Cognitive efficiency in stimulant abusers with and without alcohol dependence

Driving under the influence of drugs: Correlation between blood psychoactive drug concentrations and cognitive impairment. A narrative review taking into account forensic issues

Driving under the influence of alcohol has been shown to increase the risk of involvement in road traffic collisions (RTCs) however, less is known about the effects of illicit drugs, and a clear correlation between drug concentrations and RTC risk is still debated. The goal of this narrative review is to assess the current literature regarding the most detected psychoactive drugs in RTC (ethanol, amphetamines, cannabis, opioids and cocaine), in relation to driving performance. Evidence on impaired driving due to psychoactive substances, forensic issues relating to the assessment of the impact of drugs, blood cut-off values proposed to date as well as scientific basis for proposed legislative limits are discussed. At present there is no unequivocal evidence demonstrating a clear dose/concentration dependent impairment in many substances. Per se and zero tolerance approaches seem to have negative effect on drugged driving fatalities. However, the weight of these approaches needs further investigation.

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Driving under the influence of psychotropic substances has become a widespread phenomenon.

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Only a few substances have been reported to have a clear dose/concentration dependent impairment.

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Statistically significant differences should not be considered as clinically significant per se

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There is wide variability in legislative cut-offs.

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Detection limits seems to be the most public safety-oriented legislative approach.

Cognitive training as a component of treatment of alcohol use disorder: A review

OBJECTIVE

Cognitive training is an effective means of improving performance in a range of populations. Whether it may serve to facilitate cognitive recovery and longer-term outcomes in persons with alcohol use disorders (AUDs) is unclear. Here, we review historical and current literature and offer perspectives for model development and potential implementation.

METHOD

We considered a large literature regarding the nature of alcohol-related compromise, early efforts to clarify the nature of recovery and current models and methods underlying cognitive training paradigms. We then constructed a narrative review demonstrating evolving frameworks and empirical data informing the critical review of cognitive training methods as a means of mitigating compromise and facilitating functional outcomes.

RESULTS

Cognitive improvement with abstinence is generally noted, but training protocols may enhance performance and generalize benefit to untrained, but highly similar, tasks. Transfer of training to dissimilar tasks and functional outcomes is uncommonly reported. It is noteworthy that some work suggests that clinician ratings for participants are improved. Inconsistency in sample characteristics, training protocols, and outcome measures constrain general conclusions while suggesting opportunities for study and development.

CONCLUSIONS

Cognitive training protocols have shown benefit in a variety of populations but have been examined infrequently in persons with AUDs. This overview indicates significant opportunity for cognitive improvement and recovery and thus a strong potential role for training protocols. However, supportive data are not robustly obtained. We suggest that one step in bridging this gap is the implementation of a conceptual framework incorporating contextual, behavioral, and neurobiological variables. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Adverse effect of catechol-O-methyltransferase (COMT) Val158Met met/met genotype in methamphetamine-related executive dysfunction

INTRODUCTION

The Val allele of the Val158Met single-nucleotide polymorphism of the catechol-o-methyltransferase gene (COMT) confers greater catabolism of dopamine (DA) in the prefrontal cortex (PFC) than the Met allele. Met/Met homozygotes typically outperform Val-carriers on tests of executive function (EF), perhaps resulting from increased DA bioavailability. Methamphetamine (METH) causes large releases of DA, which is associated with neurotoxicity and executive dysfunction in chronic METH users. We hypothesized that, contrary to its effect in non-METH-using populations, slower DA clearance conferred by Met/Met will relate to worse EF in METH users.

METHODS

149 non-Hispanic White men, stratified by METH dependence (METH+/-) and COMT (Val/Val, Val/Met, Met/Met), completed three tests of EF: Wisconsin Card Sorting Test (WCST), Stroop Color-Word Test (Stroop), and Trail Making Test Part B (Trails B). Demographically-adjusted test scores were averaged to create an EF composite T-score. We examined the interaction of METH and COMT on the EF composite and individual test T-scores, controlling for premorbid functioning and alcohol use.

RESULTS

METH group differences in EF were evident only among Met/Met carriers (beta = -9.36, p < .001) but not among Val carriers: Val/Met (beta = -1.38, p = .44) and Val/Val (beta = -4.34, p = .10). These effects were most salient on the WCST.

CONCLUSIONS

In the pre-frontal hyperdopaminergic state triggered by methamphetamine, greater DA inactivation conferred by the Val allele may protect against METH-related executive dysfunction, suggesting genetically-driven differences in vulnerability to METH.

Conditional Effects of Lifetime Alcohol Consumption on Methamphetamine-Associated Neurocognitive Performance

OBJECTIVES

Methamphetamine (MA) dependence contributes to neurotoxicity and neurocognitive deficits. Although combined alcohol and MA misuse is common, how alcohol consumption relates to neurocognitive performance among MA users remains unclear. We hypothesized that alcohol and MA use would synergistically diminish neurocognitive functioning, such that greater reported alcohol consumption would exert larger negative effects on neurocognition among MA-dependent individuals compared to MA-nonusing persons.

METHODS

Eighty-seven MA-dependent (MA+) and 114 MA-nonusing (MA-) adults underwent neuropsychological and substance use assessments. Linear and logistic regressions examined the interaction between MA status and lifetime average drinks per drinking day on demographically corrected global neurocognitive T scores and impairment rates, controlling for recent alcohol use, lifetime cannabis use, WRAT reading performance, and lifetime depression.

RESULTS

MA+ displayed moderately higher rates of impairment and lower T scores compared to MA-. Lifetime alcohol use significantly interacted with MA status to predict global impairment (ORR = 0.70, p = .003) such that greater lifetime alcohol use increased likelihood of impairment in MA-, but decreased likelihood of impairment in MA+. Greater lifetime alcohol use predicted poorer global T scores among MA- (b = -0.44, p = .030) but not MA+ (b = 0.08, p = .586).

CONCLUSIONS

Contrary to expectations, greater lifetime alcohol use related to reduced risk of neurocognitive impairment among MA users. Findings are supported by prior research identifying neurobiological mechanisms by which alcohol may attenuate stimulant-driven vasoconstriction and brain thermotoxicity. Replication and examination of neurophysiologic mechanisms underlying alcohol use in the context of MA dependence are warranted to elucidate whether alcohol confers a degree of neuroprotection.

Adolescent neurocognitive development and impacts of substance use: Overview of the adolescent brain cognitive development (ABCD) baseline neurocognition battery

Adolescence is characterized by numerous social, hormonal and physical changes, as well as a marked increase in risk-taking behaviors. Dual systems models attribute adolescent risk-taking to tensions between developing capacities for cognitive control and motivational strivings, which may peak at this time. A comprehensive understanding of neurocognitive development during the adolescent period is necessary to permit the distinction between premorbid vulnerabilities and consequences of behaviors such as substance use. Thus, the prospective assessment of cognitive development is fundamental to the aims of the newly launched Adolescent Brain and Cognitive Development (ABCD) Consortium. This paper details the rationale for ABC'lected measures of neurocognition, presents preliminary descriptive data on an initial sample of 2299 participants, and provides a context for how this large-scale project can inform our understanding of adolescent neurodevelopment.

Cognitive deficits in individuals with methamphetamine use disorder: A meta-analysis

BACKGROUND

Methamphetamine has long been considered as a neurotoxic substance causing cognitive deficits. Recently, however, the magnitude and the clinical significance of the cognitive effects associated with methamphetamine use disorder (MUD) have been debated. To help clarify this controversy, we performed a meta-analysis of the cognitive deficits associated with MUD.

METHODS

A literature search yielded 44 studies that assessed cognitive dysfunction in 1592 subjects with MUD and 1820 healthy controls. Effect size estimates were calculated using the Comprehensive Meta-Analysis, for the following 12 cognitive domains: attention, executive functions, impulsivity/reward processing, social cognition, speed of processing, verbal fluency/language, verbal learning and memory, visual learning and memory, visuo-spatial abilities and working memory.

RESULTS

Findings revealed moderate impairment across most cognitive domains, including attention, executive functions, language/verbal fluency, verbal learning and memory, visual memory and working memory. Deficits in impulsivity/reward processing and social cognition were more prominent, whereas visual learning and visuo-spatial abilities were relatively spared cognitive domains. A publication bias was observed.

DISCUSSION

These results show that MUD is associated with broad cognitive deficits that are in the same range as those associated with alcohol and cocaine use disorder, as recently shown by way of meta-analysis. The prominent effects of MUD on social cognition and impulsivity/reward processing are based on a small number of studies, and as such, these results will need to be replicated. The functional consequences (social and occupational) of the cognitive deficits of methamphetamine will also need to be determined.

Development of a Contextualized Version of the Multiple Errands Test for People with Substance Dependence

BACKGROUND

Substance dependence is associated with deficits in several areas of executive functioning, such as planning and multitasking. Traditional tests of executive functioning have been criticized for their low ecological validity. Shallice and Burgess (1991) developed the Multiple Errands Test (MET), where participants are required to perform multiple tasks in a real-world setting. In this study, we aimed to adapt the MET for use in populations with substance dependence.

OBJECTIVES

This study aimed to: (1) examine the applicability of a contextualized version of the Multiple Errands Test, namely, the Multiple Errands Test - Contextualized Version (MET-CV); (2) study the testing context reliability and convergent validity of MET-CV scores; (3) compare the performance of people with substance dependence to a control group.

METHODS

Data were collected from 60 participants with substance dependence and 30 healthy controls. Both groups performed a neuropsychological assessment, which consisted of the MET-CV and traditional neuropsychological tests (Letter Number Sequencing, Zoo Map Test, Revised Strategy Application Test, Information Sampling Test, Stockings of Cambridge).

RESULTS

The MET-CV has adequate testing context reliability and moderate convergent validity relative to traditional planning measures. People with substance dependence (PWSD) showed significant deficits in executive function tests compared to healthy controls, most notably on the MET-CV rather than on traditional neuropsychological tests.

CONCLUSIONS

The MET-CV can be feasibly applied in the context of therapeutic communities treatment in PWSD. The MET-CV showed adequate reliability and validity, and detected planning deficits in PWSD. (JINS, 2018, 24, 347-359).

Correlation between Blood and Oral Fluid Psychoactive Drug Concentrations and Cognitive Impairment in Driving under the Influence of Drugs

BACKGROUND

The effects of drugs on driving performance should be checked with drug concentration in the brain and at the same time with the evaluation of both the behavioural and neurophysiological effects. The best accessible indicator of this information is the concentration of the drug and/or metabolites in blood and, to a certain extent, oral fluid. We sought to review international studies on correlation between blood and oral fluid drug concentrations, neurological correlates and cognitive impairment in driving under the influence of drugs.

METHODS

Relevant scientific articles were identified from PubMed, Cochrane Central, Scopus, Web of Science, Science Direct, EMBASE up to April 2017.

RESULTS

Up to 2010, no epidemiological studies were available on this matter and International scientists suggested that even minimal amounts of parent drugs in blood and oral fluid could affect driving impairment. More recently, epidemiological data, systematic reviews and meta-analysis on drugged drivers allowed the suggestion of impairment concentration limits for the most common illicit drugs. These values were obtained comparing driving disability induced by psychotropic drugs with that of established blood alcohol limits. Differently from ethyl alcohol where both detection methods and concentration limits have been well established even with inhomogeneity of ranges within different countries, in case of drugs of abuse no official cut-offs have yet been established, nor any standardized analytical protocols.

CONCLUSION

Multiple aspects of driving performance can be differently affected by illicit drugs, and even if for few of them some dose/concentration dependent impairment has been reported, a wider knowledge on concentration/impairment relationship is still missing.

Molecular, Behavioral, and Physiological Consequences of Methamphetamine Neurotoxicity: Implications for Treatment

Understanding the relationship between the molecular mechanisms underlying neurotoxicity of high-dose methamphetamine (METH) and related clinical manifestations is imperative for providing more effective treatments for human METH users. This article provides an overview of clinical manifestations of METH neurotoxicity to the central nervous system and neurobiology underlying the consequences of administration of neurotoxic METH doses, and discusses implications of METH neurotoxicity for treatment of human abusers of the drug.

Attention and memory deficits in crack-cocaine users persist over four weeks of abstinence

BACKGROUND

Crack-cocaine addiction is an important public health problem worldwide. Although there is not a consensus, preliminary evidence has suggested that cognitive impairments in patients with crack-cocaine dependence persist during abstinence, affecting different neuropsychological domains. However, few studies have prospectively evaluated those deficits in different phases of abstinence.

OBJECTIVES

The main aim of present study was to examine neuropsychological performance of patients with crack-cocaine dependence during early abstinence and after four weeks, comparing with matched controls.

METHODS

Thirty-five males with crack-cocaine dependence, aged 18 to 50years, who met DSM-IV criteria for cocaine dependence and a control group of 33 healthy men were enrolled. They were assessed through Block Design, Digit Span and Vocabulary of Wechsler Adult Intelligence Scale (WAIS-III), the Rey Auditory Learning Test (RAVLT) and the Verbal Fluency (FAS) between 3 and 10days (mean of 6.1±2.0days) and after 4weeks of abstinence.

RESULTS

Compared to controls, the crack-cocaine dependent group exhibited deficits in cognitive performance affecting attention, verbal memory and learning tasks in early withdrawal. Most of the cognitive deficits persisted after four weeks of abstinence.

CONCLUSION

Present results observed that the group of patients with crack-cocaine dependence presented persistent deficits affecting memory and attention even after four weeks of abstinence, confirming previous studies that had disclosed such cognitive impairments.

Sex differences in alcohol-related neurobehavioral consequences

In this chapter, we review existing research regarding sex differences in alcohol's effects on neurobehavioral functions/processes. Drawn largely from laboratory studies, literature regarding acute alcohol administration and chronic alcohol misuse is explored focusing on commonly employed neuropsychologic domains (e.g., executive function, visuospatial skills, learning and memory, gait and balance), neurophysiologic measures (e.g., electroencephalography and event-related potentials), and structural and functional neuroimaging (e.g., magnetic resonance imaging (MRI), functional MRI, diffusion tensor imaging, positron emission tomography, and magnetic resonance spectroscopy). To provide a historical perspective on the development of these questions, we have included reference to early and more recent research. Additionally, specific biases, knowledge gaps, and continuing controversies are noted.

Reaction time variability and related brain activity in methamphetamine psychosis

BACKGROUND

This study investigated the dynamics of cognitive control instability in methamphetamine (MA) abuse, as well its relationship to substance-induced psychiatric symptoms and drug use patterns.

METHODS

We used an ex-Gaussian reaction time (RT) distribution to examine intraindividual variability (IIV) and excessively long RTs (tau) in an individual's RT on a Stroop task in 30 currently drug-abstinent (3 months to 2 years) MA abusers compared with 27 nonsubstance-abusing control subjects. All subjects underwent functional magnetic resonance imaging while performing the Stroop task, which allowed us to measure the relationship between IIV and tau to functional brain activity.

RESULTS

Elevated IIV in the MA compared with the control group did not reach significance; however, when the MA group was divided into those subjects who had experienced MA-induced psychosis (MAP+) (n = 19) and those who had not (n = 11), the MAP+ group had higher average IIV compared with the other groups (p < .03). In addition, although control subjects displayed a relationship between IIV and conflict-related brain activity in bilateral prefrontal cortex such that increased IIV was associated with increased activity, the MAP+ group displayed this relationship in right prefrontal cortex only, perhaps reflecting elevated vigilance in the MAP+ group. Greater IIV did not correlate with severity of use or months MA abstinent. No group differences emerged in tau values.

CONCLUSIONS

These results suggest increased cognitive instability in those MA-dependent subjects who had experienced MA-induced psychosis.

Anomalous temporoparietal activity in individuals with a family history of alcoholism: studies from the Oklahoma Family Health Patterns Project

BACKGROUND

Individuals with a family history of alcoholism (FH+) are at enhanced risk of developing alcohol or other substance use disorders relative to those with no family history (FH-). Alcoholics and FH+ subjects have greater interference scores on the Stroop color-word task, suggesting these impairments may be a component of the cognitive phenotype of at-risk individuals.

METHODS

In this study, we examined whole-brain activations in 24 FH+ and 28 FH- young adults performing the counting Stroop task, a variant of the Stroop task adapted for neuroimaging studies.

RESULTS

Across all subjects, incongruent versus congruent comparisons showed activations in regions including parietal lobe areas, frontal eye fields, premotor areas, the anterior cingulate cortex, dorsolateral prefrontal cortex, and bilateral insula, indicating typical regions of activation involved in conflict resolution tasks. Compared with FH- participants, FH+ participants had greater activations in the left superior parietal lobule and precuneus (BA 7 and 19), inferior parietal lobule (BA 40), and middle temporal gyrus (BA 39 and 19), indicating a predominance of greater left hemisphere activity among FH+ in temporoparietal regions. There were no regions showing greater activations in the FH- group compared with the FH+ group.

CONCLUSIONS

These results are consistent with less efficient cognitive functioning potentially due to poorer communication over long pathways connecting temporoparietal regions to prefrontal brain regions that participate in a distributed network involved in cognitive processing and working memory necessary for conflict resolution.

Compensatory recruitment of neural resources in chronic alcoholism

Functional recovery occurs with sustained sobriety, but the neural mechanisms enabling recovery are only now emerging. Theories about promising mechanisms involve concepts of neuroadaptation, where excessive alcohol consumption results in untoward structural and functional brain changes which are subsequently candidates for reversal with sobriety. Views on functional adaptation in chronic alcoholism have expanded with results from neuroimaging studies. Here, we first describe and define the concept of neuroadaptation according to emerging theories based on the growing literature in aging-related cognitive functioning. Then we describe findings as they apply to chronic alcoholism and factors that could influence compensation, such as functional brain reserve and the integrity of brain structure. Finally, we review brain plasticity based on physiologic mechanisms that could underlie mechanisms of neural compensation. Where possible, we provide operational criteria to define functional and neural compensation.

Widespread and sustained cognitive deficits in alcoholism: a meta-analysis

The cognitive repercussions of alcohol dependence are well documented. However, the literature remains somewhat ambiguous with respect to which distinct cognitive functions are more susceptible to impairment in alcoholism and to how duration of abstinence affects cognitive recovery. Some theories claim alcohol negatively affects specific cognitive functions, while others assert that deficits are more diffuse in nature. This is the first meta-analysis to examine cognition in alcohol abuse/dependence and the duration of abstinence necessary to achieve cognitive recovery. A literature search yielded 62 studies that assessed cognitive dysfunction among alcoholics. Effect size estimates were calculated using the Comprehensive Meta-Analysis V2, for the following 12 cognitive domains: intelligence quotient, verbal fluency/language, speed of processing, working memory, attention, problem solving/executive functions, inhibition/impulsivity, verbal learning, verbal memory, visual learning, visual memory and visuospatial abilities. Within these 12 domains, three effect size estimates were calculated based on abstinence duration. The three groups were partitioned into short- (< 1 month), intermediate- (2 to 12 months) and long- (> 1 year) term abstinence. Findings revealed moderate impairment across 11 cognitive domains during short-term abstinence, with moderate impairment across 10 domains during intermediate term abstinence. Small effect size estimates were found for long-term abstinence. These results suggest significant impairment across multiple cognitive functions remains stable during the first year of abstinence from alcohol. Generally, dysfunction abates by 1 year of sobriety. These findings support the diffuse brain hypothesis and suggest that cognitive dysfunction may linger for up to an average of 1 year post-detoxification from alcohol.

Differences in delay discounting between smokers and nonsmokers remain when both rewards are delayed

RATIONALE

When offered a choice between a small monetary reward available immediately (SmallNow) versus a larger reward available after a delay (LargeLater), smokers select the SmallNow alternative more than nonsmokers. That is, smokers discount the value of the LargeLater reward more than nonsmokers.

OBJECTIVES

To investigate whether this group difference was due to smokers overweighting the value of rewards available immediately compared with nonsmokers, we examined whether the group difference was also seen when both alternatives were delayed, i.e., when choosing between a SmallSoon reward and a LargeLater reward.

METHODS

In Experiment 1, smokers and nonsmokers completed a task including SmallNow versus LargeLater choices and SmallSoon versus LargeLater choices. In Experiment 2, smokers and nonsmokers completed the same task but with hypothetical choices.

RESULTS

Analyses using hyperbolic and double exponential (β-δ) models replicate prior findings that smokers discount the LargeLater reward more than nonsmokers when the smaller reward is available immediately. The smoker-nonsmoker difference was also seen when the smaller reward was slightly delayed, though this effect was primarily driven by heightened discounting in male smokers. However, for potentially real rewards only, this smoker-nonsmoker difference was significantly reduced when the smaller reward was delayed.

CONCLUSIONS

The smoker-nonsmoker difference in discounting is not confined to situations involving immediate rewards. Differences associated with potentially real versus hypothetical rewards and gender underscore the complexity of the smoking-delay discounting relationship.

Nicotine effects on immediate and delayed verbal memory after substance use detoxification

Decrements in verbal memory are commonly reported by detoxified treatment-seeking individuals. Although acute nicotine has been shown to improve attentional performance, its effects on verbal memory in substance abusers have not been addressed. Treatment-seeking alcohol-dependent (ALCs, n = 29; 14 male), illicit-stimulant-dependent (predominantly cocaine; STIMs, n = 25; 15 male), and alcohol- and illicit-stimulant-dependent (ALC/STIMs, n = 50; 35 male) participants with comorbid nicotine dependence were studied. Subjects had been abstinent from their drugs of choice for 41 (±18) days and were in short-term abstinence from tobacco (∼8-10 hours). Subjects received double-blind administration of either transdermal nicotine (high dose: 21/14 mg for men and women, respectively, or low dose: 7 mg) or placebo. The Logical Memory (LM) subtest from the Wechsler Memory Scale-Revised (WMS-R) was used to assess immediate and delayed verbal memory recall. Results indicated that STIMs receiving the high dose of nicotine recalled more words at immediate recall than STIMs who received placebo. Trend level differences were also noted at delayed recall between STIM nicotine and placebo doses. Nicotine failed to impact either recall in alcoholic subgroups. Although not the primary focus, results also revealed differences in the forgetting rates between the groups with the ALC/STIMs demonstrating the steepest forgetting slope. In summary, this study suggests that nicotine effects may be differentially experienced by substance-using subgroups; that nicotine may have a direct effect on memory; and that in considering neurocognitive processes (e.g., encoding vs. retrieval), underlying endpoint indicators (e.g., correct recall) may be critical in predicting outcomes.

Methamphetamine use parameters do not predict neuropsychological impairment in currently abstinent dependent adults

Methamphetamine (meth) abuse is increasingly of public health concern and has been associated with neurocognitive dysfunction. Some previous studies have been hampered by background differences between meth users and comparison subjects, as well as unknown HIV and hepatitis C (HCV) status, which can also affect brain functioning. We compared the neurocognitive functioning of 54 meth dependent (METH+) study participants who had been abstinent for an average of 129 days, to that of 46 demographically comparable control subjects (METH-) with similar level of education and reading ability. All participants were free of HIV and HCV infection. The METH+ group exhibited higher rates of neuropsychological impairment in most areas tested. Among meth users, neuropsychologically normal (n=32) and impaired (n=22) subjects did not differ with respect to self-reported age at first use, total years of use, route of consumption, or length of abstinence. Those with motor impairment had significantly greater meth use in the past year, but impairment in cognitive domains was unrelated to meth exposure. The apparent lack of correspondence between substance use parameters and cognitive impairment suggests the need for further study of individual differences in vulnerability to the neurotoxic effects of methamphetamine.

The impacts of substance abuse and dependence on neuropsychological functions in a sample of patients from Saudi Arabia

BACKGROUND

A lot of studies were directed to explore the relation between drug abuse and neuropsychological functions. Some studies reported that even after a long duration of disappearance of withdrawal or intoxication symptoms, many patients have obvious deterioration of cognitive functions. The aim of this study was to explore the relationship between the substance use disorders and the executive functions.

METHODS

Two groups were selected for this study. An experimental group consisted of 154 patients and further subdivided according to the substance used into three different subgroups: opioid, amphetamine and alcohol groups which included 49, 56 and 49 patients respectively. The control group was selected matching the experimental group in the demographic characteristics and included 100 healthy persons. Tools used were: Benton visual retention tests, color trail making test, Stroop colors-word test, symbol digit modalities test, the five dots cognitive flexibility test, and TAM verbal flexibility test. All the data were subjected to statistical analysis

RESULTS

The study showed that the group of drug-dependent subjects performed significantly worse than the comparison group on all measures Also, there were significant differences among the subgroups as the alcoholic group was much worse followed by the amphetamine then the opioids groups. Patients with longer duration of dependence and multiple hospital readmissions were much worse in comparison to patients with shorter duration of dependence and less readmission.

CONCLUSION

The study confirmed that the functions of specific brain regions underlying cognitive control are significantly impaired in patients of drug addiction. This impairment was significantly related to type of substance, duration of use and number of hospitalization and may contribute to most of behavioral disturbances found in addicts and need much attention during tailoring of treatment programs.

Neurotoxicity of drugs of abuse--the case of methylenedioxyamphetamines (MDMA, ecstasy), and amphetamines

Ecstasy (MDMA, 3,4-methylendioxymethamphetamine) and the stimulants methamphetamine (METH, speed) and amphetamine are popular drugs among young people, particularly in the dance scene. When given in high doses both MDMA and the stimulant amphetamines are clearly neurotoxic in laboratory animals. MDMA causes selective and persistent lesions of central serotonergic nerve terminals, whereas amphetamines damage both the serotonergic and dopaminergic systems. In recent years, the question of ecstasy-induced neurotoxicity and possible functional sequelae has been addressed in several studies in drug users. Despite large methodological problems, the bulk of evidence suggests residual alterations of serotonergic transmission in MDMA users, although at least partial recovery may occur after long-term abstinence. However, functional sequelae may persist even after longer periods of abstinence. To date, the most consistent findings associate subtle cognitive impairments with ecstasy use, particularly with memory. In contrast, studies on possible long-term neurotoxic effects of stimulant use have been relatively scarce. Preliminary evidence suggests that alterations of the dopaminergic system may persist even after years of abstinence from METH, and may be associated with deficits in motor and cognitive performance. In this paper, we will review the literature focusing on human studies.

The relationships of sociodemographic factors, medical, psychiatric, and substance-misuse co-morbidities to neurocognition in short-term abstinent alcohol-dependent individuals

Co-morbidities that commonly accompany those afflicted with an alcohol use disorder (AUD) may promote variability in the pattern and magnitude of neurocognitive abnormalities demonstrated. The goal of this study was to investigate the influence of several common co-morbid medical conditions (primarily hypertension and hepatitis C), psychiatric (primarily unipolar mood and anxiety disorders), and substance use (primarily psychostimulant and cannabis) disorders, and chronic cigarette smoking on the neurocognitive functioning in short-term abstinent, treatment-seeking individuals with AUD. Seventy-five alcohol-dependent participants (ALC; 51+/-9 years of age; three females) completed comprehensive neurocognitive testing after approximately 1 month of abstinence. Multivariate multiple linear regression evaluated the relationships among neurocognitive variables and medical conditions, psychiatric, and substance-use disorders, controlling for sociodemographic factors. Sixty-four percent of ALC had at least one medical, psychiatric, or substance-abuse co-morbidity (excluding smoking). Smoking status (smoker or nonsmoker) and age were significant independent predictors of cognitive efficiency, general intelligence, postural stability, processing speed, and visuospatial memory after age-normed adjustment and control for estimated pre-morbid verbal intelligence, education, alcohol consumption, and medical, psychiatric, and substance-misuse co-morbidities. Results indicated that chronic smoking accounted for a significant portion of the variance in the neurocognitive performance of this middle-aged AUD cohort. The age-related findings for ALC suggest that alcohol dependence, per se, was associated with diminished neurocognitive functioning with increasing age. The study of participants who demonstrate common co-morbidities observed in AUD is necessary to fully understand how AUD, as a clinical syndrome, affects neurocognition, brain neurobiology, and their changes with extended abstinence.

Findings of preserved implicit attention in methamphetamine dependent subjects

Long-term methamphetamine (MA) abuse is associated with a wide range of deficits on explicit tasks of selective attention. Less is known however about the effects of MA abuse on implicit measures of attention. Accordingly, we used a computerized spatial priming task to assess implicit attentional processes in 54 MA dependent subjects (mean age=37.04+/-8.9 years) and 32 healthy controls without history of any form of substance abuse (mean age=33.63+/-7.05 years). The MA dependent subjects had been drug-abstinent a minimum of 3 weeks with a mean duration of MA use of 13.27+/-7.75 years. The MA dependent subjects did not differ significantly from controls on either inhibitory priming [p=.37] or facilitory priming) [p=.69]. This result comports with our earlier findings of intact object-based priming in MA dependent individuals and suggests that intact priming effects extend across spatial domains. Further, this pattern of sparing suggests that cortical brain systems typically supporting implicit attentional functioning are relatively intact in long-term MA dependent individuals whereas brain systems supporting explicit attentional processes are affected.

Chronic cigarette smoking and heavy drinking in human immunodeficiency virus: consequences for neurocognition and brain morphology

Alcohol use disorders (AUD) and chronic cigarette smoking are common among individuals with human immunodeficiency virus infection (HIV). Concurrent AUD in HIV is related to greater abnormalities in brain morphology and neurocognition than either condition alone. However, the potential influence of chronic smoking on brain morphology and neurocognition in those concurrently afflicted with AUD and HIV has not been examined. The goal of this retrospective analysis was to determine if chronic smoking affected neurocognition and brain morphology in a subsample of HIV-positive non-treatment-seeking heavy drinking participants (HD+) from our earlier work. Regional volumetric and neurocognitive comparisons were made among age-equivalent smoking HD+(n=17), nonsmoking HD+ (n=27), and nonsmoking HIV-negative light drinking controls (n=27) obtained from our original larger sample. Comprehensive neuropsychological assessment evaluated multiple neurocognitive domains of functioning and for potential psychiatric comorbidities. Quantitative volumetric measures of neocortical gray matter (GM), white matter (WM), subcortical structures, and sulcal and ventricular cerebral spinal fluid (CSF) were derived from high-resolution magnetic resonance images. The main findings were (1) smoking HD+ performed significantly worse than nonsmoking HD+ on measures of auditory-verbal (AV) learning, AV memory, and cognitive efficiency; (2) relative to controls, smoking HD+ demonstrated significantly lower neocortical GM volumes in all lobes except the occipital lobe, while nonsmoking HD+ showed only lower frontal GM volume compared with controls; (3) in the HD+ group, regional brain volumes and neurocognition were not influenced by viremia, highly active antiretroviral treatment, or Center for Disease Control symptom status, and no interactions were apparent with these variables or smoking status. Overall, the findings suggested that the direct and/or indirect effects of chronic cigarette smoking created an additional burden on the integrity of brain neurobiology and neurocognition in this cohort of HIV-positive heavy drinkers.

Nicotine's effects on attentional efficiency in alcoholics

BACKGROUND

Historically, the concomitant use of nicotine among alcoholics has not been methodologically accounted for. Given the observed cognitive enhancing effects of acute nicotine on attentional processes, it is important that the potentially positive effects of nicotine be disentangled from the negative effects of chronic alcohol dependence. The current study was conducted to address this question and to test the hypothesis that alcoholics who are regular smokers are more sensitive to the effects of nicotine on cognition as compared to regular smoking community controls.

METHODS

A 2 [drug group; alcoholics (n = 28), community controls (n = 27)] X 2 nicotine dose level [low (7 mg dose) vs. high (14 or 21 mg dose)] double-blind design was used to assess the differential effects of nicotine dose on a battery of neurocognitive tests focusing on attentional efficiency.

RESULTS

As expected, the alcoholic group performed more poorly than did the control group. However, of greater interest to the current study was the finding that alcoholic participants differentially benefited from nicotine administration, as demonstrated in the differential dose effect.

CONCLUSION

The concomitant use of nicotine may serve to "mask" or "overcome" some of the negative effects of chronic alcohol dependence in newly recovering alcoholics. This potential effect has significant implications for treatment development and further understanding of the process of recovery of function in chronic alcoholics.

Escalating dose-multiple binge methamphetamine exposure results in degeneration of the neocortex and limbic system in the rat

Abuse of stimulant drugs such as methamphetamine (METH) and cocaine has been associated with long-lasting persistent behavioral alterations. Although METH-induced changes in the striatal dopaminergic system might play a role in these effects, the potential underlying neuroanatomical substrate for the chronic cognitive dysfunction in METH users is unclear. To investigate the involvement of non-dopaminergic systems in the neurotoxic effects of METH, we treated rats with an escalating dose-multiple binge regimen, which we have suggested may more closely simulate human METH exposure profiles. Combined neuropathological and stereological analyses showed that 30 days after the last binge, there was shrinkage and degeneration in the pyramidal cell layers of the frontal cortex and in the hippocampal CA3 region. Further immunocytochemical analysis showed that METH exposure resulted in loss of calbindin interneurons in the neocortex and selective damage to pyramidal neurons in the CA3 region of the hippocampus and granular cells in the dentate gyrus that was accompanied by microglial activation. Taken together, these studies suggest that selective degeneration of pyramidal neurons and interneurons in the neocortex and limbic system might be involved in the cognitive alterations in METH users.

Chronic Smoking Is Associated With Differential Neurocognitive Recovery in Abstinent Alcoholic Patients: A Preliminary Investigation

BACKGROUND

Approximately 50 to 90% of individuals in North America seeking treatment for alcoholism are chronic smokers. A growing body of evidence suggests that chronic cigarette smokers show a pattern of neurocognitive dysfunction similar to that observed in alcoholic patients. However, previous studies investigating neurocognitive recovery in abstinent alcoholic patients did not specifically consider the potential effects of chronic cigarette smoking.

METHODS

This study comprehensively compared longitudinal neurocognitive changes over 6 to 9 months of abstinence among 13 nonsmoking recovering alcoholic patients (ALC) and 12 actively smoking ALC. The neurocognitive performance of the alcoholic groups was compared with nonsmoking light-drinking controls (nonsmoking LD).

RESULTS

Nonsmoking ALC exhibited a significantly greater magnitude of longitudinal improvement than smoking ALC on measures of cognitive efficiency, executive skills, visuospatial skills, and working memory. Both nonsmoking ALC and smoking ALC demonstrated equivalent improvement on auditory-verbal learning, auditory-verbal memory, and processing speed. Nonsmoking LD showed no significant changes in neurocognition over time. In cross-sectional comparisons at 6 to 9 months of abstinence, nonsmoking ALC were superior to smoking ALC on measures of auditory-verbal learning, auditory-verbal memory, cognitive efficiency, executive skills, processing speed, and working memory. The longitudinal and cross-sectional neurocognitive differences observed between nonsmoking and smoking ALC remained significant after covarying for group differences in education, estimated premorbid intelligence alcohol consumption, and other potentially confounding variables. In smoking ALC, greater smoking severity was inversely related to longitudinal improvement on multiple neurocognitive measures.

CONCLUSIONS

These preliminary results suggest that chronic smoking may modulate neurocognitive recovery in abstinent alcoholic patients. More generally, chronic smoking may impact neurocognition in other conditions where is it a prevalent behavior.

Context-dependent prefrontal cortex regulation of cocaine self-administration and reinstatement behaviors in rats

Evidence of stimulus attribute-specificity within the prefrontal cortex (PFC) suggests that different prefrontal subregions may contribute to cocaine addiction in functionally distinct ways. Thus, the present study examined the effects of lidocaine-induced inactivation of two distinct PFC subregions, the prelimbic (PL) or dorsal agranular insular (AId) cortices, on drug-seeking and drug-taking behaviors under cocaine maintenance and reinstatement testing conditions in rats trained to self-administer 1 mg/kg cocaine under a second-order schedule of drug delivery. Throughout maintenance and reinstatement phases, rats were exposed to conditioned light cues and contextual odor or sound cues. Results showed that PL inactivation during maintenance test sessions significantly reduced drug-seeking and drug-taking behaviors, and disrupted patterns of responding in rats exposed to light-sound, but not light-odor, cues. Moreover, lidocaine-induced inactivation of the PL significantly attenuated drug-seeking behavior during cue-induced and cocaine prime-induced reinstatement in rats exposed to light-sound cues only. In contrast, AId inactivation significantly attenuated cue-induced reinstatement of drug-seeking behavior in rats exposed to light-odor cues only. Drug-seeking and drug-taking behaviors in these rats were not disrupted during maintenance and cocaine prime-induced reinstatement testing regardless of the type of contextual cues used. Together, these data suggest that PL and AId subregions play separate yet overlapping roles in regulating cocaine addiction in rats in ways that are dependent on the presence or absence of cocaine and on the types of contextual cues present in the cocaine self-administration environment.

Tobacco Use, Alcohol Dependence, and Cognitive Performance

Chronic alcohol abuse has long been associated with a mild, generalized pattern of cognitive decrements. However, it is important to note that problem drinking rarely occurs in isolation from abuse of other drugs. For people dependent upon alcohol, tobacco is one of the mostly commonly coabused substances. Recent research suggests that individuals with alcohol dependency may gravitate toward tobacco use, in part, because of the positive effects of nicotine on aspects of cognitive performance that may be compromised as a consequence of chronic alcohol misuse. In this article, the author focuses on the effects of nicotine on behavioral and electrophysiological indexes of cognitive performance, and the impact of these effects on alcohol-related cognitive decrements. The author discusses implications of these findings in the context of treatment and recovery of people with alcoholism.

Alcohol attentional bias: drinking salience or cognitive impairment?

OBJECTIVE

This study evaluated whether alcohol attentional bias is an artifact of excessive drinkers' impaired cognitive functioning, which adversely affects their performance on the classic Stroop test (a measure of inhibitory control) and the Shipley Institute of Living Scale (SILS; a measure of verbal and abstraction ability). Both tests measure aspects of executive cognitive functioning (ECF).

METHODS

Social drinkers (N=87) and alcohol-dependent drinkers (N=47) completed a measure of alcohol consumption, classic and alcohol-related Stroop tests, and the SILS.

RESULTS

A multivariate analysis of variance (MANOVA) showed that the dependent drinkers were poorer on the cognitive measures (SILS scores and classic Stroop interference) and had greater alcohol attentional bias than the social drinkers. An analysis of covariance (ANCOVA) in which the cognitive measures were controlled showed that the dependent drinkers' greater alcohol attentional bias was not an artifact of their poorer cognitive performance.

CONCLUSION

The results are discussed in terms of cognitive-motivational models, which suggest that excessive drinking sensitizes alcohol abusers' attentional responsiveness to alcohol-related stimuli to a degree that exceeds the adverse effects of alcohol on their general cognitive functioning.

The confounding problem of polydrug use in recreational ecstasy/MDMA users: a brief overview

The popular dance drug ecstasy (3,4-methylenedioxymethamphetamine -- MDMA) is neurotoxic upon central serotonergic neurons in laboratory animals and possibly also in humans. In recent years, several studies reported alterations of serotonergic transmission and neuropsychiatric abnormalities in ecstasy users which might be related to MDMA-induced neurotoxic brain damage. To date, the most consistent findings associate subtle cognitive, particularly memory, deficits with heavy ecstasy use. However, most studies have important inherent methodological problems. One of the most serious confounds is the widespread pattern of polydrug use which makes it dif.cult to relate the findings in user populations to one specific drug. The present paper represents a brief overview on this issue. The most commonly co-used substances are alcohol, cannabis and stimulants (amphetamines and cocaine). Stimulants are also neurotoxic upon both serotonergic and dopaminergic neurons. Hence, they may act synergistically with MDMA and enhance its long-term adverse effects. The interactions between MDMA and cannabis use may be more complex: cannabis use is a well-recognized risk factor for neuropsychiatric disorders and it was shown to contribute to psychological problems and cognitive failures in ecstasy users. However, at the cellular level, cannabinoids have neuroprotective actions and they were shown to (partially) block MDMA-induced neurotoxicity in laboratory animals. In future, longitudinal and prospective research designs should hopefully lead to a better understanding of the relation between drug use and subclinical psychological symptoms or neurocognitive failures and, also, of questions around interactions between the various substances of abuse.

Nicotine and cognitive efficiency in alcoholics and illicit stimulant abusers: implications of smoking cessation for substance users in treatment

Cigarette smoking is prevalent among alcoholics and illicit substance abusers. However, the potentially confounding effect of nicotine on studies of cognition in detoxified substance users has rarely been addressed. In the current study of 87 participants, behavioral and electrophysiological indices of cognitive efficiency were measured in tobacco smokers from four groups: alcoholics, illicit stimulant abusers, concurrent abusers, and control subjects. Data were collected from 2001 to 2003. We hypothesized that acute nicotine administration would modify cognitive deficits in alcoholics and illicit stimulant abusing groups. An adaptation of the Rapid Visual Information Processing task was administered after stabilization of nicotine levels via a high- or low-dose transdermal nicotine patch. Across groups, increased nicotine dose was associated with decreased reaction time (p = .03). A group x nicotine dose interaction trend was noted in which increased nicotine was associated with increased correct responding within the alcoholic group (p = .02). No significant differences in electrophysiology were observed. These results suggest that nicotine may modify cognitive efficiency in alcoholics and illicit stimulant abusers, a concept with relevance to both the design of experimental work and the treatment of alcohol and illicit stimulant dependence. Further work is needed to determine whether this effect predominantly reflects facilitation of cognition function or alleviation of nicotine withdrawal.

N400 as an index of semantic expectancies: differential effects of alcohol and cocaine dependence

BACKGROUND

Chronic substance abuse has been associated with decrements in the processing and expression of language. The present study utilized the N400 event-related electroencephalographic potential to index semantic processing in 133 adults with (n=49) or without (n=84) a history of alcohol and/or cocaine dependence. The contributions of age, gender, and comorbid marijuana and nicotine dependence, and antisocial symptomology to N400 decrements were either covaried or controlled.

METHODS

A continuous series of 300 stimuli was presented for 150 ms each (interstimulus interval=1475 ms) on a computer screen. The series was arranged such that a word (approximately 17% of stimuli) immediately preceded presentations of its antonym (primed condition; approximately 17% of stimuli), or a semantically unrelated word (unprimed condition; approximately 17% of stimuli). The remaining 50% of stimuli consisted of unpronounceable letter combinations (non-word condition). EEG responses to the antonyms, unrelated words, and letter jumbles were retained for analysis. Throughout the task, the subject pressed response keys to discriminate words from non-words.

RESULTS

Analyses revealed a detrimental effect of alcohol dependence on N400 amplitude and no significant main or interactive effects of cocaine dependence.

CONCLUSION

The present findings suggest that alcohol-dependent individuals may exhibit verbal processing decrements. These findings also challenge hypotheses suggesting that the combined use of cocaine and alcohol is more deleterious to brain function than alcohol use alone.

Risky decision making and the anterior cingulate cortex in abstinent drug abusers and nonusers

Risky decision making is a hallmark behavioral phenotype of drug abuse; thus, an understanding of its biological bases may inform efforts to develop therapies for addictive disorders. A neurocognitive task that measures this function (Rogers Decision-Making Task; RDMT) was paired with measures of regional cerebral perfusion to identify brain regions that may underlie deficits in risky decision making in drug abusers. Subjects were abstinent drug abusers (> or =3 months) and healthy controls who underwent positron emission tomography scans with H(2)(15)O. Drug abusers showed greater risk taking and heightened sensitivity to rewards than control subjects. Both drug abusers and controls exhibited significant activations in a widespread network of brain regions, primarily in the frontal cortex, previously implicated in decision-making tasks. The only significant group difference in brain activation, however, was found in the left pregenual anterior cingulate cortex, with drug abusers exhibiting less task-related activation than control subjects. There were no significant correlations between neural activity and task performance within the control group. In the drug abuse group, on the other hand, increased risky choices on the RDMT negatively correlated with activation in the right hippocampus, left anterior cingulate gyrus, left medial orbitofrontal cortex, and left parietal lobule, and positively correlated with activation in the right insula. Drug abuse severity was related positively to right medial orbitofrontal activity. Attenuated activation of the pregenual ACC in the drug abusers relative to the controls during performance on the RDMT may underlie the abusers' tendency to choose risky outcomes.

Deficient Strategic Control of Verbal Encoding and Retrieval in Individuals With Methamphetamine Dependence

Methamphetamine (MA) dependence is associated with deficits in episodic verbal memory, but the cognitive mechanisms underlying such impairments are not known. The authors evaluated a component process model of episodic verbal memory in 87 persons with MA dependence (MA+) and 71 demographically similar non-MA-using controls (MA-). Compared with MA- controls, MA+ participants demonstrated deficient overall learning, free recall, and utilization of semantic clustering, as well as higher rates of repetitions and intrusions. No between-groups differences were evident on measures of serial clustering, retention, or recognition discrimination. Taken together, these findings indicate that MA dependence is associated with deficient strategic (i.e., executive) control of verbal encoding and retrieval, which is consistent with the sequelae of MA-related prefronto-striatal circuit neurotoxicity.

Visual-spatial attention in alcoholics and illicit stimulant abusers: effects of nicotine replacement

Reports of alcohol or illicit drug-related cognitive impairments have frequently disregarded the potentially confounding effects of smoking status and nicotine withdrawal on these measures. This study addressed this issue by measuring visual-spatial attention via an adaptation of the Posner paradigm in three groups of tobacco smokers: controls without a history of alcoholism or illicit drug use (n=27; 20 male), chronic alcoholics (n=22; 18 male), and illicit stimulant abusers (n=36; 21 male). Throughout testing, nicotine levels were stabilized by the double-blind administration of a high (14 or 21 mg) or low (7 mg) dose transdermal nicotine patch. A significant effect of group was observed for number of correct responses to restriction trials (F=5.48, 2/79 df; p=.006). Performance was normalized in the illicit stimulant group, and alcoholic participants exhibited superior performance relative to both illicit stimulant abusers (p=.002) and controls (p=.01). These findings support the hypothesis that nicotine may have a compensatory or normalizing effect on attentional functions in substance abusers. Whether these results reflect the central nervous system-activating effects of nicotine or merely alleviation of nicotine withdrawal is a topic of ongoing research.