Cognitive enhancers in the treatment of substance use disorders: clinical evidence

Human laboratory models of reward in substance use disorder

Human laboratory models in substance use disorder provide a key intermediary step between highly controlled and mechanistically informative non-human preclinical methods and clinical trials conducted in human populations. Much like preclinical models, the variety of human laboratory methods provide insights into specific features of substance use disorder rather than modelling the diverse causes and consequences simultaneously in a single model. This narrative review provides a discussion of popular models of reward used in human laboratory research on substance use disorder with a focus on the specific contributions that each model has towards informing clinical outcomes (forward translation) and analogs within preclinical models (backward translation). Four core areas of human laboratory research are discussed: drug self-administration, subjective effects, behavioral economics, and cognitive and executive function. Discussion of common measures and models used, the features of substance use disorder that these methods are purported to evaluate, unique issues for measure validity and application, and translational links to preclinical models and special considerations for studies wishing to evaluate homology across species is provided.

Modafinil, an atypical CNS stimulant?

Modafinil is a central nervous system stimulant approved for the treatment of narcolepsy and sleep disorders. Due to its wide range of biochemical actions, modafinil has been explored for other potential therapeutic uses. Indeed, it has shown promise as a therapy for cognitive disfunction resulting from neurologic disorders like ADHD, and as a smart drug in non-medical settings. The mechanism(s) of actions underlying the therapeutic efficacy of this agent remains largely elusive. Modafinil is known to inhibit the dopamine transporter, thus decreasing dopamine reuptake following neuronal release, an effect shared by addictive psychostimulants. However, modafinil is unique in that only a few cases of dependence on this drug have been reported, as compared to other psychostimulants. Moreover, modafinil has been tested, with some success, as a potential therapeutic agent to combat psychostimulant and other substance use disorders. Modafinil has additional, but less understood, actions on other neurotransmitter systems (GABA, glutamate, serotonin, norepinephrine, etc.). These interactions, together with its ability to activate selected brain regions, are likely one of the keys to understand its unique pharmacology and therapeutic activity as a CNS stimulant. In this chapter, we outline the pharmacokinetics and pharmacodynamics of modafinil that suggest it has an "atypical" CNS stimulant profile. We also highlight the current approved and off label uses of modafinil, including its beneficial effects as a treatment for sleep disorders, cognitive functions, and substance use disorders.

Substance Use Disorders: Basic Overview for the Anesthesiologist

Substance use disorders (SUDs) represent a current major public health concern in the United States and around the world. Social and economic stressors secondary to the coronavirus disease 2019 (COVID-19) pandemic have likely led to an increase in SUDs around the world. This chronic, debilitating disease is a prevalent health problem, and yet many clinicians do not have adequate training or clinical experience diagnosing and treating SUDs. Anesthesiologists and other perioperative medical staff frequently encounter patients with co-occurring SUDs. By such, through increased awareness and education, physicians and other health care providers have a unique opportunity to positively impact the lives and improve the perioperative outcomes of patients with SUDs. Understanding commonly used terms, potentially effective perioperative screening tools, diagnostic criteria, basics of treatment, and the perioperative implications of SUDs is essential to providing adequate care to patients experiencing this illness.

Evaluation of two different Cannabis sativa L. extracts as antioxidant and neuroprotective agents

Cannabis sativa L. is a plant that contains numerous chemically active compounds including cannabinoids such as trans-Δ-9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), and flavone derivatives, such as luteolin-7-O-glucuronide and apigenin glucuronide. In particular, the polar fraction of hemp including many phenolic compounds has been overlooked when compared with the more lipophilic fraction containing cannabinoids. Therefore, the aim of this study was to assess two extracts of industrial hemp (C. sativa) of different polarity (aqueous and hexane) by evaluating their antioxidant profile and their neuroprotective potential on pharmacological targets in the central nervous system (CNS). Several assays on in vitro antioxidant capacity (DPPH, superoxide radical, FRAP, ORAC), as well as inhibition of physiological enzymes such as acetylcholinesterase (AChE) and monoaminooxidase A (MAO-A) were carried out in order to find out how these extracts may be helpful to prevent neurodegenerative disorders. Neuro-2a cell line was selected to test the cytotoxic and neuroprotective potential of these extracts. Both extracts showed striking antioxidant capacity in the FRAP and ORAC assays, particularly the hexane extract, and interesting results for the DPPH and superoxide radical uptake assays, with the aqueous extract standing out especially in the latter. In enzyme inhibition assays, the aqueous extract showed AChE and MAO-A inhibitory activity, while the hexane extract only reached IC₅₀ value for AChE inhibitory bioassay. Neuro-2a assays demonstrated that polyphenolic extract was not cytotoxic and exhibited cytoprotective properties against hydrogen peroxide and antioxidant response decreasing reactive oxygen species (ROS) production. These extracts could be a source of compounds with potential benefit on human health, especially related to neurodegenerative disorders.

Dynamic task-belief is an integral part of decision-making

Natural decisions involve two seemingly separable processes: inferring the relevant task (task-belief) and performing the believed-relevant task. The assumed separability has led to the traditional practice of studying task-switching and perceptual decision-making individually. Here, we used a novel paradigm to manipulate and measure macaque monkeys' task-belief and demonstrated inextricable neuronal links between flexible task-belief and perceptual decision-making. We showed that in animals, but not in artificial networks that performed as well or better than the animals, stronger task-belief is associated with better perception. Correspondingly, recordings from neuronal populations in cortical areas 7a and V1 revealed that stronger task-belief is associated with better discriminability of the believed-relevant, but not the believed-irrelevant, feature. Perception also impacts belief updating; noise fluctuations in V1 help explain how task-belief is updated. Our results demonstrate that complex tasks and multi-area recordings can reveal fundamentally new principles of how biology affects behavior in health and disease.

Effects of Exercise on Neural Changes in Inhibitory Control: An ALE Meta-Analysis of fMRI Studies

It is widely known that exercise improves inhibitory control; however, the mechanisms behind the cognitive improvement remain unclear. This study analyzes the extant literature on the neuronal effects of exercise on inhibitory control functions. We searched four online databases (Pubmed, Scopus, PsycINFO, and Web of Science) for relevant peer-reviewed studies to identify eligible studies published before September 1, 2021. Among the 4,090 candidate studies identified, 14 meet the inclusion criteria, and the results of 397 participants in these 14 studies are subsequently analyzed. We quantify the neural effects on the entire brain by using GingerALE software and identify 10 clusters of exercise-induced neuronal with either increases/decreases in the superior temporal gyrus (BA 22), precuneus (BA 7), superior frontal gyrus (BA 10), cuneus (BA 19), precuneus (BA 19), caudate, posterior cingulate (BA 19), middle temporal gyrus (B 37), parahippocampal gyrus (BA 30), precentral gyrus (BA 6). Meta-analytic coactivation map (MACM) showed that multiple functional networks overlap with brain regions with activation likelihood estimation (ALE) results. We propose the effect of exercise on neural activity is related to inhibitory control in the extended frontoparietal, default mode network (DMN), visual network, and other pathways. These results provide preliminary evidence of the neural effects of exercise on inhibitory control.

Is the relapse concept in studies of substance use disorders a 'one size fits all' concept? A systematic review of relapse operationalisations

ISSUES

Relapse is a theoretical construct and empirical object of inquiry. It is unclear how relapse is operationalised with regard to the various phases in substance use disorders (SUD). The aim was to investigate relapse operationalisations in SUDs studies after short- and long-term abstinence and remission, recovery and slip/lapse.

APPROACH

Systematic review using the following databases: Epistemonikos, Cochrane Central Register of Controlled Trials (CENTRAL and DARE), MEDLINE, EMBASE, Google Scholar, CINAHL, Web of Science and PsycINFO. Search returned 3426 articles, with 276 meeting the following inclusion criteria: empirical study published in English in a peer-reviewed journal; samples meet diagnostic criteria for dependence syndrome or moderate-severe drug use disorder or alcohol use disorder; reports relapse, abstinence, recovery, remission, slip or lapse. Review protocol registration: PROSPERO (CRD42020154062).

KEY FINDINGS

Thirty-two percent of the studies had no definition of 'relapse'. Most relapse operationalisations were defined according to measure (26%), time (17%), use (26%) and amount and frequency (27%). Of the 16 studies with a follow-up duration of up to 2 years, one (6%) contained a definition of 'long-term abstinence'. Of the 64 studies with a follow-up duration of more than 2 years, four (6%) contained a definition of 'long-term abstinence'. Of those, one (2%) mentioned 'early relapse' and one (2%) mentioned 'late relapse'.

IMPLICATIONS

Future research is needed to explore the possible difference between early and late relapse. Moreover, working to increase consensus on relapse operationalisations in SUD research is warranted.

CONCLUSIONS

We identified no consensus on relapse operationalisations nor agreement on the differentiation between early and late relapse. The clinical utility of current relapse operationalisations seems low and may compromise knowledge accumulation about relapse and implementation of research into treatment.

The possible role of CREB-BDNF signaling pathway in neuroprotective effects of minocycline against alcohol-induced neurodegeneration: molecular and behavioral evidences

Abuse of alcohol triggers neurodegeneration in human brain. Minocycline has characteristics conferring neuroprotection. Current study evaluates the role of the CREB-BDNF signaling pathway in mediating minocycline's neuroprotective effects against alcohol-induced neurodegeneration. Seventy adult male rats were randomly split into groups 1 and 2 that received saline and alcohol (2 g/kg/day by gavage, once daily), respectively, and groups 3, 4, 5, and 6 were treated simultaneously with alcohol and minocycline (10, 20, 30 and 40 mg/kg I.P, respectively) for 21 days. Group 7 received minocycline alone (40 mg/kg, i.p) for 21 days. Morris water maze (MWM) has been used to assess cognitive activity. Hippocampal neurodegenerative and histological parameters as well as cyclic AMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) levels were assessed. Alcohol impaired cognition, and concurrent therapy with various minocycline doses attenuated alcohol-induced cognition disturbances. Additionally, alcohol administration boosted lipid peroxidation and levels of glutathione in oxidized form (GSSG), tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and Bax protein, while decreased reducing type of glutathione (GSH), Bcl-2 protein, phosphorylated CREB, and BDNF levels in rat hippocampus. Alcohol also decreased the activity in the hippocampus of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR). In comparison, minocycline attenuated alcohol-induced neurodegeneration; elevating expression levels of P-CREB and BDNF and inhibited alcohol induced histopathological changes in both dentate gyrus (DG) and CA1 of hippocampus. Thus, minocycline is likely to provide neuroprotection against alcohol-induced neurodegeneration through mediation of the P-CREB/BDNF signaling pathway.

Acute methylphenidate administration reduces cocaine-cue attentional bias

Mechanistic research on behavioral processes underlying substance use disorder might help identify novel targets for interventions development. Drug-related attentional bias and response inhibition deficits have received a great deal of consideration in substance use research, broadly, and cocaine use research, specifically. Studies investigating pharmacological mechanisms that may ameliorate, or further impair, these behaviors relevant to cocaine use are relatively lacking. This study evaluated the impact of acute administration of methylphenidate, a dopamine-favoring reuptake inhibitor, on both gaze-related cocaine-cue-attentional bias and cocaine-cue related disruptions in response inhibition among individuals with cocaine use disorder. Participants (N = 12; 33% female) completed a within-subject, outpatient, acute dosing study. Two sessions were completed in which methylphenidate (60 mg) or placebo were administered followed by completion of an attentional bias task using eye-tracking technology and neutral-cue and cocaine-cue response inhibition tasks. Subjective and physiological effects were also recorded. Significant cocaine cue attentional bias and response inhibition failures were observed during placebo administration. Acute methylphenidate administration reduced cocaine-cue attentional bias as measured by cocaine-cue gaze fixations (d_z = 1.04; Bayes Factor = 12.37). No statistically significant effects of methylphenidate were observed on response inhibition (Bayes Factors = 0.17-1.04). Methylphenidate produced prototypical subjective and physiological effects. Although the small sample should be considered, these findings indicate acute manipulation of dopaminergic activity reduced cue-related attentional allocation related to cocaine use disorder. Future research evaluating alternative dopaminergic agents and applications within a clinical setting are needed to determine the clinical significance of targeting this neurobehavioral mechanism.

“I’d Probably Be Dead Now”: Evaluating the Impact of Theatre Practitioners Working on a Recovery-Based Community Drama Project

Aside from the often-fatal consequences of substance abuse, people recovering from addiction suffer greater adverse childhood experiences, trauma in adulthood, and inequalities than non-addicts. As a result, psychological, emotional, and developmental barriers can prevent effective recovery, leaving people traumatised, vulnerable, and doubly stigmatised. The challenge, therefore, is for recovery practitioners to deliver responses that not only treat biological problems resulting from addiction but also address psychological, social, and cultural needs. One group of professionals providing holistic approaches to people in recovery are arts-based practitioners. This paper derives from a 3-year longitudinal study using Interpretative Phenomenological Analysis, to examine the psychosocial impact of one community-based drama project called Staging Recovery. The study found the work of theatre practitioners not only provided recovery participants safe spaces to explore sensitive and difficult recovery themes but the use of theatre techniques and ethically driven practice exposed participants to high-quality, social, cultural, and human capital.

Modafinil potentiates cocaine self-administration by a dopamine-independent mechanism: possible involvement of gap junctions

Modafinil and methylphenidate are medications that inhibit the neuronal reuptake of dopamine, a mechanism shared with cocaine. Their use as "smart drugs" by healthy subjects poses health concerns and requires investigation. We show that methylphenidate, but not modafinil, maintained intravenous self-administration in Sprague-Dawley rats similar to cocaine. Both modafinil and methylphenidate pretreatments potentiated cocaine self-administration. Cocaine, at self-administered doses, stimulated mesolimbic dopamine levels. This effect was potentiated by methylphenidate, but not by modafinil pretreatments, indicating dopamine-dependent actions for methylphenidate, but not modafinil. Modafinil is known to facilitate electrotonic neuronal coupling by actions on gap junctions. Carbenoxolone, a gap junction inhibitor, antagonized modafinil, but not methylphenidate potentiation of cocaine self-administration. Our results indicate that modafinil shares mechanisms with cocaine and methylphenidate but has a unique pharmacological profile that includes facilitation of electrotonic coupling and lower abuse liability, which may be exploited in future therapeutic drug design for cocaine use disorder.

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.


Cannabis Constituents and Acetylcholinesterase Interaction: Molecular Docking, In Vitro Studies and Association with CNR1 rs806368 and ACHE rs17228602

The study documented here was aimed to find the molecular interactions of some of the cannabinoid constituents of cannabis with acetylcholinesterase (AChE). Molecular docking and LogP determination were performed to predict the AChE inhibitory effect and lipophilicity. AChE enzyme activity was measured in the blood of cannabis addicted human subjects. Further, genetic predisposition to cannabis addiction was investigated by association analysis of cannabinoid receptor 1 (CNR1) single nucleotide polymorphism (SNP) rs806368 and ACHE rs17228602 using restriction fragment length polymorphism (RFLP) method. All the understudied cannabis constituents showed promising binding affinities with AChE and are lipophilic in nature. The AChE activity was observed to be indifferent in cannabis addicted and non-addicted healthy controls. There was no significant association with CNR1 SNP rs806368 and ACHE rs17228602. The study concludes that in silico prediction for individual biomolecules of cannabis is different from in vivo physiological action in human subjects when all are present together. However, for a deeper mechanistic insight into these interactions and association, multi-population studies are suggested. Further studies to explore the inhibitory potential of different cannabis constituents for intended AChE inhibitor-based drug are warranted.

Sex Differences in Neural Correlates of Inhibitory Control

This chapter reviews the current evidence for sex differences in neural function underlying inhibitory control. Specifically, the chapter focuses on sex differences in functional magnetic resonance imaging (fMRI) measures of brain engagement during response inhibition on stop signal and go/no-go tasks. Sex differences appear to exist in these measures, but the direction of effect depends on the population studied, the task used, and whether successful or unsuccessful inhibition is examined. For successful inhibition, healthy men typically show greater brain engagement in right frontal regions typically implicated in inhibitory control (e.g., inferior frontal gyrus and supplementary motor area) than women, especially when performing the stop signal task. However, in younger populations or when controlling for the effects of age, women tend to show greater brain engagement than men, especially when performing the go/no-go task. For unsuccessful inhibition, women tend to show greater brain engagement compared to men in the anterior cingulate cortex and thalamus. Taken together, findings suggest that sex differences in neural responses to response inhibition depend on the specific type of inhibition studied and on whether the inhibition is successful or unsuccessful. Men exhibit greater response during successful inhibition, whereas women consistently display greater neural responses during unsuccessful inhibition. The chapter highlights limitations and gaps in this research to date, including a lack of consideration of the role of sex hormones and menstrual cycle phase, and suggests future directions for this line of research.

The cognitive cost of reducing relapse to cocaine-seeking with mGlu5 allosteric modulators

RATIONALE

Cocaine use disorder (CUD) remains difficult to treat with no FDA-approved medications to reduce relapse. Antagonism of metabotropic glutamate receptor 5 (mGlu5) has been demonstrated to decrease cocaine-seeking but may also further compromise cognitive function in long-term cocaine users.

OBJECTIVES

Here we assessed the effect of repeated administration of negative or positive allosteric modulators (NAM or PAM) of mGlu5 on both cognitive performance and (context+cue)-primed cocaine-seeking after prolonged abstinence (≥ 45 days).

METHODS

Adult male Sprague-Dawley rats underwent 6 days of short-access (1 h/day) and 12 days of long-access (6 h/day) cocaine self-administration. Rats were then trained and tested in a delayed match-to-sample (DMS) task to establish baseline working memory performance over a 5-day block of testing. Next, rats received daily systemic administration of the mGlu5 NAM 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine hydrochloride (MTEP; 3 mg/kg), the mGlu5 PAM 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB; 30 mg/kg) or vehicle prior to DMS testing during a block of 5 days, followed by a 5-day washout DMS testing block.

RESULTS

MTEP and CDPPB decreased drug-seeking in response to cocaine-associated cues after prolonged abstinence. However, repeated treatment with MTEP impaired working memory, while CDPPB had no effects on performance.

CONCLUSIONS

These results emphasize the relevance of evaluating cognitive function within the context of investigating pharmacotherapies to treat CUD. Further research is needed to determine how two mechanistically different pharmacological compounds can exert the same behavioral effects to reduce cocaine-seeking.

Galantamine and Computerized Cognitive Behavioral Therapy for Cocaine Dependence: A Randomized Clinical Trial

OBJECTIVE

To examine whether galantamine, a cognitive-enhancing medication that is both acetylcholinesterase inhibitor and agonist at nicotinic acetylcholine receptors, is effective at improving cocaine use outcomes and cognitive functioning, alone and in combination with computerized cognitive behavioral therapy (CBT).

METHOD

A 12-week, randomized 2 × 2, factorial trial was conducted to evaluate galantamine versus placebo (double-blind) and computerized CBT plus standard methadone treatment versus standard methadone treatment alone in a community-based methadone maintenance program (September 2009-April 2015). One hundred twenty individuals diagnosed with DSM-IV cocaine use disorder were randomly assigned to the following conditions: (1) galantamine (8 mg/d) plus standard methadone maintenance treatment (treatment as usual [TAU]), (2) placebo plus TAU, (3) galantamine plus computerized CBT plus TAU, or (4) placebo plus computerized CBT plus TAU; medication administration was supervised at the time of daily methadone dosing. The primary cocaine use outcome was change in percent days of abstinence over time. Number of cocaine-negative urine toxicology screens submitted and cognitive function were secondary outcomes.

RESULTS

Random effect regression analysis indicated significant reductions in frequency of cocaine use over time, with significant treatment-by-time effects for both galantamine over placebo (F = 5.3, P = .02, d = 0.34) and computerized CBT over standard methadone treatment (F = 4.2, P = .04, d = 0.30) but no evidence of significant benefit of the combination over either treatment alone. Pretreatment to posttreatment comparisons of multiple indices of cognitive functioning, including sustained attention, indicated no benefit of galantamine over placebo.

CONCLUSIONS

Findings suggest benefits of galantamine and computerized CBT for reducing cocaine use in this sample. Although galantamine did not improve measures of cognitive function in this sample, multiple measures of cognitive function were associated with cocaine use outcomes, underlining the significance of cognitive function in cocaine treatment outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00809835.

Association of status of acetylcholinesterase and ACHE gene 3' UTR variants (rs17228602, rs17228616) with drug addiction vulnerability in pakistani population

Substance addiction is a chronic, relapsing mental disorder Characterized by compulsive drug seeking, and loss of control over drug intake and relapse after prolonged abstinence. Genetics has been shown to contribute towards an individual's vulnerability to addiction. Acetylecholine (ACh), a cholinergic neurotransmitter hydrolyzed by acetylcholinesterase (AChE), is an essential neurotransmitter and neuromodulator in central and peripheral nervous system and has regulatory influence on numerous neuronal functions including addiction. The present study was carried out to investigate the role of acetylcholinesterase (AChE) in addiction through measurement of enzyme activity and to find potential association of ACHE gene 3'UTR variants rs17228602 and rs17228616 in heroin, hashish and poly drug addicts. Both SNPs are located within microRNA (miRNA) recognition sites with potential to affect miRNA/transcript interaction. A total of 122 addicts of heroin, hashish and polydrug were recruited from local rehabilitation centers to participate in this study. AChE activity was measured in blood by Ellman's method. SNP genotyping was performed by restriction fragment length polymorphism (PCR-RFLP) and Sanger sequencing. The AChE activity was found significantly higher (p ≤ 0.005) in addicted cohort (mean ± standard error of mean 0.020 ± 0.001 μmol/L/min; 95% confidence interval (CI) 0.018-0.022) in comparison to non-addicted healthy subjects (0.011 ± 0.001 μmol/L/min; 95% confidence interval CI 0.010-0.013). A statistically significant association of ACHE rs17228602 SNP with addiction vulnerability in dominant (DM: Odd's ratio OR = 2.095, 95% CI = 1.157-3.807 p = 0.009) and allelic genetic models (OR = 1.854 95% CI = 1.082-3.187, p = 0.016) was observed. However, no statistically significant association of rs17228616 SNP with substance abuse disorder was found. The data presented here shows that AChE could play significant role in substance addiction. Further studies with larger sample size and other variants of AChE are recommended to identify novel therapeutic approaches for cholinergic based treatment of addiction.

Impact of Substance Use Disorder Pharmacotherapy on Executive Function: A Narrative Review

Substance use disorders are chronic, relapsing, and harmful conditions characterized by executive dysfunction. While there are currently no approved pharmacotherapy options for stimulant and cannabis use disorders, there are several evidence-based options available to help reduce symptoms during detoxification and aid long-term cessation for those with tobacco, alcohol and opioid use disorders. While these medication options have shown clinical efficacy, less is known regarding their potential to enhance executive function. This narrative review aims to provide a brief overview of research that has investigated whether commonly used pharmacotherapies for these substance use disorders (nicotine, bupropion, varenicline, disulfiram, acamprosate, nalmefene, naltrexone, methadone, buprenorphine, and lofexidine) effect three core executive function components (working memory, inhibitory control and cognitive flexibility). While pharmacotherapy-induced enhancement of executive function may improve cessation outcomes in dependent populations, there are limited and inconsistent findings regarding the effects of these medications on executive function. We discuss possible reasons for the mixed findings and suggest some future avenues of work that may enhance the understanding of addiction pharmacotherapy and cognitive training interventions and lead to improved patient outcomes.

Neurocognitive Profiling of Adult Treatment Seekers Enrolled in a Clinical Trial of a Web-delivered Intervention for Substance Use Disorders

OBJECTIVE

This study is a secondary descriptive analysis that explores and compares the cognitive profiles of adults entering treatment at geographically diverse community-based substance use disorder treatment facilities.

METHODS

Performance on cognitive measures at baseline was compared across 5 primary substance subgroups of individuals (alcohol = 104; cocaine = 102; stimulants = 69; opioids = 108; marijuana = 114) enrolled in a web-based psychosocial treatment study conducted within the National Drug Abuse Treatment Clinical Trials Network. MicroCog subtests were used to assess cognitive domains of attention and mental control, reasoning and cognitive flexibility, and spatial processing.

RESULTS

The average age of onset for a substance use disorder was early to mid-20s, with marijuana users reporting the earliest age of onset (mean 19.9, SD 7.5) and stimulant users reporting the latest (mean 25.2, SD 9.9). Among the total sample, half (49.7%) demonstrated impairment in cognitive flexibility and reasoning, and over one-third (37.3%) had impairment in verbal learning and memory. Stimulant (37.68%) and cocaine (34.31%) users showed significantly greater clinical impairment in attention and mental control compared with alcohol users (17.31%) and opioid (21.30%) users (stimulant subgroup only) (χ [4] = 10.97, P = 0.027). Cocaine users showed the greatest overall impairment across total and proficiency subtest scores, although these were not statistically different from other subgroups.

CONCLUSIONS

These findings confirmed previous studies, indicating a high prevalence of significant cognitive dysfunction across all substance use categories among treatment-seeking adults, and found that cocaine use appears to be associated with the most impairment. Increasing knowledge of similarities and differences between primary substance subgroups can help guide substance use disorder treatment planning.

Event-Related Potentials as Biomarkers of Behavior Change Mechanisms in Substance Use Disorder Treatment

Substance use disorders (SUDs) are one of the most prevalent psychiatric conditions and represent a significant public health concern. Substantial research has identified key processes related to reinforcement and cognition for the development and maintenance of SUDs, and these processes represent viable treatment targets for psychosocial and pharmacological interventions. Research on SUD treatments has suggested that most approaches are comparable in effectiveness. As a result, recent work has focused on delineating the underlying mechanisms of behavior change that drive SUD treatment outcome. Given the rapid fluctuations associated with the key neurocognitive processes associated with SUDs, high-temporal-resolution measures of human brain processing, namely event-related potentials (ERPs), are uniquely suited to expand our understanding of the underlying neural mechanisms of change during and after SUD treatment. The value of ERPs in the context of SUD treatment are discussed along with work demonstrating the predictive validity of ERPs as biomarkers of SUD treatment response. Example associations between multiple ERP components and psychosocial and/or pharmacological treatment outcome include the P3a and P3b (in response to neutral and substance-related cues), the attention-related negativities (e.g., N170, N200), the late positive potential, and the error-related negativity. Also addressed are limitations of the biomarker approach to underscore the need for research programs evaluating mechanisms of change. Finally, we emphasize the advantages of ERPs as indices of behavior change in SUD treatment and outline issues relevant for future directions in this context.

Effect of Modafinil on Cognitive Function in Intensive Care Unit Patients: A Retrospective Cohort Study

Modafinil therapy, a nonamphetamine cognition-enhancing agent, holds the potential to improve recovery from cognitive impairment after intensive care unit (ICU) admission. To date, however, there is a paucity of data on modafinil use in the ICU setting. The purpose of this study was to explore the role of modafinil for improvement in cognition in ICU patients. This retrospective cohort study evaluated a total of 60 ICU patients with any ventilatory support who started on modafinil during their ICU stay from January 1, 2010, to March 19, 2016. The requirements of opioids and sedatives, as well as the lowest and average scores of the Glasgow Coma Scale (GCS) and Riker Sedation-Agitation Scale (SAS), were recorded during 48 hours before and after the start of modafinil therapy in 6-hour periods. The average daily modafinil dose of 170 mg was given for a median duration of 9 days. Modafinil administration was associated with a small, nonsignificant increase in GCS by 0.34 points after controlling for age, baseline severity of illness, and changes in sedation and analgesia over time (95%CI, -0.34 to 0.73 points; P = .0743). No major modafinil-associated adverse effects were observed. Modafinil administration did not significantly improve cognitive function in ICU patients within 48 hours of initiation. However, because of lack of robust evidence, the impact of modafinil on overall patient outcomes in the ICU remains unclear and needs further investigation.

Repetitive Transcranial Magnetic Stimulation for Wernicke-Korsakoff Syndrome: A Case Report

A 57-year-old man who was diagnosed with Wernicke-Korsakoff syndrome showed severe impairment of cognitive function and a craving for alcohol, even after sufficient supplementation with thiamine. After completing 10 sessions of 10 Hz repetitive transcranial magnetic stimulation (rTMS) at 100% of the resting motor threshold over the left dorsolateral prefrontal cortex, dramatic improvement in cognitive function and a reduction in craving for alcohol were noted. This is the first case report of the efficacy of a high-frequency rTMS in the treatment of Wernicke-Korsakoff syndrome.

Exploring the Effect of Ginsenoside Rh1 in a Sleep Deprivation-Induced Mouse Memory Impairment Model

Panax ginseng C.A. Meyer (Araliaceae) has been used in traditional Chinese medicine for enhancing cognition for thousands of years. Ginsenoside Rh1, a constituent of ginseng root, as with other constituents, has memory-improving effects in normal mice and scopolamine-induced amnesic mice. Sleep deprivation (SD) is associated with memory impairment through induction of oxidative stress. The present study investigated the effect of Rh1 against SD-induced cognitive impairment and attempted to define the possible mechanisms involved. Ginsenoside Rh1 (20 μmol/kg; 40 μmol/kg) and modafinil (0.42 g/kg) were administered to the mice intraperitoneally for 23 days. After 14-day SD, locomotor activity was examined using the open field test, and the object location recognition and Morris water maze tests were used to evaluate cognitive ability. The cortex and hippocampus were then dissected and homogenized, and levels and activities of antioxidant defense biomarkers were evaluated to determine the level of oxidative stress. The results revealed that Rh1 prevented cognitive impairment induced by SD, and its ability to reduce oxidative stress in cortex and hippocampus may contribute to the mechanism of action. Copyright © 2017 John Wiley & Sons, Ltd.

Effects of acute buspirone administration on inhibitory control and sexual discounting in cocaine users

OBJECTIVE

Cocaine users display deficits in inhibitory control and make impulsive choices that may increase risky behavior. Buspirone is an anxiolytic that activates dopaminergic and serotonergic systems and improves impulsive choice (i.e., reduces sexual risk-taking intent) in cocaine users when administered chronically. We evaluated the effects of acutely administered buspirone on inhibitory control and impulsive choice.

METHODS

Eleven subjects with a recent history of cocaine use completed this within-subject, placebo-controlled study. Subjects performed two cued go/no-go and a sexual risk delay-discounting task following oral administration of buspirone (10 and 30 mg), triazolam (0.375 mg; positive control), and placebo (negative control). Physiological and psychomotor performance and subject-rated data were also collected.

RESULTS

Buspirone failed to change inhibitory control or impulsive choice; however, slower reaction times were observed at the highest dose tested. Buspirone did not produce subject-rated drug effects but dose-dependently decreased diastolic blood pressure. Triazolam impaired psychomotor performance and increased ratings of positive subject-rated effects (e.g., Like Drug).

CONCLUSIONS

These findings indicate that acutely administered buspirone has little impact on behavioral measures of inhibitory control and impulsive sexual decision-making. Considering previous findings with chronic dosing, these findings highlight that the behavioral effects of buspirone differ as a function of dosing conditions.

Chronic methamphetamine self-administration disrupts cortical control of cognition

Methamphetamine (meth) is one of the most abused substances worldwide. Chronic use has been associated with repeated relapse episodes that may be exacerbated by cognitive impairments during drug abstinence. Growing evidence demonstrates that meth compromises prefrontal cortex activity, resulting in persisting attentional and memory impairments. After summarizing recent studies of meth-induced cognitive dysfunction using a translationally relevant model of self-administered meth, this review emphasizes the cortical brain changes contributing to cognitive dysregulation during abstinence. Finally, we propose the use of cognitive enhancers during abstinence that may promote a drug-free state by reversing cortical dysfunction linked with prolonged meth abuse.

Dose-response relationships between exercise intensity, cravings, and inhibitory control in methamphetamine dependence: An ERPs study

BACKGROUND

The present study integrated behavioral and neuroelectric approaches for determining the dose-response relationships between exercise intensity and methamphetamine (MA) craving and between exercise intensity and inhibitory control in individuals with MA dependence.

METHODS

Ninety-two individuals with MA dependence were randomly assigned to an exercise group (light, moderate, or vigorous intensity) or to a reading control group. The participants then completed a craving self-report at four time points: before exercise, during exercise, immediately after exercise, and 50 min after exercise. Event-related potentials were also recorded while the participants completed a standard Go/NoGo task and an MA-related Go/NoGo task approximately 20 min after exercise cessation.

RESULTS

The reduction in self-reported MA craving scores of the moderate and vigorous intensity groups was greater than that of the light intensity and control groups during acute exercise as well as immediately and 50 min following exercise termination. Additionally, an inverted-U-shaped relationship between exercise intensity and inhibitory control was generally observed for the behavioral and neuroelectric indices, with the moderate intensity group exhibiting shorter Go reaction times, increased NoGo accuracy, and larger NoGo-N2 amplitudes.

CONCLUSIONS

Acute exercise may provide benefits for MA-associated craving and inhibitory control in MA-dependent individuals, as revealed by behavioral and neuroelectric measures. Moderate-intensity exercise may be associated with more positive effects, providing preliminary evidence for the establishment of an exercise prescription regarding intensity for MA dependence.

Correlating behaviour and gene expression endpoints in the dopaminergic system after modafinil administration in mouse

The mechanisms of action of modafinil continue to be poorly characterised and its potential for abuse in preclinical models remains controverted. The aim of this study was to further elucidate the mechanism of action of modafinil, through a potential behavioural and molecular association in the mouse. A conditioned place preference (CPP) paradigm was implemented to investigate the rewarding properties of modafinil. Whole genome expression and qRT-PCR analysis were performed on the ventral tegmental area (VTA), nucleus accumbens (NAC) and prefrontal cortex (PFC) of modafinil-treated and control animals. Modafinil administration (65 mg/kg) induced an increase in locomotor activity, an increase in the change of preference for the drug paired side after a conditioning period as well as changes to gene expression profiles in the VTA (120 genes), NAC (23 genes) and PFC (19 genes). A molecular signature consisting of twelve up-regulated genes was identified as common to the three brain regions. Multiple linear correlation analysis showed a strong correlation (R(2)>0.70) between the behavioural and molecular endpoints in the three brain regions. We show that modafinil had a concomitant effect on CPP, locomotor activity, and up-regulation of interferon-γ (IFN-γ) regulated genes (Gbp2, Gbp3, Gbp10, Cd274, Igtp), while correlating the latter set of genes with behaviour changes evaluated through the CPP. A potential association can be proposed based on the dysregulation of p47 family genes and Gbp family of IFN-γ induced GTPases. In conclusion, these findings suggest a link between the behavioural and molecular events in the context of modafinil administration.

Cocaine Abuse in Later Life: A Case Series and Review of the Literature

OBJECTIVE

To raise awareness about the growing trend of cocaine abuse in later years as an underdiagnosed, undertreated, and comorbid condition in older individuals. Three cases of cocaine use in patients over the age of 50 years in the Malcolm Randall Veterans Medical Center, Gainesville, Florida, within a 10-day span in 2013 are presented.

DATA SOURCES

PubMed was searched using combinations of keywords, including cocaine, addiction, elderly, and aging, to find articles published between 1986 and 2013.

STUDY SELECTION

In total, 37 articles were selected for inclusion on the basis of their relevance to the objective and importance to the representation of cocaine abuse, including international guidelines for addiction.

DATA EXTRACTION

Each article was reviewed for eligibility. Final decisions were made following full-text review.

RESULTS

Cocaine addiction remains a high-morbidity chronic-relapsing illness with few treatment options. A review of the literature shows that late-life cocaine use is sparsely recognized. Of particular interest are the clinical presentations in which a higher index for detection is warranted. The high rate of medical comorbidity associated with cocaine use, especially cerebrovascular deficits, presents special treatment and social challenges.

CONCLUSIONS

As the number of older individuals admitted for substance use continues to climb, clinicians must adapt to the changing demographics by increasing screening, early detection, and treatment options for older persons.

Alcohol use disorder with and without stimulant use: brain morphometry and its associations with cigarette smoking, cognition, and inhibitory control

OBJECTIVE

Little is known about the effects of polysubstance use and cigarette smoking on brain morphometry. This study examined neocortical brain morphometric differences between abstinent polysubstance dependent and alcohol-only dependent treatment seekers (ALC) as well as light drinking controls (CON), the associations of cigarette smoking in these polysubstance users (PSU), and morphometric relationships to cognition and inhibitory control.

METHODS

All participants completed extensive neuropsychological assessments and 4 Tesla brain magnetic resonance imaging. PSU and ALC were abstinent for one month at the time of study. Parcellated morphological data (volume, surface area, thickness) were obtained with FreeSurfer methodology for the following bilateral components: dorso-prefrontal cortex (DPFC), anterior cingulate cortex (ACC), orbitofrontal cortex (OFC), and insula. Regional group differences were examined and structural data correlated with domains of cognition and inhibitory control.

RESULTS

PSU had significantly smaller left OFC volume and surface area and trends to smaller right DPFC volume and surface area compared to CON; PSU did not differ significantly from ALC on these measures. PSU, however, had significantly thinner right ACC than ALC. Smoking PSU had significantly larger right OFC surface area than non-smoking PSU. No significant relationships between morphometry and quantity/frequency of substance use, alcohol use, or age of onset of heavy drinking were observed. PSU exhibited distinct relationships between brain structure and processing speed, cognitive efficiency, working memory and inhibitory control that were not observed in ALC or CON.

CONCLUSION

Polysubstance users have unique morphometric abnormalities and structure-function relationships when compared to individuals dependent only on alcohol and light drinking controls. Chronic cigarette smoking is associated with structural brain irregularities in polysubstance users. Further elucidation of these distinctive characteristics could help inform the development of targeted and thus potentially more effective treatments in this large but understudied population.

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.

Future pharmacological treatments for substance use disorders

Substance use disorders represent a serious public health and social issue worldwide. Recent advances in our understanding of the neurobiological basis of the addictive processes have led to the development of a growing number of pharmacological agents to treat addictions. Despite this progress, there are no approved pharmacological treatments for cocaine, methamphetamine and cannabis addiction. Moving treatment development to the next stage will require novel ways of approaching substance use disorders. One such novel approach is to target individual vulnerabilities, such as cognitive function, sex differences and psychiatric comorbidities. This review provides a summary of promising pharmacotherapies for alcohol, opiate, stimulant and nicotine addictions. Many medications that target positive and negative reinforcement of drugs, as well as individual vulnerabilities to addiction, are in different phases of development. Clinical trials testing the efficacy of these medications for substance use disorder are warranted.

Administration of the nicotinic acetylcholine receptor agonists ABT-089 and ABT-107 attenuates the reinstatement of nicotine-seeking behavior in rats

Current smoking cessation pharmacotherapies have modest efficacy, and most smokers relapse within the first few days after a quit attempt. Nicotine withdrawal-induced craving and cognitive impairments predict smoking relapse during abstinence and suggest that cognitive-enhancing drugs may prevent relapse. ABT-089 and ABT-107 are subtype-selective nAChR agonists that improve cognitive performance in laboratory animals. However, there are no studies examining the effects of ABT-089 and ABT-107 on nicotine self-administration and the reinstatement of nicotine-seeking behavior, an animal model of relapse in human smokers. The goal of the present study was to determine the effects of the α4β2*/α6β2* nAChR agonist ABT-089 and the α7 nAChR agonist ABT-107 on nicotine taking and seeking in rats. The effects of acute ABT-089 and ABT-107 pretreatment on nicotine self-administration and reinstatement were tested in male Sprague Dawley rats. Parallel studies of ABT-089 and ABT-107 on sucrose self-administration and reinstatement were tested in separate groups of rats to determine if the effects of these drug treatments generalized to other reinforced behaviors. Nicotine and sucrose self-administration behaviors were not altered following acute administration of ABT-089 (0, 0.12, 1.2 and 12.0mg/kg) or ABT-107 (0, 0.03 and 0.3mg/kg). In contrast, both ABT-089 and ABT-107 pretreatment dose-dependently attenuated nicotine reinstatement. These effects were reinforcer-specific as no effects of ABT-089 or ABT-107 pretreatment on sucrose seeking were noted. Taken together, these findings suggest that ABT-089 and ABT-107 do not affect nicotine consumption, but may reduce the likelihood that a smoking lapse will lead to relapse.

Donepezil, an acetylcholinesterase inhibitor, attenuates nicotine self-administration and reinstatement of nicotine seeking in rats

Nicotine craving and cognitive impairments represent core symptoms of nicotine withdrawal and predict relapse in abstinent smokers. Current smoking cessation pharmacotherapies have limited efficacy in preventing relapse and maintaining abstinence during withdrawal. Donepezil is an acetylcholinesterase inhibitor that has been shown previously to improve cognition in healthy non-treatment-seeking smokers. However, there are no studies examining the effects of donepezil on nicotine self-administration and/or the reinstatement of nicotine-seeking behavior in rodents. The present experiments were designed to determine the effects of acute donepezil administration on nicotine taking and the reinstatement of nicotine-seeking behavior, an animal model of relapse in abstinent human smokers. Moreover, the effects of acute donepezil administration on sucrose self-administration and sucrose seeking were also investigated in order to determine whether donepezil's effects generalized to other reinforced behaviors. Acute donepezil administration (1.0 or 3.0 mg/kg, i.p.) attenuated nicotine, but not sucrose self-administration maintained on a fixed-ratio 5 schedule of reinforcement. Donepezil administration also dose-dependently attenuated the reinstatement of both nicotine- and sucrose-seeking behaviors. Commonly reported adverse effects of donepezil treatment in humans are nausea and vomiting. However, at doses required to attenuate nicotine self-administration in rodents, no effects of donepezil on nausea/malaise as measured by pica were observed. Collectively, these results indicate that increased extracellular acetylcholine levels are sufficient to attenuate nicotine taking and seeking in rats and that these effects are not due to adverse malaise symptoms such as nausea.

Cognitive control in alcohol use disorder: deficits and clinical relevance

Cognitive control refers to the internal representation, maintenance, and updating of context information in the service of exerting control over thoughts and behavior. Deficits in cognitive control likely contribute to difficulty in maintaining abstinence in individuals with alcohol use disorders (AUD). In this article, we define three cognitive control processes in detail (response inhibition, distractor interference control, and working memory), review the tasks measuring performance in these areas, and summarize the brain networks involved in carrying out these processes. Next, we review evidence of deficits in these processes in AUD, including both metrics of task performance and functional neuroimaging. Finally, we explore the clinical relevance of these deficits by identifying predictors of clinical outcome and markers that appear to change (improve) with treatment. We observe that individuals with AUD experience deficits in some, but not all, metrics of cognitive control. Deficits in cognitive control may predict clinical outcome in AUD, but more work is necessary to replicate findings. It is likely that performance on tasks requiring cognitive control improves with abstinence, and with some psychosocial and medication treatments. Future work should clarify which aspects of cognitive control are most important to target during treatment of AUD.

William L. Woolverton: a case history in unraveling the behavioral pharmacology of stimulants

Clinical findings suggest that the most promising strategy for cocaine addiction is a combination of indirect-acting monoamine agonists with some form of behavioral intervention. This approach can be traced back to preclinical research, some of which was conducted by William L. Woolverton. The goal of this brief review is to provide readers with an appreciation for the experimental breadth involving both behavior and pharmacology that encompassed Woolverton's amazing career, from the evaluation of abuse liability of drugs to the use of complex behavioral contingencies to better model the human condition. We begin with Woolverton's research using simple and complex schedules of reinforcement to evaluate abuse liability and how that has impacted current animal models. We also discuss his use of cocaine vs. food choice schedules of reinforcement as a model to evaluate potential medications for treating cocaine use disorders. Woolverton concluded that drug taking behavior was not "impulsive" and "out of control" as has often been proposed, but rather directly determined by the environmental contingencies and the context of its availability, providing a nuanced understanding of drug-behavior interactions. This article is part of the Special Issue entitled 'CNS Stimulants'

Systematic review of ERP and fMRI studies investigating inhibitory control and error processing in people with substance dependence and behavioural addictions

BACKGROUND

Several current theories emphasize the role of cognitive control in addiction. The present review evaluates neural deficits in the domains of inhibitory control and error processing in individuals with substance dependence and in those showing excessive addiction-like behaviours. The combined evaluation of event-related potential (ERP) and functional magnetic resonance imaging (fMRI) findings in the present review offers unique information on neural deficits in addicted individuals.

METHODS

We selected 19 ERP and 22 fMRI studies using stop-signal, go/no-go or Flanker paradigms based on a search of PubMed and Embase.

RESULTS

The most consistent findings in addicted individuals relative to healthy controls were lower N2, error-related negativity and error positivity amplitudes as well as hypoactivation in the anterior cingulate cortex (ACC), inferior frontal gyrus and dorsolateral prefrontal cortex. These neural deficits, however, were not always associated with impaired task performance. With regard to behavioural addictions, some evidence has been found for similar neural deficits; however, studies are scarce and results are not yet conclusive. Differences among the major classes of substances of abuse were identified and involve stronger neural responses to errors in individuals with alcohol dependence versus weaker neural responses to errors in other substance-dependent populations.

LIMITATIONS

Task design and analysis techniques vary across studies, thereby reducing comparability among studies and the potential of clinical use of these measures.

CONCLUSION

Current addiction theories were supported by identifying consistent abnormalities in prefrontal brain function in individuals with addiction. An integrative model is proposed, suggesting that neural deficits in the dorsal ACC may constitute a hallmark neurocognitive deficit under lying addictive behaviours, such as loss of control.

Optimizing treatments for nicotine dependence by increasing cognitive performance during withdrawal

INTRODUCTION

Current FDA-approved smoking cessation pharmacotherapies have limited efficacy and are associated with high rates of relapse. Therefore, there is a clear need to develop novel antismoking medications. Nicotine withdrawal is associated with cognitive impairments that predict smoking relapse. It has been proposed that these cognitive deficits are a hallmark of nicotine withdrawal that could be targeted in order to prevent smoking relapse. Thus, pharmacotherapies that increase cognitive performance during nicotine withdrawal may represent potential smoking cessation agents.

AREAS COVERED

The authors review the clinical literature demonstrating that nicotine withdrawal is associated with deficits in working memory, attention and response inhibition. They then briefly summarize different classes of compounds and strategies to increase cognitive performance during nicotine withdrawal. Particular emphasis has been placed on translational research in order to highlight areas for which there is strong rationale for pilot clinical trials of potential smoking cessation medications.

EXPERT OPINION

There is emerging evidence that supports deficits in cognitive function as a plausible nicotine withdrawal phenotype. The authors furthermore believe that the translational paradigms presented here may represent efficient and valid means for the evaluation of cognitive-enhancing medications as possible treatments for nicotine dependence.

The role of guanfacine as a therapeutic agent to address stress-related pathophysiology in cocaine-dependent individuals

The pathophysiology of cocaine addiction is linked to changes within neural systems and brain regions that are critical mediators of stress system sensitivity and behavioral processes associated with the regulation of adaptive goal-directed behavior. This is characterized by the upregulation of core adrenergic and corticotropin-releasing factor mechanisms that subserve negative affect and anxiety and impinge upon intracellular pathways in the prefrontal cortex underlying cognitive regulation of stress and negative emotional state. Not only are these mechanisms essential to the severity of cocaine withdrawal symptoms, and hence the trajectory of clinical outcome, but also they may be particularly pertinent to the demography of cocaine dependence. The ability of guanfacine to target overlapping stress, reward, and anxiety pathophysiology suggests that it may be a useful agent for attenuating the stress- and cue-induced craving state not only in women but also in men. This is supported by recent research findings from our own laboratory. Additionally, the ability of guanfacine to improve regulatory mechanisms that are key to exerting cognitive and emotional control over drug-seeking behavior also suggests that guanfacine may be an effective medication for reducing craving and relapse vulnerability in many drugs of abuse. As cocaine-dependent individuals are typically polydrug abusers and women may be at a greater disadvantage for compulsive drug use than men, it is plausible that medications that target catecholaminergic frontostriatal inhibitory circuits and simultaneously reduce stress system arousal may provide added benefits for attenuating cocaine dependence.

Association of abstinence-induced alterations in working memory function and COMT genotype in smokers

RATIONALE

The common methionine (met) for valine (val) at codon 158 (val(158)met) polymorphism in the catechol-O-methyltransferase (COMT) gene has been associated with nicotine dependence, alterations in executive cognitive function, and abstinence-induced working memory deficits in smokers.

OBJECTIVES

We sought to replicate the association of the COMT val allele with abstinence-induced alterations in working memory-related activity in task-positive (executive control) and task-negative (default mode network) regions.

METHODS

Forty smokers (20 val/val and 20 met/met) performed an N-back task while undergoing blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) on two separate occasions: following 72 h of confirmed abstinence and during smoking as usual. An independent sample of 48 smokers who completed the identical N-back task during fMRI in smoking vs. abstinence for another study was used as a validation sample.

RESULTS

Contrary to expectations, genotype by session interactions on BOLD signal in executive control regions (dorsolateral prefrontal cortex and dorsal cingulate/medial prefrontal cortex) revealed significant abstinence-induced reductions in the met/met group, but not the val/val group. Results also revealed that val/val smokers may exhibit less suppression of activation in task-negative regions such as the posterior cingulate cortex during abstinence (vs. smoking). These patterns were confirmed in the validation sample and in the whole-brain analysis, though the regions differed from the a priori regions of interest (ROIs) (e.g., precuneus, insula).

CONCLUSIONS

The COMT val(158)met polymorphism was associated with abstinence-related working memory deficits in two independent samples of smokers. However, inconsistencies compared to prior findings and across methods (ROI vs. whole-brain analysis) highlight the challenges inherent in reproducing results of imaging genetic studies in addiction.

Effect of modafinil on cognitive functions in alcohol dependent patients: a randomized, placebo-controlled trial

Cognitive deficits are highly prevalent in alcohol-dependent (AD) patients and may have a detrimental impact on treatment response and treatment outcome. Enhancing cognitive functions may improve treatment success. Modafinil is a promising compound in this respect. Therefore, a randomized double-blind placebo-controlled trial was conducted with modafinil (300 mg/d) or placebo in 83 AD patients for 10 weeks. Various cognitive functions (digit span task, Tower of London task, Stroop task) were measured at baseline, during and after treatment. Compared to placebo, modafinil improved verbal short-term memory (number of forward digit spans) (p=0.030), but modafinil exerted a negative effect on the working memory score of the digit span task (p=0.003). However, subgroup analyses revealed that modafinil did improve both working memory and verbal short-term memory in AD patients with a poor working memory ability at baseline (25% worst performers), whereas no significant treatment effect of modafinil was found on these two dependent variables in patients with good working memory skills at baseline (25% best performers). No effect of modafinil was found on measures of planning (Tower of London task) and selective attention (Stroop task). Further research is needed to better understand the relationship between cognitive remediation and treatment outcome in order to design targeted treatments.

Relationship of age to impulsivity and decision making: a baseline secondary analysis of a behavioral treatment study in stimulant use disorders

Because stimulant use disorders remain prevalent across the lifespan, cognition is an important area of clinical care and research focus among aging adults with stimulant use disorders. This secondary analysis of a National Institute on Drug Abuse Clinical Trials Network study suggests that decision making, verbal learning/memory, executive function, and set shifting are important cognitive domains to screen clinically and treat in aging adults with stimulant use disorders. Some suggestions are made on how clinical treatment providers can practically use these results. An important direction for future research is the development of cognitively remediating treatments for impaired cognitive domains in aging adults with stimulant use disorders.

The neurobiology of modafinil as an enhancer of cognitive performance and a potential treatment for substance use disorders

RATIONALE AND OBJECTIVES

Modafinil (MOD) and its R-enantiomer (R-MOD) are approved medications for narcolepsy and other sleep disorders. They have also been used, off-label, as cognitive enhancers in populations of patients with mental disorders, including substance abusers that demonstrate impaired cognitive function. A debated nonmedical use of MOD in healthy individuals to improve intellectual performance is raising questions about its potential abuse liability in this population.

RESULTS AND CONCLUSIONS

MOD has low micromolar affinity for the dopamine transporter (DAT). Inhibition of dopamine (DA) reuptake via the DAT explains the enhancement of DA levels in several brain areas, an effect shared with psychostimulants like cocaine, methylphenidate, and the amphetamines. However, its neurochemical effects and anatomical pattern of brain area activation differ from typical psychostimulants and are consistent with its beneficial effects on cognitive performance processes such as attention, learning, and memory. At variance with typical psychostimulants, MOD shows very low, if any, abuse liability, in spite of its use as a cognitive enhancer by otherwise healthy individuals. Finally, recent clinical studies have focused on the potential use of MOD as a medication for treatment of drug abuse, but have not shown consistent outcomes. However, positive trends in several result measures suggest that medications that improve cognitive function, like MOD or R-MOD, may be beneficial for the treatment of substance use disorders in certain patient populations.

The role of dopamine in inhibitory control in smokers and non-smokers: a pharmacological fMRI study

Contemporary theoretical models of substance dependence posit that deficits in inhibitory control play an important role in substance dependence. The neural network underlying inhibitory control and its association with substance dependence have been widely investigated. However, the pharmacology of inhibitory control is still insufficiently clear. The aims of the current study were twofold. First, we investigated the role of dopamine in inhibitory control and associated brain activation. Second, the proposed link between dopamine and impaired inhibitory control in nicotine dependence was investigated by comparing smokers and non-smoking controls. Haloperidol (2 mg), a dopamine D2/D3 receptor antagonist, and placebo were administered to 25 smokers and 25 non-smoking controls in a double-blind randomized cross-over design while performing a Go/NoGo task during fMRI scanning. Haloperidol reduced NoGo accuracy and associated brain activation in the ACC, right SFG and left IFG, showing that optimal dopamine levels are crucial to effectively implement inhibitory control. In addition, smokers showed behavioral deficits on the Go/NoGo task as well as hypoactivity in the left IFG, right MFG and ACC after placebo, supporting the hypothesis of a hypoactive prefrontal system in smokers. Haloperidol had a stronger impact on prefrontal brain activation in non-smoking controls compared to smokers, which is in line with the inverted 'U' curve theory of dopamine and cognitive control. The current findings suggest that altered baseline dopamine levels in addicted individuals may contribute to the often observed reduction in inhibitory control in these populations.

Effects of non-invasive neurostimulation on craving: a meta-analysis

This meta-analysis was conducted to evaluate the available evidence regarding the effects of non-invasive neurostimulation of the dorsolateral prefrontal cortex (DLPFC), on craving in substance dependence and craving for high palatable food. Non-invasive neurostimulation techniques were restricted to repetitive Transcranial Magnetic Stimulation (rTMS) and transcranial Direct Current Stimulation (tDCS). A total of 17 eligible studies were identified. Random effects analysis revealed a pooled standardized effect size (Hedge's g) of 0.476 (CI: 0.316-0.636), indicating a medium effect size favouring active non-invasive neurostimulation over sham stimulation in the reduction of craving (z=5.832, p<0.001). No significant differences were found between rTMS and tDCS, between the various substances of abuse and between substances of abuse and food, or between left and right DLPFC stimulation. In conclusion, this meta-analysis provides the first clear evidence that non-invasive neurostimulation of the DLPFC decreases craving levels in substance dependence.

Acute effects of modafinil on brain resting state networks in young healthy subjects

Background

There is growing debate on the use of drugs that promote cognitive enhancement. Amphetamine-like drugs have been employed as cognitive enhancers, but they show important side effects and induce addiction. In this study, we investigated the use of modafinil which appears to have less side effects compared to other amphetamine-like drugs. We analyzed effects on cognitive performances and brain resting state network activity of 26 healthy young subjects.

Methodology

A single dose (100 mg) of modafinil was administered in a double-blind and placebo-controlled study. Both groups were tested for neuropsychological performances with the Raven’s Advanced Progressive Matrices II set (APM) before and three hours after administration of drug or placebo. Resting state functional magnetic resonance (rs-FMRI) was also used, before and after three hours, to investigate changes in the activity of resting state brain networks. Diffusion Tensor Imaging (DTI) was employed to evaluate differences in structural connectivity between the two groups. Protocol ID: Modrest_2011; NCT01684306; http://clinicaltrials.gov/ct2/show/NCT01684306.

Principal Findings

Results indicate that a single dose of modafinil improves cognitive performance as assessed by APM. Rs-fMRI showed that the drug produces a statistically significant increased activation of Frontal Parietal Control (FPC; p<0.04) and Dorsal Attention (DAN; p<0.04) networks. No modifications in structural connectivity were observed.

Conclusions and Significance

Overall, our findings support the notion that modafinil has cognitive enhancing properties and provide functional connectivity data to support these effects.

Trial Registration

ClinicalTrials.gov NCT01684306 http://clinicaltrials.gov/ct2/show/NCT01684306.

The context dependency of extinction negates the effectiveness of cognitive enhancement to reduce cocaine-primed reinstatement

With respect to the treatment of addiction, the objective of extinction training is to decrease drug-seeking behavior by repeatedly exposing the patient to cues in the absence of unconditioned reinforcement. Such exposure therapy typically takes place in a novel (clinical) environment. This is potentially problematic, as the effects of extinction training include a context dependent component and therefore diminished efficacy is expected upon the patient's return to former drug-seeking/taking environments. We have reported that treatment with the NMDAR coagonist d-serine is effective in facilitating the effects of extinction to reduce cocaine-primed reinstatement. The present study assesses d-serine's effectiveness in reducing drug-primed reinstatement under conditions in which extinction training occurs in a novel environment. After 22 days of cocaine self-administration (0.5 mg/kg) in context "A", animals underwent 5 extinction training sessions in context "B". Immediately after each extinction session in "B", animals received either saline or d-serine (60 mg/kg) treatment. Our results indicate that d-serine treatment following extinction in "B" had no effect on either IV or IP cocaine-primed reinstatement conducted in "A". These results stand in contrast to our previous findings where extinction occurred in "A", indicating that d-serine's effectiveness in facilitating extinction training to reduce drug-primed reinstatement is not transferable to a novel extinction environment. This inability of d-serine treatment to reduce the context specificity of extinction training may explain the inconsistent effects observed in clinical studies published to date in which adjunctive cognitive enhancement treatment has been combined with behavioral therapy without significant benefit.