The neurobiology of cognitive control in successful cocaine abstinence

Fronto-striatal circuits in response-inhibition: Relevance to addiction

Disruptions to inhibitory control are believed to contribute to multiple aspects of drug abuse, from preexisting vulnerability in at-risk individuals, through escalation to dependence, to promotion of relapse in chronic users. Paradigms investigating the suppression of actions have been investigated in animal and human research on drug addiction. Rodent research has focused largely on impulsive behaviors, often gauged by premature responding, as a viable model highlighting the relevant role of dopamine and other neurotransmitters primarily in the striatum. Human research on action inhibition in stimulant dependence has highlighted impaired performance and largely prefrontal cortical abnormalities as part of a broader pattern of cognitive abnormalities. Animal and human research implicate inhibitory difficulties mediated by fronto-striatal circuitry both preceding and as a result of excessive stimulus use. In this regard, response-inhibition has proven a useful cognitive function to gauge the integrity of fronto-striatal systems and their role in contributing to impulsive and compulsive features of drug dependence.

Impaired learning from errors in cannabis users: Dorsal anterior cingulate cortex and hippocampus hypoactivity

BACKGROUND

The chronic use of cannabis has been associated with error processing dysfunction, in particular, hypoactivity in the dorsal anterior cingulate cortex (dACC) during the processing of cognitive errors. Given the role of such activity in influencing post-error adaptive behaviour, we hypothesised that chronic cannabis users would have significantly poorer learning from errors.

METHODS

Fifteen chronic cannabis users (four females, mean age=22.40 years, SD=4.29) and 15 control participants (two females, mean age=23.27 years, SD=3.67) were administered a paired associate learning task that enabled participants to learn from their errors, during fMRI data collection.

RESULTS

Compared with controls, chronic cannabis users showed (i) a lower recall error-correction rate and (ii) hypoactivity in the dACC and left hippocampus during the processing of error-related feedback and re-encoding of the correct response. The difference in error-related dACC activation between cannabis users and healthy controls varied as a function of error type, with the control group showing a significantly greater difference between corrected and repeated errors than the cannabis group.

CONCLUSIONS

The present results suggest that chronic cannabis users have poorer learning from errors, with the failure to adapt performance associated with hypoactivity in error-related dACC and hippocampal regions. The findings highlight a consequence of performance monitoring dysfunction in drug abuse and the potential consequence this cognitive impairment has for the symptom of failing to learn from negative feedback seen in cannabis and other forms of dependence.

Atlas-based diffusion tensor imaging correlates of executive function

Impairment in executive function (EF) is commonly found in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Atlas-based diffusion tensor imaging (DTI) methods may be useful in relating regional integrity to EF measures in MCI and AD. Sixty-six participants (25 normal controls, 22 MCI, and 19 AD) received DTI scans and clinical evaluation. DTI scans were applied to a pre-segmented atlas and fractional anisotropy (FA) and mean diffusivity (MD) were calculated. ANOVA was used to assess group differences in frontal, parietal, and cerebellar regions. For regions differing between groups (p < 0.01), linear regression examined the relationship between EF scores and regional FA and MD. Anisotropy and diffusivity in frontal and parietal lobe white matter structures were associated with EF scores in MCI and only frontal lobe structures in AD. EF was more strongly associated with FA than MD. The relationship between EF and anisotropy and diffusivity was strongest in MCI. These results suggest that regional white matter integrity is compromised in MCI and AD and that FA may be a better correlate of EF than MD.

The Imperial College Cambridge Manchester (ICCAM) platform study: An experimental medicine platform for evaluating new drugs for relapse prevention in addiction. Part A: Study description

Drug and alcohol dependence are global problems with substantial societal costs. There are few treatments for relapse prevention and therefore a pressing need for further study of brain mechanisms underpinning relapse circuitry. The Imperial College Cambridge Manchester (ICCAM) platform study is an experimental medicine approach to this problem: using functional magnetic resonance imaging (fMRI) techniques and selective pharmacological tools, it aims to explore the neuropharmacology of putative relapse pathways in cocaine, alcohol, opiate dependent, and healthy individuals to inform future drug development. Addiction studies typically involve small samples because of recruitment difficulties and attrition. We established the platform in three centres to assess the feasibility of a multisite approach to address these issues. Pharmacological modulation of reward, impulsivity and emotional reactivity were investigated in a monetary incentive delay task, an inhibitory control task, and an evocative images task, using selective antagonists for µ-opioid, dopamine D3 receptor (DRD3) and neurokinin 1 (NK1) receptors (naltrexone, GSK598809, vofopitant/aprepitant), in a placebo-controlled, randomised, crossover design. In two years, 609 scans were performed, with 155 individuals scanned at baseline. Attrition was low and the majority of individuals were sufficiently motivated to complete all five sessions (n=87). We describe herein the study design, main aims, recruitment numbers, sample characteristics, and explain the test hypotheses and anticipated study outputs.

Cue-induced craving in patients with cocaine use disorder predicts cognitive control deficits toward cocaine cues

INTRODUCTION

Cue-induced craving is a clinically important aspect of cocaine addiction influencing ongoing use and sobriety. However, little is known about the relationship between cue-induced craving and cognitive control toward cocaine cues. While studies suggest that cocaine users have an attentional bias toward cocaine cues, the present study extends this research by testing if cocaine use disorder patients (CDPs) can control their eye movements toward cocaine cues and whether their response varied by cue-induced craving intensity.

METHODS

Thirty CDPs underwent a cue exposure procedure to dichotomize them into high and low craving groups followed by a modified antisaccade task in which subjects were asked to control their eye movements toward either a cocaine or neutral drug cue by looking away from the suddenly presented cue. The relationship between breakdowns in cognitive control (as measured by eye errors) and cue-induced craving (changes in self-reported craving following cocaine cue exposure) was investigated.

RESULTS

CDPs overall made significantly more errors toward cocaine cues compared to neutral cues, with higher cravers making significantly more errors than lower cravers even though they did not differ significantly in addiction severity, impulsivity, anxiety, or depression levels. Cue-induced craving was the only specific and significant predictor of subsequent errors toward cocaine cues.

CONCLUSION

Cue-induced craving directly and specifically relates to breakdowns of cognitive control toward cocaine cues in CDPs, with higher cravers being more susceptible. Hence, it may be useful identifying high cravers and target treatment toward curbing craving to decrease the likelihood of a subsequent breakdown in control.

Effects of an opioid (proenkephalin) polymorphism on neural response to errors in health and cocaine use disorder

Chronic exposure to drugs of abuse perturbs the endogenous opioid system, which plays a critical role in the development and maintenance of addictive disorders. Opioid genetics may therefore play an important modulatory role in the expression of substance use disorders, but these genes have not been extensively characterized, especially in humans. In the current imaging genetics study, we investigated a single nucleotide polymorphism (SNP) of the protein-coding proenkephalin gene (PENK: rs2609997, recently shown to be associated with cannabis dependence) in 55 individuals with cocaine use disorder and 37 healthy controls. Analyses tested for PENK associations with fMRI response to error (during a classical color-word Stroop task) and gray matter volume (voxel-based morphometry) as a function of Diagnosis (cocaine, control). Results revealed whole-brain Diagnosis×PENK interactions on the neural response to errors (fMRI error>correct contrast) in the right putamen, left rostral anterior cingulate cortex/medial orbitofrontal cortex, and right inferior frontal gyrus; there was also a significant Diagnosis×PENK interaction on right inferior frontal gyrus gray matter volume. These interactions were driven by differences between individuals with cocaine use disorders and controls that were accentuated in individuals carrying the higher-risk PENK C-allele. Taken together, the PENK polymorphism-and potentially opioid neurotransmission more generally-modulates functioning and structural integrity of brain regions previously implicated in error-related processing. PENK could potentially render a subgroup of individuals with cocaine use disorder (i.e., C-allele carriers) more sensitive to mistakes or other related challenges; in future studies, these results could contribute to the development of individualized genetics-informed treatments.

Attenuated Neural Processing of Risk in Young Adults at Risk for Stimulant Dependence

Objective

Approximately 10% of young adults report non-medical use of stimulants (cocaine, amphetamine, methylphenidate), which puts them at risk for the development of dependence. This fMRI study investigates whether subjects at early stages of stimulant use show altered decision making processing.

Methods

158 occasional stimulants users (OSU) and 50 comparison subjects (CS) performed a “risky gains” decision making task during which they could select safe options (cash in 20 cents) or gamble them for double or nothing in two consecutive gambles (win or lose 40 or 80 cents, “risky decisions”). The primary analysis focused on risky versus safe decisions. Three secondary analyses were conducted: First, a robust regression examined the effect of lifetime exposure to stimulants and marijuana; second, subgroups of OSU with >1000 (n = 42), or <50 lifetime marijuana uses (n = 32), were compared to CS with <50 lifetime uses (n = 46) to examine potential marijuana effects; third, brain activation associated with behavioral adjustment following monetary losses was probed.

Results

There were no behavioral differences between groups. OSU showed attenuated activation across risky and safe decisions in prefrontal cortex, insula, and dorsal striatum, exhibited lower anterior cingulate cortex (ACC) and dorsal striatum activation for risky decisions and greater inferior frontal gyrus activation for safe decisions. Those OSU with relatively more stimulant use showed greater dorsal ACC and posterior insula attenuation. In comparison, greater lifetime marijuana use was associated with less neural differentiation between risky and safe decisions. OSU who chose more safe responses after losses exhibited similarities with CS relative to those preferring risky options.

Discussion

Individuals at risk for the development of stimulant use disorders presented less differentiated neural processing of risky and safe options. Specifically, OSU show attenuated brain response in regions critical for performance monitoring, reward processing and interoceptive awareness. Marijuana had additive effects by diminishing neural risk differentiation.

A Randomized Placebo-Controlled Trial of Targeted Prefrontal Cortex Modulation with Bilateral tDCS in Patients with Crack-Cocaine Dependence

BACKGROUND

Transcranial direct current stimulation over the dorsolateral prefrontal cortex has been shown to be clinically useful in the treatment of drug addiction.

METHODS

We conducted a double-blind randomized clinical trial aiming to assess the effects of bilateral dorsolateral prefrontal cortex transcranial direct current stimulation (left cathodal/right anodal) on crack-cocaine addiction. We defined craving as the primary outcome, and other clinical measurements, including depressive and anxiety symptoms, and quality of life, as secondary outcomes. Seventeen male crack-cocaine users (mean age 30.4 ± 9.8 SD) were randomized to receive 5 sessions of active transcranial direct current stimulation (2 mA, 35 cm(2), for 20 minutes), every other day, and 19 males (mean age 30.3 ± 8.4 SD) to receive sham-transcranial direct current stimulation (placebo) as control group.

RESULTS

Craving scores were significantly reduced in the transcranial direct current stimulation group after treatment when compared with sham-transcranial direct current stimulation (P = .028) and baseline values (P = .003), and decreased linearly over 4 weeks (before, during, and after treatment) in the transcranial direct current stimulation group only (P = .047). Changes of anxiety scores towards increase in the sham-transcranial direct current stimulation and decrease in the transcranial direct current stimulation group (P = .03), and of the overall perception of quality of life (P = .031) and of health (P = .048) towards decrease in the sham-transcranial direct current stimulation group and increase in the transcranial direct current stimulation group differed significantly between groups.

CONCLUSIONS

Repetitive bilateral transcranial direct current stimulation over the dorsolateral prefrontal cortex reduced craving for crack-cocaine use, decreased anxiety, and improved quality of life. We hypothesize that transcranial direct current stimulation effects may be associated with increased prefrontal processing and regulation of craving behavior.

Emergence of sex differences in the development of substance use and abuse during adolescence

Substance use and abuse begin during adolescence. Male and female adolescent humans initiate use at comparable rates, but males increase use faster. In adulthood, more men than women use and abuse addictive drugs. However, some women progress more rapidly from initiation of use to entry into treatment. In animal models, adolescent males and females consume addictive drugs similarly. However, reproductively mature females acquire self-administration faster, and in some models, escalate use more. Sex/gender differences exist in neurobiologic factors mediating both reinforcement (dopamine, opioids) and aversiveness (CRF, dynorphin), as well as intrinsic factors (personality, psychiatric co-morbidities) and extrinsic factors (history of abuse, environment especially peers and family) which influence the progression from initial use to abuse. Many of these important differences emerge during adolescence, and are moderated by sexual differentiation of the brain. Estradiol effects which enhance both dopaminergic and CRF-mediated processes contribute to the female vulnerability to substance use and abuse. Testosterone enhances impulsivity and sensation seeking in both males and females. Several protective factors in females also influence initiation and progression of substance use including hormonal changes of pregnancy as well as greater capacity for self-regulation and lower peak levels of impulsivity/sensation seeking. Same sex peers represent a risk factor more for males than females during adolescence, while romantic partners increase risk for women during this developmental epoch. In summary, biologic factors, psychiatric co-morbidities as well as personality and environment present sex/gender-specific risks as adolescents begin to initiate substance use.

Take it or leave it: prefrontal control in recreational cocaine users

Though stimulant drugs such as cocaine are considered highly addictive, some individuals report recreational use over long periods without developing dependence. Difficulties in response inhibition have been hypothesized to contribute to dependence, but previous studies investigating response inhibition in recreational cocaine users have reported conflicting results. Performance on a stop-signal task was examined in 24 recreational cocaine users and 32 healthy non-drug using control participants matched for age, gender and verbal intelligence during functional magnetic resonance imaging scanning. The two groups were further matched on traumatic childhood histories and the absence of family histories of addiction. Results revealed that recreational cocaine users did not significantly differ from controls on any index of task performance, including response execution and stop-signal reaction time, with the latter averaging 198 ms in both groups. Functional magnetic resonance imaging analyses indicated that, compared with controls, stopping in the recreational users was associated with increased activation in the pre-supplementary motor area but not the right inferior frontal cortex. Thus, findings imply intact response inhibition abilities in recreational cocaine users, though the distinct pattern of accompanying activation suggests increased recruitment of brain areas implicated in response inhibition. This increased recruitment could be attributed to compensatory mechanisms that enable preserved cognitive control in this group, possibly relating to their hypothetical resilience to stimulant drug dependence. Such overactivation, alternatively, may be attributable to prolonged cocaine use leading to neuroplastic adaptations.

Impaired Bayesian learning for cognitive control in cocaine dependence

BACKGROUND

Cocaine dependence is associated with cognitive control deficits. Here, we apply a Bayesian model of stop-signal task (SST) performance to further characterize these deficits in a theory-driven framework.

METHODS

A "sequential effect" is commonly observed in SST: encounters with a stop trial tend to prolong reaction time (RT) on subsequent go trials. The Bayesian model accounts for this by assuming that each stop/go trial increases/decreases the subject's belief about the likelihood of encountering a subsequent stop trial, P(stop), and that P(stop) strategically modulates RT accordingly. Parameters of the model were individually fit, and compared between cocaine-dependent (CD, n = 51) and healthy control (HC, n = 57) groups, matched in age and gender and both demonstrating a significant sequential effect (p < 0.05). Model-free measures of sequential effect, post-error slowing (PES) and post-stop slowing (PSS), were also compared across groups.

RESULTS

By comparing individually fit Bayesian model parameters, CD were found to utilize a smaller time window of past experiences to anticipate P(stop) (p < 0.003), as well as showing less behavioral adjustment in response to P(stop) (p < 0.015). PES (p = 0.19) and PSS (p = 0.14) did not show group differences and were less correlated with the Bayesian account of sequential effect in CD than in HC.

CONCLUSIONS

Cocaine dependence is associated with the utilization of less contextual information to anticipate future events and decreased behavioral adaptation in response to changes in such anticipation. These findings constitute a novel contribution by providing a computationally more refined and statistically more sensitive account of altered cognitive control in cocaine addiction.

Acute exercise ameliorates craving and inhibitory deficits in methamphetamine: An ERP study

This study aimed to determine the effect of acute exercise in the potential context of non-pharmacological intervention for methamphetamine (MA)-related craving; we additionally determine its effect on the inhibitory control induced by standard and MA-related tasks according to behavioral and neuroelectric measurements among MA-dependent individuals. The present study employed a within-subjects, counterbalanced design. A total of 24 participants who met the DSM-IV criteria for MA dependence were recruited. The craving level, reaction time, and response accuracy, as well as the event-related potential (ERP) components N2 and P3, were measured following exercise and the control treatment in a counterbalanced order. The exercise session consisted of an acute stationary cycle exercise at a moderate intensity, whereas the control treatment consisted of an active reading session. The self-reported MA craving was significantly attenuated during, immediately following, and 50min after the exercise session compared with the pre-exercise ratings, whereas the craving scores at these time points following exercise were lower than those for the reading control session. Acute exercise also facilitated inhibitory performance in both the standard and MA-related Go/Nogo tasks. A larger N2 amplitude, but not a larger P3 amplitude, was observed during both tasks in the exercise session and the Nogo condition compared with the reading control session and the Go condition. This is the first empirical study to demonstrate these beneficial effects of acute aerobic exercise at a moderate intensity on MA-related craving and inhibitory control in MA-dependent individuals. These results suggest a potential role for acute aerobic exercise in treating this specific type of substance abuse.

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

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

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

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

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

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

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

Dorsal medial prefrontal cortex (MPFC) circuitry in rodent models of cocaine use: implications for drug addiction therapies

Although the importance of the medial prefrontal cortex (MPFC) in cocaine addiction is well established, its precise contribution to cocaine seeking, taking and relapse remains incompletely understood. In particular, across two different models of cocaine self-administration, pharmacological or optogenetic activation of the dorsal MPFC has been reported to sometimes promote and sometimes inhibit cocaine seeking. We highlight important methodological differences between the two experimental paradigms and propose a framework to potentially reconcile the apparent discrepancy. We also draw parallels between these pre-clinical models of cocaine self-administration and human neuro-imaging studies in cocaine users, and argue that both lines of evidence point to dynamic interactions between cue-reactivity processes and control processes within the dorsal MPFC circuitry. From a translational perspective, these findings underscore the importance of interventions and therapeutics targeting not just a brain region, but a specific computational process within that brain region, and may have implications for the design and implementation of more effective treatments for human cocaine addiction.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

Impaired self-awareness in human addiction: deficient attribution of personal relevance

Compromised self-awareness of illness-related deficits and behaviors in psychopathology (e.g., schizophrenia) has been associated with deficient functioning of cortical midline regions including the ventromedial prefrontal cortex (vmPFC), implicated in personal relevance. Here, we review and critically analyze recent evidence to suggest that vmPFC abnormalities could similarly underlie deficient tagging of personal relevance in drug addiction, evidenced by a constellation of behaviors encompassing drug-biased attention, negative outcome insensitivity, self-report/behavior dissociation, and social inappropriateness. This novel framework might clarify, for example, why drug-addicted individuals often ruin long-standing relationships or forego important job opportunities while continuing to engage in uncontrolled drug-taking. Therapeutic interventions targeting personal relevance and associated vmPFC functioning could enhance self-awareness and facilitate more adaptive behavior in this chronically relapsing psychopathology.

Altered cerebellar and prefrontal cortex function in rhesus monkeys that previously self-administered cocaine

RATIONALE

Differences in brain function in cocaine users can occur even when frank deficits are not apparent, indicating neuroadaptive consequences of use. Using monkeys to investigate altered metabolic activity following chronic cocaine self-administration allows an assessment of altered function due to cocaine use, without confounding pre-existing differences or polysubstance use often present in clinical studies.

OBJECTIVES

To evaluate alterations in metabolic function during a working memory task in the prefrontal cortex and the cerebellum following 1 year of chronic cocaine self-administration followed by a 20 month drug-free period.

METHODS

Fluorodeoxyglucose ((18)F) PET imaging was used to evaluate changes in relative regional metabolic activity associated with a delayed match to sample working memory task. Chronic cocaine animals were compared to a control group, and region of interest analyses focused on the dorsolateral prefrontal cortex (DLPFC) and cerebellum.

RESULTS

Despite no differences in task performance, in the cocaine group, the cerebellum showed greater metabolic activity during the working memory task (relative to the control task) compared to the control group. There was also a trend toward a significant difference between the groups in DLPFC activity (p = 0.054), with the cocaine group exhibiting lower DLPFC metabolic activity during the delay task (relative to the control task) than the control group.

CONCLUSION

The results support clinical indications of increased cerebellar activity associated with chronic cocaine exposure. Consistent with evidence of functional interactions between cerebellum and prefrontal cortex, these changes may serve to compensate for potential impairments in functionality of DLPFC.

Recent Insights into the Neurobiology of Impulsivity

Impulsivity is associated with various psychopathologies, and elevated impulsivity is typically disadvantageous. This manuscript reviews recent investigations into the neurobiology of impulsivity using human imaging techniques and animal models. Both human imaging and preclinical pharmacological manipulations have yielded important insights into the neurobiological underpinnings of impulsivity. A more thorough understanding of the complex neurobiology underlying aspects of impulsivity may provide insight into new treatment options that target elevated impulsivity and psychopathologies such as addictions.

Cannabis abstinence during treatment and one-year follow-up: relationship to neural activity in men

Cannabis is among the most frequently abused substances in the United States. Cognitive control is a contributory factor in the maintenance of substance-use disorders and may relate to treatment response. Therefore, we assessed whether cognitive-control-related neural activity before treatment differs between treatment-seeking cannabis-dependent and healthy individuals and relates to cannabis-abstinence measures during treatment and 1-year follow-up. Cannabis-dependent males (N=20) completed a functional magnetic resonance imaging (fMRI) cognitive-control (Stroop) task before a 12-week randomized controlled trial of cognitive-behavioral therapy and/or contingency management. A healthy-comparison group (N=20) also completed the fMRI task. Cannabis use was assessed by urine toxicology and self-report during treatment, and by self-report across a 1-year follow-up period (N=18). The cannabis-dependent group displayed diminished Stroop-related neural activity relative to the healthy-comparison group in multiple regions, including those strongly implicated in cognitive-control and addiction-related processes (eg, dorsolateral prefrontal cortex and ventral striatum). The groups did not differ significantly in response times (cannabis-dependent, N=12; healthy-comparison, N=14). Within the cannabis-dependent group, greater Stroop-related activity in regions including the dorsal anterior cingulate cortex was associated with less cannabis use during treatment. Greater activity in regions including the ventral striatum was associated with less cannabis use during 1-year posttreatment follow-up. These data suggest that lower cognitive-control-related neural activity in classic 'control' regions (eg, dorsolateral prefrontal cortex and dorsal anterior cingulate) and classic 'salience/reward/learning' regions (eg, ventral striatum) differentiates cannabis-dependent individuals from healthy individuals and relates to less abstinence within-treatment and during long-term follow-up. Clinically, results suggest that treatment development efforts that focus on enhancing cognitive control in addition to abstinence may improve treatment outcomes in cannabis dependence.

Abstinence duration modulates striatal functioning during monetary reward processing in cocaine patients

Pre-clinical and clinical studies in cocaine addiction highlight alterations in the striatal dopaminergic reward system that subserve maintenance of cocaine use. Using an instrumental conditioning paradigm with monetary reinforcement, we studied striatal functional alterations in long-term abstinent cocaine-dependent patients and striatal functioning as a function of abstinence and treatment duration. Eighteen patients and 20 controls underwent functional magnetic resonance imaging during a Monetary Incentive Delay task. Region of interest analyses based on masks of the dorsal and ventral striatum were conducted to test between-group differences and the functional effects in the cocaine group of time (in months) with no more than two lapses from the first time patients visited the clinical service to seek treatment at the scanning time (duration of treatment), and the functional effects of the number of months with no lapses or relapses at the scanning session time (length of abstinence). We applied a voxel-wise and a cluster-wise FWE-corrected level (pFWE) at a threshold of P < 0.05. The patient group showed lower activation in the right caudate during reward anticipation than the control group. The regression analyses in the patients group revealed a positive correlation between duration of treatment and brain activity in the left caudate during reward anticipation. Likewise, length of abstinence negatively correlated with brain activity in the bilateral nucleus accumbens during monetary outcome processing. In conclusion, caudate and nucleus accumbens show a different brain response pattern to non-drug rewards during cocaine addiction, which can be modulated by treatment success.

Cocaine dependent individuals with attenuated striatal activation during reinforcement learning are more susceptible to relapse

Cocaine-dependent individuals show altered brain activation during decision making. It is unclear, however, whether these activation differences are related to relapse vulnerability. This study tested the hypothesis that brain-activation patterns during reinforcement learning are linked to relapse 1 year later in individuals entering treatment for cocaine dependence. Subjects performed a Paper-Scissors-Rock task during functional magnetic resonance imaging (fMRI). A year later, we examined whether subjects had remained abstinent (n=15) or relapsed (n=15). Although the groups did not differ on demographic characteristics, behavioral performance, or lifetime substance use, abstinent patients reported greater motivation to win than relapsed patients. The fMRI results indicated that compared with abstinent individuals, relapsed users exhibited lower activation in (1) bilateral inferior frontal gyrus and striatum during decision making more generally; and (2) bilateral middle frontal gyrus and anterior insula during reward contingency learning in particular. Moreover, whereas abstinent patients exhibited greater left middle frontal and striatal activation to wins than losses, relapsed users did not demonstrate modulation in these regions as a function of outcome valence. Thus, individuals at high risk for relapse relative to those who are able to abstain allocate fewer neural resources to action-outcome contingency formation and decision making, as well as having less motivation to win on a laboratory-based task.

Neural correlates of craving and impulsivity in abstinent former cocaine users: Towards biomarkers of relapse risk

A significant hindrance to effective treatment of addiction is identifying those most likely to relapse. Cocaine addiction is characterized by deficits in inhibitory control and elevated reactivity to cocaine cues, both hypothesized to be integral to development of addiction and propensity to relapse. It follows that reduction of both impulsivity and cue-reactivity following abstinence is protective against relapse, and that persistence of these factors increases vulnerability. Using functional magnetic resonance imaging, we examined neural activation patterns in dorsal and ventral striatum in abstinent cocaine dependent (CD) individuals (N=20) and non-using controls (N=19) as they performed a cocaine craving task. We also examined activations in nodes of the response inhibition circuit (RIC) as they performed an inhibition task. At the between-groups level, no differences in RIC or striatal activation were seen in former users, in contrast to previous investigations in current users, suggesting large-scale functional recovery with abstinence. However, at the individual participant-level, abstinent CD individuals displayed an association between cocaine cue-related neural activations in the right ventral striatum and compulsive cocaine craving scores. Compulsive craving scores were also negatively correlated with duration of abstinence. Further, there was an association between motor impulsivity scores and inhibition-related activations in the right inferior frontal gyrus and pre-supplementary motor area in abstinent CD individuals. Thus, while former users as a group did not show deficits in inhibitory function or cocaine-cue reactivity, participant-level results pointed to activation patterns in a minority of these individuals that likely contributes to enduring relapse vulnerability.

Executive dysfunction and reward dysregulation: a high-density electrical mapping study in cocaine abusers

Executive function deficits and reward dysregulation, which mainly manifests as anhedonia, are well documented in drug abusers. We investigated specific aspects of executive function (inhibitory control and cognitive control), as well as anhedonia, in a cohort of current cocaine abusers in order to ascertain to what extent these factors are associated with more severe drug dependence. Participants filled out questionnaires relating to anhedonia and their addiction history. Participants also performed a response inhibition task while high-density event-related potentials (ERPs) were recorded. Electrophysiological responses to successful inhibitions (N2/P3 components) and to commission errors (ERN/Pe components) were compared between 23 current users of cocaine and 27 non-using controls. A regression model was performed to determine the association of our measures of reward dysregulation and executive function with addiction severity. As expected, cocaine users performed more poorly than controls on the inhibitory control task and showed significant electrophysiological differences. They were also generally more anhedonic than controls. Higher levels of anhedonia were associated with more severe substance use, whereas the level of executive dysfunction was not associated with more severe substance use. However, N2 amplitude was associated with duration of drug use. Further, inhibitory control and anhedonia were correlated, but only in controls. These data suggest that while executive dysfunction characterizes drug abuse, it is anhedonia, independent of executive dysfunction, that is most strongly associated with more severe use.

Multimodal evidence of regional midcingulate gray matter volume underlying conflict monitoring

Functional neuroimaging studies have long implicated the mid-cingulate cortex (MCC) in conflict monitoring, but it is not clear whether its structural integrity (i.e., the gray matter volume) influences its conflict monitoring function. In this multimodal study, we used T1-weighted MRI scans as well as event-related potentials (ERPs) to test whether the MCC gray matter volume is associated with the electrocortical marker (i.e., No-go N200 ERP component) of conflict monitoring in healthy individuals. The specificity of such a relationship in health was determined in two ways: by (A) acquiring the same data from individuals with cocaine use disorder (CUD), known to have deficits in executive function including behavioral monitoring; and (B) acquiring the P300 ERP component that is linked with attention allocation and not specifically with conflict monitoring. Twenty-five (39.1 ± 8.4 years; 8 females) healthy individuals and 25 (42.7 ± 5.9 years; 6 females) individuals with CUD underwent a rewarded Go/No-go task during which the ERP data was collected, and they also underwent a structural MRI scan. The whole brain regression analysis showed a significant correlation between MCC structural integrity and the well-known ERP measure of conflict monitoring (N200, but not the P300) in healthy individuals, which was absent in CUD who were characterized by reduced MCC gray matter volume, N200 abnormalities as well as reduced task accuracy. In individuals with CUD instead, the N200 amplitude was associated with drug addiction symptomatology. These results show that the integrity of MCC volume is directly associated with the electrocortical correlates of conflict monitoring in healthy individuals, and such an association breaks down in psychopathologies that impact these brain processes. Taken together, this MCC–N200 association may serve as a biomarker of improved behavioral monitoring processes in diseased populations.

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No-go N200 amplitude is correlated with gray matter volume of the midcingulate cortex in controls.

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Such N200-midcingulate association is absent in individuals with cocaine use disorder (CUD).

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In the CUD group, No-go N200 amplitude is correlated with withdrawal symptoms.

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N200-midcingulate association can serve as a biomarker of intact conflict monitoring.

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

BACKGROUND

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

METHODS

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

RESULTS

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

LIMITATIONS

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

CONCLUSION

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

Cognitive control in opioid dependence and methadone maintenance treatment

BACKGROUND

Substance misuse is associated with cognitive dysfunction. We used a stop signal task to examine deficits in cognitive control in individuals with opioid dependence (OD). We examined how response inhibition and post-error slowing are compromised and whether methadone maintenance treatment (MMT), abstinence duration, and psychiatric comorbidity are related to these measures in individuals with OD.

METHODS

Two-hundred-and-sixty-four men with OD who were incarcerated at a detention center and abstinent for up to 2 months (n = 108) or at a correctional facility and abstinent for approximately 6 months (n = 156), 65 OD men under MMT at a psychiatric clinic, and 64 age and education matched healthy control (HC) participants were assessed. We computed the stop signal reaction time (SSRT) to index the capacity of response inhibition and post-error slowing (PES) to represent error-related behavioral adjustment, as in our previous work. We examined group effects with analyses of variance and covariance analyses, followed by planned comparisons. Specifically, we compared OD and HC participants to examine the effects of opioid dependence and MMT and compared OD sub-groups to examine the effects of abstinence duration and psychiatric comorbidity.

RESULTS

The SSRT was significantly prolonged in OD but not MMT individuals, as compared to HC. The extent of post-error slowing diminished in OD and MMT, as compared to HC (trend; p = 0.061), and there was no difference between the OD and MMT groups. Individuals in longer abstinence were no less impaired in these measures. Furthermore, these results remained when psychiatric comorbidities including misuse of other substances were accounted for.

CONCLUSIONS

Methadone treatment appears to be associated with relatively intact cognitive control in opioid dependent individuals. MMT may facilitate public health by augmenting cognitive control and thereby mitigating risky behaviors in heroin addicts.

Systematic review of neuroimaging correlates of executive functioning: converging evidence from different clinical populations

Executive functioning (EF) is an important cognitive domain that is negatively affected in a number of neuropsychiatric conditions. Neuroimaging methods have led to insights into the anatomical and functional nature of EF. The authors conducted a systematic review of the recent cognitive and neuroimaging literature to investigate how the neuroimaging correlates of EF compare between different diagnostic groups. The authors found that the frontal, parietal, and cerebellar lobes were most frequently associated with EF when comparing results from different clinical populations; the occipital lobe was not correlated with EF in any group. These findings suggest that individual disease processes affect circuits within an identifiable distributed network rather than isolated regions.

Estrogen receptors mediate estradiol's effect on sensitization and CPP to cocaine in female rats: role of contextual cues

Preclinical studies show that estradiol enhances sensitization to cocaine in females by mechanisms not fully understood. These studies consistently show that ovariectomized (OVX) rats exhibit little or no sensitization to cocaine compared to OVX rats administered estradiol. In this study we varied the dose of cocaine (10, 15, and 30mg/kg), the length of cocaine treatment (from 5 to 10days) and the context of cocaine injections to determine if these factors play a role on estradiol's effects on cocaine sensitization. Because OVX rats are hormonally compromised, they are not representative of the natural state of the animal, and thus the physiological context of these studies remains unclear. To address this issue, we blocked ERs in gonadally intact females by icv administration of the antiestrogen ICI-182,780. Varying the dose or length of exposure to cocaine does not alter estradiol's effect on cocaine sensitization. In contrast, a highly context-dependent sensitization protocol results in robust sensitization even in OVX rats. Interestingly, using this protocol, sensitization in OVX rats diminished with time, suggesting that estradiol is necessary for the maintenance of cocaine sensitization. Blocking brain ERs with ICI completely abolishes the development and expression of cocaine sensitization in gonadally intact female rats, even when tested in a highly context-dependent sensitization protocol. Given these findings, we propose that activation of brain ERs is required for the development and maintenance of sensitization and CPP.

The clinical relevance of neurocognitive measures in addiction

One of the major challenges in addiction treatment is relapse prevention, as rates of relapse following treatment remain very high across the main classes of drugs of abuse. Relapse prevention could be improved by a better understanding of the factors that influence treatment outcomes, including better predictors of risk of relapse following treatment. Recent developments in cognitive neuroscience point to neurocognitive measures (i.e., brain-imaging measures during cognitive-task performance) as potential predictors of relapse. These might even be better predictors than self-report measures, such as craving. We first give an overview of the current state of the field, and then discuss the outstanding challenges and future directions in this area of research.

Altered frontocingulate activation during aversive interoceptive processing in young adults transitioning to problem stimulant use

Problems associated with stimulant use have been linked to frontocingulate, insular, and thalamic dysfunction during decision making and alterations in interoceptive processing. However, little is known about how interoception and decision making interact and contribute to dysfunctions that promote the transition from recreational drug use to abuse or dependence. Here, we investigate brain activation in response to reward, punishment, and uncertainty during an aversive interoceptive challenge in current and former stimulant (cocaine and amphetamine) users using functional magnetic resonance imaging (fMRI). Young adults previously identified as recreational users (n = 184) were followed up 3 years later. Of these, 18 individuals progressed to problem stimulant use (PSU), whereas 15 desisted stimulant use (DSU). PSU, DSU, and 14 healthy comparison subjects (CTL) performed a two-choice prediction task at three fixed error rates (20% = reward, 50% = uncertainty, 80% = punishment) during which they anticipated and experienced episodes of inspiratory breathing load. Although groups did not differ in insula activation or subjective breathing load ratings, PSU exhibited lower right inferior frontal gyrus (IFG) and bilateral anterior cingulate (ACC) activation than DSU and CTL during aversive interoceptive processing as well as lower right IFG in response to decision making involving uncertainty. However, PSU exhibited greater bilateral IFG activation than DSU and CTL while making choices within the context of punishing feedback, and both PSU and DSU showed lower thalamic activation during breathing load than CTL. Findings suggest that frontocingulate attenuation, reflecting reduced resources devoted to goal maintenance and action selection in the presence of uncertainty and interoceptive perturbations, may be a biomarker for susceptibility to PSU.

A phenotypic structure and neural correlates of compulsive behaviors in adolescents

BACKGROUND

A compulsivity spectrum has been hypothesized to exist across Obsessive-Compulsive disorder (OCD), Eating Disorders (ED), substance abuse (SA) and binge-drinking (BD). The objective was to examine the validity of this compulsivity spectrum, and differentiate it from an externalizing behaviors dimension, but also to look at hypothesized personality and neural correlates.

METHOD

A community-sample of adolescents (N=1938; mean age 14.5 years), and their parents were recruited via high-schools in 8 European study sites. Data on adolescents' psychiatric symptoms, DSM diagnoses (DAWBA) and substance use behaviors (AUDIT and ESPAD) were collected through adolescent- and parent-reported questionnaires and interviews. The phenotypic structure of compulsive behaviors was then tested using structural equation modeling. The model was validated using personality variables (NEO-FFI and TCI), and Voxel-Based Morphometry (VBM) analysis.

RESULTS

Compulsivity symptoms best fit a higher-order two factor model, with ED and OCD loading onto a compulsivity factor, and BD and SA loading onto an externalizing factor, composed also of ADHD and conduct disorder symptoms. The compulsivity construct correlated with neuroticism (r=0.638; p ≤ 0.001), conscientiousness (r=0.171; p ≤ 0.001), and brain gray matter volume in left and right orbitofrontal cortex, right ventral striatum and right dorsolateral prefrontal cortex. The externalizing factor correlated with extraversion (r=0.201; p ≤ 0.001), novelty-seeking (r=0.451; p ≤ 0.001), and negatively with gray matter volume in the left inferior and middle frontal gyri.

CONCLUSIONS

Results suggest that a compulsivity spectrum exists in an adolescent, preclinical sample and accounts for variance in both OCD and ED, but not substance-related behaviors, and can be differentiated from an externalizing spectrum.

The influence of monetary punishment on cognitive control in abstinent cocaine-users

BACKGROUND

Dependent drug users show a diminished neural response to punishment, in both limbic and cortical regions, though it remains unclear how such changes influence cognitive processes critical to addiction. To assess this relationship, we examined the influence of monetary punishment on inhibitory control and adaptive post-error behavior in abstinent cocaine dependent (CD) participants.

METHODS

15 abstinent CD and 15 matched control participants performed a Go/No-go response inhibition task, which administered monetary fines for failed response inhibition, during collection of fMRI data.

RESULTS

CD participants showed reduced inhibitory control and significantly less adaptive post-error slowing in response to punishment, when compared to controls. The diminished behavioral punishment sensitivity shown by CD participants was associated with significant hypoactive error-related BOLD responses in the dorsal anterior cingulate cortex (ACC), right insula and right prefrontal regions. Specifically, CD participants' error-related response in these regions was not modulated by the presence of punishment, whereas control participants' response showed a significant BOLD increase during punished errors.

CONCLUSIONS

CD participants showed a blunted response to failed control (errors) that was not modulated by punishment. Consistent with previous findings of reduced sensitivity to monetary loss in cocaine users, we further demonstrate that such insensitivity is associated with an inability to increase cognitive control in the face of negative consequences, a core symptom of addiction. The pattern of deficits in the CD group may have implications for interventions that attempt to improve cognitive control in drug dependent groups via positive/negative incentives.

Hyperactivation of the cognitive control network in cocaine use disorders during a multisensory Stroop task

BACKGROUND

It has been suggested that individuals with cocaine use disorders (chronic cocaine abusers, CCA) have impairments in cognitive control, which likely contribute to impairments in decision making around drug use and relapse. However, deficits in cognitive control have currently only been studied under conditions of unisensory stimulation, which may not be reflective of more realistic multisensory drug cues.

METHODS

The current study employed functional magnetic resonance imaging (fMRI) to measure neuronal activity during a multisensory numeric Stroop task.

RESULTS

Despite few differences in reaction time, recently abstinent CCA (N=14) exhibited increased activation in prefrontal cortex, striatum and thalamus during cognitive control relative to a group of carefully matched controls (N=16). Importantly, these neuronal differences were relatively robust in classifying patients from controls (approximately 90% accuracy) and evident during conditions of both low (slow stimulus presentation rate) and relatively high (faster stimulus presentation rate) cognitive demand. In addition, CCA also failed to deactivate the default-mode network during high frequency visual trials.

CONCLUSIONS

In summary, current results indicate compensatory activation within the cognitive control network in recently abstinent CCA to achieve similar levels of behavioral performance.

Prefrontal hypoactivity associated with impaired inhibition in stimulant-dependent individuals but evidence for hyperactivation in their unaffected siblings

A neurocognitive endophenotype has been proposed for stimulant dependence, based on behavioral measures of inhibitory response control associated with white matter changes in the frontal cortex. This study investigated the functional neuroimaging correlates of inhibitory response control, as functional activity serves as a more dynamic measure than brain structure, allowing refinement of the suggested endophenotype. Stimulant-dependent individuals (SDIs), their unaffected siblings (SIBs), and healthy controls (CTs) performed the stop-signal task, including stop-signal reaction time (SSRT) as a measure of response inhibition, while undergoing functional magnetic resonance imaging. SDIs had impaired response inhibition accompanied by hypoactivation in the ventrolateral prefrontal cortex (PFC). In addition, they demonstrated hypoactivation in the anterior cingulate when failing to stop. In contrast, no hypoactivations were noted in their unaffected SIBs. Rather, they exhibited increased activation in the dorsomedial PFC relative to controls, together with inhibitory performance that was intermediate between that of the stimulant group and the healthy CT group. Such hyperactivations within the neurocircuitry underlying response inhibition and control are suggestive of compensatory mechanisms that could be protective in nature or could reflect coping with a pre-existing vulnerability, thus expressing potential aspects of resilience. The functional activation associated with response inhibition and error monitoring showed differential patterns of results between SDIs and their unaffected first-degree relatives, suggesting that the proposed endophenotype does not generalize to functional brain activity.

The neurobiology of successful abstinence

This review focuses on the neurobiological processes involved in achieving successful abstinence from drugs of abuse. While there is clinical and public health value in knowing if the deficits associated with drug use correct with abstinence, studying the neurobiology that underlies successful abstinence can also illuminate the processes that enable drug-dependent individuals to successfully quit. Here, we review studies on human addicts that assess the neurobiological changes that arise with abstinence and the neurobiological predictors of successfully avoiding relapse. The literature, while modest in size, suggests that abstinence is associated with improvement in prefrontal structure and function, which may underscore the importance of prefrontally mediated cognitive control processes in avoiding relapse. Given the implication that the prefrontal cortex may be an important target for therapeutic interventions, we also review evidence indicating the efficacy of cognitive control training for abstinence.

Response inhibition and elevated parietal-cerebellar correlations in chronic adolescent cannabis users

The ability to successfully inhibit an inappropriate behaviour is a crucial component of executive functioning and its impairment has been linked to substance dependence. Cannabis is the most widely used illicit drug in adolescence and, given the accelerated neuromaturation during adolescence, it is important to determine the effects of cannabis use on neurocognitive functioning during this developmental period. In this study, a cohort of adolescent heavy cannabis users and age-matched non-cannabis-using controls completed a Go/No-Go paradigm. Users were impaired in performance on the task but voxelwise and region-of-interest comparisons revealed no activation differences between groups. Instead, an analysis of correlation patterns between task-activated areas revealed heightened correlation scores in the users between bilateral inferior parietal lobules and the left cerebellum. The increased correlation activity between these regions was replicated with resting state fMRI data and was positively correlated with self-reported, recent cannabis usage. The results suggests that the poorer inhibitory control of adolescent cannabis users might be related to aberrant connectivity between nodes of the response inhibition circuit and that this effect is observable in both task-induced and intrinsic correlation patterns. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.

An exploratory pilot study of the relationship between neural correlates of cognitive control and reduction in cigarette use among treatment-seeking adolescent smokers

Despite high rates of tobacco use during adolescence, few empirically validated smoking cessation strategies exist for adolescent smokers. Developing an understanding of the neural underpinnings of cognitive control processes in adolescent smokers, and their relationship to quit behaviors, may help advance the development of enhanced behavioral and pharmacological therapies. The current pilot study explored the relationship between brain responses during performance of the Stroop color-word interference task and reduction in tobacco use (as measured by changes in cotinine levels) in treatment-seeking adolescent smokers participating in a high school-based smoking-cessation program. Eleven adolescent daily smokers participated in a prequit session during which neural activity in response to congruent and incongruent events in a Stroop task was examined using functional MRI (fMRI). Changes in urine cotinine levels from prequit baseline to end of treatment were calculated and correlated with brain activity. Adolescents with greater activation in the inferior frontal gyrus, insula, thalamus, and anterior cingulate had greater reductions in cotinine levels. The preliminary observation of a relationship between treatment outcome and neural correlates of cognitive control prior to treatment onset provides insight into individual differences in adolescent brain function that might relate importantly to treatment outcome.

Recovering from cocaine: insights from clinical and preclinical investigations

Cocaine remains one of the most addictive substances of abuse and one of the most difficult to treat. Although increasingly sophisticated experimental and technologic advancements in the last several decades have yielded a large body of clinical and preclinical knowledge on the direct effects of cocaine on the brain, we still have a relatively incomplete understanding of the neurobiological processes that occur when drug use is discontinued. The goal of this manuscript is to review both clinical and preclinical data related to abstinence from cocaine and discuss the complementary conclusions that emerge from these different levels of inquiry. This commentary will address observed alterations in neural function, neural structure, and neurotransmitter system regulation that are present in both animal models of cocaine abstinence and data from recovering clinical populations. Although these different levels of inquiry are often challenging to integrate, emerging data discussed in this commentary suggest that from a structural and functional perspective, the preservation of cortical function that is perhaps the most important biomarker associated with extended abstinence from cocaine.

Dissociated grey matter changes with prolonged addiction and extended abstinence in cocaine users

Extensive evidence indicates that current and recently abstinent cocaine abusers compared to drug-naïve controls have decreased grey matter in regions such as the anterior cingulate, lateral prefrontal and insular cortex. Relatively little is known, however, about the persistence of these deficits in long-term abstinence despite the implications this has for recovery and relapse. Optimized voxel based morphometry was used to assess how local grey matter volume varies with years of drug use and length of abstinence in a cross-sectional study of cocaine users with various durations of abstinence (1–102 weeks) and years of use (0.3–24 years). Lower grey matter volume associated with years of use was observed for several regions including anterior cingulate, inferior frontal gyrus and insular cortex. Conversely, higher grey matter volumes associated with abstinence duration were seen in non-overlapping regions that included the anterior and posterior cingulate, insular, right ventral and left dorsal prefrontal cortex. Grey matter volumes in cocaine dependent individuals crossed those of drug-naïve controls after 35 weeks of abstinence, with greater than normal volumes in users with longer abstinence. The brains of abstinent users are characterized by regional grey matter volumes, which on average, exceed drug-naïve volumes in those users who have maintained abstinence for more than 35 weeks. The asymmetry between the regions showing alterations with extended years of use and prolonged abstinence suggest that recovery involves distinct neurobiological processes rather than being a reversal of disease-related changes. Specifically, the results suggest that regions critical to behavioral control may be important to prolonged, successful, abstinence.

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.

Striatocortical pathway dysfunction in addiction and obesity: differences and similarities

Neuroimaging techniques are starting to reveal significant overlap in the brain circuitry underlying addiction and disorders of dyscontrol over rewarding behaviors (such as binge eating disorder and obesity). Positron emission tomography (PET) has demonstrated impaired striatal dopamine (DA) signaling (decreased D2 receptors) in drug addiction and obesity that is associated with reduced baseline glucose metabolism in medial and ventral prefrontal brain regions. Functional magnetic resonance imaging (fMRI) has documented brain activation abnormalities that also implicate DA-modulated striato-cortical pathways. In this review we map findings from recent neuroimaging studies that differentiate brain activation in drug/food addiction from those in controls within brain networks functionally connected with ventral and dorsal striatum. We show that regions found to be abnormal in addiction and obesity frequently emerge at the overlap of the dorsal and the ventral striatal networks. Medial temporal and superior frontal regions functionally connected with dorsal striatum display greater vulnerability in obesity and eating disorders than in drug addictions, indicating more widespread abnormalities for obesity and eating disorders than for addictions. This corroborates involvement of both ventral striatal (predominantly associated with reward and motivation) and dorsal striatal networks (associated with habits or stimulus response learning) in addiction and obesity but also identify distinct patterns between these two disorders.

The neurobiology of reward and cognitive control systems and their role in incentivizing health behavior

OBJECTIVE

This article reviews the neurobiology of cognitive control and reward processes and addresses their role in the treatment of addiction. We propose that the neurobiological mechanisms involved in treatment may differ from those involved in the etiology of addiction and consequently are worthy of increased investigation.

METHOD

We review the literature on reward and control processes and evidence of differences in these systems in drug addicted individuals. We also review the relatively small literature on neurobiological predictors of abstinence.

RESULTS

We conclude that prefrontal control systems may be central to a successful recovery from addiction. The frontal lobes have been shown to regulate striatal reward-related processes, to be among the regions that predict treatment outcome, and to show elevated functioning in those who have succeeded in maintaining abstinence.

CONCLUSION

The evidence of the involvement of the frontal lobes in recovery is consistent with the hypothesis that recovery is a distinct process that is more than the undoing of those processes involved in becoming addicted and a return to the pre-addiction state of the individual. The extent to which these frontal systems are engaged by treatment interventions may contribute to their efficacy.