Effects of modafinil on neural correlates of response inhibition in alcohol-dependent patients

Caffeine and modafinil modulate the effects of sleep deprivation on thalamic resting-state functional connectivity: A double-blind pilot study

BACKGROUND

Studies have found that the use of clinically approved caffeine and modafinil can alleviate cognitive impairment due to sleep deprivation (SD) to some extent. However, the neural mechanisms by which these two cognitive enhancers work to counteract the effects of SD on cognitive impairment remain unclear.

METHODS

A double-blind within-subjects experiment using resting-state functional magnetic resonance imaging (rs-fMRI) was designed. Participants underwent three 36-h SD trials, each of which involved taking 200 mg of caffeine, modafinil, or placebo at the 28th and 32 nd h of SD. Sixteen subregions of the thalamus were selected as the regions of interest and changes in functional connectivity (FC) between the thalamus and the other brain regions were explored after the participants took caffeine or modafinil.

RESULTS

The subjective sleepiness of the participants increased with the duration of SD. compared with placebo, modafinil and caffeine had insignificant effects on wakefulness or sleepiness. However, in terms of neural FC, we found varying degrees of attenuation or enhancement of the FC between the thalamus and other regions. Taking caffeine during SD weakened the FC between the right rostral temporal thalamus (rTtha) subregion and the left lingual gyrus compared with placebo. Caffeine enhanced the FC between three subregions of the thalamus, namely the left sensory thalamus, the left rTtha, and the right lateral pre-frontal thalamus, and the right inferior temporal, left orbitofrontal, and right superior occipital gyris. Modafinil weakened the FC between the right posterior parietal thalamus and left middle temporal gyrus, and enhanced the FC between the left medial pre-frontal thalamus, left rTtha, and right occipital thalamus and left middle frontal gyrus.

CONCLUSIONS

After 36 h of total SD, modafinil and caffeine administration enhanced or attenuated the time-domain correlations between various subregions of the thalamus and brain regions of the frontal and temporal lobes in healthy adults, compared with placebo. These results provide valuable evidence for further unraveling the neuropharmacological mechanisms of caffeine and modafinil, as well as important insights for exploring effective pharmacological intervention strategies against SD.

The resting-state brain activity signatures for addictive disorders

BACKGROUND

Addiction is a chronic and relapsing brain disorder. Despite numerous neuroimaging and neurophysiological studies on individuals with substance use disorder (SUD) or behavioral addiction (BEA), currently a clear neural activity signature for the addicted brain is lacking.

METHODS

We first performed systemic coordinate-based meta-analysis and partial least-squares regression to identify shared or distinct brain regions across multiple addictive disorders, with abnormal resting-state activity in SUD and BEA based on 46 studies (55 contrasts), including regional homogeneity (ReHo) and low-frequency fluctuation amplitude (ALFF) or fractional ALFF. We then combined Neurosynth, postmortem gene expression, and receptor/transporter distribution data to uncover the potential molecular mechanisms underlying these neural activity signatures.

FINDINGS

The overall comparison between addiction cohorts and healthy subjects indicated significantly increased ReHo and ALFF in the right striatum (putamen) and bilateral supplementary motor area, as well as decreased ReHo and ALFF in the bilateral anterior cingulate cortex and ventral medial prefrontal cortex, in the addiction group. On the other hand, neural activity in cingulate cortex, ventral medial prefrontal cortex, and orbitofrontal cortex differed between SUD and BEA subjects. Using molecular analyses, the altered resting activity recapitulated the spatial distribution of dopaminergic, GABAergic, and acetylcholine system in SUD, while this also includes the serotonergic system in BEA.

CONCLUSIONS

These results indicate both common and distinctive neural substrates underlying SUD and BEA, which validates and supports targeted neuromodulation against addiction.

FUNDING

This work was supported by the National Natural Science Foundation of China and Intramural Research Program of the National Institute on Drug Abuse, National Institutes of Health.

Translational models of addiction phenotypes to advance addiction pharmacotherapy

Alcohol and substance use disorders are heterogeneous conditions with limited effective treatment options. While there have been prior attempts to classify addiction subtypes, they have not been translated into clinical practice. In an effort to better understand heterogeneity in psychiatric disorders, the National Institute for Mental Health Research Domain Criteria (RDoC) has challenged scientists to think beyond diagnostic symptoms and to consider the underlying features of psychopathology from a neuroscience-based framework. The field of addiction has grappled with this approach by considering several key constructs with the potential to capture RDoC domains. This critical review will focus on the efforts to apply translational models of addiction phenomenology in human clinical samples, including their relative strengths and weaknesses. Opportunities for forward and reverse translation are also discussed. Deep behavioral phenotyping using neuroscience-informed batteries shows promise for a better understanding of the clinical neuroscience of addiction and advancing precision medicine for alcohol and substance use disorders.

Pharmacological compounds targeting emotional cognition in alcohol use disorder: A systematic review

Non-emotional (e.g., executive functions) and emotional cognitive (e.g., facial emotion recognition) impairments are a well-known aspect of alcohol use disorder (AUD). These deficits may impede on treatment outcomes, increase the risk of relapse, and lead to socio-occupational disabilities. Previous systematic reviews have examined the effectiveness of cognitive enhancing pharmacological agents (CEPAs) targeting non-emotional, but not emotional, cognition in AUD. Our aim was to systematically review the effectiveness of CEPAs targeting emotional cognition in subclinical and clinical AUD populations. A qualitative synthesis of controlled trials was conducted, and the studies were assessed for risk of bias. Eight studies were eligible (15 ≤ ns ≤ 143), and they all had a moderate risk of bias. Modafinil and nalmefene were the most examined agents, with the findings suggesting a potential beneficial effect of the agents on implicit emotional domains (i.e., reward processing). Methodological shortcomings and heterogeneous findings across the studies do not allow inferences about the effectiveness of these compounds in AUD. Future studies should examine CEPAs targeting emotional cognition in more detail.

Effect of alcohol use disorder family history on cognitive function

BACKGROUND

Alcohol use disorder (AUD) is associated with cognitive deficits but little is known to what degree this is caused by genetically influenced traits, i.e. endophenotypes, present before the onset of the disorder. The aim of the current study was to investigate to what degree family history (FH) of AUD is associated with cognitive functions.

METHODS

Case-control cross-sectional study at an outpatient addiction research clinic. Treatment-seeking AUD patients (n = 106) were compared to healthy controls (HC; n = 90), matched for age and sex. The HC group was further subdivided into AUD FH positive (FH+; n = 47) or negative (FH-; n = 39) based on the Family Tree Questionnaire. Participants underwent psychiatric and substance use assessments, completed the Barratt Impulsiveness Scale and performed a comprehensive battery of neuropsychological tests assessing response inhibition, decision making, attention, working memory, and emotional recognition.

RESULTS

Compared to HC, AUD patients exhibited elevated self-rated impulsivity (p < 0.001; d = 0.62), as well as significantly poorer response inhibition (p = 0.001; d = 0.51), attention (p = 0.021; d = 0.38) and information gathering in decision making (p = 0.073; d = 0.34). Similar to AUD patients, FH+ individuals exhibited elevated self-rated impulsivity (p = 0.096; d = 0.46), and in addition significantly worse future planning capacity (p < 0.001; d = 0.76) and prolonged emotional recognition response time (p = 0.010; d = 0.60) compared to FH-, while no other significant differences were found between FH+ and FH-.

CONCLUSIONS

Elevated impulsivity, poor performance in future planning and emotional processing speed may be potential cognitive endophenotypes in AUD. These cognitive domains represent putative targets for prevention strategies and treatment of AUD.

Alteration of Behavioral Inhibitory Control in High-Altitude Immigrants

Behavioral inhibitory control (BIC) acts as a key cognitive ability, which is essential for humans to withhold inappropriate behaviors. Meanwhile, many studies reported that long-term exposure to high altitude (HA) may affect cognitive ability. However, it is not clear whether long-term exposure to HAs may affect the BIC of an individual. To clarify the role of altitude in the behavioral control of adults and the underlying neural mechanism, we explored the BIC neural activity profiles of healthy immigrants from low-altitude (LA) regions to HA regions. Combining a two-choice oddball paradigm and electrophysiological techniques, this study monitored the N2 and P3 event-related components and neural oscillations across LA and HA groups. Results showed longer reaction times (RTs) for the HA group than the LA group. Relative to the LA group, lower N2 and P3 amplitudes were observed for the HA group. Significant positive correlations were also found between P3 amplitude and theta/delta band power across both groups. Importantly, lower theta/delta band powers were only observed for the HA group under the deviant condition. Collectively, these findings suggest that long-term exposure to HAs may attenuate BIC during the response inhibition stage and provide valuable insights into the neurocognitive implications of environmental altitude on BIC.

Neurobiological mechanisms of control in alcohol use disorder - moving towards mechanism-based non-invasive brain stimulation treatments

Alcohol use disorder (AUD) is characterized by excessive habitual drinking and loss of control over alcohol intake despite negative consequences. Both of these aspects foster uncontrolled drinking and high relapse rates in AUD patients. Yet, common interventions mostly focus on the phenomenological level, and prioritize the reduction of craving and withdrawal symptoms. Our review provides a mechanistic understanding of AUD and suggests alternative therapeutic approaches targeting the mechanisms underlying dysfunctional alcohol-related behaviours. Specifically, we explain how repeated drinking fosters the development of rigid drinking habits and is associated with diminished cognitive control. These behavioural and cognitive effects are then functionally related to the neurobiochemical effects of alcohol abuse. We further explain how alterations in fronto-striatal network activity may constitute the neurobiological correlates of these alcohol-related dysfunctions. Finally, we discuss limitations in current pharmacological AUD therapies and suggest non-invasive brain stimulation (like TMS and tDCS interventions) as a potential addition/alternative for modulating the activation of both cortical and subcortical areas to help re-establish the functional balance between controlled and automatic behaviour.

Cognitive boosting interventions for impulsivity in addiction: a systematic review and meta-analysis of cognitive training, remediation and pharmacological enhancement

AIMS

To evaluate and compare the effects of three cognitive boosting intervention approaches (computerised cognitive training, cognitive remediation and pharmacological cognitive enhancers) on measures of impulsive action and impulsive choice.

DESIGN

Systematic review and meta-analysis of publications that reported original controlled trials of cognitive boosting interventions.

SETTING

Studies conducted anywhere in the world. No language restrictions were applied.

PARTICIPANTS

Treatment-seeking adults with substance use disorder or gambling disorder.

MEASUREMENTS

Our primary outcome was a reduction in impulsive action or choice on a validated cognitive measure post-intervention. We assessed risk of bias using the Cochrane Collaboration tool and determined pooled estimates from published reports. We performed random-effects analyses for impulsive action and impulsive choice outcomes and planned moderator analyses.

FINDINGS

Of 2204 unique studies identified, 60 were included in the full-text review. Twenty-three articles were considered eligible for inclusion in the qualitative synthesis and 16 articles were included in our meta-analysis. Articles eligible for pooled analyses included five working memory training (computerised cognitive training) studies with 236 participants, three goal management training (cognitive remediation) studies with 99 participants, four modafinil (cognitive enhancer) studies with 160 participants and four galantamine (cognitive enhancer) studies with 131 participants. Study duration ranged from 5 days to 13 weeks, with immediate follow-up assessments. There were no studies identified that specifically targeted gambling disorder. We only found evidence for a benefit on impulsive choice of goal management training, although only in two studies involving 66 participants (standardised mean difference (SMD) = 0.86; 95% CI = 0.49-1.23; P = 0.02; I²  = 0%, P = 0.95).

CONCLUSION

Cognitive remediation, and specifically goal management training, may be an effective treatment for addressing impulsive choice in addiction. Preliminary evidence does not support the use of computerised cognitive training or pharmacological enhancers to boost impulse control in addiction.

Memory enhancement with stimulants: Differential neural effects of methylphenidate, modafinil, and caffeine. A pilot study

Human memory is susceptible to manipulation in many respects. While consolidation is well known to be prone to disruption, there is also growing evidence for the enhancement of memory function. Beside cognitive strategies and mnemonic training, the use of stimulants may improve memory processing in healthy adults. In this single-dose, double-blind, within-subject, randomized, placebo-controlled pilot study, 20 mg methylphenidate (N = 13) or 200 mg modafinil (N = 12) or 200 mg caffeine (N = 14) were administrated to in total 39 healthy participants while performing a declarative memory task. Each participant received only one substance and functional magnetic resonance imaging (fMRI) was used to assess drug-dependent memory effects of the substance for encoding and recognition compared to task-related activation under placebo. While methylphenidate showed some behavioral effect regarding memory recall performance, on the neural level, methylphenidate-dependent deactivations were found in fronto-parietal and temporal regions during recognition of previously learned words. No BOLD alterations were seen during encoding. Caffeine led to deactivations in the precentral gyrus during encoding whereas modafinil did not show any BOLD signal alterations at all. These results should be interpreted with caution since this a pilot study with several limitations, most importantly the small number of participants per group. However, our main finding of task-related deactivations may point to a drug-dependent increase of efficiency in physiological response to memory processing.

Neural correlates of inhibitory control are associated with stimulant-like effects of alcohol

Poor inhibitory control and heightened feelings of stimulation after alcohol are two well-established risk factors for alcohol use disorder (AUD). Although these risk factors have traditionally been viewed as orthogonal, recent evidence suggests that the two are related and may share common neurobiological mechanisms. Here we examined the degree to which neural activity during inhibition was associated with subjective reports of stimulation following alcohol. To assess neural changes during inhibition, moderate alcohol drinkers performed a stop signal task during fMRI without drug. To assess subjective responses to alcohol they ingested alcohol (0.8 g/kg) or placebo beverages under double-blind conditions and provided subjective reports of stimulation and sedation. Feelings of stimulation following alcohol were inversely associated with activity in the supplementary motor area, insula, and middle frontal gyrus during inhibition (successful stop trials compared to go trials). Feelings of sedation did not correlate with brain activation. These results extend previous findings suggesting that poor inhibitory control is associated with more positive subjective responses to alcohol. These interrelated risk factors may contribute to susceptibility to future excessive alcohol use, and ultimately lead to neurobiological targets to prevent or treat AUD.

Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap?

The number of individuals affected by psychostimulant use disorder (PSUD) has increased rapidly over the last few decades resulting in economic, emotional, and physical burdens on our society. Further compounding this issue is the current lack of clinically approved medications to treat this disorder. The dopamine transporter (DAT) is a common target of psychostimulant actions related to their use and dependence, and the recent availability of atypical DAT inhibitors as a potential therapeutic option has garnered popularity in this research field. Modafinil (MOD), which is approved for clinical use for the treatment of narcolepsy and sleep disorders, blocks DAT just like commonly abused psychostimulants. However, preclinical and clinical studies have shown that it lacks the addictive properties (in both behavioral and neurochemical studies) associated with other abused DAT inhibitors. Clinical availability of MOD has facilitated its off-label use for several psychiatric disorders related to alteration of brain dopamine (DA) systems, including PSUD. In this review, we highlight clinical and preclinical research on MOD and its R-enantiomer, R-MOD, as potential medications for PSUD. Given the complexity of PSUD, we have also reported the effects of MOD on psychostimulant-induced appearance of several symptoms that could intensify the severity of the disease (i.e., sleep disorders and impairment of cognitive functions), besides the potential therapeutic effects of MOD on PSUD.

Pharmacological enhancing agents targeting cognition in patients with alcohol-induced neurocognitive disorders: A systematic review

Debilitating neurocognitive deficits are seen in alcohol use disorders (AUD) and Wernicke-Korsakoff's syndrome (WKS). These shared characteristics suggest a spectrum of alcohol-induced neurocognitive disorders (AIND). Cognitive pharmacological enhancing agents (CPEA) have been examined in the treatment of other psychiatric disorders, but little is known about the effects of these agents on AINDs. Our aim was to synthesize the evidence for the effectiveness of CPEAs on AINDs. Databases were searched for controlled trials examining CPEAs on AUD, WKS, and alcohol-related dementia (ARD). Eligible studies were included in a qualitative synthesis and a quality assessment was conducted. The search identified 23 studies (4 ≤ ns ≤ 98). Evidence suggests that modafinil may improve executive functions in AUD and ARD, but this effect may only be present in patients with severe deficits. The studies were rated as having a moderate risk of bias. Despite the promising effects of modafinil, small samples and inconsistent evidence deem the results preliminary. More research is warranted examining the effects of transdiagnostic CPEAs on deficits across AINDs.

Impulsivity in heroin-dependent individuals: structural and functional abnormalities within frontostriatal circuits

High levels of impulsivity are a risk factor for the initiation of heroin use and a core behavioral characteristic of heroin dependence. Impulsivity also contributes to the maintenance of drug use and hinders effective therapy. Here we sought to identify neuroimaging markers of impulsivity in heroin-dependent individuals (HDI), with a focus on the nucleus accumbens (NAc), a key region implicated in impulsivity and drug addiction generally. Volume and resting-state functional connectivity (RSFC) differences of the bilateral NAc were investigated between 21 HDI and 21 age-, gender-, nicotine-, alcohol-matched healthy controls (HC). The neuroimaging results were then correlated with the Barratt Impulsivity Scales (BIS-11). Higher motor impulsivity (t = 2.347, p = 0.0253) and larger right NAc volume (F (1,38) = 4.719, p = 0.036) was observed in HDI. The right NAc volume was positively correlated with BIS total (r = 0.6196, p = 0.0239) /motor (r = 0.5921, p = 0.0330) scores in HC and BIS motor (r = 0.5145, p = 0.0170) score in HDI. A negative correlation was found between RSFC of the right NAc-bilateral superior frontal gyrus (SFG) and motor impulsivity in HDI (left: r=-0.6537, p = 0.0013; right: r=-0.6167, p = 0.0029) and HC (left: r=-0.6490,p = 0.0164; right: r=-0.6993, p = 0.0078). We aimed to reveal novel multimodality neuroimaging biomarkers of the higher impulsivity in HDI by focusing on the NAc and corresponding functional circuits. Higher motor impulsivity was observed in HDI. Furthermore, the volume of the right NAc and the RSFC strength of right NAc-SFG could be neuroimaging biomarkers for the severity of impulsivity in HDI. These potential biomarkers could be a target for novel treatments in HDI.

Stroop-related cerebellar and temporal activation is correlated with negative affect and alcohol use disorder severity

Impairment in cognitive control in alcohol use disorder (AUD) contributes to difficulty controlling alcohol use and, in many populations, difficulties with emotion regulation. However, the most reliable and robust marker of clinically-relevant deficits in cognitive control in AUD is unclear. Our aims were to measure relationships between BOLD signal during a Stroop task and AUD severity and change in BOLD signal and change in drinking over three weeks. We also aimed to explore the relationships between BOLD signal and subjective negative affect. Thirty-three individuals with AUD underwent a multisensory Stroop task during functional magnetic resonance imaging (fMRI), as well as a battery of neuropsychological tests and self-report assessments of negative affect and AUD severity. Greater activation in temporal gyrus and cerebellum during incongruent trials compared to congruent trials was observed, and percent signal change (incongruent minus congruent) in both clusters was positively correlated with AUD severity and self-reported negative affect. Neuropsychological task performance and self-reported impulsivity were not highly correlated with AUD severity. Hierarchical regression analyses indicated that percent signal change (incongruent minus congruent) in cerebellum was independently associated with negative affect after controlling for recent and chronic drinking. In a subset of individuals (n = 23) reduction in cerebellar percent signal change (incongruent minus congruent) was correlated with increases in percent days abstinent over 3 weeks. BOLD activation during this Stroop task may therefore be an important objective marker of AUD severity and negative affect. The potential importance of the cerebellum in emotion regulation and AUD severity is highlighted.

The Effect of Response Inhibition Training on Risky Decision-Making Task Performance

Response inhibition is an important component of executive function and plays an indispensable role in decision-making and other advanced cognitive processes. At the same time, we need an effective way to improve decision-making in the face of complex and limited information. This study mainly explored the influence of response inhibition training on college students' risky decision-making. The recruited students were randomly divided into the training group (n = 28) and the control group (n = 28). The training group engaged in Go/NoGo and stop-signal tasks for 2 weeks, while the control group was given the task of reading and summarizing popular science articles related to self-control. The Stroop task and Balloon Analog Risk Task were used to evaluate the pretest and posttest performance in inhibitory control and risky decision-making tasks, respectively, for all subjects. The results showed that response inhibition training can be effectively transferred to interference control task performance. The results showed that both the reward acquired and adjusted Balloon Analog Risk Task score (adj BART) significantly improved compared to the pretest in the training group, while the control group showed no significant differences in the reward acquired and the adj BART between the pretest and the posttest. Although response inhibition training increased risky behaviors in the Balloon Analog Risk Task, it substantially reduced overly conservative behaviors and participants gained more money.

Cognition and addiction

In this targeted review, we summarize current knowledge on substance-use disorder (SUD)-related cognitive deficits, the link between these deficits and clinical outcomes, and the cognitive training, remediation, and pharmacological approaches that have the potential to rescue cognition. We conclude that: (i) people with SUDs have moderate deficits in memory, attention, executive functions, and decision-making (including reward expectancy, valuation, and learning); (ii) deficits in higher-order executive functions and decision-making are significant predictors of relapse; (iii) cognitive training programs targeting reward-related appetitive biases, cognitive remediation strategies targeting goal-based decision-making, and pharmacotherapies targeting memory, attention, and impulsivity have potential to rescue SUD-related cognitive deficits. We suggest avenues for future research, including developing brief, clinically oriented harmonized cognitive testing suites to improve individualized prediction of treatment outcomes; computational modeling that can achieve deep phenotyping of cognitive subtypes likely to respond to different interventions; and phenotype-targeted cognitive, pharmacological, and combined interventions. We conclude with a tentative model of neuroscience-informed precision medicine.


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.

The Efficacy of Modafinil as a Cognitive Enhancer: A Systematic Review and Meta-Analysis

BACKGROUND

Animal models and human studies have identified the potential of modafinil as a cognitive enhancing agent, independent of its effects on promoting wakefulness in sleep-deprived samples. Given that single-dose applications of other putative memory enhancers (eg, D-cycloserine, yohimbine, and methylene blue) have shown success in enhancing clinical outcomes for anxiety-related disorders, we conducted a meta-analytic review examining the potential for single-dose effects for modafinil on cognitive functioning in non-sleep-deprived adults.

METHODS

A total of 19 placebo-controlled trials that examined the effects of single-dose modafinil versus placebo on the cognitive domains of attention, executive functioning, memory, or processing speed were identified, allowing for the calculation of 67 cognitive domain-specific effect sizes.

RESULTS

The overall positive effect of modafinil over placebo across all cognitive domains was small and significant (g = 0.10; 95% confidence interval, 0.05-0.15; P < 0.001). No significant differences between cognitive domains were found. Likewise, no significant moderation was found for modafinil dose (100 mg vs 200 mg) or for the populations studied (psychiatric vs nonpsychiatric).

CONCLUSIONS

In conclusion, the available evidence indicates only limited potential for modafinil to act as a cognitive enhancer outside sleep-deprived populations.

Effects of the monoamine stabilizer (-)OSU6162 on cognitive function in alcohol dependence

INTRODUCTION

Alcohol dependence (AD) is associated with a dysregulated mesolimbocortical dopamine system-a pathway which is also implicated in both reward and cognition. The monoamine stabilizer (-)-OSU6162 (OSU) is a novel pharmacological compound with the ability to reduce ethanol intake and ethanol seeking in long-term drinking rats as well as reducing alcohol craving in AD patients. Dopaminergic drugs can both impair and improve cognitive functions, and the aim of the current study was to investigate the effect of OSU treatment on cognitive functioning in AD patients.

METHOD

In a randomized double-blind placebo-controlled study, 56 individuals with AD received 14 days of OSU or placebo treatment. Neuropsychological tasks from the Cambridge Automated Neuropsychological Test Battery (CANTAB®) and other tasks were used to evaluate treatment effect on executive function/impulsivity, working memory, attention, emotional recognition, and divergent thinking.

RESULTS

Treatment with OSU did not impair neuropsychological function in any of the cognitive domains investigated (all p > 0.1). In fact, OSU treatment did, compared to placebo, improve future planning ability (F_(1,46) = 6.9; p = 0.012; Cohen's d = 0.54), verbal divergent thinking (F_(1,44) = 10.1; p = 0.003; d = 0.96), and response time for emotional recognition (F_(1,47) = 6.7; p = 0.013; d = 0.44).

CONCLUSION

OSU treatment did not cause short-term cognitive side effects, further supporting the potential of OSU as a clinically feasible pharmacological treatment in AD patients. OSU treatment might improve future planning, verbal divergent thinking, and emotional recognition latency, which in turn may have a beneficial impact on alcohol use outcomes. Future studies are needed to confirm these preliminary findings.

Combinatorial Targeting of Distributed Forebrain Networks Reverses Noise Hypersensitivity in a Model of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is associated with noise hypersensitivity, the suboptimal extraction of meaningful signals in noisy environments. Because sensory filtering can involve distinct automatic and executive circuit mechanisms, however, developing circuit-specific therapeutic strategies for ASD noise hypersensitivity can be challenging. Here, we find that both of these processes are individually perturbed in one monogenic form of ASD, Ptchd1 deletion. Although Ptchd1 is preferentially expressed in the thalamic reticular nucleus during development, pharmacological rescue of thalamic perturbations in knockout (KO) mice only normalized automatic sensory filtering. By discovering a separate prefrontal perturbation in these animals and adopting a combinatorial pharmacological approach that also rescued its associated goal-directed noise filtering deficit, we achieved full normalization of noise hypersensitivity in this model. Overall, our work highlights the importance of identifying large-scale functional circuit architectures and utilizing them as access points for behavioral disease correction.

The Use of Functional Magnetic Resonance Imaging to Test Pharmacotherapies for Alcohol Use Disorder: A Systematic Review

Alcohol use disorder (AUD) is a chronic relapsing condition that represents a significant public health concern. Pharmacological treatment development for AUD is a top research priority, and many studies are being conducted to evaluate potential AUD treatments. Understanding the brain circuitry impacted by addiction is crucial for the development of efficacious pharmacological interventions. These neuroadaptations can be probed noninvasively using functional magnetic resonance neuroimaging (fMRI). fMRI may be an effective tool to identify biomarkers for AUD pharmacotherapies, evaluating changes associated with pharmacological treatment. Thus, the present qualitative review of the literature focuses on the role of fMRI as a tool for medication development for AUD. The aim of this review was to assemble research across a range of fMRI paradigms to study the effectiveness of pharmacological treatments of adult AUD. First, we present a qualitative review of fMRI AUD pharmacotherapy studies, differentiating studies based on their dosing regimen. Second, we provide recommendations for the field to improve the use of fMRI as a biomarker for AUD pharmacotherapy.

Reduced resting-state functional connectivity and sleep impairment in abstinent male alcohol-dependent patients

Alcohol dependence is associated with poor sleep quality, which has both been implicated with thalamocortical circuits function. To identify the possible roles of these circuits in the alcohol-sleep association, we investigated the volume of both left and right thalamus and corresponding resting-state functional connectivity (RSFC) differences between 15 alcohol-dependent patients (AD) and 15 healthy controls (HC) male participants. The neuroimaging findings were then correlated with clinical variables, that is, Alcohol Use Disorders Identification Test (AUDIT) and Pittsburgh Sleep Quality Index (PSQI). Additionally, mediation analysis was carried out to test whether the thalamocortical RSFC mediates the relationship between drinking behavior and sleep impairments in AD when applicable. We observed a significant positive correlation between AUDIT score and PSQI score in AD. Compared with HC, AD showed reduced RSFC between the left thalamus and medial prefrontal cortex (mPFC), orbitofrontal cortex, anterior cingulate cortex (ACC), and right caudate. We also observed a negative correlation between RSFC of the left thalamus-mPFC and PSQI score in AD. More importantly, the left thalamus-mPFC RSFC strength mediated the relationship between AUDIT score and PSQI score in AD. No significant difference was detected in the normalized volume of both left and right thalamus, and volumes were not significantly correlated with clinical variables. Our results demonstrate that AD show abnormal interactions within thalamocortical circuits in association with drinking behaviors and sleep impairments. It is hoped that our study focusing on thalamocortical circuits could provide new information on potential novel therapeutic targets for treatment of sleep impairment in alcohol-dependent patients.

Neural correlates of inhibition and reward are negatively associated

Individuals with impulsive and addictive disorders, including drug addiction, binge eating/obesity, and problem gambling, exhibit both impaired control over behavior and heightened sensitivity to reward. However, it is not known whether such deviation in inhibitory and reward circuitry among clinical populations is a cause or consequence of the disorders. Recent evidence suggests that these constructs may be related at the neural level, and together, increase risk for engaging in maladaptive behaviors. The current study examined the degree to which brain function during inhibition relates to brain function during receipt of reward in healthy young adults who have not yet developed problem behaviors. Participants completed the stop signal task to assess inhibitory control and the doors task to assess reactivity to monetary reward (win vs loss) during functional magnetic resonance imaging (fMRI). Brain activation during response inhibition was negatively correlated with brain activation during reward. Specifically, less brain activation in right prefrontal regions during inhibition, including the right inferior frontal gyrus, middle frontal gyrus, and supplementary motor area, was associated with greater brain activation in left ventral striatum during receipt of monetary reward. Moreover, these associations were stronger in binge drinkers compared to non-binge drinkers. These findings suggest that the systems are related even before the onset of impulsive or addictive disorders. As such, it is possible that the association between inhibitory and reward circuitry may be a prospective marker of risk.

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'.

Effects of Naltrexone on Large-Scale Network Interactions in Methamphetamine Use Disorder

Naltrexone attenuates craving, and the subjective effects of methamphetamine and extended-release naltrexone (XR-NTX) reduces functional connectivity between regions of the striatum and limbic cortex. Naltrexone modulates neural activity at dopaminergic synapses; however, it is unclear whether naltrexone has an effect on large-scale brain networks. Functional networks interact to coordinate behavior, and as substance-use disorders are associated with an imbalance between reward and cognitive control networks, treatment approaches that target interactive brain systems underlying addiction may be a useful adjunct for behavioral therapies. The objective of this study was to examine the effect of XR-NTX on large-scale brain networks and to determine whether changes in network relationships attenuate drug use, craving, and addiction severity. Thirty-nine participants in or seeking treatment for methamphetamine-use disorder were enrolled in a clinical trial of XR-NTX between May 2013 and March 2015 (Clinicaltrials.gov NCT01822132). Functional magnetic resonance imaging (fMRI) and questionnaires were conducted before and after double-blinded randomization to a 4-week injection of XR-NTX or placebo. In the XR-NTX group, methamphetamine use was reduced along with a decrease in the coupling between executive control (ECN) and default mode (DMN) networks. As decoupling of ECN and DMN networks was associated with change in the severity of dependence, the results suggest that XR-NTX may modulate and enhance ECN attentional resources and suppress DMN self-referential and emotional processing. This study identifies the effect of naltrexone on changes in the intrinsic functional coupling of large-scale brain networks and provides a more systematic understanding of how large-scale networks interact to promote behavioral change in methamphetamine-use disorder.

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

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

Investigational drug therapies in phase I and phase II clinical trials for alcohol use disorders

INTRODUCTION

Alcohol use disorder (AUD) is a complex psychiatric condition characterized by craving, compulsive seeking, loss of control of alcohol consumption as well as the emergence of negative emotional states during withdrawal. Despite the large socioeconomic burden of AUD, therapeutic treatment options lag behind.

AREAS COVERED

This review covers pharmacotherapies currently in phase I/II clinical trials for the treatment of AUDs listed on clinicaltrials.gov. We discuss drug therapies that modulate monoamine, GABA/Glutamate, neuropeptide and neuroimmune systems. We examine in depth preclinical and clinical evidence of a select range of these compounds and consider their utility in treating AUDs.

EXPERT OPINION

Current therapeutic options to treat AUD are inadequate at a population level. Currently there are 30 different compounds and one compound combination in phase I/II clinical trials for AUD. These compounds target various aspects of neurotransmitter signaling, neuroimmune modulation, and alcohol metabolism. Almost 75% of these compounds under trial are Food and Drug Administration (FDA) approved for other indications, which may save time and costs in treatment development. Further, development of therapeutics focused on genetic biomarkers and behavioral screening may improve how treatment decisions are made in the future on a case-by-case basis.

Cortico-Amygdala-Striatal Activation by Modafinil/Flecainide Combination

Background

Modafinil, a nonamphetaminic wake-promoting compound, is prescribed as first line therapy in narcolepsy, an invalidating disorder characterized by excessive daytime sleepiness and cataplexy. Although its mode of action remains incompletely known, recent studies indicated that modafinil modulates astroglial connexin-based gap junctional communication as administration of a low dose of flecainide, an astroglial connexin inhibitor, enhanced the wake-promoting and procognitive activity of modafinil in rodents and healthy volunteers. The aim of this study is to investigate changes in glucose cerebral metabolism in rodents, induced by the combination of modafinil+flecainide low dose (called THN102).

Methods

The impact of THN102 on brain glucose metabolism was noninvasively investigated using 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography imaging in Sprague-Dawley male rats. Animals were injected with vehicle, flecainide, modafinil, or THN102 and further injected with 18F-2-fluoro-2-deoxy-D-glucose followed by 60-minute Positron Emission Tomography acquisition. 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography images were coregistered to a rat brain template and normalized from the total brain Positron Emission Tomography signal. Voxel-to-voxel analysis was performed using SPM8 software. Comparison of brain glucose metabolism between groups was then performed.

Results

THN102 significantly increased regional brain glucose metabolism as it resulted in large clusters of 18F-2-fluoro-2-deoxy-D-glucose uptake localized in the cortex, striatum, and amygdala compared with control or drugs administered alone. These regions, highly involved in the regulation of sleep-wake cycle, emotions, and cognitive functions were hence quantitatively modulated by THN102.

Conclusion

Data presented here provide the first evidence of a regional brain activation induced by THN102, currently being tested in a phase II clinical trial in narcoleptic patients.

Profiling attention and cognition enhancing drugs in a rat touchscreen-based continuous performance test

RATIONALE

A novel rodent continuous performance test (CPT) was developed as one of the goals of the NEWMEDS (Novel Methods leading to New Medications in Depression and Schizophrenia) consortium to improve its translatability to the CPT test used in human subjects.

OBJECTIVES

The objective of the study is to investigate the effects of attention and cognition enhancing drugs in rodent CPT.

METHODS

A single cohort of rats were trained to asymptotic performance in the test. Pharmacological test sessions were then performed twice per week in a full crossover design with the following drugs tested: methylphenidate (0.3, 1, and 3 mg/kg), the α4β2 nicotinic agonist ABT-594 (0.0023, 0.007 and 0.023 mg/kg), modafinil (8, 16, and 32 mg/kg), atomoxetine (0.3, 1, and 3 mg/kg), donepezil (0.1, 0.3, and 1 mg/kg), and memantine (1.25, 2.5, and 5 mg/kg).

RESULTS

The stimulant-like drugs methylphenidate, ABT-594, and modafinil were found to increase measures of impulsivity and overall responding with generally no positive effects on d', a putative measure of attention, with the exception of ABT-594 which improved d' at the highest dose tested. Atomoxetine and the memory-enhancing drugs donepezil and memantine, on the other hand, were found to reduce measures of impulsivity and responding and had either negligible or worsening effects on d'.

CONCLUSIONS

Our results suggest rodent CPT can detect changes in impulsivity resulting from drugs known to improve attention in rodents and humans. However, additional work is needed to assess the sensitivity and validity of this assay for assessing effects on attention.

MAM-E17 rat model impairments on a novel continuous performance task: effects of potential cognitive enhancing drugs

RATIONALE

Impairments in attention and inhibitory control are endophenotypic markers of neuropsychiatric disorders such as schizophrenia and represent key targets for therapeutic management. Robust preclinical models and assays sensitive to clinically relevant treatments are crucial for improving cognitive enhancement strategies.

OBJECTIVES

We assessed a rodent model with neural and behavioral features relevant to schizophrenia (gestational day 17 methylazoxymethanol acetate treatment (MAM-E17)) on a novel test of attention and executive function, and examined the impact of putative nootropic drugs.

METHODS

MAM-E17 and sham control rats were trained on a novel touchscreen-based rodent continuous performance test (rCPT) designed to closely mimic the human CPT paradigm. Performance following acute, systemic treatment with an array of pharmacological compounds was investigated.

RESULTS

Two cohorts of MAM-E17 rats were impaired on rCPT performance including deficits in sensitivity (d') and increased false alarm rates (FARs). Sulpiride (0-30 mg/kg) dose-dependently reduced elevated FAR in MAM-E17 rats whereas low-dose modafinil (8 mg/kg) only improved d' in sham controls. ABT-594 (5.9-19.4 μg/kg) and modafinil (64 mg/kg) showed expected stimulant-like effects, while LSN2463359 (5 mg/kg), RO493858 (10 mg/kg), atomoxetine (0.3-1 mg/kg), and sulpiride (30 mg/kg) showed expected suppressant effects on performance across all animals. Donepezil (0.1-1 mg/kg) showed near-significant enhancements in d', and EVP-6124 (0.3-3 mg/kg) exerted no effects in the rCPT paradigm.

CONCLUSION

The MAM-E17 model exhibits robust and replicable impairments in rCPT performance that resemble attention and inhibitory control deficits seen in schizophrenia. Pharmacological profiles were highly consistent with known drug effects on cognition in preclinical and clinical studies. The rCPT is a sensitive and reliable tool with high translational potential for understanding the etiology and treatment of disorders affecting attention and executive dysfunction.

Macro and micro structures in the dorsal anterior cingulate cortex contribute to individual differences in self-monitoring

Individual differences in self-monitoring, which are the capability to adjust behavior to adapt to social situations, influence a wide range of social behaviors. However, understanding of focal differences in brain structures related to individual self-monitoring is minimal, particularly when micro and macro structures are considered simultaneously. The present study investigates the relationship between self-monitoring and brain structure in a relatively large sample of young adults. Voxel-based morphometry (VBM) revealed a significant positive correlation between self-monitoring and gray matter volume in the dorsal cingulate anterior cortex (dACC), dorsal lateral prefrontal cortex (DLPFC), and bilateral ventral striatum (VS). Further analysis revealed a significant negative correlation between self-monitoring and white matter (WM) integrity, as indexed by fractional anisotropy (FA) in the anterior cingulum (ACG) bundle. Moreover, there was a significant positive correlation between self-monitoring and mean radius diffusion (RD). These results shed light on the structural neural basis of variation in self-monitoring.

Comparative Effects of Methylphenidate, Modafinil, and MDMA on Response Inhibition Neural Networks in Healthy Subjects

BACKGROUND

Psychostimulants such as methylphenidate and modafinil are increasingly used by healthy people for cognitive enhancement purposes, whereas the acute effect of 3,4-methylenedioxymethamphetamine (ecstasy) on cognitive functioning in healthy subjects remains unclear. This study directly compared the acute effects of methylphenidate, modafinil, and 3,4-methylenedioxymethamphetamine on the neural mechanisms underlying response inhibition in healthy subjects.

METHODS

Using a double-blind, within-subject, placebo-controlled, cross-over design, methylphenidate, modafinil, and 3,4-methylenedioxymethamphetamine were administrated to 21 healthy subjects while performing a go/no-go event-related functional magnetic resonance imaging task to assess brain activation during motor response inhibition.

RESULTS

Relative to placebo, methylphenidate and modafinil but not 3,4-methylenedioxymethamphetamine improved inhibitory performance. Methylphenidate significantly increased activation in the right middle frontal gyrus, middle/superior temporal gyrus, inferior parietal lobule, presupplementary motor area, and anterior cingulate cortex compared with placebo. Methylphenidate also induced significantly higher activation in the anterior cingulate cortex and presupplementary motor area and relative to modafinil. Relative to placebo, modafinil significantly increased activation in the right middle frontal gyrus and superior/inferior parietal lobule, while 3,4-methylenedioxymethamphetamine significantly increased activation in the right middle/inferior frontal gyrus and superior parietal lobule.

CONCLUSIONS

Direct comparison of methylphenidate, modafinil, and 3,4-methylenedioxymethamphetamine revealed broad recruitment of fronto-parietal regions but specific effects of methylphenidate on middle/superior temporal gyrus, anterior cingulate cortex, and presupplementary motor area activation, suggesting dissociable modulations of response inhibition networks and potentially the superiority of methylphenidate in the enhancement of cognitive performance in healthy subjects.

Methylphenidate, modafinil, and caffeine for cognitive enhancement in chess: A double-blind, randomised controlled trial

Stimulants and caffeine have been proposed for cognitive enhancement by healthy subjects. This study investigated whether performance in chess - a competitive mind game requiring highly complex cognitive skills - can be enhanced by methylphenidate, modafinil or caffeine. In a phase IV, randomized, double-blind, placebo-controlled trial, 39 male chess players received 2×200mg modafinil, 2×20mg methylphenidate, and 2×200mg caffeine or placebo in a 4×4 crossover design. They played twenty 15-minute games during two sessions against a chess program (Fritz 12; adapted to players' strength) and completed several neuropsychological tests. Marked substance effects were observed since all three substances significantly increased average reflection time per game compared to placebo resulting in a significantly increased number of games lost on time with all three treatments. Treatment effects on chess performance were not seen if all games (n=3059) were analysed. Only when controlling for game duration as well as when excluding those games lost on time, both modafinil and methylphenidate enhanced chess performance as demonstrated by significantly higher scores in the remaining 2876 games compared to placebo. In conjunction with results from neuropsychological testing we conclude that modifying effects of stimulants on complex cognitive tasks may in particular result from more reflective decision making processes. When not under time pressure, such effects may result in enhanced performance. Yet, under time constraints more reflective decision making may not improve or even have detrimental effects on complex task performance.

The neurobiology of addiction: the perspective from magnetic resonance imaging present and future

BACKGROUND AND AIMS

Addiction is associated with severe economic and social consequences and personal tragedies, the scientific exploration of which draws upon investigations at the molecular, cellular and systems levels with a wide variety of technologies. Magnetic resonance imaging (MRI) has been key to mapping effects observed at the microscopic and mesoscopic scales. The range of measurements from this apparatus has opened new avenues linking neurobiology to behaviour. This review considers the role of MRI in addiction research, and what future technological improvements might offer.

METHODS

A hermeneutic strategy supplemented by an expansive, systematic search of PubMed, Scopus and Web of Science databases, covering from database inception to October 2015, with a conjunction of search terms relevant to addiction and MRI. Formal meta-analyses were prioritized.

RESULTS

Results from methods that probe brain structure and function suggest frontostriatal circuitry disturbances within specific cognitive domains, some of which predict drug relapse and treatment response. New methods of processing imaging data are opening opportunities for understanding the role of cerebral vasculature, a global view of brain communication and the complex topology of the cortical surface and drug action. Future technological advances include increases in MRI field strength, with concomitant improvements in image quality.

CONCLUSIONS

The magnetic resonance imaging literature provides a limited but convergent picture of the neurobiology of addiction as global changes to brain structure and functional disturbances to frontostriatal circuitry, accompanied by changes in anterior white matter.

Right inferior frontal cortex activity correlates with tolcapone responsivity in problem and pathological gamblers

Failures of self-regulation in problem and pathological gambling (PPG) are thought to emerge from failures of top-down control, reflected neurophysiologically in a reduced capacity of prefrontal cortex to influence activity within subcortical structures. In patients with addictions, these impairments have been argued to alter evaluation of reward within dopaminergic neuromodulatory systems. Previously we demonstrated that augmenting dopamine tone in frontal cortex via use of tolcapone, an inhibitor of the dopamine-degrading enzyme catechol-O-methyltransferase (COMT), reduced delay discounting, a measure of impulsivity, in healthy subjects. To evaluate this potentially translational approach to augmenting prefrontal inhibitory control, here we hypothesized that increasing cortical dopamine tone would reduce delay discounting in PPG subjects in proportion to its ability to augment top-down control. To causally test this hypothesis, we administered the COMT inhibitor tolcapone in a randomized, double-blind, placebo-controlled, within-subject study of 17 PPG subjects who performed a delay discounting task while functional MRI images were obtained. In this subject population, we found that greater BOLD activity during the placebo condition within the right inferior frontal cortex (RIFC), a region thought to be important for inhibitory control, correlated with greater declines in impulsivity on tolcapone versus placebo. Intriguingly, connectivity between RIFC and the right striatum, and not the level of activity within RIFC itself, increased on tolcapone versus placebo. Together, these findings support the hypothesis that tolcapone-mediated increases in top-down control may reduce impulsivity in PPG subjects, a finding with potential translational relevance for gambling disorders, and for behavioral addictions in general.

Pramipexole Increases Go Timeouts but Not No-go Errors in Healthy Volunteers

Parkinson's disease (PD) is characterized by motor symptoms, such as resting tremor, bradykinesia and rigidity, but also features non-motor complications. PD patients taking dopaminergic therapy, such as levodopa but especially dopamine agonists (DAs), evidence an increase in impulse control disorders (ICDs), suggesting a link between dopaminergic therapy and impulsive pursuit of pleasurable activities. However, impulsivity is a multifaceted construct. Motor impulsivity refers to the inability to overcome automatic responses or cancel pre-potent responses. Previous research has suggested that PD patients, on dopaminergic medications, have decreased motor impulsivity. Whether effects on impulsivity are main effects of dopaminergic therapies or are specific to PD is unclear. Using a Go No-go task, we investigated the effect of a single dose of the DA pramipexole on motor impulsivity in healthy participants. The Go No-go task consisted of Go trials, for which keystroke responses were made as quickly as possible, and lesser frequency No-go trials, on which motor responses were to be inhibited. We hypothesized that pramipexole would decrease motor impulsivity. This would manifest as: (a) fewer No-go errors (i.e., fewer responses on trials in which a response ought to have been inhibited); and (b) more timed-out Go trials (i.e., more trials on which the deadline elapsed before a decision to make a keystroke occurred). Healthy volunteers were treated with either 0.5 mg of pramipexole or a standard placebo (randomly determined). During the 2-h wait period, they completed demographic, cognitive, physiological and affective measures. The pramipexole group had significantly more Go timeouts (p < 0.05) compared to the placebo group though they did not differ in percent of No-go errors. In contrast to its effect on pursuit of pleasurable activities, pramipexole did not increase motor impulsivity. In fact, in line with findings in PD and addiction, dopaminergic therapy might increase motor impulse control. In these patient groups, by enhancing function of the dorsal striatum (DS) of the basal ganglia in contrast to its effect on impulsive pursuit of pleasurable activities. These findings have implications for use and effects of pramipexole in PD as well as in other conditions (e.g., restless leg, dystonia, depression, addiction-related problems).

Neuroimaging the Effectiveness of Substance Use Disorder Treatments

Neuroimaging techniques to measure the function and biochemistry of the human brain such as positron emission tomography (PET), proton magnetic resonance spectroscopy ((1)H MRS), and functional magnetic resonance imaging (fMRI), are powerful tools for assessing neurobiological mechanisms underlying the response to treatments in substance use disorders. Here, we review the neuroimaging literature on pharmacological and behavioral treatment in substance use disorder. We focus on neural effects of medications that reduce craving (e.g., naltrexone, bupropion hydrochloride, baclofen, methadone, varenicline) and that improve cognitive control (e.g., modafinil, N-acetylcysteine), of behavioral treatments for substance use disorders (e.g., cognitive bias modification training, virtual reality, motivational interventions) and neuromodulatory interventions such as neurofeedback and transcranial magnetic stimulation. A consistent finding for the effectiveness of therapeutic interventions identifies the improvement of executive control networks and the dampening of limbic activation, highlighting their values as targets for therapeutic interventions in substance use disorders.

Response to Cognitive impulsivity and the behavioral addiction model of obsessive-compulsive disorder: Abramovitch and McKay (2016)

In our recently published article, we investigated the behavioral addiction model of obsessive-compulsive disorder (OCD), by assessing three core dimensions of addiction in patients with OCD healthy participants. Similar to the common findings in addiction, OCD patients demonstrated increased impulsivity, risky decision-making, and biased probabilistic reasoning compared to healthy controls. Thus, we concluded that these results support the conceptualization of OCD as a disorder of behavioral addiction. Here, we answer to Abramovitch and McKay (2016) commentary on our paper and we support our conclusions by explaining how cognitive impulsivity is also a typical feature of addiction and how our results on decision-making and probabilistic reasoning tasks reflect cognitive impulsivity facets that are consistently replicated in OCD and addiction.

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.

Impulsivity and attentional bias as predictors of modafinil treatment outcome for retention and drug use in crack-cocaine dependent patients: Results of a randomised controlled trial

BACKGROUND

High impulsivity and attentional bias are common in cocaine-dependent patients and predict poor treatment outcomes. The pharmacological agent modafinil is studied for its cognitive-enhancing capacities and may therefore improve clinical outcomes in crack-cocaine dependent patients. In this study, we investigated first whether pre-treatment impulsivity and attentional bias predict treatment outcome; next whether the drug modafinil given as an add-on treatment to cognitive behavioural therapy (CBT) improves impulsivity and attentional bias; and last, whether changes in impulsivity and attentional bias are related to improvements in treatment outcome.

METHODS

Crack-cocaine dependent outpatients (n = 65) were randomised to 12 weeks CBT plus modafinil (400 mg/day) or only CBT. Self-reported impulsivity was assessed at baseline using the Barratt Impulsiveness Scale. At baseline and Week 12, we assessed inhibitory control as a behavioural measure of impulsivity, in terms of cognitive interference (Stroop task) and response inhibition ('stop-signal task'), and attentional bias with the addiction Stroop task. Clinical outcomes were CBT-retention and crack-cocaine use.

RESULTS

At baseline, self-reported impulsivity predicted better CBT-retention; low self-reported and behavioural impulsivity and attentional bias predicted less crack-cocaine use. Changes in cognitive performance were not modafinil-related, but most likely due to low adherence. Improvements in impulsivity or attentional bias were not associated with CBT-retention nor changes in crack-cocaine use.

CONCLUSIONS

Baseline impulsivity and attentional bias predicted clinical outcomes in crack-cocaine dependent patients. There were no firm indications that modafinil reduced impulsivity nor attentional bias in this population. Future studies involving cognitive-enhancing medications should include strategies to optimise adherence, to be better able to evaluate their potential.

Genetic overlap between impulsivity and alcohol dependence: a large-scale national twin study

BACKGROUND

Alcohol dependence is associated with increased levels of impulsivity, but the genetic and environmental underpinnings of this overlap remain unclear. The purpose of the current study was to investigate the degree to which genetic and environmental factors contribute to the overlap between alcohol dependence and impulsivity.

METHOD

Univariate and bivariate twin model fitting was conducted for alcohol dependence and impulsivity in a national sample of 16 819 twins born in Sweden from 1959 to 1985.

RESULTS

The heritability estimate for alcohol dependence was 44% [95% confidence interval (CI) 31-57%] for males and 62% (95% CI 52-72%) for females. For impulsivity, the heritability was 33% (95% CI 30-36%) in males and females. The bivariate twin analysis indicated a statistically significant genetic correlation between alcohol dependence and impulsivity of 0.40 (95% CI 0.23-0.58) in males and 0.20 (95% CI 0.07-0.33) in females. The phenotypic correlation between alcohol dependence and impulsivity was 0.20 and 0.17 for males and females, respectively, and the bivariate heritability was 80% (95% CI 47-117%) for males and 53% (95% CI 19-86%) for females. The remaining variance in all models was accounted for by non-shared environmental factors.

CONCLUSIONS

The association between alcohol dependence and impulsivity can be partially accounted for by shared genetic factors. The genetic correlation was greater in men compared with women, which may indicate different pathways to the development of alcohol dependence between sexes. The observed genetic overlap has clinical implications regarding treatment and prevention, and partially explains the substantial co-morbidity between alcohol dependence and psychiatric disorders characterized by impulsive behaviour.

Neural Circuitry of Impaired Emotion Regulation in Substance Use Disorders

Impaired emotion regulation contributes to the development and severity of substance use disorders (substance disorders). This review summarizes the literature on alterations in emotion regulation neural circuitry in substance disorders, particularly in relation to disorders of negative affect (without substance disorder), and it presents promising areas of future research. Emotion regulation paradigms during functional magnetic resonance imaging are conceptualized into four dimensions: affect intensity and reactivity, affective modulation, cognitive modulation, and behavioral control. The neural circuitry associated with impaired emotion regulation is compared in individuals with and without substance disorders, with a focus on amygdala, insula, and prefrontal cortex activation and their functional and structural connectivity. Hypoactivation of the rostral anterior cingulate cortex/ventromedial prefrontal cortex (rACC/vmPFC) is the most consistent finding across studies, dimensions, and clinical populations (individuals with and without substance disorders). The same pattern is evident for regions in the cognitive control network (anterior cingulate and dorsal and ventrolateral prefrontal cortices) during cognitive modulation and behavioral control. These congruent findings are possibly related to attenuated functional and/or structural connectivity between the amygdala and insula and between the rACC/vmPFC and cognitive control network. Although increased amygdala and insula activation is associated with impaired emotion regulation in individuals without substance disorders, it is not consistently observed in substance disorders. Emotion regulation disturbances in substance disorders may therefore stem from impairments in prefrontal functioning, rather than excessive reactivity to emotional stimuli. Treatments for emotion regulation in individuals without substance disorders that normalize prefrontal functioning may offer greater efficacy for substance disorders than treatments that dampen reactivity.

The effects of the monoamine stabilizer (-)-OSU6162 on craving in alcohol dependent individuals: A human laboratory study

Alcohol dependence is associated with a dysregulated dopamine system modulating reward, craving and cognition. The monoamine stabilizer (-)-OSU6162 (OSU6162) can counteract both hyper- and hypo-dopaminergic states and we recently demonstrated that it attenuates alcohol-mediated behaviors in long-term drinking rats. The present Phase II exploratory human laboratory study investigated to our knowledge for the first time the effects of OSU6162 on cue- and priming-induced craving in alcohol dependent individuals. Fifty-six alcohol dependent individuals were randomized to a 14-day-treatment period of OSU6162 or placebo after their baseline impulsivity levels had been determined using the Stop Signal Task. On Day 15, participants were subjected to a laboratory alcohol craving test comprised of craving sessions induced by: i) active - alcohol specific cues, ii) neutral stimuli and iii) priming - intake of an alcoholic beverage (0.20g ethanol/kg bodyweight). Subjective ratings of alcohol craving were assessed using the shortened version of the Desire for Alcohol Questionnaire and visual analog scales (VAS). OSU6162 treatment had no significant effect on cue-induced alcohol craving, but significantly attenuated priming-induced craving. Exploratory analysis revealed that this effect was driven by the individuals with high baseline impulsivity. In addition, OSU6162 significantly blunted the subjective liking of the consumed alcohol (VAS). Although the present 14-day-treatment period, showed that OSU6162 was safe and well tolerated, this exploratory human laboratory study was not designed to evaluate the efficacy of OSU6162 to affect alcohol consumption. Thus a larger placebo-controlled efficacyclinical trial is needed to further investigate the potential of OSU6162 as a novel medication for alcohol dependence.

Neuroscience of inhibition for addiction medicine: from prediction of initiation to prediction of relapse

A core deficit in drug addiction is the inability to inhibit maladaptive drug-seeking behavior. Consistent with this deficit, drug-addicted individuals show reliable cross-sectional differences from healthy nonaddicted controls during tasks of response inhibition accompanied by brain activation abnormalities as revealed by functional neuroimaging. However, it is less clear whether inhibition-related deficits predate the transition to problematic use, and, in turn, whether these deficits predict the transition out of problematic substance use. Here, we review longitudinal studies of response inhibition in children/adolescents with little substance experience and longitudinal studies of already addicted individuals attempting to sustain abstinence. Results show that response inhibition and its underlying neural correlates predict both substance use outcomes (onset and abstinence). Neurally, key roles were observed for multiple regions of the frontal cortex (e.g., inferior frontal gyrus, dorsal anterior cingulate cortex, and dorsolateral prefrontal cortex). In general, less activation of these regions during response inhibition predicted not only the onset of substance use, but interestingly also better abstinence-related outcomes among individuals already addicted. The role of subcortical areas, although potentially important, is less clear because of inconsistent results and because these regions are less classically reported in studies of healthy response inhibition. Overall, this review indicates that response inhibition is not simply a manifestation of current drug addiction, but rather a core neurocognitive dimension that predicts key substance use outcomes. Early intervention in inhibitory deficits could have high clinical and public health relevance.

Associations between regional brain physiology and trait impulsivity, motor inhibition, and impaired control over drinking

Trait impulsivity and poor inhibitory control are well-established risk factors for alcohol misuse, yet little is known about the associated neurobiological endophenotypes. Here we examined correlations among brain physiology and self-reported trait impulsive behavior, impaired control over drinking, and a behavioral measure of response inhibition. A sample of healthy drinkers (n = 117) completed a pulsed arterial spin labeling (PASL) scan to quantify resting regional cerebral blood flow (rCBF), as well as measures of self-reported impulsivity (Eysenck I7 Impulsivity scale) and impaired control over drinking. A subset of subjects (n = 40) performed a stop signal task during blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging to assess brain regions involved in response inhibition. Eysenck I7 scores were inversely related to blood flow in the right precentral gyrus. Significant BOLD activation during response inhibition occurred in an overlapping right frontal motor/premotor region. Moreover, impaired control over drinking was associated with reduced BOLD response in the same region. These findings suggest that impulsive personality and impaired control over drinking are associated with brain physiology in areas implicated in response inhibition. This is consistent with the idea that difficulty controlling behavior is due in part to impairment in motor restraint systems.

Impulsivity in disorders of food and drug misuse

BACKGROUND

Evidence suggests some overlap between the pathological use of food and drugs, yet how impulsivity compares across these different clinical disorders remains unclear. Substance use disorders are commonly characterized by elevated impulsivity, and impulsivity subtypes may show commonalities and differences in various conditions. We hypothesized that obese subjects with binge-eating disorder (BED) and abstinent alcohol-dependent cohorts would have relatively more impulsive profiles compared to obese subjects without BED. We also predicted decision impulsivity impairment in obesity with and without BED.

METHOD

Thirty obese subjects with BED, 30 without BED and 30 abstinent alcohol-dependent subjects and age- and gender-matched controls were tested on delay discounting (preference for a smaller immediate reward over a larger delayed reward), reflection impulsivity (rapid decision making prior to evidence accumulation) and motor response inhibition (action cancellation of a prepotent response).

RESULTS

All three groups had greater delay discounting relative to healthy volunteers. Both obese subjects without BED and alcohol-dependent subjects had impaired motor response inhibition. Only obese subjects without BED had impaired integration of available information to optimize outcomes over later trials with a cost condition.

CONCLUSIONS

Delay discounting appears to be a common core impairment across disorders of food and drug intake. Unexpectedly, obese subjects without BED showed greater impulsivity than obese subjects with BED. We highlight the dissociability and heterogeneity of impulsivity subtypes and add to the understanding of neurocognitive profiles across disorders involving food and drugs. Our results have therapeutic implications suggesting that disorder-specific patterns of impulsivity could be targeted.

PTSD-related alcohol expectancies and impulsivity interact to predict alcohol use severity in a substance dependent sample with PTSD

INTRODUCTION

Problematic alcohol use is highly comorbid with posttraumatic stress disorder (PTSD), and prior work has demonstrated that individuals with PTSD may self-medicate with alcohol in an effort to reduce their symptoms. The combination of impulsivity and alcohol-related expectancies influences the development of problematic drinking patterns. When examining individuals diagnosed with PTSD, PTSD-related alcohol expectancies may be particularly relevant to the etiology of problematic drinking. To date, no studies have specifically examined PTSD-specific alcohol expectancies as they relate to alcohol use severity in a clinical sample.

METHODS

The current study examined the relationship between impulsivity, PTSD-related alcohol expectancies, and severity of alcohol use in a sample of 63 individuals diagnosed with comorbid PTSD and substance use disorders who were receiving treatment in a residential substance use treatment program.

RESULTS

Results indicated that PTSD-related alcohol expectancies moderated the relationship between impulsivity and alcohol use severity. Specifically, at low to moderate levels of positive PTSD-related alcohol expectancies, impulsivity significantly predicted alcohol use severity, while impulsivity had no impact on the prediction of alcohol use severity when such expectancies were high. Additionally, the relationship between impulsivity, expectancies, and alcohol use severity was significant for positive, but not negative, PTSD-related alcohol expectancies.

CONCLUSIONS

Overall, these results suggest that impulsivity and PTSD-related alcohol expectancies interact to predict alcohol use severity in a comorbid PTSD and substance dependent sample.