The effects of methylphenidate on cognitive control in active methamphetamine dependence using functional magnetic resonance imaging

Neural Correlates of Impaired Cognitive Control in Individuals with Methamphetamine Dependence: An fMRI Study

Impaired cognitive and behavioral control has often been observed in people who use methamphetamine (MA). However, a comprehensive understanding of the neural substrates underlying these impairments is still lacking. The goal of the present study was to study the neural correlates of impaired cognitive control in individuals with MA dependence according to DSM-IV criteria. Eighteen individuals with MA dependence and 21 healthy controls were investigated using Stroop task, fMRI, and an impulsivity questionnaire. Overall, patients were found to have significantly poorer accuracy on the Stroop task and higher self-rated impulsivity. Comparing brain activations during the task, decreased activation in the dorsolateral prefrontal cortex (DLPFC), anterior midcingulate cortex (aMCC), and dorsal striatum was observed in individuals with MA dependence, compared to healthy controls. Altered fMRI signal in DLPFC and aMCC significantly correlated with impaired behavioral task performance in individuals with MA dependence. Furthermore, significantly lower and pronounced brain activations in the MA group were additionally detected in several sensory cortical regions, i.e., in the visual, auditory, and somatosensory cortices. The results of the current study provide evidence for the negative impact of chronic crystal meth consumption on the proper functioning of the fronto-cingulate and striatal brain regions, presumably underlying the often-observed deficits in executive functions in individuals with MA use disorder. As a new finding, we also revealed abnormal activation in several sensory brain regions, suggesting the negative effect of MA use on the proper neural activity of these regions. This blunted activation could be the cause of the observed deficits in executive functions and the associated altered brain activation in higher-level brain networks.

Statistical Nonparametric fMRI Maps in the Analysis of Response Inhibition in Abstinent Individuals with History of Alcohol Use Disorder

Inhibitory impairments may persist after abstinence in individuals with alcohol use disorder (AUD). Using traditional statistical parametric mapping (SPM) fMRI analysis, which requires data to satisfy parametric assumptions often difficult to satisfy in biophysical system as brain, studies have reported equivocal findings on brain areas responsible for response inhibition, and activation abnormalities during inhibition found in AUD persist after abstinence. Research is warranted using newer analysis approaches. fMRI scans were acquired during a Go/NoGo task from 30 abstinent male AUD and 30 healthy control participants with the objectives being (1) to characterize neuronal substrates associated with response inhibition using a rigorous nonparametric permutation-based fMRI analysis and (2) to determine whether these regions were differentially activated between abstinent AUD and control participants. A blood oxygen level dependent contrast analysis showed significant activation in several right cortical regions and deactivation in some left cortical regions during successful inhibition. The largest source of variance in activation level was due to group differences. The findings provide evidence of cortical substrates employed during response inhibition. The largest variance was explained by lower activation in inhibition as well as ventral attentional cortical networks in abstinent individuals with AUD, which were not found to be associated with length of abstinence, age, or impulsiveness.

Valuation system connectivity is correlated with poly-drug use in young adults

Poly-drug consumption contributes to fatal overdose in more than half of all poly-drug users. Analyzing decision-making networks may give insight into the motivations behind poly-drug use. We correlated average functional connectivity of the valuation system (VS), executive control system (ECS) and valuation-control complex (VCC) in a large population sample (n = 992) with drug use behaviour. VS connectivity is correlated with sedative use, ECS connectivity is separately correlated with hallucinogens and opiates. Network connectivity is also correlated with drug use via two-way interactions with other substances including alcohol and tobacco. These preliminary findings can contribute to our understanding of the common combinations of substance co-use and associated neural patterns.

Distinct patterns of prefrontal cortical disengagement during inhibitory control in addiction: A meta-analysis based on population characteristics

Prefrontal cortical dysfunctions underlying inhibitory control deficits in addiction are complex and likely dependent on population characteristics. Here, we conducted a meta-analysis to examine alterations in brain activations during response inhibition in addicted individuals. We characterized imaging findings based on substance use status, diagnosis, substance classes, and task performance. Results revealed in those with active drug addiction hypoactivation of the left dorsal anterior cingulate cortex (dACC) and right middle frontal gyrus (MFG), compared with healthy controls. Weakening of the dACC and MFG activations was particularly pronounced in nicotine users, respectively. Impaired task performance was also associated with diminished MFG activation. In contrast, abstinent users did not exhibit any significant differences compared with healthy controls. Those with behavioral addictions were characterized by higher midcingulate cortical activation. Thus, the neural disengagement during response inhibition in active drug addiction was limited to a small number of prefrontal cortical regions and dependent on population characteristics. Finally, the evidence for potential normalization of hypofrontality following substance use cessation highlights the benefits of abstinence in restoring cerebral functions.

Altered neural activities during response inhibition in adults with addiction: a voxel-wise meta-analysis

BACKGROUND

Previous literature has extensively investigated the brain activity during response inhibition in adults with addiction. Inconsistent results including both hyper- and hypo-activities in the fronto-parietal network (FPN) and the ventral attention network (VAN) have been found in adults with addictions, compared with healthy controls (HCs).

METHODS

Voxel-wise meta-analyses of abnormal task-evoked regional activity were conducted for adults with substance dependence (SD) and behavioral addiction during response inhibition tasks to solve previous inconsistencies. Twenty-three functional magnetic resonance imaging studies including 479 substance users, 38 individuals with behavioral addiction and 494 HCs were identified.

RESULTS

Compared with HCs, all addictions showed hypo-activities in regions within FPN (inferior frontal gyrus and supramarginal gyrus) and VAN (inferior frontal gyrus, middle temporal gyrus, temporal pole and insula), and hyper-activities in the cerebellum during response inhibition. SD subgroup showed almost the same activity patterns, with an additional hypoactivation of the precentral gyrus, compared with HCs. Stronger activation of the cerebellum was associated with longer addiction duration for adults with SD. We could not conduct meta-analytic investigations into the behavioral addiction subgroup due to the small number of datasets.

CONCLUSION

This meta-analysis revealed altered activation of FPN, VAN and the cerebellum in adults with addiction during response inhibition tasks using non-addiction-related stimuli. Although FPN and VAN showed lower activity, the cerebellum exhibited stronger activity. These results may help to understand the neural pathology of response inhibition in addiction.

Frontocingulate Dysfunction Is Associated with Depression and Decreased Serum PON1 in Methamphetamine-Dependent Patients

INTRODUCTION

Studies have been reported that frequent use of methamphetamine (MA) is associated with brain function impairment, mood disorders and excessive free radical production accompanied by the decreased level of the antioxidant response elements, but no study investigated their correlations simultaneously. In the current study, the correlation of brain function, depression and anxiety levels, and the serum levels of PON1 (an antioxidant) in MA-dependent patients were investigated.

METHODS

Nineteen active MA abusers and 18 control subjects performed color-word Stroop task during fMRI and the state of their depression, anxiety, and stress were measured by the Depression, Anxiety and Stress Scale-21 Items (DASS-21) questionnaire. Their blood samples were collected to measure the level of PON1 by the human enzyme-linked immunosorbent assay (ELISA) kit and its correlation with the measured variables was studied.

RESULTS

Analysis of fMRI findings showed frontocingulate dysfunction in Stroop effect condition, including left anterior cingulate cortex, paracingulate gyrus, superior frontal gyrus, and frontal pole in MA-dependent patients, which was associated with a higher level of depression and decreased level of serum PON1 in these patients.

DISCUSSION

The results of the current study showed that MA-dependency is associated with frontocingulate dysfunction, decreased serum PON1 concentration, and increased depression/anxiety, which is worth to be more studied to elucidate their roles in the pathophysiology of MA addiction.

Neuroimaging Impaired Response Inhibition and Salience Attribution in Human Drug Addiction: A Systematic Review

The impaired response inhibition and salience attribution (iRISA) model proposes that impaired response inhibition and salience attribution underlie drug seeking and taking. To update this model, we systematically reviewed 105 task-related neuroimaging studies (n > 15/group) published since 2010. Results demonstrate specific impairments within six large-scale brain networks (reward, habit, salience, executive, memory, and self-directed networks) during drug cue exposure, decision making, inhibitory control, and social-emotional processing. Addicted individuals demonstrated increased recruitment of these networks during drug-related processing but a blunted response during non-drug-related processing, with the same networks also being implicated during resting state. Associations with real-life drug use, relapse, therapeutic interventions, and the relevance to initiation of drug use during adolescence support the clinical relevance of the results. Whereas the salience and executive networks showed impairments throughout the addiction cycle, the reward network was dysregulated at later stages of abuse. Effects were similar in alcohol, cannabis, and stimulant addiction.

Methamphetamine Users Show No Behavioral Deficits in Response Selection After Protracted Abstinence

Introduction: Chronic recreational methamphetamine use causes dopaminergic neurotoxicity, which has been linked to impairments in executive functioning. Within this functional domain, response selection and the resolution of associated conflicts have repeatedly been demonstrated to be strongly modulated by dopamine. Yet, it has never been investigated whether chronic methamphetamine use leads to general impairments in response selection (i.e., irrespective of consumption-associated behavior) after substance use is discontinued. Materials and Methods: We tested n = 24 abstinent methamphetamine users (on average 2.7 years of abstinence) and n = 24 individually matched controls in a cross-sectional design with a flanker task. Results: Compared to healthy controls, former methamphetamine consumers had significantly slower reaction times, but did not show differences in the size of the flanker or Gratton effect, or post-error slowing. Complementary Bayesian analyses further substantiated this lack of effects despite prior consumption for an average of 7.2 years. Discussion: The ability to select a correct response from a subset of conflicting alternatives, as well as the selective attention required for this seem to be largely preserved in case of prolonged abstinence. Likewise, the ability to take previous contextual information into account during response selection and to process errors seem to be largely preserved as well. Complementing previously published finding of worse inhibition/interference control in abstinent consumers, our results suggest that not all executive domains are (equally) impaired by methamphetamine, possibly because different cognitive processes require different levels of dopamine activity.

Functional neural changes following behavioral therapies and disulfiram for cocaine dependence

A growing literature exists on neural correlates of treatment outcome. However, different types-or components of-treatment have distinct theorized mechanisms of action. And it is not yet known how changes in neural activity across treatment relate to engagement in different treatment components. Participants with cocaine use disorders in a randomized clinical trial received cognitive-behavioral therapy (CBT) plus, in a 2 × 2 design, contingency management (CM) or no CM, and disulfiram or placebo. Participants performed a functional MRI Stroop task, a measure of cognitive control, at the beginning of and after the 12-week treatment. Analyses assessed changes in Stroop-related neural activity within the sample overall and assessed how changes in Stroop-related activity correlated with measures of treatment process specific to each form of treatment (i.e., participation in CBT sessions, receipt of CM prizes, administration of disulfiram pills). Within the sample overall, compared with beginning of treatment, posttreatment Stroop-related neural activity was diminished in the hippocampus, thalamus, cingulate, precentral, post- and precentral gyrus, and precuneus and culmen regions (pFWE < .05). In separate whole-brain correlation analyses, greater reductions in Stroop-related activity were associated with more treatment engagement-"CBT sessions" with the precentral gyrus, inferior parietal lobule, and middle and medial frontal gyrus; "CM prizes" with the postcentral frontal gyrus. Disulfiram "medication days" were not associated with changes in Stroop-related activity. Findings suggest that key process indicators of CBT and CM may be associated with functional changes in cognitive-control-related neurocircuitry. (PsycINFO Database Record

The role of impulsivity in psychostimulant- and stress-induced dopamine release: Review of human imaging studies

Drug addiction is a debilitating disorder and its pivotal problem is the high relapse rate. To solve this problem, the aim is to prevent people from becoming addicted in the first place. One of the key questions that is still unanswered is why some people become addicted to drugs and others, who take drugs regularly, do not. In recent years extensive research has been done to untangle the many factors involved in this disorder. Here, we review some of the factors that are related to dopamine, i.e., impulsivity and stress (hormones), and aim to integrate this into a neurobiological model. Based on this, we draw two conclusions: (1) in order to understand the transition from recreational drug use to addiction, we need to focus more on these recreational users; and (2) research should be aimed at finding therapies that can restore inhibitory control/frontal functioning and improve stress resiliency in addicts.

Assessment of Executive Functions in Methamphetamine-addicted Individuals: Emphasis on Duration of Addiction and Abstinence

Introduction:

Several studies have conducted on impairments of executive functions in individuals with methamphetamine addiction; however, only a few have investigated the relationship between executive functions and duration of addiction or abstinence. This study was designed to assess the executive functions in methamphetamine-addicted individuals in relation to the duration of addiction or abstinence.

Methods:

A total of 161 subjects aged between 20 and 45 years were categorized into three subgroups: currently abusing (n=41), abstinent (n=60), and control healthy individuals (n=60). A battery of standardized executive function tasks, including Stroop test, Wisconsin Card Sorting test, and Tower of London task, were administered. Data were analyzed using Pearson correlation coefficient, analysis of variance, and post hoc Bonferroni test with SPSS16.0.

Results:

Methamphetamine-addicted and abstinent subjects performed worse than the controls. Methamphetamine-abstinent subjects performed better than the currently methamphetamine abusers in most executive functions. Duration of addiction and abstinence were correlated with executive dysfunctions.

Conclusion:

This study revealed that although executive functions may be improved by protracted abstinence, executive dysfunctions are not completely relieved, and specific attention to planning and implementation of intervention programs are necessary.

Abnormal response to methylphenidate across multiple fMRI procedures in cocaine use disorder: feasibility study

RATIONALE

The indirect dopamine agonist methylphenidate remediates cognitive deficits in psychopathology, but the individual characteristics that determine its effects on the brain are not known.

OBJECTIVES

We aimed to determine whether targeted dopaminergically modulated traits and individual differences could predict neural response to methylphenidate across multiple functional magnetic resonance imaging (fMRI) procedures.

METHODS

We combined neural measures from three separate procedures (two inhibitory control tasks differing in their degree of emotional salience and resting-state functional connectivity) during methylphenidate (20 mg oral, versus randomized and counterbalanced placebo) and correlated these aggregated responses with cocaine use disorder diagnosis (22 cocaine abusers, 21 controls), symptoms of attention deficit hyperactivity disorder, and working memory capacity.

RESULTS

Cocaine abusers, relative to controls, had a lower response in the dorsolateral prefrontal cortex to methylphenidate across all three procedures, driven by responses to the two inhibitory control tasks; reduced methylphenidate fMRI response in this region further correlated with more frequent cocaine use.

CONCLUSIONS

Cocaine abuse (and its frequency), associated with lower tonic dopamine levels, correlated with a reduction in activation to methylphenidate (versus placebo). These initial results provide feasibility to the idea that multimodal fMRI tasks can be meaningfully aggregated, and that these aggregated procedures show a common disruption in addiction in a highly anticipated region relevant to cognitive control. Results also suggest that drug use frequency may represent an important modulatory variable in interpreting the efficacy of pharmacologically enhanced cognitive interventions in addiction.

Methylphenidate alters selective attention by amplifying salience

RATIONALE

Methylphenidate, the most common treatment of attention deficit hyperactivity disorder (ADHD), is increasingly used by healthy individuals as a "smart drug" to enhance cognitive abilities like attention. A key feature of (selective) attention is the ability to ignore irrelevant but salient information in the environment (distractors). Although crucial for cognitive performance, until now, it is not known how the use of methylphenidate affects resistance to attentional capture by distractors.

OBJECTIVES

The present study aims to clarify how methylphenidate affects distractor suppression in healthy individuals.

METHODS

The effect of methylphenidate (20 mg) on distractor suppression was assessed in healthy subjects (N = 20), in a within-subject double-blind placebo-controlled crossover design. We used a visuospatial attention task with target faces flanked by strong (faces) or weak distractors (scrambled faces).

RESULTS

Methylphenidate increased accuracy on trials that required gender identification of target face stimuli (methylphenidate 88.9 ± 1.4 [mean ± SEM], placebo 86.0 ± 1.2 %; p = .003), suggesting increased processing of the faces. At the same time, however, methylphenidate increased reaction time when the target face was flanked by a face distractor relative to a scrambled face distractor (methylphenidate 34.9 ± 3.73, placebo 26.7 ± 2.84 ms; p = .027), suggesting enhanced attentional capture by distractors with task-relevant features.

CONCLUSIONS

We conclude that methylphenidate amplifies salience of task-relevant information at the level of the stimulus category. This leads to enhanced processing of the target (faces) but also increased attentional capture by distractors drawn from the same category as the target.

New perspectives on using brain imaging to study CNS stimulants

While the recent application of brain imaging to study CNS stimulants has offered new insights into the fundamental factors that contribute to their use and abuse, many gaps remain. Brain circuits that mediate pleasure, dependence, craving and relapse are anatomically, neurophysiologically and neurochemically distinct from one another, which has guided the search for correlates of stimulant-seeking and taking behavior. However, unlike other drugs of abuse, metrics for tolerance and physical dependence on stimulants are not obvious. The dopamine theory of stimulant abuse does not sufficiently explain this disorder as serotonergic, GABAergic and glutamagergic circuits are clearly involved in stimulant pharmacology and so tracking the source of the "addictive" processes must adopt a more multimodal, multidisciplinary approach. To this end, both anatomical and functional magnetic resonance imaging (MRI), MR spectroscopy (MRS) and positron emission tomography (PET) are complementary and have equally contributed to our understanding of how stimulants affect the brain and behavior. New vistas in this area include nanotechnology approaches to deliver small molecules to receptors and use MRI to resolve receptor dynamics. Anatomical and blood flow imaging has yielded data showing that cognitive enhancers might be useful adjuncts in treating CNS stimulant dependence, while MRS has opened opportunities to examine the brain's readiness to accept treatment as GABA tone normalizes after detoxification. A desired outcome of the above approaches is being able to offer evidence-based rationales for treatment approaches that can be implemented in a more broad geographic area, where access to brain imaging facilities may be limited. This article is part of the Special Issue entitled 'CNS Stimulants'.