Error-processing deficits in patients with cocaine dependence

Diminished error-related brain activity as a promising endophenotype for substance-use disorders: evidence from high-risk offspring

One of the core features of individuals with a substance-use disorder (SUD) is the reduced ability to successfully process errors and monitor performance, as reflected by diminished error-related negativities (ERN). However, whether these error-related brain abnormalities are caused by chronic substance use or rather predates it remains unclear. The present study elucidated whether hypoactive performance monitoring represents an endophenotypic vulnerability marker for SUD by using a high-risk paradigm. We assessed the behavioral components of error-processing, as well as the amplitude of the ERN in the event-related brain potential (ERP) during performance of the Eriksen Flanker Task among high-risk adolescents of parents with a SUD (HR; n = 28) and normal-risk controls (NR; n = 40). Results revealed that HR offspring were characterized by a higher prevalence of internalizing symptoms and more frequent cannabis use, the latter having a significant influence on the ERN. Interestingly, risk group uniquely predicted the negativity amplitude in response to error trials above and beyond confounding variables. Moreover, we found evidence of smaller ERN amplitudes in (cannabis use-naïve) HR offspring, reflecting impaired early processing of error information and suboptimal performance monitoring, whereas no robust group differences were found for overall behavioral performance. This effect was independent of an overall reduction in brain activity. Taken together, although we cannot rule out alternative explanations, the results of our study may provide evidence for the idea that diminished error-processing represents a promising endophenotype for SUD that may indicate a vulnerability to the disorder.

The effects of acute abstinence from smoking and performance-based rewards on performance monitoring

RATIONALE

Abstinence from smoking disrupts performance in multiple cognitive domains, and such cognitive effects may serve to maintain smoking behavior. Rather than having specific effects on a narrow domain of processing, abstinence may disrupt more general cognitive control processes and/or motivation.

OBJECTIVES

The present study tested the prediction that overnight abstinence from smoking would disrupt a general performance monitoring system indexed via the error-related negativity (ERN). A secondary aim was to determine the extent to which performance-based monetary rewards improved the ERN among smokers and whether the effect of the reward was diminished during abstinence.

METHODS

The ERN was assessed during a flanker task among 25 heavy, non-treatment-seeking smokers both when smoking as usual and after overnight abstinence; reward and no-reward trial blocks occurred within each session.

RESULTS

As predicted, mean ERN amplitude was reduced during abstinence. The ERN was enhanced by reward; this effect did not vary with smoking abstinence.

CONCLUSION

This study provides novel data which suggest that acute abstinence from smoking disrupts a neurophysiological index of a general performance monitoring system that is involved in a range of cognitive functions. The ERN may be a useful complement to narrow-band cognitive studies of abstinence and interventions designed to target cognition in addiction. Because the ERN was concurrently sensitive to abstinence and performance-based incentives, it may be particularly useful for examining the interplay of cognition and motivation in smoking and smoking cessation.

An error-related negativity potential investigation of response monitoring function in individuals with internet addiction disorder

Internet addiction disorder (IAD) is an impulse disorder or at least related to impulse control disorder. Deficits in executive functioning, including response monitoring, have been proposed as a hallmark feature of impulse control disorders. The error-related negativity (ERN) reflects individual's ability to monitor behavior. Since IAD belongs to a compulsive-impulsive spectrum disorder, theoretically, it should present response monitoring functional deficit characteristics of some disorders, such as substance dependence, ADHD, or alcohol abuse, testing with an Erikson flanker task. Up to now, no studies on response monitoring functional deficit in IAD were reported. The purpose of the present study was to examine whether IAD displays response monitoring functional deficit characteristics in a modified Erikson flanker task. Twenty-three subjects were recruited as IAD group. Twenty-three matched age, gender, and education healthy persons were recruited as control group. All participants completed the modified Erikson flanker task while measured with event-related potentials. IAD group made more total error rates than did controls (p < 0.01); Reactive times for total error responses in IAD group were shorter than did controls (p < 0.01). The mean ERN amplitudes of total error response conditions at frontal electrode sites and at central electrode sites of IAD group were reduced compared with control group (all p < 0.01). These results revealed that IAD displays response monitoring functional deficit characteristics and shares ERN characteristics of compulsive-impulsive spectrum disorder.

Migraine Mistakes: Error Awareness

Error awareness or detection is the conscious and subconscious processing to evaluate physiological signals that are different from a baseline or homeostatic level. Migraine is a unique neurological disorder in which there are repeated attacks interspersed by attack-free periods. These attacks are dynamic and multidimensional in the sense that sensory, affective, autonomic, and cognitive functions are altered and these changes evolve differently before (pre-ictal), during (ictal), and immediately after (post-ictal) an attack. Thus migraine serves as a model disease to understand how the brain monitors and react to the presence of errors.

Altered functional connectivity of the insular cortex across prefrontal networks in cocaine addiction

Interoception is theorized to be an important process mediating substance use disorders, and the insular cortex is recognized as a core neural region supporting interoception. The purpose of this study was to compare the integration of the insular cortex into prefrontal-related resting-state networks between individuals with cocaine dependence and healthy controls. Participants comprised 41 patients with cocaine dependence and 19 controls who underwent a resting-state 3-T functional magnetic resonance imaging scan. Individuals with cocaine dependence demonstrated altered functional connectivity of the insular cortex, predominantly the right insular cortex, with all eight prefrontal-related resting-state networks identified through Independent Component Analysis (ICA). A conjunction analysis demonstrated that the right insular cortex was the neural region with the highest number of common group differences across the networks. There was no evidence that insular cortex connectivity commonly differed between groups for non-prefrontal-related networks. Further, seed-based functional connectivity analyses extended the network analyses and indicated that cocaine dependence was associated with greater connectivity of the right insula with the dorsomedial prefrontal cortex, inferior frontal gyrus, and bilateral dorsolateral prefrontal cortex. These data support the hypothesis that cocaine dependence is related to altered functional interactions of the insular cortex with prefrontal networks. The results suggest possible neural mechanisms by which the insular cortex and interoceptive information influence cognitive control and decision-making processes presumably mediated by prefrontal networks in the cocaine dependence process.

Characterizing the cognitive effects of cocaine: a comprehensive review

Understanding the cognitive sequela of repeated cocaine use is a growing area of research and is crucial to the development of cognitive models of addiction. We systematically reviewed all available placebo-controlled and case-controlled studies on the acute and long-term effects of cocaine on cognitive functioning. In order to compare the magnitude of cognitive effects across cognitive domains we conducted several meta-analyses on a subset of data from long-term effect studies. Studies on acute cocaine administration suggest enhancement of response inhibition and psychomotor speed, while all other domains appear to be unaffected or not investigated adequately. Long-term effects of cocaine show a wide array of deteriorated cognitive functions, indicating that long term cocaine use is characterized by a general cognitive impairment across functions, rather than by specific cognitive deficits. Literature on long-term cocaine effects is more substantial than literature on acute effects. This comprehensive review outlines possible dissociations and similarities of acute vs. long-term cocaine effects in the human brain. Atherosclerosis after cocaine exposure may underlie cognitive dysfunction, suggesting involvement of multiple brain areas. Acute drug studies are important to the future development of addiction models.

Neural correlates of performance monitoring in chronic cannabis users and cannabis-naive controls

Chronic cannabis use is associated with residual negative effects on measures of executive functioning. However, little previous work has focused specifically on executive processes involved in performance monitoring in frequent cannabis users. The present study investigated event-related potential (ERP) correlates of performance monitoring in chronic cannabis users. The error-related negativity (ERN) and error positivity (Pe), ERPs sensitive to performance monitoring, were recorded from 30 frequent cannabis users (mean usage=5.52 days/week) and 32 cannabis-naïve control participants during a speeded stimulus discrimination task. The "oddball" P3 ERP was recorded as well. Users and controls did not differ on the amplitude or latency of the ERN; however, Pe amplitude was larger among users. Users also showed increased amplitude and reduced latency of the P3 in response to infrequent stimuli presented during the task. Among users, urinary cannabinoid metabolite levels at testing were unrelated to ERP outcomes. However, total years of cannabis use correlated negatively with P3 latency and positively with P3 amplitude, and age of first cannabis use correlated negatively with P3 amplitude. The results of this study suggest that chronic cannabis use is associated with alterations in neural activity related to the processing of motivationally-relevant stimuli (P3) and errors (Pe).

Safety of atomoxetine in combination with intravenous cocaine in cocaine-experienced participants

OBJECTIVES

Atomoxetine has been considered as an agonist replacement therapy for cocaine. We investigated the safety of the interaction of atomoxetine with cocaine and also whether cognitive function was affected by atomoxetine during short-term administration.

METHODS

In a double-blind placebo-controlled inpatient study of 20 cocaine-dependent volunteers, participants received atomoxetine 80 mg daily followed by 100 mg daily for 5 days each. On the fourth and fifth day at each dose, cocaine (20 and 40 mg) was infused intravenously in sequential daily sessions.

RESULTS

Preinfusion mean systolic pressures showed a small but statistically significant difference between placebo and both doses of atomoxetine. Preinfusion mean diastolic pressures were significant between placebo and atomoxetine 80 mg only. The diastolic pressure response to 40 mg cocaine was statistically significant only between the 80- and 100-mg atomoxetine doses. All electrocardiogram parameters were unchanged. Visual Analog Scale (VAS) scores for "bad effect" in the atomoxetine group were significantly higher at baseline, then declined, and for "likely to use" declined with atomoxetine treatment. On the Addiction Research Center Inventory, the atomoxetine group scored significantly lower on amphetamine, euphoria, and energy subscales (P < 0.0001). Other VAS descriptors, Brief Substance Craving Scale, Profile of Moods State, and Brief Psychiatric Rating Scale showed no differences. Atomoxetine did not affect cocaine pharmacokinetics. In tests of working memory, sustained attention, cognitive flexibility, and decision-making, atomoxetine improved performance on the visual n-back task. There were no differences in any pharmacokinetic parameters for cocaine with atomoxetine.

CONCLUSIONS

Atomoxetine was tolerated safely by all participants. Certain cognitive improvements and a dampening effect on VAS scores after cocaine were observed, but should be weighed against small but significant differences in hemodynamic responses after atomoxetine.

Error-related brain activity predicts cocaine use after treatment at 3-month follow-up

BACKGROUND

Relapse after treatment is one of the most important problems in drug dependency. Several studies suggest that lack of cognitive control is one of the causes of relapse. In this study, a relative new electrophysiologic index of cognitive control, the error-related negativity, is investigated to examine its suitability as a predictor of relapse.

METHODS

The error-related negativity was measured in 57 cocaine-dependent patients during their first week in detoxification treatment. Data from 49 participants were used to predict cocaine use at 3-month follow-up. Cocaine use at follow-up was measured by means of self-reported days of cocaine use in the last month verified by urine screening.

RESULTS

A multiple hierarchical regression model was used to examine the predictive value of the error-related negativity while controlling for addiction severity and self-reported craving in the week before treatment. The error-related negativity was the only significant predictor in the model and added 7.4% of explained variance to the control variables, resulting in a total of 33.4% explained variance in the prediction of days of cocaine use at follow-up.

CONCLUSIONS

A reduced error-related negativity measured during the first week of treatment was associated with more days of cocaine use at 3-month follow-up. Moreover, the error-related negativity was a stronger predictor of recent cocaine use than addiction severity and craving. These results suggest that underactive error-related brain activity might help to identify patients who are at risk of relapse as early as in the first week of detoxification treatment.

Intact inhibitory control processes in abstinent drug abusers (II): a high-density electrical mapping study in former cocaine and heroin addicts

Response inhibition deficits are well-documented in drug users, and are related to the impulsive tendencies characteristic of the addictive phenotype. Addicts also show significant motivational issues that may accentuate these inhibitory deficits. We investigated the extent to which these inhibitory deficits are present in abstinence. Salience of the task stimuli was also manipulated on the premise that emotionally-valenced inputs might impact inhibitory efficacy by overcoming the blunted responses to everyday environmental inputs characteristic of this population. Participants performed response inhibition tasks consisting of both neutral and emotionally valenced stimuli while high-density event-related potentials (ERPs) were recorded. Electrophysiological responses (N2/P3 components) to successful inhibitions in abstinent abusers (N = 20) and non-using participants (N = 21) were compared. In contrast to previous work in current users, our abstinent cohort showed no detectable behavioral or electrophysiological differences in their inhibitory responses, and no differences on self-reports of impulsivity, despite their long histories of chronic use (mean = 10.3 years). The current findings are consistent with a recovery of inhibitory control processes as a function of abstinence. Abstinent former users, however, did show a reduced modulation, relative to controls, of their ERPs to valenced input while performing successful inhibitions, although contrary to our hypothesis, the use of valenced inputs had no impact on inhibitory performance. Reduced ERP modulation to emotionally valenced inputs may have implications for relapse in emotional contexts outside the treatment center.

Error processing and gender-shared and -specific neural predictors of relapse in cocaine dependence

Deficits in cognitive control are implicated in cocaine dependence. Previously, combining functional magnetic resonance imaging and a stop signal task, we demonstrated altered cognitive control in cocaine-dependent individuals. However, the clinical implications of these cross-sectional findings and, in particular, whether the changes were associated with relapse to drug use, were not clear. In a prospective study, we recruited 97 treatment-seeking individuals with cocaine dependence to perform the stop signal task during functional magnetic resonance imaging and participate in follow-up assessments for 3 months, during which time cocaine use was evaluated with timeline follow back and ascertained by urine toxicology tests. Functional magnetic resonance imaging data were analysed using general linear models as implemented in Statistical Parametric Mapping 8, with the contrast 'stop error greater than stop success trials' to index error processing. Using voxelwise analysis with logistic and Cox regressions, we identified brain activations of error processing that predict relapse and time to relapse. In females, decreased error-related activations of the thalamus and dorsal anterior cingulate cortex predicted relapse and an earlier time to relapse. In males, decreased error-related activations of the dorsal anterior cingulate cortex and left insula predicted relapse and an earlier time to relapse. These regional activations were validated with data resampling and predicted relapse with an average area under the curve of 0.849 in receiver operating characteristic analyses. These findings provide direct evidence linking deficits in cognitive control to clinical outcome in a moderate-sized cohort of cocaine-dependent individuals. These results may provide a useful basis for future studies to examine how psychosocial factors interact with cognitive control to determine drug use and to evaluate the efficacy of pharmacological or behavioural treatment in remediating deficits of cognitive control in cocaine addicts.

Intact inhibitory control processes in abstinent drug abusers (I): a functional neuroimaging study in former cocaine addicts

Neuroimaging studies in current cocaine dependent (CD) individuals consistently reveal cortical hypoactivity across regions of the response inhibition circuit (RIC). Dysregulation of this critical executive network is hypothesized to account for the lack of inhibitory control that is a hallmark of the addictive phenotype, and chronic abuse is believed to compound the issue. A crucial question is whether deficits in this circuit persist after drug cessation, and whether recovery of this system will be seen after extended periods of abstinence, a question with implications for treatment course and outcome. Utilizing functional magnetic resonance imaging (fMRI), we examined activation in nodes of the RIC in abstinent CD individuals (n = 27) and non-using controls (n = 45) while they performed a motor response inhibition task. In contrast to current users, these abstinent individuals, despite extended histories of chronic cocaine-abuse (average duration of use = 8.2 years), performed the task just as efficiently as non-users. In line with these behavioral findings, no evidence for between-group differences in activation of the RIC was found and instead, robust activations were apparent in both groups within the well-characterized nodes of the RIC. Similarly, our complementary Electroencephalography (EEG) investigation also showed an absence of behavioral and electrophysiological deficits in abstinent drug abusers. These results are consistent with an amelioration of neurobiological deficits in inhibitory circuitry following drug cessation, and could help explain how long-term abstinence is maintained. Finally, regression analyses revealed a significant association between level of activation in the right insula with inhibition success and increased abstinence duration in the CD cohort suggesting that this region may be integral to successful recovery from cocaine addiction.

Fronto-striatal dysregulation in drug addiction and pathological gambling: Consistent inconsistencies?

Alterations in appetitive processing are central to the major psychological theories of addiction, with differential predictions made by the reward deficiency, incentive salience, and impulsivity hypotheses. Functional MRI has become the chief means of testing these predictions, with experiments reliably highlighting disturbances at the level of the striatum, medial prefrontal cortex, and affiliated regions. However, demonstrations of hypo-reactivity and hyper-reactivity of this circuitry in drug addicted groups are reported in approximately equal measure. Similar findings are echoed in the emergent neuroimaging literature on pathological gambling, which has recently witnessed a coming of age. The first aim of this article is to consider some of the methodological aspects of these experiments that could influence the observed direction of group-level effects, including the baseline condition, trial structure and timing, and the nature of the appetitive cues (drug-related, monetary, or primary rewards). The second aim is to highlight the conceptual traction that is offered by pathological gambling, as a model of a ‘toxicity free’ addiction and an illness where tasks of monetary reinforcement afford a more direct mapping to the abused commodity. Our conclusion is that relatively subtle decisions in task design appear capable of driving group differences in fronto-striatal circuitry in entirely opposing directions, even with tasks and task variants that look ostensibly similar. Differentiation between the psychological theories of addiction will require a greater breadth of experimental designs, with more research needed on processing of primary appetitive cues, aversive processing, and in vulnerable/at-risk groups.

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We outline the current psychological theories of addiction and their predictions.

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We review recent fMRI literature of substance addictions and appetitive processing.

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Reasons for opposing results (hyper- vs hypo-active reward regions) are discussed.

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Recent fMRI findings of appetitive processing in pathological gambling are reviewed.

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Pathological gambling is suggested as a prototypical addiction for imaging research.

Young adults at risk for stimulant dependence show reward dysfunction during reinforcement-based decision making

BACKGROUND

While stimulant-dependent individuals continue to make risky decisions, in spite of poor outcomes, much less is known about decision-making characteristics of occasional stimulant users (OSU) at risk for developing stimulant dependence. This study examines whether OSU exhibit inefficient learning and execution of reinforced decision-outcome contingencies.

METHODS

Occasional stimulant users (n = 161) and stimulant-naïve comparison subjects (CTL) (n = 48) performed a Paper Scissors Rock task during functional magnetic resonance imaging. Selecting a particular option was associated with a predetermined probability of winning, which was altered repeatedly to examine neural and behavioral characteristics of reinforced contingencies.

RESULTS

Occasional stimulant users displayed greater anterior insula, inferior frontal gyrus, and dorsal striatum activation than CTL during late trials when contingencies were familiar (as opposed to being learned) in the presence of comparable behavioral performance in both groups. Follow-up analyses demonstrated that during late trials: 1) OSU with high cannabis use displayed greater activation in these brain regions than CTL, whereas OSU with low cannabis use did not differ from the other two groups; and 2) OSU preferring cocaine exhibited greater anterior insula, inferior frontal gyrus, and dorsal striatum activation than CTL and also displayed higher activation in the former two regions than OSU who preferred prescription stimulants.

CONCLUSIONS

Occasional stimulant users exhibit inefficient resource allocation during the execution of reinforced contingencies that may be a result of additive effects of cocaine and cannabis use. A critical next step is to establish whether this inefficiency predicts transition to stimulant dependence.

Impaired error-monitoring function in people with Internet addiction disorder: an event-related fMRI study

BACKGROUND

Internet addiction disorder (IAD) is rapidly becoming a prevalent mental health concern around the world. The neurobiological underpinnings of IAD should be studied to unravel the potential heterogeneity. This study was set to investigate the error-monitoring ability in IAD subjects.

METHODS

Fifteen IAD subjects and 15 healthy controls (HC) participated in this study. Participants were asked to perform a fast Stroop task that may show error responses. Behavioral and neurobiological results in relation to error responses were compared between IAD subjects and HC.

RESULTS

Compared to HC, IAD subjects showed increased activation in the anterior cingulate cortex (ACC) and decreased activation in the orbitofrontal cortex following error responses. Significant correlation was found between ACC activation and the Internet addiction test scores.

CONCLUSIONS

IAD subjects show an impaired error-monitoring ability compared to HC, which can be detected by the hyperactivation in ACC in error responses.

Better than I thought: positive evaluation bias in hypomania

Background

Mania is characterised by increased impulsivity and risk-taking, and psychological accounts argue that these features may be due to hypersensitivity to reward. The neurobiological mechanisms remain poorly understood. Here we examine reinforcement learning and sensitivity to both reward and punishment outcomes in hypomania-prone individuals not receiving pharmacotherapy.

Method

We recorded EEG from 45 healthy individuals split into three groups by low, intermediate and high self-reported hypomanic traits. Participants played a computerised card game in which they learned the reward contingencies of three cues. Neural responses to monetary gain and loss were measured using the feedback-related negativity (FRN), a component implicated in motivational outcome evaluation and reinforcement learning.

Results

As predicted, rewards elicited a smaller FRN in the hypomania-prone group relative to the low hypomania group, indicative of greater reward responsiveness. The hypomania-prone group also showed smaller FRN to losses, indicating diminished response to negative feedback.

Conclusion

Our findings indicate that proneness to hypomania is associated with both reward hypersensitivity and discounting of punishment. This positive evaluation bias may be driven by aberrant reinforcement learning signals, which fail to update future expectations. This provides a possible neural mechanism explaining risk-taking and impaired reinforcement learning in BD. Further research will be needed to explore the potential value of the FRN as a biological vulnerability marker for mania and pathological risk-taking.

Error processing and response inhibition in excessive computer game players: an event-related potential study

Excessive computer gaming has recently been proposed as a possible pathological illness. However, research on this topic is still in its infancy and underlying neurobiological mechanisms have not yet been identified. The determination of underlying mechanisms of excessive gaming might be useful for the identification of those at risk, a better understanding of the behavior and the development of interventions. Excessive gaming has been often compared with pathological gambling and substance use disorder. Both disorders are characterized by high levels of impulsivity, which incorporates deficits in error processing and response inhibition. The present study aimed to investigate error processing and response inhibition in excessive gamers and controls using a Go/NoGo paradigm combined with event-related potential recordings. Results indicated that excessive gamers show reduced error-related negativity amplitudes in response to incorrect trials relative to correct trials, implying poor error processing in this population. Furthermore, excessive gamers display higher levels of self-reported impulsivity as well as more impulsive responding as reflected by less behavioral inhibition on the Go/NoGo task. The present study indicates that excessive gaming partly parallels impulse control and substance use disorders regarding impulsivity measured on the self-reported, behavioral and electrophysiological level. Although the present study does not allow drawing firm conclusions on causality, it might be that trait impulsivity, poor error processing and diminished behavioral response inhibition underlie the excessive gaming patterns observed in certain individuals. They might be less sensitive to negative consequences of gaming and therefore continue their behavior despite adverse consequences.

Similar hyporesponsiveness of the dorsomedial prefrontal cortex in problem gamblers and heavy smokers during an inhibitory control task

BACKGROUND

Behavioral addictions like pathological gambling share many clinical characteristics with substance dependence. In addition, both types of disorders are associated with impairments in inhibitory control. Studies in patients with substance use disorders point to hyporesponsiveness of the dorsomedial prefrontal cortex. However, no such data exist on behavioral addictions.

METHODS

Using functional magnetic resonance imaging, we investigated the neural circuitry associated with impaired response inhibition in a group of male problem gamblers (n=17) using a stop signal task. We included control conditions tailored to specifically isolate neural correlates of inhibitory control. To investigate the specificity of effects, a group of heavy smokers (n=18) and a group of healthy controls (n=17) were also included.

RESULTS

Groups did not differ in behavioral performance on the stop signal task. However, both problem gamblers and heavy smokers showed hyporesponsiveness of the dorsomedial prefrontal cortex compared to healthy controls, during successful as well as failed response inhibition. These effects were robust against adjustments for depression and adult attention deficit scores.

CONCLUSIONS

These findings suggest that hypoactivation of the inhibition circuit is a shared neural mechanism in substance use disorders and behavioral addictions. As such, they support the reclassification of pathological gambling as a behavioral addiction in DSM-V.

Event-Related Oscillations in Alcoholism Research: A Review

Alcohol dependence is characterized as a multi-factorial disorder caused by a complex interaction between genetic and environmental liabilities across development. A variety of neurocognitive deficits/dysfunctions involving impairments in different brain regions and/or neural circuitries have been associated with chronic alcoholism, as well as with a predisposition to develop alcoholism. Several neurobiological and neurobehavioral approaches and methods of analyses have been used to understand the nature of these neurocognitive impairments/deficits in alcoholism. In the present review, we have examined relatively novel methods of analyses of the brain signals that are collectively referred to as event-related oscillations (EROs) and show promise to further our understanding of human brain dynamics while performing various tasks. These new measures of dynamic brain processes have exquisite temporal resolution and allow the study of neural networks underlying responses to sensory and cognitive events, thus providing a closer link to the physiology underlying them. Here, we have reviewed EROs in the study of alcoholism, their usefulness in understanding dynamical brain functions/dysfunctions associated with alcoholism as well as their utility as effective endophenotypes to identify and understand genes associated with both brain oscillations and alcoholism.

Executive dysfunction in chronic cocaine users: an exploratory study

INTRODUCTION

Chronic cocaine use is associated with some executive deficits. We assessed executive functions using ecologically valid tests in chronic cocaine users.

OBJECTIVES

To investigate the relationship between executive deficits and three measures of severity of cocaine use: years of use, quantity used, and frequency of use.

METHODS

Twenty-four cocaine users were compared with twenty-seven community controls. We used Student's t-test and Chi-squared to compare means and categorical variables, respectively. Linear regression analyses for the adjusted comparative analysis between cases and controls, and severity of cocaine use among cocaine users were performed.

RESULTS

Chronic cocaine users performed worse on measures of attention and working memory (Forward and Backward Digit Span, p<.001), set-shifting abilities (difference score between the Trail Making B and A, TMB-A, p=.006), cognitive test of mental flexibility and response inhibition (Rule Shift Cards) (p<.001), and prefrontal functioning (Wisconsin Card Sorting Test, WCST, p=.023) than controls. Years of cocaine use were associated with deficits in the Backward Digit Span (p=.041; CI 95%: -.760 to -.002), the TMB-A (p=.026; CI 95%: .687 to 9.761), the Zoo Map (p=.034; CI 95%: -.480 to -.021), and the Rule Shift Cards (p=.006; CI 95%: -.836 to -.164), among others. Quantity of cocaine use was associated with executive deficits measured by the Forward Digit Span (p=.007; CI 95%: -.727 to -.133), the TMB-A (p=.021; CI 95%: 5.304-57.945), and the number of perseverative errors in the WSCT (p=.002; CI 95%: -10.654 to -2.800). Frequency of cocaine was associated with deficits in the Backward Digit Span (p=.042; CI 95%: -1.548 to -.030).

CONCLUSIONS

Chronic use of cocaine is associated with executive deficits, which may influence patients' functionality, prognosis, and therapeutic failure.

The molecular genetics of executive function: role of monoamine system genes

Executive control processes, such as sustained attention, response inhibition, and error monitoring, allow humans to guide behavior in appropriate, flexible, and adaptive ways. The consequences of executive dysfunction for humans can be dramatic, as exemplified by the large range of both neurologic and neuropsychiatric disorders in which such deficits negatively affect outcome and quality of life. Much evidence suggests that many clinical disorders marked by executive deficits are highly heritable and that individual differences in quantitative measures of executive function are strongly driven by genetic differences. Accordingly, intense research effort has recently been directed toward mapping the genetic architecture of executive control processes in both clinical (e.g., attention-deficit/hyperactivity disorder) and nonclinical populations. Here we review the extant literature on the molecular genetic correlates of three exemplar but dissociable executive functions: sustained attention, response inhibition, and error processing. Our review focuses on monoaminergic gene variants given the strong body of evidence from cognitive neuroscience and pharmacology implicating dopamine, noradrenaline, and serotonin as neuromodulators of executive function. Associations between DNA variants of the dopamine beta hydroxylase gene and measures of sustained attention accord well with cognitive-neuroanatomical models of sustained attention. Equally, functional variants of the dopamine D2 receptor gene are reliably associated with performance monitoring, error processing, and reinforcement learning. Emerging evidence suggests that variants of the dopamine transporter gene (DAT1) and dopamine D4 receptor gene (DRD4) show promise for explaining significant variance in individual differences in both behavioral and neural measures of inhibitory control.

Alcohol dependence and anxiety increase error-related brain activity

AIMS

Detection of errors is crucial for efficient goal-directed behaviour. The ability to monitor behaviour is found to be diminished in patients with substance dependence, as reflected in decreased error-related brain activity, i.e. error-related negativity (ERN). The ERN is also decreased in other psychiatric disorders with impaired response inhibition, such as attention-deficit hyperactivity disorder and borderline personality disorder, but increased in anxiety disorders. The objective of the current study was to assess error monitoring in alcohol-dependent patients in relation to psychiatric comorbidity. We expected decreased error monitoring in alcohol-dependent patients with impulse control disorders and increased error monitoring in anxious alcohol-dependent patients.

DESIGN

In a case-control design alcohol-dependent patients were compared with healthy controls.

SETTING AND PARTICIPANTS

A consecutive series of 29 male alcohol-dependent patients, between 18 and 55 years of age, applying for in-patient detoxification were recruited at Novadic Kentron Center for Addiction Treatment. Fifteen age-matched healthy controls were recruited through advertisements in regional newspapers.

MEASUREMENTS

Event-related potentials were recorded while performing a speeded choice-reaction task, from which ERN amplitudes were calculated. Axis-I and -II psychiatric comorbidity were assessed using the MINI International Neuropsychiatric Interview and the Structured Interview for DSM-IV Personality disorders. All participants completed the Temperament and Character Inventory and Profile of Mood States.

FINDINGS

ERN amplitudes were increased for alcohol-dependent patients compared to healthy controls, particularly in patients with comorbid anxiety disorders.

CONCLUSIONS

Increased error monitoring in alcohol-dependent patients, particularly those with comorbid anxiety disorders, is in contrast with previous studies that suggested decreased error monitoring to be a general feature in substance use disorders. Psychiatric disorders co-occurring with alcohol dependence, such as anxiety disorders, may indicate subpopulations of alcohol-dependent patients, with distinct neurobiological and genetic characteristics, possibly requiring different treatment strategies.

Diminished error processing in smokers during smoking cue exposure

Deficits in error processing may contribute to the continuation of impulsive behaviors such as smoking. Previous studies show deficits in error processing among substance abuse patients. However, these studies were all conducted during affectively neutral conditions. Deficits in error processing in smokers may become more pronounced under affectively challenging conditions, such as during smoking cue exposure. The aim of the present study was to investigate whether smokers showed initial error processing deficits, as measured with the error-related negativity (ERN), and decreased motivational significance attributed to an error, as measured with the error positivity (Pe) when exposed to smoking cues. Additionally, we examined the nature of the ERN and Pe amplitudes in more detail by investigating their associations with trait impulsivity, nicotine dependence levels and cigarette craving. Event-related potentials were measured during a modified Erikson flanker task in both smokers and non-smoking controls. Smokers showed reduced ERN and Pe amplitudes after making an error, accompanied by diminished post-error slowing of reaction times. These results suggest that initial error processing and motivational significance attributed to an error are affected in smokers during smoking cue exposure. Furthermore, individual variation in impulsivity and nicotine dependence was associated with reduced ERN amplitudes.

Does traumatic brain injury increase risk for substance abuse?

Wars in Afghanistan and Iraq have resulted in thousands of military personnel suffering traumatic brain injury (TBI), including closed-head injuries. Of interest is whether these individuals and other TBI survivors are at increased risk for substance use disorder (SUD). While it has been well established that drug or alcohol intoxication itself increases probability of suffering a TBI in accidents or acts of violence, little is known about whether the brain insult itself increases the likelihood that a previously non-drug-abusing individual would develop SUD. Might TBI survivors be unusually vulnerable to addiction to opiate analgesics compared to other pain patients? Similarly, it is not known if TBI increases the likelihood of relapse among persons with SUD in remission. We highlight challenges in answering these questions, and review neurochemical and behavioral evidence that supports a causal relationship between TBI and SUD. In this review, we conclude that little is known regarding the directionality of TBI increasing drug abuse, and that collaborative research in this area is critically needed.

Self-regulation in ADHD: the role of error processing

Attention-deficit hyperactivity disorder (ADHD) is characterized by persistent and impairing developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. Such behavioral dysregulation may be a consequence of deficits in self-monitoring or adaptive control, both of which are required for adaptive behavior. Processing of contextual demands, ongoing monitoring of one's behavior to evaluate whether it is appropriate for a particular situation, and adjusting behavior when it is suboptimal are components of self-regulation. This review examines and integrates the emerging literature on error-processing and adaptive control as components of self-regulation into the prominent etiological theories of ADHD. Available data on error-processing, as reflected in event-related potentials (ERN and Pe) and behavioral performance, suggest that both early error detection and later error-evaluation may be diminished in ADHD, thereby interfering with adaptive control processes. However, variability in results limit broad conclusions, particularly for early error detection. A range of methodological issues, including ERP parameters and sample and task characteristics, likely contribute to this variability, and recommendations for future work are presented. The emerging literature on error-processing and adaptive control informs etiological theories of ADHD in general and may provide a method for testing self-regulation models in particular.

Increased error-related thalamic activity during early compared to late cocaine abstinence

Altered cognitive control is implicated in the shaping of cocaine dependence. One of the key component processes of cognitive control is error monitoring. Our previous imaging work highlighted greater activity in distinct cortical and subcortical regions including the dorsal anterior cingulate cortex (dACC), thalamus and insula when participants committed an error during the stop signal task (Li et al., 2008b). Importantly, dACC, thalamic and insular activity has been associated with drug craving. One hypothesis is that the intense interoceptive activity during craving prevents these cerebral structures from adequately registering error and/or monitoring performance. Alternatively, the dACC, thalamus and insula show abnormally heightened responses to performance errors, suggesting that excessive responses to salient stimuli such as drug cues could precipitate craving. The two hypotheses would each predict decreased and increased activity during stop error (SE) as compared to stop success (SS) trials in the SST. Here we showed that cocaine dependent patients (PCD) experienced greater subjective feeling of loss of control and cocaine craving during early (average of day 6) compared to late (average of day 18) abstinence. Furthermore, compared to PCD during late abstinence, PCD scanned during early abstinence showed increased thalamic as well as insular but not dACC responses to errors (SE>SS). These findings support the hypothesis that heightened thalamic reactivity to salient stimuli co-occur with cocaine craving and loss of self control.

Impaired Error Monitoring and Correction Function in Autism

INTRODUCTION: Error monitoring and correction is one of the executive functions and is important for effective goal directed behavior. Deficient executive functioning, including reduced error monitoring ability, is one of the typical features of such neurodevelopmental disorders as autism, probably related to perseverative responding, stereotyped repetitive behaviors, and an inability to accurately monitor ongoing behavior. Our prior studies of behavioral and event-related potential (ERP) measures during performance on visual oddball tasks in high-functioning autistic (HFA) children showed that despite only minor differences in reaction times HFA children committed significantly more errors. METHODS: This study investigated error monitoring in children with autism spectrum disorder (ASD) with response-locked event-related potentials - the Error-related Negativity (ERN) and Error-related Positivity (Pe) recorded at fronto-central sites. The ERN reflects early error detection processes, while the Pe has been associated with later conscious error evaluation and attention re-allocation. Reaction times (RT) in correct trials and post-error slowing in reaction times were measured. In this study fourteen subjects with ASD and 14 age- and IQ- matched controls received a three-category visual oddball task with novel distracters. RESULTS: ERN had a lower amplitude and longer latency in the ASD group but was localized in the caudal part of anterior cingulate cortex (ACC) in both groups. The Pe component was significantly prolonged in the ASD group but did not reach significance in amplitude differences compared to controls. We found significant post-error slowing in RTs in controls, and post-error acceleration in RTs in the ASD group. CONCLUSIONS: The reduced ERN and altered Pe along with a lack of post-error RT slowing in autism might be interpreted as insensitivity in the detection and monitoring of response errors and a reduced ability of execute corrective actions. This might result in reduced error awareness and failure in adjustment when dealing with situations where erroneous responses may occur. This deficit might be manifested in the perseverative behaviors often seen in individuals with ASD. The results are discussed in terms of a general impairment in self-monitoring and other executive functions underlying behavioral and social disturbances in ASD.

Evidence for a deficit in the salience attribution to errors in smokers

The persisting use of substances despite of adverse consequences is one of the hallmarks of addictive behaviors such as cigarette smoking. In the present study we used event-related potentials (ERPs) to investigate one aspect of adverse consequences: responses to errors in smokers versus non-smokers. The aim of this study was to determine whether cigarette smokers display error-processing deficits as measured using error-related negativity (ERN) and error positivity (Pe). ERPs during an Eriksen flanker task were recorded from smokers and a non-smoking control group. Smokers showed the same ERN response as controls after making an error. However, the later Pe response was reduced as compared to the control group. On the behavioral level, we observed a trend towards increased error rates of smokers on incongruent trials. The present findings reveal that cigarette smoking is associated with reduced error processing. More specifically, while initial error processing seem intact, brain systems reflecting the motivational significance of a performance error seem compromised. It is argued that these cognitive deficits may cause or contribute to the persistence of smoking behavior and addictive behaviors in general.

Reduced attentional scope in cocaine polydrug users

Cocaine is Europe's second preferred recreational drug after cannabis but very little is known about possible cognitive impairments in the upcoming type of recreational cocaine user (monthly consumption). We asked whether recreational use of cocaine impacts early attentional selection processes. Cocaine-free polydrug controls (n = 18) and cocaine polydrug users (n = 18) were matched on sex, age, alcohol consumption, and IQ (using the Raven's progressive matrices), and were tested by using the Global-Local task to measure the scope of attention. Cocaine polydrug users attended significantly more to local aspects of attended events, which fits with the idea that a reduced scope of attention may be associated with the perpetuation of the use of the drug.

Recent EEG and ERP findings in substance abusers

Research on electroencephalographic (EEG) correlates of substance use has a long history. The present paper provides a review of recent studies--2001 to the present--with a focus on EEG findings in human participants characterized by a history of chronic substance use, abuse or dependence. In some areas (e.g., alcohol and cocaine dependence), the field has attempted to build upon earlier work by incorporating different methodologies or pursuing research questions of a transdisciplinary nature. New areas of inquiry, such as the investigation of EEG differences among users of ecstasy (MDMA) and methamphetamine, have emerged, primarily as a result of an alarming rise in popularity of these drugs.

Task-related dissociation in ERN amplitude as a function of obsessive-compulsive symptoms

Hyperactive cortico-striatal circuits including the anterior cingulate cortex (ACC) have been implicated to underlie obtrusive thoughts and repetitive behaviors in obsessive-compulsive disorder (OCD). Larger error-related negativities (ERNs) in OCD patients during simple flanker tasks have been proposed to reflect an amplified error signal in these hyperactive circuits. Such amplified error signals typically are associated with an adaptive change in response, yet in OCD these same repetitive responses persist to the point of distress and impairment. In contrast to this repetitive character of OC behavior, larger ERN amplitudes have been linked to better avoidance learning in reinforcement learning tasks. Study I thus investigated if OC symptomatology in non-patients predicted an enhanced ERN after suboptimal choices in a probabilistic learning task. Absent any behavioral differences, higher OC symptoms predicted smaller ERNs. Study II replicated this effect in an independent sample while also replicating findings of a larger ERN in a flanker task. There were no relevant behavioral differences in reinforcement learning or error monitoring as a function of symptom score. These findings implicate different, yet overlapping neural mechanisms underlying the negative deflection in the ERP following the execution of an erroneous motor response and the one following a suboptimal choice in a reinforcement learning paradigm. OC symptomatology may be dissociated in these neural systems, with hypoactivity in a system that enables learning to avoid maladaptive choices, and hyperactivity in another system that enables the same behavior to be repeated when it was assessed as not quite good enough the first time.

Recreational cocaine polydrug use impairs cognitive flexibility but not working memory

RATIONALE

Chronic use of cocaine is associated with dysfunctions in frontal brain regions and dopamine D2 receptors, with poorer mental flexibility and a reduced ability to inhibit manual and attentional responses. Little is known, however, about cognitive impairments in the upcoming type of recreational cocaine polydrug user (1-4 g monthly consumption).

OBJECTIVE

We studied whether recreational cocaine polydrug users, who do not meet the criteria for abuse or dependence, showed impairments in working memory (WM) and cognitive flexibility.

METHODS

Controls and recreational cocaine polydrug users (who abstained from cocaine and other substances more than 1 week) were matched by sex, age, alcohol consumption, and IQ (Raven's Standard Progressive Matrices). Groups were tested by using two cognitive tasks measuring cognitive flexibility and three tasks investigating the maintenance and monitoring of information in WM.

RESULTS

Recreational cocaine polydrug users performed significantly worse than controls on tasks tapping cognitive flexibility, but show comparable performance in the active maintenance and monitoring of information in WM.

CONCLUSIONS

The findings suggest that recreational use of cocaine selectively impairs cognitive flexibility but not the maintenance of information in WM. The inability to adjust behavior rapidly and flexibly may have repercussions for daily life activities.

Neurocomputational mechanisms of reinforcement-guided learning in humans: a review

Adapting decision making according to dynamic and probabilistic changes in action-reward contingencies is critical for survival in a competitive and resource-limited world. Much research has focused on elucidating the neural systems and computations that underlie how the brain identifies whether the consequences of actions are relatively good or bad. In contrast, less empirical research has focused on the mechanisms by which reinforcements might be used to guide decision making. Here, I review recent studies in which an attempt to bridge this gap has been made by characterizing how humans use reward information to guide and optimize decision making. Regions that have been implicated in reinforcement processing, including the striatum, orbitofrontal cortex, and anterior cingulate, also seem to mediate how reinforcements are used to adjust subsequent decision making. This research provides insights into why the brain devotes resources to evaluating reinforcements and suggests a direction for future research, from studying the mechanisms of reinforcement processing to studying the mechanisms of reinforcement learning.

Attentional deficits in cocaine-dependent patients: converging behavioral and electrophysiological evidence

Although there are several reports of patients with cocaine dependence displaying cognitive deficits, the nature of their information processing deficits is not well characterized. In the present study, the attentional performance of cocaine-dependent patients (n=14) was examined and compared with that of healthy control individuals (n=15). Attention was assessed using an auditory oddball event-related task as well as the Continuous Performance Test (CPT, Identical Pairs version). The cocaine-dependent group displayed P300 amplitude reduction compared to controls. The group difference in P300 response latency did not reach significance. On the CPT, the cocaine-dependent patients displayed significantly poorer discriminability and greater errors of commission than the controls. There was a positive correlation between performance on the oddball event-related task and performance on the CPT. This investigation provides converging behavioral and electrophysiological evidence of attentional deficits in cocaine-dependent patients.

The error-related negativity (ERN) and psychopathology: toward an endophenotype

The ERN is a negative deflection in the event-related potential that peaks approximately 50 ms after the commission of an error. The ERN is thought to reflect early error-processing activity of the anterior cingulate cortex (ACC). First, we review current functional, neurobiological, and developmental data on the ERN. Next, the ERN is discussed in terms of three psychiatric disorders characterized by abnormal response monitoring: anxiety disorders, depression, and substance abuse. These data indicate that increased and decreased error-related brain activity is associated with the internalizing and externalizing dimensions of psychopathology, respectively. Recent data further suggest that abnormal error-processing indexed by the ERN indexes trait- but not state-related symptoms, especially related to anxiety. Overall, these data point to utility of ERN in studying risk for psychiatric disorders, and are discussed in terms of the endophenotype construct.

Heritability of frontal brain function related to action monitoring

Monitoring the correspondence between the intended and actually executed action, a fundamental mechanism of behavioral regulation, is reflected by error-related negativity (ERN), an ERP component generated by the anterior cingulate cortex. This study examined genetic influences on the ERN and other components related to action monitoring (correct negativity, CRN, and error positivity, Pe). A flanker task was administered to adolescent twins (age 12) including 99 monozygotic (MZ) and 175 dizygotic (DZ) pairs. Genetic analysis showed substantial heritability of all three ERP components (40%-60%) and significant genetic correlations between them. This study provides the first evidence for heritable individual differences in the neural substrates of action monitoring and suggests that ERN, CRN, and Pe can potentially serve as endophenotypes for genetic studies of personality traits and psychopathology associated with abnormal regulation of behavior.

Smaller feedback ERN amplitudes during the BART are associated with a greater family history density of alcohol problems in treatment-naïve alcoholics

BACKGROUND

Alcoholism is characterized by impaired decision-making (i.e., choosing intoxication in the face of mounting negative consequences). This impairment may involve a reduced brain response to the negative consequences of behavior, which supports an inclination to engage in risky behaviors. The feedback error-related negativity (F-ERN) is hypothesized to reflect the valence attached to the negative consequences of behavior. Performance on the Balloon Analogue Risk Task (BART) measures risk-taking propensity. We recorded F-ERNs during the BART and during a BART simulation, where individuals observed the rewards and consequences of (someone else's) BART performance.

METHODS

EEGs were recorded on 22 actively drinking, treatment-naïve alcoholics during the BART and BART simulation. F-ERNs were measured and their association with psychological and alcohol use measures was examined.

RESULTS

F-ERNs over fronto-central electrode sites were observed to balloon pops in the BART and BART simulation. F-ERNs during the BART were more than twice the amplitude of F-ERNs during the BART simulation. Smaller F-ERN amplitudes from the BART (but not the BART simulation) were associated with a greater family history density of alcohol problems.

CONCLUSION

The results suggest a possible link between the genetic vulnerability toward developing alcoholism and the brain's response to the negative consequences of behavior.