection. Tasks measuring two conceptually and neurobiologically distinct types of RRI, "refraining from action initiation" (RAI) and "stopping an ongoing action" (SOA) are described. RAI and SOA tasks capture distinct aspects of RRI that may relate to distinct clinical outcomes. The InSRI group recommends that (a) selection of RRI measures should be informed by careful consideration of the strengths, limitations, and practical considerations of the available measures; (b) researchers use both RAI and SOA tasks in RRI studies to allow for direct comparison of RRI types and examination of their associations with clinically relevant measures; and (c) similar considerations be made for human and nonhuman studies in an effort to harmonize and integrate preclinical and clinical research.

Female but not male young heavy drinkers display altered performance monitoring

Difficulties in monitoring ongoing behaviour may be linked to real-life problematic drinking behaviours. Prior research suggests female heavy drinkers in particular display greater cognitive control deficits. Here, we examine trial-to-trial behavioural adaptations in a conflict monitoring task, relative to drinking behaviour and sex. Heavy drinkers (n=31, 16 male) and controls (n=35, 18 male) completed an Eriksen flanker task while brain electrical activity was recorded. For reaction time, error rates, and N2 and P3 amplitude of the event-related potential, trial-to-trial conflict adaptation was evidenced by a differential response to the current (congruent vs. incongruent) trials dependent on the identity of the previous trial. For the proportion of errors, heavy drinkers showed increased conflict adaptation compared to controls. Conflict adaptation for N2 (indexing monitoring) was larger for female heavy drinkers than controls, and the opposite was observed for males. There were no interactions involving group or sex for the P3 (indexing inhibition). The results suggest a compensatory response, such that heavy drinkers are required to increase performance monitoring in order to achieve the same behavioural outcome as controls. We also confirm the importance of sex as a factor in the relationship between behavioural control and heavy alcohol use.

Anticipating conflict: Neural correlates of a Bayesian belief and its motor consequence

Previous studies have examined the neural correlates of proactive control using a variety of behavioral paradigms; however, the neural network relating the control process to its behavioral consequence remains unclear. Here, we applied a dynamic Bayesian model to a large fMRI data set of the stop signal task to address this issue. By estimating the probability of the stop signal - p(Stop) - trial by trial, we showed that higher p(Stop) is associated with prolonged go trial reaction time (RT), indicating proactive control of motor response. In modeling fMRI signals at trial and target onsets, we distinguished activities of proactive control, prediction error, and RT slowing. We showed that the anterior pre-supplementary motor area (pre-SMA) responds specifically to increased stop signal likelihood, and its activity is correlated with activations of the posterior pre-SMA and bilateral anterior insula during prolonged response times. This directional link is also supported by Granger causality analysis. Furthermore, proactive control, prediction error, and time-on-task are each mapped to distinct areas in the medial prefrontal cortex. Together, these findings dissect regional functions of the medial prefrontal cortex in cognitive control and provide system level evidence associating conflict anticipation with its motor consequence.

Impaired Bayesian learning for cognitive control in cocaine dependence

BACKGROUND

Cocaine dependence is associated with cognitive control deficits. Here, we apply a Bayesian model of stop-signal task (SST) performance to further characterize these deficits in a theory-driven framework.

METHODS

A "sequential effect" is commonly observed in SST: encounters with a stop trial tend to prolong reaction time (RT) on subsequent go trials. The Bayesian model accounts for this by assuming that each stop/go trial increases/decreases the subject's belief about the likelihood of encountering a subsequent stop trial, P(stop), and that P(stop) strategically modulates RT accordingly. Parameters of the model were individually fit, and compared between cocaine-dependent (CD, n = 51) and healthy control (HC, n = 57) groups, matched in age and gender and both demonstrating a significant sequential effect (p < 0.05). Model-free measures of sequential effect, post-error slowing (PES) and post-stop slowing (PSS), were also compared across groups.

RESULTS

By comparing individually fit Bayesian model parameters, CD were found to utilize a smaller time window of past experiences to anticipate P(stop) (p < 0.003), as well as showing less behavioral adjustment in response to P(stop) (p < 0.015). PES (p = 0.19) and PSS (p = 0.14) did not show group differences and were less correlated with the Bayesian account of sequential effect in CD than in HC.

CONCLUSIONS

Cocaine dependence is associated with the utilization of less contextual information to anticipate future events and decreased behavioral adaptation in response to changes in such anticipation. These findings constitute a novel contribution by providing a computationally more refined and statistically more sensitive account of altered cognitive control in cocaine addiction.

Conflict anticipation in alcohol dependence - A model-based fMRI study of stop signal task

Background

Our previous work characterized altered cerebral activations during cognitive control in individuals with alcohol dependence (AD). A hallmark of cognitive control is the ability to anticipate changes and adjust behavior accordingly. Here, we employed a Bayesian model to describe trial-by-trial anticipation of the stop signal and modeled fMRI signals of conflict anticipation in a stop signal task. Our goal is to characterize the neural correlates of conflict anticipation and its relationship to response inhibition and alcohol consumption in AD.

Methods

Twenty-four AD and 70 age and gender matched healthy control individuals (HC) participated in the study. fMRI data were pre-processed and modeled with SPM8. We modeled fMRI signals at trial onset with individual events parametrically modulated by estimated probability of the stop signal, p(Stop), and compared regional responses to conflict anticipation between AD and HC. To address the link to response inhibition, we regressed whole-brain responses to conflict anticipation against the stop signal reaction time (SSRT).

Results

Compared to HC (54/70), fewer AD (11/24) showed a significant sequential effect — a correlation between p(Stop) and RT during go trials — and the magnitude of sequential effect is diminished, suggesting a deficit in proactive control. Parametric analyses showed decreased learning rate and over-estimated prior mean of the stop signal in AD. In fMRI, both HC and AD responded to p(Stop) in bilateral inferior parietal cortex and anterior pre-supplementary motor area, although the magnitude of response increased in AD. In contrast, HC but not AD showed deactivation of the perigenual anterior cingulate cortex (pgACC). Furthermore, deactivation of the pgACC to increasing p(Stop) is positively correlated with the SSRT in HC but not AD. Recent alcohol consumption is correlated with increased activation of the thalamus and cerebellum in AD during conflict anticipation.

Conclusions

The current results highlight altered proactive control that may serve as an additional behavioral and neural marker of alcohol dependence.

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We addressed the neural correlates of conflict anticipation in AD and HC in an SST.

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AD showed greater activation in preSMA and less deactivation in pgACC.

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Deactivation in pgACC inversely correlated with SSRT in HC but not AD.

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Alcohol use is correlated with greater thalamic and cerebellar activations in AD.

Altered gray matter density and disrupted functional connectivity of the amygdala in adults with Internet gaming disorder

OBJECTIVES

The aim of this study was to evaluate the altered brain structure and functional connectivity (FC) among subjects with Internet gaming disorder (IGD).

METHODS

We recruited 30 males with IGD and 30 controls and evaluated their gray matter density (GMD) and FC using resting fMRI. The severities of IGD, gaming urge, and impulsivity were also assessed.

RESULTS

The results demonstrated that the subjects with IGD had a higher impulsivity and a greater severity of IGD. The subjects with IGD had a lower GMD over the bilateral amygdala than the controls. Further, the subjects with IGD had lower FC with the left amygdala over the left dorsolateral prefrontal lobe (DLPFC) and with the right amygdala over the left DLPFC and orbital frontal lobe (OFL). They also had higher FC with the bilateral amygdala over the contralateral insula than the controls. The FC between the left amygdala and DLPFC was negatively correlated with impulsivity. The FC of the right amygdala to the left DLPFC and orbital frontal lobe was also negatively correlated with impulsivity. Our results indicated that the altered GMD over the amygdala might represent vulnerability to IGD, such as impulsivity. Further analysis of the amygdala demonstrated impaired FC to the frontal lobe, which represents impulsivity.

CONCLUSION

The results of this study suggested that the amygdala plays a very influential role in the mechanism of IGD. Its detailed role should be further evaluated in future study and should be considered in the treatment of IGD.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

Gray matter volume correlates of global positive alcohol expectancy in non-dependent adult drinkers

Alcohol use and misuse is known to involve structural brain changes. Numerous imaging studies have examined changes in gray matter (GM) volumes in dependent drinkers, but there is little information on whether non-dependent drinking is associated with structural changes and whether these changes are related to psychological factors-such as alcohol expectancy-that influence drinking behavior. We used voxel-based morphometry (VBM) to examine whether the global positive scale of alcohol expectancy, as measured by the Alcohol Expectancy Questionnaire-3, is associated with specific structural markers and whether such markers are associated with drinking behavior in 113 adult non-dependent drinkers (66 women). Alcohol expectancy is positively correlated with GM volume of left precentral gyrus (PCG) in men and women combined and bilateral superior frontal gyri (SFG) in women, and negatively correlated with GM volume of the right ventral putamen in men. Furthermore, mediation analyses showed that the GM volume of PCG mediate the correlation of alcohol expectancy and the average number of drinks consumed per occasion and monthly total number of drinks in the past year. When recent drinking was directly accounted for in multiple regressions, GM volume of bilateral dorsolateral prefrontal cortices correlated positively with alcohol expectancy in the combined sample. To our knowledge, these results are the first to identify the structural brain correlates of alcohol expectancy and its mediation of drinking behaviors. These findings suggest that more studies are needed to investigate increased GM volume in the frontal cortices as a neural correlate of alcohol expectancy.

Cognitive control in opioid dependence and methadone maintenance treatment

BACKGROUND

Substance misuse is associated with cognitive dysfunction. We used a stop signal task to examine deficits in cognitive control in individuals with opioid dependence (OD). We examined how response inhibition and post-error slowing are compromised and whether methadone maintenance treatment (MMT), abstinence duration, and psychiatric comorbidity are related to these measures in individuals with OD.

METHODS

Two-hundred-and-sixty-four men with OD who were incarcerated at a detention center and abstinent for up to 2 months (n = 108) or at a correctional facility and abstinent for approximately 6 months (n = 156), 65 OD men under MMT at a psychiatric clinic, and 64 age and education matched healthy control (HC) participants were assessed. We computed the stop signal reaction time (SSRT) to index the capacity of response inhibition and post-error slowing (PES) to represent error-related behavioral adjustment, as in our previous work. We examined group effects with analyses of variance and covariance analyses, followed by planned comparisons. Specifically, we compared OD and HC participants to examine the effects of opioid dependence and MMT and compared OD sub-groups to examine the effects of abstinence duration and psychiatric comorbidity.

RESULTS

The SSRT was significantly prolonged in OD but not MMT individuals, as compared to HC. The extent of post-error slowing diminished in OD and MMT, as compared to HC (trend; p = 0.061), and there was no difference between the OD and MMT groups. Individuals in longer abstinence were no less impaired in these measures. Furthermore, these results remained when psychiatric comorbidities including misuse of other substances were accounted for.

CONCLUSIONS

Methadone treatment appears to be associated with relatively intact cognitive control in opioid dependent individuals. MMT may facilitate public health by augmenting cognitive control and thereby mitigating risky behaviors in heroin addicts.

Neuroimaging in Alcohol and Drug Dependence

Neuroimaging, including PET, MRI, and MRS, is a powerful approach to the study of brain function. This article reviews neuroimaging findings related to alcohol and other drugs of abuse that have been published since 2011. Uses of neuroimaging are to characterize patients to determine who will fare better in treatment and to investigate the reasons underlying the effect on outcomes. Neuroimaging is also used to characterize the acute and chronic effects of substances on the brain and how those effects are related to dependence, relapse, and other drug effects. The data can be used to provide encouraging information for patients, as several studies have shown that long-term abstinence is associated with at least partial normalization of neurological abnormalities.

Changes in cerebral morphometry and amplitude of low-frequency fluctuations of BOLD signals during healthy aging: correlation with inhibitory control

Aging is known to be associated with changes in cerebral morphometry and in regional activations during resting or cognitive challenges. Here, we investigated the effects of age on cerebral gray matter (GM) volumes and fractional amplitude of low-frequency fluctuation (fALFF) of blood oxygenation level-dependent signals in 111 healthy adults, 18-72 years of age. GM volumes were computed using voxel-based morphometry as implemented in Statistical Parametric Mapping, and fALFF maps were computed for task-residuals as described in Zhang and Li (Neuroimage 49:1911-1918, 2010) for individual participants. Across participants, a simple regression against age was performed for GM volumes and fALFF, respectively, with quantity of recent alcohol use as a covariate. At cluster level p < 0.05, corrected for family-wise error of multiple comparisons, GM volumes declined with age in prefrontal/frontal regions, bilateral insula, and left inferior parietal lobule (IPL), suggesting structural vulnerability of these areas to aging. FALFF was negatively correlated with age in the supplementary motor area (SMA), pre-SMA, anterior cingulate cortex, bilateral dorsal lateral prefrontal cortex (DLPFC), right IPL, and posterior cingulate cortex, indicating that spontaneous neural activities in these areas during cognitive performance decrease with age. Notably, these age-related changes overlapped in the prefrontal/frontal regions including the pre-SMA, SMA, and DLPFC. Furthermore, GM volumes and fALFF of the pre-SMA/SMA were negatively correlated with the stop signal reaction time, in accord with our earlier work. Together, these results describe anatomical and functional changes in prefrontal/frontal regions and how these changes are associated with declining inhibitory control during aging.

Effects of alcohol dependence on cortical thickness as determined by magnetic resonance imaging

Alterations of brain structures have been seen in patients suffering from drug abuse or mental disorders like schizophrenia. Similar changes in volume of brain structures have been observed in both alcoholic men and women. We examined the thickness of gray matter in the cerebral cortex in control men and women (n=69, 47 men) and alcohol-dependent subjects (n=130, 83 men) to test the hypothesis that alcoholic inpatients would have more cortical damage than controls. We also hypothesized that alcoholic women would be more affected than alcoholic men. Alcoholic participants with a history of schizophrenia, psychotic, or bipolar disorder were excluded from the study. Volumetric structural magnetic resonance images were collected, 3D surfaces were created using Freesurfer, and statistical testing for cortical thickness differences was carried out using AFNI/SUMA. Covarying for age and years of education, we confirmed significant differences between alcoholics and healthy controls in cortical thickness in both the left and right hemispheres. Significant differences in cortical thickness between control men and women were also observed. These differences may reflect sexual dimorphisms in the human brain, a genetic predisposition to alcoholism and comorbid drug use, and the extent of gray matter damage in alcoholism and substance use.

The effects of age on cerebral activations: internally versus externally driven processes

Numerous studies using functional magnetic resonance imaging (fMRI) have described increased or decreased regional brain activations in older as compared to younger adults. This seeming inconsistency may reflect differences in the psychological constructs examined across studies. We hypothesized that behavioral tasks/contrasts engaging internally and externally driven processes are each associated with age-related decreases and increases, respectively, in cerebral activations. We examined the fMRI data of 103 healthy adults, 18–72 years of age, performing a stop signal task (SST), in which a frequent “go” signal triggered a prepotent response and a less frequent “stop” signal prompted inhibition of this response. Greater internally driven processes lead to stop successes (SS) as compared to stop errors (SE), and to speeding up instead of slowing down in go trials. Conversely, externally driven processes contribute to SE trials, which resulted from habitual, unmonitored responses triggered by the go signal (as compared to SS trials), and involved perceptual and cognitive processes elicited by the stop signal (as compared to go trials). Consistent with our hypothesis, the results showed age-related decreases and increases in cerebral activations each during these respective internally and externally driven processes. These findings further elucidate the influence of age on cognitive functioning and provide an additional perspective to understand the imaging literature of aging.

Adolescent brain development and underage drinking in the United States: identifying risks of alcohol use in college populations

Alcohol use typically is initiated during adolescence, a period that coincides with critical structural and functional maturation of the brain. Brain maturation and associated improvements in decision making continue into the third decade of life, reaching a plateau within the period referred to as emerging adulthood (18-24 years). This particular period covers that of traditionally aged college students, and includes the age (21 years) when alcohol consumption becomes legal in the United States. This review highlights neurobiological evidence indicating the vulnerabilities of the emerging-adult brain to the effects of alcohol. Factors increasing the risks associated with underage alcohol use include the age group's reduced sensitivity to alcohol sedation and increased sensitivity to alcohol-related disruptions in memory. On the individual level, factors increasing those risks are a positive family history of alcoholism, which has a demonstrated effect on brain structure and function, and emerging comorbid psychiatric conditions. These vulnerabilities-of the age group, in general, as well as of particular individuals-likely contribute to excessive and unsupervised drinking in college students. Discouraging alcohol consumption until neurobiological adulthood is reached is important for minimizing alcohol-related disruptions in brain development and decision-making capacity, and for reducing the negative behavioral consequences associated with underage alcohol use.