Neuropsychological performance of methadone-maintained opiate users

Regaining control over opioid use? The potential application of auricular transcutaneous vagus nerve stimulation to improve opioid treatment in China

Opioid use disorder (OUD) is a critical problem in China and is accompanied by depression and deficits in cognitive control. In China, the most successful intervention for OUD is the community drug rehabilitation where methadone maintenance treatment (MMT) plays a key role. Even though methadone for the treatment of OUD can be helpful, it can cause severe somatic side-effects, which limit its effectivity. Even worse, it can have detrimental effects on cognitive control, which is crucial to regain control over drug intake. Here, we consider the potential use of auricular transcutaneous vagus nerve stimulation (atVNS) as an addition to MMT for opioid withdrawal treatment. Compared to other non-invasive brain stimulation methods, atVNS also targets the locus coeruleus (LC) important for noradrenaline (NA) synthesis. NA is an essential neurotransmitter impacted in opioid withdrawal and also critically involved in cognitive control processes. Its ADD-ON to MMT might be a useful mean to improve mood and enhance cognitive control processes impacted in OUD. We discuss the translational advantages of atVNS in China such as the cultural acceptance of the modality of treatment similar to electroacupuncture. Additionally, the wearability of the ear electrode and at-home self-administration without intense medical supervision makes of atVNS a useful tool to enhance clinical and cognitive outcomes especially in everyday life situation. We discuss how atVNS can be integrated in tele-medical health approaches allowing that innovative treatments can widely be disseminated and continued even in situations of restricted medical access.

Methadone maintenance treatment and impulsivity: premature responding

INTRODUCTION

Previous research showed that methadone maintenance treatment (MMT) is linked to impulsivity, with higher impulsivity levels being associated with for example, increased drug use. One aspect of impulsivity, most commonly studied in rodent research, is premature responding, the failure to wait for a starting signal. Premature responding is of high translational significance since it predicts the development of addiction-like behaviors in rodents.

METHODS

We assessed 45 MMT patients and 46 demographically matched (age, sex, education, and handedness) healthy volunteers (HVs) on premature responding alongside action and inhibition of instructed and intentional trials using the Intentional Hand Task (IHT).

RESULTS

The results showed markedly enhanced premature responses in the MMT vs. the HV group, which correlated positively with methadone dosage in the MMT patients. Throughout the task, MMT patients were faster across all trial parts and less accurate in response to instructed trials compared to HVs.

CONCLUSIONS

The increase in premature motor reactions during variable waiting periods alongside increased motion speed and lower accuracy might reflect a specific motor inhibition deficit in MMT, a subcomponent of impulsivity not previously assessed in MMT. Incorporating an experimentally defined measure of impulsivity, such as premature responding, into existing test batteries used by clinicians might enable more tailored treatments addressing the increased impulsivity levels and associated dysfunctional behaviors in MMT.

Disrupted resting-state functional connectivity of frontal network in opium use disorder

Opioid use disorder (OUD) as a chronic relapsing disorder is initially driven by dysfunction of brain reward networks and associated with several psychiatric disorders. Resting-state EEG was recorded in 24 healthy participants as well as 31 patients with OUD. Healthy participants do not meet OUD criteria. After pre-processing of the raw EEG, functional connectivity in the frontal network using eLORETA and all networks using graph analysis method were calculated. Patients with OUD had higher electrical neuronal activity compared to healthy participants in higher frequency bands. The statistical analysis revealed that patients with OUD had significantly decreased phase synchronization in β1 and β2 frequency bands compared with the healthy group in the frontal network. Regarding global network topology, we found a significant decrease in the characteristic path length and an increase in global efficiency, clustering coefficient, and transitivity in patients compared with the healthy group. These changes indicated that local specialization and global integration of the brain were disrupted in OUD and it suggests a tendency toward random network configuration of functional brain networks in patients with OUD. Disturbances in EEG-based brain network indices might reflect an altered cortical functional network in OUD. These findings might provide useful biomarkers to understand cortical brain pathology in opium use disorder.

Inflammatory, oxidative stress and cognitive functions in patients under maintenance treatment with methadone or buprenorphine and healthy subjects

BACKGROUND

Methadone and buprenorphine which are widely used for opioid maintenance treatment can affect redox status and also brain functions. The present study aimed to compare inflammation, oxidative stress, and cognitive function in methadone maintenance patients (MMP), buprenorphine maintenance patients (BMP), and healthy participants.

METHOD

Oxidative- antioxidant markers, inflammatory factors were investigated in MMP (n = 30), BMP (n = 30), and healthy participants (n = 30) by evaluating the ferritin, malondialdehyde (MDA), total antioxidant capacity (TAC), and also High-sensitivity C-reactive protein (hs-CRP). Also, executive function was evaluated using Wisconsin Card Sorting Test (WCST).

FINDINGS

MMP and BMP showed impairment in executive function compared to the healthy participants. Both buprenorphine and methadone treatments induced oxidative stress. The ferritin level in BMP was significantly lower compared to MMP and healthy participants (P = 0.01). There was a significant difference between control and MMP and BMP (P > 0.0001) in terms of hs-CRP level. BMP had the highest and healthy participant's lowest MDA level (P < 0.001). The TAC levels in BMP were lower than in MMP (p = 0.002) and healthy participants (p = 0.001). Finally, executive function was significantly correlated with oxidative-antioxidant status.

DISCUSSION

Both methadone and buprenorphine induced severe oxidative activity (especially buprenorphine) and cognitive deficits compared to healthy participants. Stress oxidative can affect normal brain activity and consequently cognitive functions. It's suggested that concomitant antioxidant administration with buprenorphine or methadone can potentially enhance their beneficial action by regulating blood redox status.

Underrepresentation of diverse populations and clinical characterization in opioid agonist treatment research: A systematic review of the neurocognitive effects of buprenorphine and methadone treatment

INTRODUCTION

The relative neurocognitive effects of the two most common opioid agonist treatments (OAT; buprenorphine and methadone) for opioid use disorder (OUD) are poorly understood. The aim of this systematic review is to examine the neurocognitive effects of OAT (buprenorphine and methadone) and the clinical and sociodemographic characteristics of study samples.

METHODS

The research team queried PubMed, PsycINFO and Cochrane Reviews for articles (01/1980-01/2020) with terms related to neurocognitive testing in adults (age ≥ 18) prescribed OAT. The team extracted neurocognitive data and grouped them by domain (e.g., executive functioning, learning/memory), and assessed study quality.

RESULTS

The search retrieved 2341 abstracts, the team reviewed 278 full articles, and 32 met inclusion criteria. Of these, 31 were observational designs and one was an experimental design. Healthy controls performed better across neurocognitive domains than OAT-treated persons (buprenorphine or methadone). Compared to those with active OUD, OAT-treated persons had better neurocognition in various domains. However, in seven studies comparing buprenorphine- and methadone-treated persons, buprenorphine was associated with better neurocognition than was methadone, with moderate to large effect sizes in executive functioning, attention/working memory, and learning/memory. Additionally, OAT research underreports clinical characteristics and underrepresents Black and Latinx adults, as well as women.

CONCLUSIONS

Findings suggest that compared to active opioid use, both buprenorphine and methadone treatment are associated with better neurocognitive functioning, but buprenorphine is associated with better executive functioning, attention/working memory, and learning/memory. These findings should be interpreted with caution given widespread methodological heterogeneity, and limited representation of ethnoracially diverse adults and women. Rigorous longitudinal comparisons with more diverse, better characterized samples will help to inform treatment and policy recommendations for persons with OUD.

Cognitive Effect Following a Blended (Face to Face and Videoconference-Delivered) Format Mindfulness Training

While evidence supports the feasibility of online mindfulness training (MT), the effect of this approach on cognition remains unclear. The present study investigated changes in cognition following a newly developed 6-week videoconference-delivered MT program on cognitive function in two groups. The first group (n = 17) had two baseline assessments prior to MT [3 weeks after group two (n = 15)] to allow for evaluation of practice and learning effects. Four participants from each group were excluded from the final analysis due to missing data. Following MT, there was an improvement in switching of attention, working memory, executive function, and social cognition, but some of these effects were not easily accounted for by learning or practice effects. No significant changes were found on tasks measuring sustained attention, cognitive flexibility and inhibition, information processing, and sensory-motor function. Our findings suggest that domain-specific cognition might be enhanced by a brief videoconference-delivered MT, and larger, controlled studies to delineate the effects of online MT on subdomains of cognition are needed.

Cognitive function in methadone maintenance patients compared with abstinent opioid users

BACKGROUND

Opioid is the second most prevalent illicit drug worldwide, whose consumption is very high in Iran, due to Iran's geographical proximity to producing countries. Methadone maintenance therapy is one of the most prevalent and accepted methods of substance abuse treatment. Nevertheless, cognitive disorders have been reported as one of its complications.

AIM

This study was conducted to evaluate cognitive impairment in methadone maintenance patients (MMPs) and to compare it with abstinent opioid users (AOUs).

MATERIALS AND METHODS

This cross-sectional analytical study was performed on 25 MMPs and 25 AOUs. Samples were selected through convenience sampling method whereby a self-made questionnaire was distributed among them to assess demographic information, clinical variables such as methadone and opioid use history, underlying disease and medication history, as well as 13-item Beck depression inventory. Then, they were interviewed using the Montreal Cognitive Assessment (MoCA) questionnaire.

RESULTS

Significant differences were found in MoCA questionnaire total scores (p = 0.018) and orientation to time and place dimension (p = 0.008) between the two groups, with the mean scores being higher in AOU group. Duration of opioid use was the only factor influencing cognitive assessment score in both Groups. (p = 0.029).

CONCLUSION

We suggest monitoring and assessing cognition function in patients receiving methadone especially for those with a long history of opioid use.

Factors mediating pain-related risk for opioid use disorder

Pain is a complex experience with far-reaching organismal influences ranging from biological factors to those that are psychological and social. Such influences can serve as pain-related risk factors that represent susceptibilities to opioid use disorder. This review evaluates various pain-related risk factors to form a consensus on those that facilitate opioid abuse. Epidemiological findings represent a high degree of co-occurrence between chronic pain and opioid use disorder that is, in part, driven by an increase in the availability of opioid analgesics and the diversion of their use in a non-medical context. Brain imaging studies in individuals with chronic pain that use/abuse opioids suggest abuse-related mechanisms that are rooted within mesocorticolimbic processing. Preclinical studies suggest that pain states have a limited impact on increasing the rewarding effects of opioids. Indeed, many findings indicate a reduction in the rewarding and reinforcing effects of opioids during pain states. An increase in opioid use may be facilitated by an increase in the availability of opioids and a decrease in access to non-opioid reinforcers that require mobility or social interaction. Moreover, chronic pain and substance abuse conditions are known to impair cognitive function, resulting in deficits in attention and decision making that may promote opioid abuse. A better understanding of pain-related risk factors can improve our knowledge in the development of OUD in persons with pain conditions and can help identify appropriate treatment strategies. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'.

Opioid Use and Driving Performance

INTRODUCTION

The USA is in an opioid epidemic, with an increased number of individuals taking psychoactive drugs while executing the tasks of everyday life, including operating a motor vehicle. The pharmacology of opioids has been widely studied, but the effects of opioids on psychomotor function, driving performance, and the risk of motor vehicle collision remain less clear. Clinicians are faced with the challenge of controlling patient pain while also reconciling conflicting messages from the literature about how safe it is for their patients taking opioids to engage in potentially dangerous routine tasks.

DISCUSSION

This review assesses the current literature regarding opioids as they relate to neurocognitive function, driving performance, and accident risk. Manuscripts are categorized by study context and subject matter: controlled experimental administration, illicit use, prescription use, retrospective forensic toxicology, and polydrug consumption.

CONCLUSION

Illicit use, initiation of therapy, and opioid use in combination with other psychoactive medications are contexts most clearly associated with impairment of driving-related functions and/or operation of a motor vehicle. Clinicians should counsel patients on the risk of impairment when initiating therapy, when co-prescribing opioids and other psychoactive drugs, or when a patient is suspected of having an opioid use disorder.

Profiles of visuospatial memory dysfunction in opioid-exposed and dependent populations

BACKGROUND

Chronic opioid exposure is common world-wide, but behavioural performance remains under-investigated. This study aimed to investigate visuospatial memory performance in opioid-exposed and dependent clinical populations and its associations with measures of intelligence and cognitive impulsivity.

METHODS

We recruited 109 participants: (i) patients with a history of opioid dependence due to chronic heroin use (n = 24), (ii) heroin users stabilised on methadone maintenance treatment (n = 29), (iii) participants with a history of chronic pain and prescribed tramadol and codeine (n = 28) and (iv) healthy controls (n = 28). The neuropsychological tasks from the Cambridge Neuropsychological Test Automated Battery included the Delayed Matching to Sample (DMS), Pattern Recognition Memory, Spatial Recognition Memory, Paired Associate Learning, Spatial Span Task, Spatial Working Memory and Cambridge Gambling Task. Pre-morbid general intelligence was assessed using the National Adult Reading Test.

RESULTS

As hypothesised, this study identified the differential effects of chronic heroin and methadone exposures on neuropsychological measures of visuospatial memory (p &lt; 0.01) that were independent of injecting behaviour and dependence status. The study also identified an improvement in DMS performance (specifically at longer delays) when the methadone group was compared with the heroin group and also when the heroin group was stabilised onto methadone. Results identified differential effects of chronic heroin and methadone exposures on various neuropsychological measures of visuospatial memory independently from addiction severity measures, such as injecting behaviour and dependence status.

Cognitive function is largely intact in methadone maintenance treatment patients

OBJECTIVES

To confirm our previous findings of less cognitive impairments (based on cognitive screening tools) among methadone maintenance treatment (MMT) patients who achieved take-home dose (THD) privileges.

METHODS

a random sample of 65 Israeli MMT patients were studied using computerised, age and education standardised, cognitive domains (attention, executive function, memory, motor skills), and non-computerised phonetic and semantic verbal fluency.

RESULTS

Cognitive scores were within ±1 standard deviation (SD) of average for most domains, including non-verbal IQ, attention and motor skills. Verbal fluency and memory were >1 SD below average (mean = 84; z = -1.1 for both). Females were younger than the males and had poorer motor skills (P = 0.005) but better verbal memory (P < 0.0005). Opiate usage duration correlated with reaction time (P = 0.05) and inversely with verbal memory (P = 0.01). Overall cognitive function was poorest among 25 (38.5%) current drug users, and 6 (9.2%) lifetime schizophrenia patients. Cognitive domains were comparable between THD privileges subgroups.

CONCLUSIONS

Despite heterogeneity in MMT duration, abuse duration, substance use and psychiatric comorbidity, all performed within ±1 SD of average for age and education in most cognitive domains. Our findings challenge the notion of MMT as being synonymous with compromised cognition and may lead to reduced bias regarding cognitive function of MMT patients.

A Patient-Tailored Evidence-Based Approach for Developing Early Neuropsychological Training Programs in Addiction Settings

Substance use disorders (SUDs) are associated with impairments of cognitive functions, and cognitive training programs are thus rapidly developing in SUD treatment. However, neuropsychological impairments observed early after withdrawal (i.e., early impairments), that is, approximately in the first six months, may be widespread. Consequently, it might not be possible to train all the identified early impairments. In these situations, we propose that the priority of cognitive training should be given to the early impairments found to be associated with early dropout or relapse (i.e., relapse-related impairments). However, substance-specific relapse-related impairments have not been singled out among all early impairments so far. Using a systematic literature search, we identified the types of established early impairments for all SUDs, and we assessed the extent to which these early impairments were found to be associated with relapse-related impairments. All cognitive functions were investigated according to a classification based on current neuropsychological models, distinguishing classical cognitive, substance-bias, and social cognition systems. According to the current evidence, demonstrated relapse-related impairments in alcohol use disorder comprised impulsivity, long-term memory, and higher-order executive functions. For cannabis use disorder, the identified relapse-related impairments were impulsivity and working memory. For stimulant use disorder, the identified relapse-related impairments were attentional abilities and higher-order executive functions. For opioid use disorder, the only identified relapse-related impairments were higher executive functions. However, many early impairments were not explored with respect to dropout/relapse, particularly for stimulant and opioid use disorders. The current literature reveals substance-specific relapse-related impairments, which supports a pragmatic patient-tailored approach for defining which early impairments should be prioritized in terms of training among patients with SUDs.

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

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

Acute effects of methadone on EEG power spectrum and event-related potentials among heroin dependents

Methadone as the most prevalent opioid substitution medication has been shown to influence the neurophysiological functions among heroin addicts. However, there is no firm conclusion on acute neuroelectrophysiological changes among methadone-treated subjects as well as the effectiveness of methadone in restoring brain electrical abnormalities among heroin addicts. This study aims to investigate the acute and short-term effects of methadone administration on the brain's electrophysiological properties before and after daily methadone intake over 10 weeks of treatment among heroin addicts. EEG spectral analysis and single-trial event-related potential (ERP) measurements were used to investigate possible alterations in the brain's electrical activities, as well as the cognitive attributes associated with MMN and P3. The results confirmed abnormal brain activities predominantly in the beta band and diminished information processing ability including lower amplitude and prolonged latency of cognitive responses among heroin addicts compared to healthy controls. In addition, the alteration of EEG activities in the frontal and central regions was found to be associated with the withdrawal symptoms of drug users. Certain brain regions were found to be influenced significantly by methadone intake; acute effects of methadone induction appeared to be associative to its dosage. The findings suggest that methadone administration affects cognitive performance and activates the cortical neuronal networks, resulting in cognitive responses enhancement which may be influential in reorganizing cognitive dysfunctions among heroin addicts. This study also supports the notion that the brain's oscillation powers and ERPs can be utilized as neurophysiological indices for assessing the addiction treatment traits.

The Cholinergic System as a Treatment Target for Opioid Use Disorder

Opioid overdoses recently became the leading cause of accidental death in the US, marking an increase in the severity of the opioid use disorder (OUD) epidemic that is impacting global health. Current treatment protocols for OUD are limited to opioid medications, including methadone, buprenorphine, and naltrexone. While these medications are effective in many cases, new treatments are required to more effectively address the rising societal and interpersonal costs associated with OUD. In this article, we review the opioid and cholinergic systems, and examine the potential of acetylcholine (ACh) as a treatment target for OUD. The cholinergic system includes enzymes that synthesize and degrade ACh and receptors that mediate the effects of ACh. ACh is involved in many central nervous system functions that are critical to the development and maintenance of OUD, such as reward and cognition. Medications that target the cholinergic system have been approved for the treatment of Alzheimer's disease, tobacco use disorder, and nausea. Clinical and preclinical studies suggest that medications such as cholinesterase inhibitors and scopolamine, which target components of the cholinergic system, show promise for the treatment of OUD and further investigations are warranted.

Neuropsychological functioning in opioid use disorder: A research synthesis and meta-analysis

BACKGROUND

Research has demonstrated that patients with opioid use disorders (OUD; including both opioid abuse and/or dependence) have poorer neuropsychological functioning compared to healthy controls; however, the pattern and robustness of the findings remain unknown.

OBJECTIVES

This study meta-analyzed the results from previous research examining the neuropsychological deficits associated with opioids across 14 neurocognitive domains.

METHOD

Articles comparing patients with OUD to healthy controls were selected based on detailed inclusion/exclusion criteria and variables of interest were coded. In total, 61 studies were selected for the analyses. These consisted of 2580 patients with OUD and 2102 healthy control participants (15.9% female). Drug-related variables were analyzed as potential moderators.

RESULTS

The largest effect size difference in neuropsychological performance was observed in complex psychomotor ability. With the exception of the motor and processing speed domains, which showed no group differences, small-to-medium effect sizes were associated with all neurocognitive domains examined. Meta-regression revealed that increases in the length of abstinence were associated with decreases in effect sizes of the complex psychomotor domain. Additionally, attentional ability predicted effect size differences in executive functioning as well as verbal memory ability. Although the majority of meta-analyzed studies demonstrated significant differences between patients with OUD and controls, the average raw scores for patients with OUD in these studies typically fell within the normal range.

CONCLUSION

The pattern of neuropsychological performance among patients with OUD appears to reflect mild generalized cognitive dysfunction, with a large effect in complex psychomotor abilities.

Cognitive effects of labeled addictolytic medications

INTRODUCTION

Alcohol, tobacco, and illegal drug usage is pervasive throughout the world, and abuse of these substances is a major contributor to the global disease burden. Many pharmacotherapies have been developed over the last 50years to target addictive disorders. While the efficacy of these pharmacotherapies is largely recognized, their cognitive impact is less known. However, all substance abuse disorders are known to promote cognitive disorders like executive dysfunction and memory impairment. These impairments are critical for the maintenance of addictive behaviors and impede cognitive behavioral therapies that are regularly administered in association with pharmacotherapies. It is also unknown if addictolytic medications have an impact on preexisting cognitive disorders, and if this impact is modulated by the indication of prescription, i.e. abstinence, reduction or substitution, or by the specific action of the medication.

METHOD

We reviewed the cognitive effects of labeled medications for tobacco addiction (varenicline, bupropion, nicotine patch and nicotine gums), alcohol addiction (naltrexone, nalmefene, baclofen, disulfiram, sodium oxybate, acamprosate), and opioid addiction (methadone, buprenorphine) in human studies. Studies were selected following MOOSE guidelines for systematic reviews of observational studies, using the keywords [Cognition] and [Cognitive disorders] and [treatment] for each medication.

RESULTS

971 articles were screened and 77 studies met the inclusion criteria and were reported in this review (for alcohol abuse, n=21, for tobacco n=22, for opioid n=34. However, very few comparative clinical trials have explored the chronic effects of addictolytic medications on cognition in addictive behaviors, and there are no clinical trials on the cognitive impact of nalmefene in patients suffering from alcohol use disorders.

DISCUSSION

Although some medications seem to enhance cognition in patients suffering from cognitive disorders, others could promote cognitive impairments, and our work highlights a lack of literature on this subject. In conclusion, more comparative clinical trials are needed to better understand the cognitive impact of addictolytic medications.

Psychosocial interventions in opiate substitution treatment services: does the evidence provide a case for optimism or nihilism?

BACKGROUND AND AIMS

Clinical guidelines from around the world recommend the delivery of psychosocial interventions as part of routine care in opiate substitution treatment (OST) programmes. However, although individual studies demonstrate benefit for structured psychosocial interventions, meta-analytical reviews find no benefit for manual-based treatments beyond 'routine counselling'.

ANALYSIS

We consider the question of whether OST medication alone is sufficient to produce the required outcomes, or whether greater efforts should be made to provide high-quality psychosocial treatment alongside medication. In so doing, we consider the nuances and limitations of the evidence and the organizational barriers to transferring it into routine practice.

CONCLUSION

The evidence base for psychosocial interventions in opiate substitution treatment (OST) services can be interpreted both positively and negatively. Steering a path between overly optimistic or nihilistic interpretations of the value of psychosocial treatment in OST programmes is the most pragmatic approach. Greater attention should be paid to elements common to all psychological treatments (such as therapeutic alliance), but also to the sequencing and packaging of psychosocial elements and their linkage to peer-led interventions.

Effect of drug-related cues on response inhibition through abstinence: A pilot study in male heroin abstainers

BACKGROUND

Chronic heroin use can cause a deficit of inhibitory function, leading to a loss of control over drug use. Exposure to drug-related cues is considered as one of the contributing factors. However, it is unclear whether there are dynamic changes on the effect of drug-related cues on response inhibition following prolonged abstinence.

OBJECTIVE

The present study investigated the effect of drug-related cues on response inhibition in heroin abstainers at different abstinent phases.

METHODS

26 shorter-term (2-6 months) and 26 longer-term (19-24 months) male heroin abstainers performed on a modified two-choice Oddball task, which included two conditions: in the cued condition, neutral pictures served as the background of standard stimuli (yellow frame) and heroin-related pictures served as the background of deviant stimuli (blue frame), reversed in the controlled conditions.

RESULTS

Compared to longer-term abstainers, mean reaction time (RT) for drug deviants in shorter-term abstainers was significantly longer. Shorter-term abstainers also showed markedly slower response to neutral deviants relative to drug deviants, but this tendency was not observed in longer-term abstainers. Nevertheless, both groups had similar RT for standard stimuli regardless of their paired background pictures.

CONCLUSION

Effect of drug-related cues on response inhibition remains at the early stage of abstinence; however, this effect may be reduced following a longer period of drug abstinence. Our findings highlight the importance of assessing and improving the ability of inhibiting drug-related cue reactivity during treatment.

Quantitative EEG and Low-Resolution Electromagnetic Tomography (LORETA) Imaging of Patients Undergoing Methadone Treatment for Opiate Addiction

Methadone maintenance treatment (MMT) has been used as a treatment for opiate dependence since the mid-1960s. Evidence suggests that methadone binds to mu opiate receptors as do other opiates and induces changes in neurophysiological function. However, little is known, about how neural activity within the higher frequency gamma band (>30 Hz) while at rest changes in those stabilized on MMT despite its association with the excitation-inhibition balance within pyramidal-interneuron networks. Our study investigated differences in resting gamma power (37-41 Hz) between patients undergoing MMT for opiate dependence, illicit opiate users, and healthy controls subjects. Electroencephalographic data were recorded from 26 sites according to the international 10-20 system. Compared with the healthy controls subjects, people either undergoing MMT (mean difference [MD] = 0.32, 95% CI = 0.09-0.55, P < .01) or currently using illicit opiates (MD = 0.31, 95% CI = 0.06-0.56, P = .01) exhibited significant increased gamma power. The sLORETA (standardized low-resolution electromagnetic tomography) between-group comparison revealed dysfunctional neuronal activity in the occipital, parietal, and frontal lobes in the patients undergoing MMT. A more severe profile of dysfunction was observed in those using illicit opiates. Our findings suggest that long-term exposure to opioids is associated with disrupted resting state network, which may be reduced after MMT.

Abnormal functional integration of thalamic low frequency oscillation in the BOLD signal after acute heroin treatment

Heroin addiction is a severe relapsing brain disorder associated with impaired cognitive control, including deficits in attention allocation. The thalamus has a high density of opiate receptors and is critically involved in orchestrating cortical activity during cognitive control. However, there have been no studies on how acute heroin treatment modulates thalamic activity. In a cross-over, double-blind, vehicle-controlled study, 29 heroin-maintained outpatients were studied after heroin and placebo administration, while 20 healthy controls were included for the placebo condition only. Resting-state functional magnetic resonance imaging was used to analyze functional integration of the thalamus by three different resting state analysis techniques. Thalamocortical functional connectivity (FC) was analyzed by seed-based correlation, while intrinsic thalamic oscillation was assessed by analysis of regional homogeneity (ReHo) and the fractional amplitude of low frequency fluctuations (fALFF). Relative to the placebo treatment and healthy controls, acute heroin administration reduced thalamocortical FC to cortical regions, including the frontal cortex, while the reductions in FC to the mediofrontal cortex, orbitofrontal cortex, and frontal pole were positively correlated with the plasma level of morphine, the main psychoactive metabolite of heroin. Furthermore, heroin treatment was associated with increased thalamic ReHo and fALFF values, whereas fALFF following heroin exposure correlated negatively with scores of attentional control. The heroin-associated increase in fALFF was mainly dominated by slow-4 (0.027-0.073 Hz) oscillations. Our findings show that there are acute effects of heroin within the thalamocortical system and may shed new light on the role of the thalamus in cognitive control in heroin addiction. Future research is needed to determine the underlying physiological mechanisms and their role in heroin addiction.

Auditory event-related potentials in methadone substituted opiate users

The effects of methadone maintenance treatment (MMT) on neurophysiological function are unclear. Using an auditory oddball paradigm, event-related potential (ERP) amplitudes and latencies were measured in 32 patients undertaking MMT, 17 opiate users who were addicted but not receiving substitution treatment and 25 healthy control subjects. Compared with healthy control subjects, the MMT and opiate user groups showed an increased P200 amplitude in response to target stimuli. The opiate user group also exhibited a decreased amplitude and an increased latency of N200, and a greater number of task-related errors than either healthy control subjects or patients undertaking MMT. There were no significant group differences in the P300 amplitude. However, it is noteworthy that the frontal P300 amplitude of the MMT group was greater than that of opiate users or healthy controls. Our findings suggest that altered sensory information processing associated with a history of opiate use remains in patients undertaking MMT. However, there are less marked ERP abnormalities in those receiving MMT than in active opiate users. The deficits in information processing associated with illicit opiate use are likely to be reduced during MMT.

Methadone use in a male with the FMRI premutation and FXTAS

The fragile X-associated tremor ataxia syndrome (FXTAS) is caused by the premutation in FMR1 gene. Recent reports of environmental toxins appear to worsen the progression of FXTAS. Here we present a case of male adult with FXTAS and a long history of methadone use. The patient shows a faster progression in both symptoms of disease and MRI changes compared to what is typically seen in FXTAS. There has been no research regarding the role of narcotics in onset, progression, and severity of FXTAS symptoms. However, research has shown that narcotics can have a negative impact on several neurodegenerative diseases, and we hypothesize that in this particular case, methadone may have contributed to a faster progression of FXTAS as well as exacerbating white matter disease through RNA toxicity seen in premutation carriers.