Error-related functional connectivity of the thalamus in cocaine dependence

Genotype-by-diagnosis interaction influences self-control in human cocaine addiction

Not everyone who uses drugs loses control over their intake, which is a hallmark of addiction. Although familial risk studies suggest significant addiction heritability, the genetic basis of vulnerability to drug addiction remains largely unknown. In the present study, we investigate the relationship between self-control, cocaine use, and the rs36024 single nucleotide polymorphism of the noradrenaline transporter gene (SLC6A2). We hypothesize that C-allele-carrying adults show impaired self-control, as measured by the stop-signal task and demonstrated previously in adolescents, and further exacerbated by chronic cocaine use. Patients with cocaine use disorder (CUD, n = 79) and healthy unrelated participants with no history of drug abuse (n = 54) completed the stop-signal task. All participants were genotyped for rs36024 allelic variants (CC/TT homozygotes, CT heterozygotes). We measured mean stop-signal reaction time, reflecting the ability to inhibit ongoing motor responses, reaction times to go stimuli, and the proportion of successful stops. CUD patients showed prolonged stop-signal reaction time, however, there was no main effect of rs36024 genotype. Importantly, there was a significant genotype-by-diagnosis interaction such that CUD patients with CC genotype had longer stop-signal reaction time and fewer successful stops compared with CC healthy controls and TT CUD patients. CT CUD patients showed an intermediate performance. Self-control deficits were associated with cocaine use disorder diagnosis, which interacts with the noradrenaline transporter rs36024 polymorphism. Our findings suggest that rs36024 may represent a potential genetic vulnerability marker, which facilitates the transition from first cocaine use to addiction by weakening the inhibitory control over behavior.

Biomarkers of Relapse in Cocaine Use Disorder: A Narrative Review

Introduction: Cocaine use disorder is a chronic disease with severe consequences and a high relapse rate. There is a critical need to explore the factors influencing relapse in order to achieve more efficient treatment outcomes. Furthermore, there is a great need for easy-to-measure, repeatable, and valid biomarkers that can predict treatment response or relapse. Methods: We reviewed the available literature on the Pubmed database concerning the biomarkers associated with relapse in CUD, including central nervous system-derived, genetic, immune, oxidative stress, and “other” biomarkers. Results: Fifty-one articles were included in our analysis. Twenty-five imaging brain anatomic and function assessment studies, mostly using fMRI, examined the role of several structures such as the striatum activity in abstinence prediction. There were fewer studies assessing the use of neuropsychological factors, neurotrophins, or genetic/genomic factors, immune system, or oxidative stress measures to predict abstinence. Conclusion: Several biomarkers have been shown to have predictive value. Prospective studies using combined multimodal assessments are now warranted.

Effect of automatic emotional processing on response inhibition among heroin abstainers

Previous studies have explored effects of the conscious processing of emotional information on the interaction between emotion and executive control. However, the conscious processing of emotional information introduces "defensive responses," which might limit the emotional effect. To avoid the limitations, this study aimed to explore the effect of automatic emotional processing on response inhibition among heroin abstainers. Individuals experiencing heroin withdrawal symptoms are not entirely exempt from the influence of drugs, and it is challenging to find heroin addicts in practice. Therefore, similar to previous studies, we recruited heroin abstainers in this study. In Experiment 1, for the heroin abstainers group, 30 participants meeting the inclusion criteria were recruited from a compulsory isolated detoxification center, whereas 30 age- and education-matched participants were recruited from the community as the control group. These participants completed the Go/No-Go task by supraliminal emotional priming. In Experiment 2, the heroin abstainers group comprised 33 eligible participants and control group comprised 33 eligible participants. These participants completed the Go/No-Go task by subliminal emotional priming. We compared the participants' rates of commission errors in the Go/No-Go tasks. The rate of commission errors was lowest upon the activation of positive emotion. Moreover, under subliminal emotional priming, the rate of commission errors for the heroin abstainers group was significantly lower than that for the control group. However, regarding supraliminal emotional priming, there was no significant difference between the rates of commission errors for the two groups. These results suggest automatic positive emotional processing can enhance response inhibition among heroin abstainers. Moreover, under subliminal emotional priming, heroin abstainers had more enhanced response inhibition than the control groups. This study plays a significant role in understanding the effect of automatic emotional processing on response inhibition among drug addicts. This study also provides a theoretical basis for ensuring enhanced response inhibition among drug addicts.

Infralimbic cortex functioning across motivated behaviors: Can the differences be reconciled?

The rodent infralimbic cortex (IL) is implicated in higher order executive functions such as reward seeking and flexible decision making. However, the precise nature of its role in these processes is unclear. Early evidence indicated that the IL promotes the extinction and ongoing inhibition of fear conditioning and cocaine seeking. However, evidence spanning other behavioral domains, such as natural reward seeking and habit-based learning, suggests a more nuanced understanding of IL function. As techniques have advanced and more studies have examined IL function, identifying a unifying explanation for its behavioral function has become increasingly difficult. Here, we discuss evidence of IL function across motivated behaviors, including associative learning, drug seeking, natural reward seeking, and goal-directed versus habit-based behaviors, and emphasize how context-specific encoding and heterogeneous IL neuronal populations may underlie seemingly conflicting findings in the literature. Together, the evidence suggests that a major IL function is to facilitate the encoding and updating of contingencies between cues and behaviors to guide subsequent behaviors.

Inhibitory failures in cocaine use disorder: Not paying attention when there is a need to be cautious

BACKGROUND

Stimulant use disorders, such as cocaine use disorder, are associated with significant impairment in inhibitory control, which has in turn been linked to difficulties maintaining abstinence following treatment. Here, we combine the Dynamic Belief Model (DBM) and a Hierarchical Drift Diffusion Model (HDDM) to examine whether individuals with cocaine use disorder have both strategic response updating and tactical speed accuracy trade-off problems during inhibitory control.

METHODS

Twenty-seven individuals with cocaine use disorder and twenty-seven healthy control participants completed a Stop-Signal-Task (SST), in which one has to inhibit a motor response to a prepotent 2-alternative forced choice task on 25 % of the trials.

RESULTS

Cocaine use disorder and control subjects did not differ on successful stopping behavior. In cocaine use disorder but not control subjects, higher likelihood of encountering a stop signal was associated with lower drift rate. Moreover, in cocaine use disorder subjects, a more negative relationship between likelihood of encountering a stop signal and drift rate was associated with lower accuracy on stop trials and slower stop reaction time.

CONCLUSIONS

These results are consistent with a dysregulation between strategic and tactical processing during inhibitory control in cocaine use disorder. Specifically, these individuals are more likely to be less attentive to sensory evidence when the expectation of a stop signal is high.

Interdependent Neural Correlates of Reward and Punishment Sensitivity During Rewarded Action and Inhibition of Action

Imaging studies have distinguished the brain correlates of approach and avoidance behaviors and suggested the influence of individual differences in trait sensitivity to reward (SR) and punishment (SP) on these neural processes. Theoretical work of reinforcement sensitivity postulates that SR and SP may interdependently regulate behavior. Here, we examined the distinct and interrelated neural substrates underlying rewarded action versus inhibition of action in relation to SR and SP as evaluated by the Sensitivity to Punishment and Sensitivity to Reward Questionnaire. Forty-nine healthy adults performed a reward go/no-go task with approximately 2/3 go and 1/3 no-go trials. Correct go and no-go responses were rewarded and incorrect responses were penalized. The results showed that SR and SP modulated rewarded go and no-go, respectively, both by recruiting the rostral anterior cingulate cortex and left middle frontal gyrus (rACC/left MFG). Importantly, SR and SP influenced these regional activations in opposite directions, thus exhibiting an antagonistic relationship as suggested by the reinforcement sensitivity theory. Furthermore, mediation analysis revealed that heightened SR contributed to higher rewarded go success rate via enhanced rACC/left MFG activity. The findings demonstrate interrelated neural correlates of SR and SP to support the diametric processes of behavioral approach and avoidance.

Altered functional network activities for behavioral adjustments and Bayesian learning in young men with Internet gaming disorder

BACKGROUND AND AIMS

Deficits in cognitive control represent a core feature of addiction. Internet Gaming Disorder (IGD) offers an ideal model to study the mechanisms underlying cognitive control deficits in addiction, eliminating the confounding effects of substance use. Studies have reported behavioral and neural deficits in reactive control in IGD, but it remains unclear whether individuals with IGD are compromised in proactive control or behavioral adjustment by learning from the changing contexts.

METHODS

Here, fMRI data of 21 male young adults with IGD and 21 matched healthy controls (HC) were collected during a stop-signal task. We employed group independent component analysis to investigate group differences in temporally coherent, large-scale functional network activities during post-error slowing, the typical type of behavioral adjustments. We also employed a Bayesian belief model to quantify the trial-by-trial learning of the likelihood of stop signal - P(Stop) - a broader process underlying behavioral adjustment, and identified the alterations in functional network responses to P(Stop).

RESULTS

The results showed diminished engagement of the fronto-parietal network during post-error slowing, and weaker activity in the ventral attention and anterior default mode network in response to P(Stop) in IGD relative to HC.

DISCUSSION AND CONCLUSIONS

These results add to the literatures by suggesting deficits in updating and anticipating conflicts as well as in behavioral adjustment according to contextual information in individuals with IGD.

Cue-elicited functional connectivity of the periaqueductal gray and tonic cocaine craving

BACKGROUND

Withdrawal from chronic cocaine use leads to anxiety and dysphoria that may perpetuate habitual drug use. The pain circuit is widely implicated in the processing and manifestations of negative emotions. Numerous studies have focused on characterizing reward circuit dysfunction but relatively little is known about the pain circuit response during cocaine withdrawal.

METHODS

Here we examined the activity and connectivity of the periaqueductal gray (PAG), a hub of the pain circuit, during cocaine cue exposure in 52 recently abstinent cocaine dependent participants (CD, 42 men). Imaging data were processed with published routines, and the results were evaluated at a corrected threshold.

RESULTS

CD showed higher activation of the PAG and connectivity of the PAG with the ventromedial prefrontal cortex (vmPFC) during cocaine as compared to neutral cue exposure. PAG-vmPFC connectivity was positively and negatively correlated with tonic cocaine craving, as assessed by the Cocaine Craving Questionnaire, in male and female CD, respectively, and the sex difference was confirmed by a slope test. Granger causality analyses showed that the PAG Granger caused vmPFC time series in men and the reverse was true in women, substantiating sex differences in the directional interactions of the PAG and vmPFC.

CONCLUSION

The findings provide the first evidence in humans implicating the PAG circuit in cocaine withdrawal and cocaine craving and advance our understanding of the role of the pain circuit and negative reinforcement in sustaining habitual drug use in cocaine addiction.

A systematic review and meta-analysis of behavioural sex differences in executive control

Literature investigating whether an individuals' sex affects their executive control abilities and performance on cognitive tasks in a normative population has been contradictory and inconclusive. Using meta-analytic procedures (abiding by PRISMA guidelines), this study attempts to identify the magnitude of behavioural sex differences in three prominent executive control domains of cognitive set-shifting, performance monitoring, and response inhibition. PubMed, Web of Science, and Scopus were systematically searched. Across 46 included studies, a total of 1988 females and 1884 males were included in the analysis. Overall, males and females did not differ on performance in any of the three domains of performance monitoring, response inhibition, or cognitive set-shifting. Task-specific sex differences were observed in the domains of performance monitoring, in the CANTAB Spatial Working Memory task-males scored statistically higher than females (Hedges' g = -0.60), and response inhibition, in the Delay Discounting task-females scored statistically higher than males (Hedges' g = 0.64). While the meta-analysis did not detect overall behavioural sex differences in executive control, significant heterogeneity and task-specific sex differences were found. To further understand sex differences within these specific tasks and domains, future research must better control for age and sex hormone levels.

Regional elevations in microglial activation and cerebral glucose utilization in frontal white matter tracts of rhesus monkeys following prolonged cocaine self-administration

It has been shown that exposure to cocaine can result in neuroinflammatory responses. Microglia, the resident CNS immune cells, undergo a transition to an activated state when challenged. In rodents, and possibly humans, cocaine exposure activates microglia. The goal of this study was to assess the extent and magnitude of microglial activation in rhesus monkeys with an extensive history of cocaine self-administration. Male rhesus monkeys (N = 4/group) were trained to respond on a fixed-interval 3-min schedule of food or 0.3 mg/kg/injection cocaine presentation (30 reinforcers/session) for 300 sessions. At the end of the final session, monkeys were administered 2-[¹⁴C]deoxyglucose intravenously and 45 min later euthanized. Brain sections were used for autoradiographic assessments of glucose utilization and for microglia activation with [³H]PK11195, a marker for the microglial 18-kDa translocator protein. There were no group differences in gray matter [³H]PK11195 binding, while binding was significantly greater in cocaine self-administration animals as compared to food controls in 8 of the 11 white matter tracts measured at the striatal level. Binding did not differ from control at other levels. There were also significant increases in white matter local cerebral glucose utilization at the striatal level, which were positively correlated with [³H]PK11195 binding. The present findings demonstrate an elevation in [³H]PK11195 binding in forebrain white matter tracts of nonhuman primates with a prolonged history of cocaine self-administration. These elevations were also associated with greater cerebral metabolic rates. These data suggest that white matter deficits may contribute to behavioral, motivational, and cognitive impairments observed in cocaine abusers.

The thalamus in drug addiction: from rodents to humans

Impairments in response inhibition and salience attribution (iRISA) have been proposed to underlie the clinical symptoms of drug addiction as mediated by cortico-striatal-thalamo-cortical networks. The bulk of evidence supporting the iRISA model comes from neuroimaging research that has focused on cortical and striatal influences with less emphasis on the role of the thalamus. Here, we highlight the importance of the thalamus in drug addiction, focusing on animal literature findings on thalamic nuclei in the context of drug-seeking, structural and functional changes of the thalamus as measured by imaging studies in human drug addiction, particularly during drug cue and non-drug reward processing, and response inhibition tasks. Findings from the animal literature suggest that the paraventricular nucleus of the thalamus, the lateral habenula and the mediodorsal nucleus may be involved in the reinstatement, extinction and expression of drug-seeking behaviours. In support of the iRISA model, the human addiction imaging literature demonstrates enhanced thalamus activation when reacting to drug cues and reduced thalamus activation during response inhibition. This pattern of response was further associated with the severity of, and relapse in, drug addiction. Future animal studies could widen their field of focus by investigating the specific role(s) of different thalamic nuclei in different phases of the addiction cycle. Similarly, future human imaging studies should aim to specifically delineate the structure and function of different thalamic nuclei, for example, through the application of advanced imaging protocols at higher magnetic fields (7 Tesla).This article is part of a discussion meeting issue 'Of mice and mental health: facilitating dialogue between basic and clinical neuroscientists'.

The importance of considering polysubstance use: lessons from cocaine research

BACKGROUND

Polysubstance use (PSU) is prevalent among individuals with substance use disorders, but the vast majority of preclinical substance use research has focused on individual substances in isolation. Cocaine has been prevalent in the repertoire of persons who use more than one illicit substance.

METHODS

We conducted a meta-analysis combining results from literature searches and secondary data analyses to estimate the prevalence of simultaneous and concurrent cocaine + alcohol and cocaine + cannabis use among cocaine users. We next summarized the small body of literature on behavioral, cognitive and neurobiological consequences of cocaine PSU across species, with a focus on alcohol and cannabis. Finally, we used systematic literature searches to assess the extent to which human and animal studies on the neurobiological consequences of cocaine include PSU subjects.

RESULTS

The estimated prevalence of simultaneous and concurrent alcohol use among human cocaine users was 74% and 77%, respectively. The estimated prevalence of simultaneous and concurrent cannabis use among cocaine users was 38% and 64%, respectively. Consumption of alcohol or cannabis with cocaine enhances subjective responses to cocaine, concomitant with changes in cocaine metabolism that increase blood cocaine levels, and, in the case of alcohol, produce the psychoactive metabolite cocaethylene. There is also consistent evidence for neurobiological effects of cocaine + alcohol combinations. However, animal PSU research with cocaine lags behind human research.

CONCLUSION

Based on the prevalence and known consequences of PSU, consideration of PSU in both human and animal research is vital for understanding patterns of substance use.

Activity and Connectivity Differences Underlying Inhibitory Control Across the Adult Life Span

Inhibitory control requires precise regulation of activity and connectivity within multiple brain networks. Previous studies have typically evaluated age-related changes in regional activity or changes in interregional interactions. Instead, we test the hypothesis that activity and connectivity make distinct, complementary contributions to performance across the life span and the maintenance of successful inhibitory control systems. A representative sample of healthy human adults in a large, population-based life span cohort performed an integrated Stop-Signal (SS)/No-Go task during functional magnetic resonance imaging (n = 119; age range, 18-88 years). Individual differences in inhibitory control were measured in terms of the SS reaction time (SSRT), using the blocked integration method. Linear models and independent components analysis revealed that individual differences in SSRT correlated with both activity and connectivity in a distributed inhibition network, comprising prefrontal, premotor, and motor regions. Importantly, this pattern was moderated by age, such that the association between inhibitory control and connectivity, but not activity, differed with age. Multivariate statistics and out-of-sample validation tests of multifactorial functional organization identified differential roles of activity and connectivity in determining an individual's SSRT across the life span. We propose that age-related differences in adaptive cognitive control are best characterized by the joint consideration of multifocal activity and connectivity within distributed brain networks. These insights may facilitate the development of new strategies to support cognitive ability in old age.SIGNIFICANCE STATEMENT The preservation of cognitive and motor control is crucial for maintaining well being across the life span. We show that such control is determined by both activity and connectivity within distributed brain networks. In a large, population-based cohort, we used a novel whole-brain multivariate approach to estimate the functional components of inhibitory control, in terms of their activity and connectivity. Both activity and connectivity in the inhibition network changed with age. But only the association between performance and connectivity, not activity, differed with age. The results suggest that adaptive control is best characterized by the joint consideration of multifocal activity and connectivity. These insights may facilitate the development of new strategies to maintain cognitive ability across the life span in health and disease.

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.

Resting State Functional Connectivity of the Lateral and Medial Hypothalamus in Cocaine Dependence: An Exploratory Study

The role of dopamine in cocaine misuse has been extensively documented for the mesocorticolimbic circuit. Preclinical work from earlier lesion studies to recent multidisciplinary investigations has suggested that the hypothalamus is critically involved in motivated behavior, with the lateral and medial hypothalamus each involved in waking/feeding and resting/satiety. However, little is known of hypothalamus function and dysfunction in cocaine misuse. Here, we examined resting state functional connectivity of the lateral and medial hypothalamus in 70 individuals with cocaine dependence (CD) and 70 age as well as gender matched healthy controls (HC). Image pre-processing and analyses followed published work. Compared to HC, CD showed increased lateral hypothalamic connectivity with dorsolateral prefrontal cortex and decreased functional connectivity with the ventral precuneus. CD showed increased medial hypothalamic connectivity with the inferior parietal lobule and decreased connectivity with the ventromedial prefrontal cortex, temporal gyrus, fusiform gyrus, and ventral striatum. Further, at trend level significance, the connectivity strength between lateral hypothalamus and dorsolateral prefrontal cortex was positively correlated with total amount of cocaine use in the past month (p = 0.004, r = 0.35) and the connectivity strength between medial hypothalamus and ventral striatum was negatively correlated with cocaine craving as assessed by the Tiffany Cocaine Craving Questionnaire (p = 0.008, r = -0.33). Together, the findings demonstrated altered resting state functional connectivity of the hypothalamus and may provide new insight on circuit level deficits in cocaine dependence.

Decreased Thalamocortical Connectivity in Chronic Ketamine Users

Disintegration in thalamocortical integration suggests its role in the mechanistic 'switch' from recreational to dysregulated drug seeking/addiction. In this study, we aimed to address whether thalamic nuclear groups show altered functional connectivity within the cerebral cortex in chronic ketamine users. One hundred and thirty subjects (41 ketamine users and 89 control subjects) underwent rsfMRI (resting-state functional Magnetic Resonance Imaging). Based on partial correlation functional connectivity analysis we partitioned the thalamus into six nuclear groups that correspond well with human histology. Then, in the area of each nuclear group, the functional connectivity differences between the chronic ketamine user group and normal control group were investigated. We found that the ketamine user group showed significantly less connectivity between the thalamic nuclear groups and the cortical regions-of-interest, including the prefrontal cortex, the motor cortex /supplementary motor area, and the posterior parietal cortex. However, no increased thalamic connectivity was observed for these regions as compared with controls. This study provides the first evidence of abnormal thalamocortical connectivity of resting state brain activity in chronic ketamine users. Further understanding of pathophysiological mechanisms of the thalamus in addiction (ketamine addiction) may facilitate the evaluation of much-needed novel pharmacological agents for improved therapy of this complex disease.

Cocaine dependence and thalamic functional connectivity: a multivariate pattern analysis

Cocaine dependence is associated with deficits in cognitive control. Previous studies demonstrated that chronic cocaine use affects the activity and functional connectivity of the thalamus, a subcortical structure critical for cognitive functioning. However, the thalamus contains nuclei heterogeneous in functions, and it is not known how thalamic subregions contribute to cognitive dysfunctions in cocaine dependence. To address this issue, we used multivariate pattern analysis (MVPA) to examine how functional connectivity of the thalamus distinguishes 100 cocaine-dependent participants (CD) from 100 demographically matched healthy control individuals (HC). We characterized six task-related networks with independent component analysis of fMRI data of a stop signal task and employed MVPA to distinguish CD from HC on the basis of voxel-wise thalamic connectivity to the six independent components. In an unbiased model of distinct training and testing data, the analysis correctly classified 72% of subjects with leave-one-out cross-validation (p < 0.001), superior to comparison brain regions with similar voxel counts (p < 0.004, two-sample t test). Thalamic voxels that form the basis of classification aggregate in distinct subclusters, suggesting that connectivities of thalamic subnuclei distinguish CD from HC. Further, linear regressions provided suggestive evidence for a correlation of the thalamic connectivities with clinical variables and performance measures on the stop signal task. Together, these findings support thalamic circuit dysfunction in cognitive control as an important neural marker of cocaine dependence.

Thalamocortical functional connectivity and behavioral disruptions in neonates with prenatal cocaine exposure

Prenatal cocaine exposure (PCE) affects neurobehavioral development, however, disentangling direct drug-related mechanisms from contextual effects (e.g., socioeconomic status) has proven challenging in humans. The effects of environmental confounds are minimal immediately after birth thus we aimed to delineate neurobehavioral correlates of PCE in a large cohort of neonates (2-6weeks of age, N=152) with and without drug exposure using resting state functional magnetic resonance imaging (rsfMRI) and developmental assessments at 3months with the Bayley Scales of Infant & Toddler Development, 3rd edition. The cohort included healthy controls and neonates with similar poly-drug exposure±cocaine. We focused on the thalamus given its critical importance in early brain development and its unique positioning in the dopamine system. Our results revealed PCE-related hyper-connectivity between the thalamus and frontal regions and a drug-common hypo-connective signature between the thalamus and motor-related regions. PCE-specific neonatal thalamo-frontal connectivity was inversely related to cognitive and fine motor scores and thalamo-motor connectivity showed a positive relationship with composite (gross plus fine) motor scores. Finally, cocaine by selective-serotonin-reuptake-inhibitor (SSRI) interactions were detected, suggesting the combined use of these drugs during pregnancy could have additional consequences on fetal development. Overall, our findings provide the first delineation of PCE-related disruptions of thalamocortical functional connectivity, neurobehavioral correlations, and drug-drug interactions during infancy.

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.

Subcortical glutamate mediates the reduction of short-range functional connectivity with age in a developmental cohort

Marked changes in brain physiology and structure take place between childhood and adulthood, including changes in functional connectivity and changes in the balance between main excitatory and inhibitory neurotransmitters glutamate (Glu) and GABA. The balance of these neurotransmitters is thought to underlie neural activity in general and functional connectivity networks in particular, but so far no studies have investigated the relationship between human development related differences in these neurotransmitters and concomitant changes in functional connectivity. GABA+/H2O and Glu/H2O levels were acquired in a group of healthy children, adolescents, and adults in a subcortical (basal ganglia) region, as well as in a frontal region in adolescents and adults. Our results showed higher GABA+/Glu with age in both the subcortical and the frontal voxel, which were differentially associated with significantly lower Glu/H2O with age in the subcortical voxel and by significantly higher GABA+/H2O with age in the frontal voxel. Using a seed-to-voxel analysis, we were further able to show that functional connectivity between the putamen (seed) and other subcortical structures was lower with age. Lower subcortical Glu/H2O with age mediated the lower connectivity in the dorsal putamen. Based on these results, and the potential role of Glu in synaptic pruning, we suggest that lower Glu mediates a reduction of local connectivity during human development.

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.

Independent component analysis of functional networks for response inhibition: Inter-subject variation in stop signal reaction time

Cognitive control is a critical executive function. Many studies have combined general linear modeling and the stop signal task (SST) to delineate the component processes of cognitive control. For instance, by contrasting stop success (SS) and stop error (SE) trials in the SST, investigators examined regional responses to stop signal inhibition. In contrast to this parameterized approach, independent component analysis (ICA) elucidates brain networks subserving cognitive control. In our earlier work of 59 adults performing the SST during fMRI, we characterized six independent components (ICs). However, none of these ICs correlated with stop signal performance, raising questions about their behavioral validity. Here, in a larger sample (n = 100), we identified and explored 23 ICs for correlation with the stop signal reaction time (SSRT), a measure of the efficiency of response inhibition. At a corrected threshold (P < 0.0005), a paracentral lobule-midcingulate network and a left inferior parietal-supplementary motor-somatomotor network showed a positive correlation between SE beta weight and SSRT. In contrast, a midline cerebellum-thalamus-pallidum network showed a negative correlation between SE beta weight and SSRT. These findings suggest that motor preparation and execution prolongs the SSRT, likely via an interaction between the go and stop processes as suggested by the race model. Behaviorally, consistent with this hypothesis, the difference in G and SE reaction times is positively correlated with SSRT across subjects. These new results highlight the importance of cognitive motor regions in response inhibition and support the utility of ICA in uncovering functional networks for cognitive control in the SST.

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.

Inhibitory behavioral control: A stochastic dynamic causal modeling study comparing cocaine dependent subjects and controls

Cocaine dependence is associated with increased impulsivity in humans. Both cocaine dependence and impulsive behavior are under the regulatory control of cortico-striatal networks. One behavioral laboratory measure of impulsivity is response inhibition (ability to withhold a prepotent response) in which altered patterns of regional brain activation during executive tasks in service of normal performance are frequently found in cocaine dependent (CD) subjects studied with functional magnetic resonance imaging (fMRI). However, little is known about aberrations in specific directional neuronal connectivity in CD subjects. The present study employed fMRI-based dynamic causal modeling (DCM) to study the effective (directional) neuronal connectivity associated with response inhibition in CD subjects, elicited under performance of a Go/NoGo task with two levels of NoGo difficulty (Easy and Hard). The performance on the Go/NoGo task was not significantly different between CD subjects and controls. The DCM analysis revealed that prefrontal–striatal connectivity was modulated (influenced) during the NoGo conditions for both groups. The effective connectivity from left (L) anterior cingulate cortex (ACC) to L caudate was similarly modulated during the Easy NoGo condition for both groups. During the Hard NoGo condition in controls, the effective connectivity from right (R) dorsolateral prefrontal cortex (DLPFC) to L caudate became more positive, and the effective connectivity from R ventrolateral prefrontal cortex (VLPFC) to L caudate became more negative. In CD subjects, the effective connectivity from L ACC to L caudate became more negative during the Hard NoGo conditions. These results indicate that during Hard NoGo trials in CD subjects, the ACC rather than DLPFC or VLPFC influenced caudate during response inhibition.

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Dynamic causal modeling was used to study response inhibition in cocaine dependence.

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A Go/NoGo task with two levels of NoGo difficulty (Easy and Hard) was used.

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Patients and controls used anterior cingulate cortex to control caudate during Easy NoGo.

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Controls used dorsolateral/ventrolateral prefrontal cortex to control caudate during Hard NoGo.

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Patients continued using anterior cingulate cortex to control caudate during Hard NoGo.

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.