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

The Effects of Cognitive Impulsivity on the Duration of Remission in Alcohol-Dependent Patients

BACKGROUND

Cognitive impulsivity manifesting in impaired inhibitory control and decision-making impulsivity is observed both in alcohol-dependent and substance-dependent individuals and may affect the ability to maintain long-term (persistent) remission.

AIM

To evaluate the effects of cognitive parameters of impulsivity on the duration of remission in alcohol-dependent patients.

METHODS

The study included 83 patients with alcohol dependence and 51 mentally healthy study subjects as the control group. The distribution of patients by duration of remission was based on the DSM-5 criteria. Patients were divided into two groups according to the duration of their most recent remission: patients with early remission (n=48) and patients with sustained remission (n=35). Impulsivity was assessed using the Go/No-Go task, which included a response inhibition component (inhibitory control). Choice impulsivity was assessed using two cognitive tests that encompass its separate components: decision-making under risk (Cambridge Gambling Task, CGT), and decision making under uncertainty (Iowa Gambling Task, IGT).

RESULTS

The study groups (patients and the controls) differed significantly in all domains of impulsivity: decision making under risk [GT: decision making quality (H(2, N=134)=30.233, p <0.001) and decision-making time (H(2, N=134)=18.433, p <0.001)] and decision making under uncertainty [IGT: selecting cards from "losing" decks (H(2, N=134)=9.291, p=0.009)]. The group of patients with sustained alcohol remission was characterized by longer decision times in CGT compared to the group of patients with early remission (z=2.398, p=0.049). Decision quality in CGT (z=0.673, p=0.999) and IGT scores (z=1.202, p=0.687) were not statistically significantly different between the groups of patients with sustained and early remission from alcohol dependence. The assessment of impulsive actions showed that the study groups were significantly different in terms of their ability to suppress their dominant behavioral response when performing the GNG task [false presses when seeing the "No-Go" signal (H(2, N=134)=28.851, p <0.001)]. The group of patients in sustained remission from alcohol dependence was characterized by better suppression of the behavioral response to the "No-Go" signal relative to the patients in early remission [H(2, N=134)=2.743, p=0.044)]. The regression analysis showed that the decision-making quality (t=2.507, р =0.049) and decision-making time (t=3.237, р=0.031) and the number of false presses when seeing the "No-Go" signal in the GNC task had a statistically significant impact on the duration of remission (t=3.091, р =0.043).

CONCLUSION

The results of this study indicate that impaired decision-making processes and the ability to inhibit the dominant behavioral response have a significant impact on the ability of alcohol-dependent patients to maintain long-term remission.

The effects of cocaine use severity and abstinence on behavioral performance and neural processes of response inhibition

Previous studies identified cerebral markers of response inhibition dysfunction in cocaine dependence. However, whether deficits in response inhibition vary with the severity of cocaine use or ameliorate during abstinence remain unclear. This study aimed to address these issues and the neural mechanisms supporting the individual variation. We examined the data of 67 individuals with cocaine dependence (CD) and 84 healthy controls (HC) who underwent functional magnetic resonance imaging during a stop-signal task (SST). The stop-signal reaction time (SSRT) was computed using the integration method, with a longer SSRT indicating poorer response inhibition. The results showed that, while CD and HC did not differ significantly in SSRT, years of cocaine use (YOC) and days of abstinence (DOA) were each positively and negatively correlated with the SSRT in CD. Whole-brain regressions of stop minus go success trials on SSRT revealed correlates in bilateral superior temporal gyrus (STG) in response inhibition across CD and HC. Further, mediation and path analyses revealed that YOC and DOA affected SSRT through the STG activities in CD. Together, the findings characterized the contrasting effects of cocaine use severity and abstinence on response inhibition as well as the neural processes that support these effects in cocaine dependence.

Event-related potential (ERP) markers of 22q11.2 deletion syndrome and associated psychosis

22q11.2 deletion syndrome (22q11.2DS) is a multisystemic disorder characterized by a wide range of clinical features, ranging from life-threatening to less severe conditions. One-third of individuals with the deletion live with mild to moderate intellectual disability; approximately 60% meet criteria for at least one psychiatric condition.22q11.2DS has become an important model for several medical, developmental, and psychiatric disorders. We have been particularly interested in understanding the risk for psychosis in this population: Approximately 30% of the individuals with the deletion go on to develop schizophrenia. The characterization of cognitive and neural differences between those individuals who develop schizophrenia and those who do not, despite being at genetic risk, holds important promise in what pertains to the clarification of paths to disease and to the development of tools for early identification and intervention.Here, we review our previous event-related potential (ERP) findings as potential markers for 22q11.2DS and the associated risk for psychosis, while discussing others' work. We focus on auditory processing (auditory-evoked potentials, auditory adaptation, and auditory sensory memory), visual processing (visual-evoked potentials and visual adaptation), and inhibition and error monitoring.The findings discussed suggest basic mechanistic and disease process effects on neural processing in 22q11.2DS that are present in both early sensory and later cognitive processing, with possible implications for phenotype. In early sensory processes, both during auditory and visual processing, two mechanisms that impact neural responses in opposite ways seem to coexist-one related to the deletion, which increases brain responses; another linked to psychosis, decreasing neural activity. Later, higher-order cognitive processes may be equally relevant as markers for psychosis. More specifically, we argue that components related to error monitoring may hold particular promise in the study of risk for schizophrenia in the general population.

Response inhibition and error-monitoring in cystinosis (CTNS gene mutations): Behavioral and electrophysiological evidence of a diverse set of difficulties

Cystinosis, a rare lysosomal storage disease, is characterized by cystine crystallization and accumulation within tissues and organs, including the kidneys and brain. Its impact on neural function appears mild relative to its effects on other organs, but therapeutic advances have led to substantially increased life expectancy, necessitating deeper understanding of its impact on neurocognitive function. Behaviorally, some deficits in executive function have been noted in this population, but the underlying neural processes are not understood. Using standardized cognitive assessments and a Go/No-Go response inhibition task in conjunction with high-density electrophysiological recordings (EEG), we sought to investigate the behavioral and neural dynamics of inhibition of a prepotent response and of error monitoring (critical components of executive function) in individuals with cystinosis, when compared to age-matched controls. Thirty-seven individuals diagnosed with cystinosis (7-36 years old, 24 women) and 45 age-matched controls (27 women) participated in this study. Analyses focused on N2 and P3 No-Go responses and error-related positivity (Pe). Atypical inhibitory processing was shown behaviorally. Electrophysiological differences were additionally found between the groups, with individuals with cystinosis showing larger No-Go P3s. Error-monitoring was likewise different between the groups, with those with cystinosis showing reduced Pe amplitudes.

Neurocognitive Impulsivity in Opiate Users at Different Lengths of Abstinence

The aim of the current study was to examine the effects of length of abstinence on decision making (impulsive choice) and response inhibition (impulsive action) in former opiate users (OU). Participants included 45 OU in early remission [0−12 months of abstinence], 68 OU in sustained remission [>12 months of abstinence], and 68 control participants. Decision making was assessed with the Iowa Gambling Task (IGT), the Cambridge Gambling Task (CGT), and the Monetary Choice Questionnaire (MCQ). Response inhibition was examined with the Stop Signal Task (SST), and the Go/No-Go Task (GNG). Results revealed group differences in decision making under risk (CGT) and ambiguity (IGT), where control participants displayed better decision making compared to OU in early remission. Both groups of former OU were also characterized by higher discounting of delayed rewards (MCQ). Regression analyses revealed minimal effects of length of abstinence on performance on decision-making tasks and no effects on delay discounting. In addition, both OU groups showed reduced action inhibition (GNG) relative to controls and there were no group differences in action cancellation (SST). Length of abstinence had no effect on response inhibition. Overall, our findings suggest that neurocognitive function may not fully recover even with protracted abstinence, which should be addressed by relapse prevention and cognitive remediation programs for OU.

Residual deficits in functional brain activity after chronic cocaine self-administration in rhesus monkeys

Previous studies in humans and in animals have shown dramatic effects of cocaine on measures of brain function that persist into abstinence. The purpose of this study was to examine the neurobiological consequences of abstinence from cocaine, using a model that removes the potential confound of cocaine cues. Adult male rhesus monkeys self-administered cocaine (0.3 mg/kg/injection; N = 8) during daily sessions or served as food-reinforcement controls (N = 4). Two times per week, monkeys were placed in a neutral environment and presented with a cartoon video for ~30 min, sometimes pre- and sometimes post-operant session, but no reinforcement was presented during the video. After ~100 sessions and when the cocaine groups had self-administered 900 mg/kg cocaine, the final experimental condition was a terminal 2-[14C]-deoxyglucose procedure, which occurred in the neutral (cartoon video) environment; for half of the monkeys in each group, this occurred after 1 day of abstinence and for the others after 30 days of abstinence. Rates of local cerebral glucose metabolism were measured in 57 brain regions. Global rates of cerebral metabolism were significantly lower in animals 1 day and 30 days post-cocaine self-administration when compared to those of food-reinforced controls. Effects were larger in 30- vs. 1-day cocaine abstinence, especially in prefrontal, parietal and cingulate cortex, as well as dorsal striatum and thalamus. Because these measures were obtained from monkeys while in a neutral environment, the deficits in glucose utilization can be attributed to the consequences of cocaine exposure and not to effects of conditioned stimuli associated with cocaine.

Influence of improved behavioral inhibition on decreased cue-induced craving in heroin use disorder: A preliminary intermittent theta burst stimulation study

BACKGROUND

Impaired behavioral inhibition is a critical factor in drug addiction and relapse. Repetitive transcranial magnetic stimulation (rTMS) reduces the craving of heroin-addicted individuals for drug-related cues. However, it is unclear whether this technique also improves impaired behavioral inhibition and how improved behavioral inhibition affects craving.

OBJECTIVE

The intermittent theta-burst stimulation (iTBS) has been recently shown to be non-inferior relative to rTMS for depression. Here, we aim to investigate the effect of iTBS on heroin-addicted individuals' behavioral inhibition and cue-induced craving and the relationship between the alteration of behavioral inhibition and craving.

METHOD

42 of 56 initially recruited individuals with the heroin-use disorder in the abstinent-course treatment were randomized to undergo active or sham iTBS to the left dorsolateral prefrontal cortex and received three daily iTBS treatments for 10 consecutive days. We measured participants' performance during a two-choice oddball task (80% standard and 20% deviant trials) and heroin-related cue-induced craving before and immediately after treatment.

RESULTS

The group that received active iTBS showed significantly improved two-choice oddball task performance after 10 days of intervention compared to both pre-intervention and the group who received sham iTBS. Similarly, a significant reduction in cue-induced craving was observed after following the intervention in the active iTBS group but not the sham iTBS group. The moderation model indicated that iTBS categories play a significant moderating role in the relationship between accuracy cost changing and altered cue-induced craving.

CONCLUSIONS

The iTBS treatment protocol positively affects behavioral inhibition in patients with heroin addiction. Improvements in behavioral inhibition can substantially reduce craving.

Patients with Methamphetamine Use Disorder Show Highly Utilized Proactive Inhibitory Control and Intact Reactive Inhibitory Control with Long-Term Abstinence

Methamphetamine use disorder (MUD) is a chronic brain disorder that involves frequent failures of inhibitory control and relapses into methamphetamine intake. However, it remains unclear whether the impairment of inhibitory control in MUD is proactive, reactive or both. To address this issue, the current study used the conditional stop-signal task to assess proactive and reactive inhibitory control in 35 MUD patients with long-term abstinence and 35 matched healthy controls. The results showed that MUD patients with long-term abstinence had greater preparation costs than healthy controls, but did not differ in performance, implying a less efficient utilization of proactive inhibitory control. In contrast, MUD patients exhibited intact reactive inhibitory control; reactive but not proactive inhibitory control was associated with high sensation seeking in MUD patients with long-term abstinence. These findings suggest that proactive and reactive inhibitory control may be two different important endophenotypes of addiction in MUD patients with long-term abstinence. The current study provides new insight into the uses of proactive and reactive inhibitory control to effectively evaluate and precisely treat MUD patients with long-term abstinence.

Comparison of Neural Correlates of Reactive Inhibition in Cocaine, Heroin, and Polydrug Users through a Contextual Go/No-Go Task Using Event-Related Potentials

Simple Summary

Witnessing the current increase in the use of substances in society and considering the associated pervasive relapse rate, the management of addictions remains a significant challenge. The identification of biomarkers that are linked to specific profiles of consumption would allow a more targeted, and therefore, more effective care. In this view, the present study evaluates and compares the cognitive performance usually associated with substance use disorder—inhibitory control, attentional bias, and error detection—of heroin, cocaine, and polydrug users to matched healthy controls. Simultaneously, the addition of measurement of the modulation of brain activity during the task (event-related potentials technique) offers a reliable representation of the neuronal mechanisms underlying cognitive functioning. The results reveal substance-specific neural patterns of response, notably a more deleterious impact on polydrug use, and, despite nonsignificant results, suggest a more drastically affected cognitive functioning in cocaine users. Such evidence refines our knowledge of the specific mode of action of each substance. Ultimately, knowing their neural signature will lead to the implementation of more targeted interventions, thereby allowing specific needs to be addressed.

Abstract

Recent global data indicates a worldwide increase in polydrug use associated with a shift from recreational to productive habits of consumption. Such non-responsible abuse of substances (alcohol, cocaine, heroin, etc.) is likely to lead to addictive disorders that are characterized by various neuropsychopharmacological effects. A main cognitive function involved in the onset and long-term maintenance of addiction is reactive inhibition, i.e., the ability to withhold a prepotent motor dominant response. In the present study, 63 (poly)drug user patients who were undergoing a detoxification program, in addition to 19 healthy controls matched for gender, age, and education, were subjected to a “contextual Go/No-Go task” with concomitant electroencephalography. Stimuli were superimposed on three contextual backgrounds: control (black screen), drug-unrelated (neutral pictures), or drug-related (pictures related to drug consumption). Of these patients, 23 were cocaine users (CU), 21 were heroin users (HU), and 19 were polydrug users (PDU). The main results showed that (1) at the behavioral level, more commission errors occurred with the PDU patients compared to the healthy controls; (2) at the neurophysiological level, specific alterations were found on classical event-related potentials that index reactive inhibition. Indeed, the higher rate of errors in the PDU group was subtended by both reduced amplitude and latency on the ∆N2 component and increased ∆P3 latency compared to controls. These data clearly suggest a more deleterious impact of polydrug use on inhibitory functions. In addition, our results provide evidence of reduced ERN amplitude in cocaine users, suggesting that impaired performance monitoring and error-processing may support impaired awareness, thereby preventing these patients from changing their behaviors.

Effect of automatic emotional processing on response inhibition among heroin abstainers

Previous studies have explored effects of the conscious processing of emotional information on the interaction between emotion and executive control. However, the conscious processing of emotional information introduces "defensive responses," which might limit the emotional effect. To avoid the limitations, this study aimed to explore the effect of automatic emotional processing on response inhibition among heroin abstainers. Individuals experiencing heroin withdrawal symptoms are not entirely exempt from the influence of drugs, and it is challenging to find heroin addicts in practice. Therefore, similar to previous studies, we recruited heroin abstainers in this study. In Experiment 1, for the heroin abstainers group, 30 participants meeting the inclusion criteria were recruited from a compulsory isolated detoxification center, whereas 30 age- and education-matched participants were recruited from the community as the control group. These participants completed the Go/No-Go task by supraliminal emotional priming. In Experiment 2, the heroin abstainers group comprised 33 eligible participants and control group comprised 33 eligible participants. These participants completed the Go/No-Go task by subliminal emotional priming. We compared the participants' rates of commission errors in the Go/No-Go tasks. The rate of commission errors was lowest upon the activation of positive emotion. Moreover, under subliminal emotional priming, the rate of commission errors for the heroin abstainers group was significantly lower than that for the control group. However, regarding supraliminal emotional priming, there was no significant difference between the rates of commission errors for the two groups. These results suggest automatic positive emotional processing can enhance response inhibition among heroin abstainers. Moreover, under subliminal emotional priming, heroin abstainers had more enhanced response inhibition than the control groups. This study plays a significant role in understanding the effect of automatic emotional processing on response inhibition among drug addicts. This study also provides a theoretical basis for ensuring enhanced response inhibition among drug addicts.

Risk of Injury to Others: The Development of an Algorithm to Identify Children and Youth at High-Risk of Aggressive Behaviours

Youth violence is considered one of the most preventable causes of morbidity and premature mortality. Various risk factors have previously been identified, however, there is presently a crucial need to develop effective decision-support tools in order to identify children and youth at increased risk for violence. The current study utilised data collected from the interRAI Child and Youth Mental Health Screener (ChYMH-S), within the province of Ontario, to develop and validate a methodology for the purpose of identifying young persons who were at greater risk of harm to others. Additional data from 59 mental health agencies validated the algorithm, and it was found to be a strong predictor of harmful behaviour toward others. The RIO algorithm provides a valuable decision-support tool with strong psychometric properties that may be used to identify young persons who exhibit signs or symptoms associated with increased likelihood of harm toward others, in order to provide early intervention efforts for these vulnerable youth, thereby reducing the likelihood of future aggressive behaviours.

Longitudinal changes in network engagement during cognitive control in cocaine use disorder

BACKGROUND

Cocaine use disorder (CUD) is characterized by poor cognitive control and has limited empirically supported treatment options. Furthermore, an understanding of brain mechanisms underlying CUD is at a relatively early stage. Thus, this study aimed to investigate longitudinal alterations in functional neural networks associated with cognitive control in cocaine use disorder (CUD).

METHODS

Secondary analysis was performed on data from 44 individuals who participated in three randomized clinical trials for CUD and completed an fMRI Stroop task both at baseline and post-treatment. Independent component analysis (ICA) was performed to assess changes in functional network engagement and investigate associations with cocaine-use behaviors. Mixed linear models were performed to test for longitudinal effects on network engagement and relationships with baseline patterns of cocaine use (i.e., past-month frequency and lifetime years of use) and periods of abstinence/use between scans (i.e., percent negative urine toxicology and maximum days of contiguous abstinence).

RESULTS

Six functional networks were identified as being related to cognitive control and/or exhibiting changes in engagement following treatment. Results indicated that engagement of amygdala-striatal, middle frontal and right-frontoparietal networks were reduced over time in CUD. Less change in the amygdala-striatal network was associated with greater lifetime years of cocaine use. Additional analyses revealed that negative toxicology results and achievement of continuous abstinence were associated with greater engagement of the right-frontoparietal network.

CONCLUSIONS

Neural systems that underlie cognitive control may change over time in individuals with CUD. A longer history of cocaine-use may hinder changes in network activity, potentially impeding recovery.

Assessing combinatorial effects of HIV infection and former cocaine dependence on cognitive control processes: A functional neuroimaging study of response inhibition

Individuals with a diagnosis of co-morbid HIV infection and cocaine use disorder are at higher risk of poor health outcomes. Active cocaine users, both with and without HIV infection, show clear deficits in response inhibition and other measures of executive function that are instrumental in maintaining drug abstinence, factors that may complicate treatment. Neuroimaging and behavioral evidence indicate normalization of executive control processes in former cocaine users as a function of the duration of drug abstinence, but it is unknown to what extent co-morbid diagnosis of HIV affects this process. To this end, we investigate the combinatorial effects of HIV and cocaine dependence on the neural substrates of cognitive control in cocaine-abstinent individuals with a history of cocaine dependence. Blood-oxygen level dependent signal changes were measured as 86 participants performed a Go/NoGo response inhibition task while undergoing functional magnetic resonance imaging (fMRI). Four groups of participants were selected based on HIV and cocaine-dependence status. Participants affected by both conditions demonstrated the lowest response accuracy of all participant groups. In a region of interest analysis, hyperactivation in the left putamen and midline-cingulate hyperactivation was observed in individuals with both HIV and cocaine dependence relative to individuals with only one condition. Results of a whole-brain analysis indicate response inhibition-related hyperactivation in the bilateral supplementary motor area, bilateral hippocampi, bilateral primary somatosensory areas, right dorsal anterior cingulate, and left insula in the CD+/HIV+ group relative to all other groups. These results indicate complex and interactive alterations in neural activation during response inhibition and highlight the importance of examining the neurocognitive effects of co-morbid conditions.

Electrophysiological indexes for impaired response inhibition and salience attribution in substance (stimulants and depressants) use disorders: A meta-analysis

The impairment of inhibitory control and reward system is the core feature underlying substance use disorder (SUD). Previous studies suggested that it can be regarded as impaired response inhibition and salience attribution syndrome (iRISA). The neural substrates of the two deficit functions were widely investigated in neuroimaging studies, and the impaired prefrontal cortex, limbic-orbitofrontal network, and fronto-insular-parietal network were observed. Previous Event-related potential (ERP) studies were also conducted to explore EEG indexes related to abnormal brain function. In the current meta-analysis, we aimed to explore the consistency of ERP indexes that can reflect the two aberrant processes: P300/slow potential (SP) for salience attribution and Error-related negativity (ERN)/Nogo-N200/Nogo-P300 for inhibitory control and conflict monitoring. Subgroup analyses for drug type and drug use conditions were also conducted. According to the 60 research studies, we found significantly enhanced drug-cue-induced P300 amplitude and attenuated Nogo-N200 amplitude in SUD individuals relative to Healthy control (HC), which supports the dual model. Moreover, the drug-cue-induced P300 displayed time-dependence recovery, suggesting a potential index for treatment evaluation. In conclusion, drug-cue-induced P300 and Nogo-N200 demonstrated high consistency, and the drug-cue-induced P300 can be used to track the changes of functional recovery for SUD. The integration of the two ERP components could be regarded as a potential biomarker for SUD, which may provide a new insight for clinical treatment and investigation.

Neural correlates of inhibitory control in relation to the degree of substance use and substance-related problems - A systematic review and perspective

Inhibitory control deficits are associated with substance use disorders (SUDs) and considered a risk factor. Most studies compare SUD groups with unaffected individuals, although the degree of substance use might relate to inhibitory control deficits and explain group differences. This raises the question to which extent these deficits are specifically linked to substance-related problems. We review studies reporting associations of inhibition-related neural activation (stop signal and go/nogo task) with continuous measures of the degree of substance use and substance-related problems, and with substance-related problems controlling for the degree of substance use. Results suggest negative associations between inhibition-related neural activation and the degree of substance use, but are inconclusive on the association with substance-related problems. Nonetheless, two studies reported significant associations of inhibition-related neural activation with substance-related problems controlling for the degree of substance use. Despite numerous studies showing alterations in inhibition-related neural activation in SUDs, the role of the degree of substance use needs further investigation and studies using dimensional approaches are necessary to uncover specific links to substance-related problems.

Assessing combinatorial effects of HIV infection and former cocaine dependence on cognitive control processes: A high-density electrical mapping study of response inhibition

Stimulant drug use in HIV + patients is associated with poor personal and public health outcomes, including high-risk sexual behavior and faster progression from HIV to AIDS. Inhibitory control--the ability to withhold a thought, feeling, or action--is a central construct involved in the minimization of risk-taking behaviors. Recent neuroimaging and behavioral evidence indicate normalization of inhibitory control processes in former cocaine users as a function of the duration of drug abstinence, but it is unknown whether this recovery trajectory persists in former users with comorbid HIV. Here, we investigate the neural correlates of inhibitory control in 103 human subjects using high-density EEG recording as participants performed a Go/NoGo response inhibition task. Four groups of participants were recruited, varying on HIV and cocaine-dependence status. Electrophysiological responses to successful inhibitions and behavioral task performance were compared among groups. Results indicate persistent behavioral and neurophysiological impairment in HIV+ patients' response inhibition despite current abstinence from cocaine. Analysis of task performance showed that HIV+ abstinent cocaine-dependent participants demonstrate the lowest performance of all groups across all metrics of task accuracy. Planned comparisons of electrophysiological components revealed a main effect of scalp site and an interaction between HIV-status and scalp site on N2 amplitudes during successful inhibitions. Analysis of the P3 time region showed a main effect of scalp site and an interaction between HIV-status and cocaine dependence. These results suggest synergistic alterations in the neurophysiology of response inhibition and indicate that abstinence-related recovery of inhibitory control may be attenuated in patients with HIV.

Updating Emotional Stimuli in Heroin Abstainers' Working Memory: An Event-Related Potential Investigation

BACKGROUND

It is well-documented that heroin users demonstrate aberrant emotion-processing abilities. However, the mechanism by which heroin users process emotional information after it has captured their attention and entered their working memory is unclear.

OBJECTIVES

A modified emotional 2-back task was used to examine whether heroin abstainers demonstrate specific bias patterns in updating emotional stimuli in their working memory.

METHODS

In total, 26 male heroin abstainers and 29 healthy controls were asked to identify whether the current picture was the same as a picture that had appeared two trials earlier, while behavioral data and electroencephalogram data were collected.

RESULTS

Contrary to predictions, the heroin abstainers and healthy controls demonstrated a similar pattern of P300 activity in response to emotional stimuli with no between-group differences in accuracy or reaction time. More specifically, the P300 amplitudes were larger for negative pictures than for positive and neutral pictures. Surprisingly, we found larger P300 amplitudes at Fz electrodes than at Cz and Pz electrodes in the control group, whereas there was no significant difference at midline electrodes in the heroin abstainers.

CONCLUSIONS/IMPORTANCE

Although subtle differences may exist in attentional engagement toward incoming emotional stimulus between two groups, the similar P300 pattern may indicate partial preservation of emotional working memory capacity associated with adaptive emotion regulation in heroin abstainers. These results deepen our understanding of the emotion regulation impairments associated with chronic drug use.

Effects of Psychopathy on Neurocognitive Domains of Impulsivity in Abstinent Opiate and Stimulant Users

Background: Psychopathy and substance use disorders (SUDs) are both characterized by neurocognitive impairments reflecting higher levels of impulsivity such as reward-driven decision-making and deficient inhibitory control. Previous studies suggest that psychopathy may exacerbate decision-making deficits, but it may be unrelated to other neurocognitive impairments among substance dependent individuals (SDIs). The aim of the present study was to examine the role of psychopathy and its interpersonal-affective and impulsive-antisocial dimensions in moderating the relationships between dependence on different classes of drugs and neurocognitive domains of impulsivity. Method: We tested 693 participants (112 heroin mono-dependent individuals, 71 heroin polysubstance dependent individuals, 115 amphetamine mono-dependent individuals, 76 amphetamine polysubstance dependent individuals, and 319 non-substance dependent control individuals). Participants were administered the Psychopathy Checklist: Screening Version (PCL:SV) and seven neurocognitive tasks measuring impulsive choice/decision-making (Iowa Gambling Task; Cambridge Gambling Task; Kirby Delay Discounting Task; Balloon Analog Risk Task), and impulsive action/response inhibition (Go/No-Go Task, Immediate Memory Task, and Stop Signal Task). Results: A series of hierarchical multiple regressions revealed that the interpersonal-affective dimension of psychopathy moderated the association between decision-making, response inhibition and both amphetamine and heroin dependence, albeit differently. For amphetamine users, low levels of interpersonal-affective traits predicted poor decision-making on the Iowa Gambling Task and better response inhibition on the Stop Signal task. In contrast, in heroin users high interpersonal-affective psychopathy traits predicted lower risk taking on the Cambridge Gambling Task and better response inhibition on the Go/No-Go task. The impulsive-antisocial dimension of psychopathy predicted poor response inhibition in both amphetamine and heroin users. Conclusions: Our findings reveal that psychopathy and its dimensions had both common and unique effects on neurocognitive function in heroin and amphetamine dependent individuals. Our results suggest that the specific interactions between psychopathy dimensions and dependence on different classes of drugs may lead to either deficient or superior decision-making and response inhibition performance in SDIs, suggesting that psychopathy may paradoxically play a protective role for some neurocognitive functions in specific subtypes of substance users.

Acute Aerobic Exercise Ameliorates Cravings and Inhibitory Control in Heroin Addicts: Evidence From Event-Related Potentials and Frequency Bands

Objective

Aerobic exercise is considered a potential adjunctive treatment for heroin addicts, but little is known about its mechanisms. Less severe cravings and greater inhibitory control have been associated with reduced substance use. The aim of the current study was to determine the effects, as measured by behavioral and neuroelectric measurements, of acute aerobic exercise on heroin cravings and inhibitory control induced by heroin-related conditions among heroin addicts.

Design

The present study used a randomized controlled design.

Methods

Sixty male heroin addicts who met the DSM-V criteria were recruited from the Isolated Detoxification Center in China and randomly assigned to one of two groups; one group completed a 20-min bout of acute stationary cycle exercise with vigorous intensity (70-80% of maximum heart rate, exercise group), and the other group rested (control group). The self-reported heroin craving levels and inhibitory control outcomes (measured by a heroin-related Go/No-Go task) were assessed pre- and post-exercise.

Results

The heroin craving levels in the exercise group were significantly attenuated during, immediately following, and 40 min after vigorous exercise compared with before exercise; moreover, during exercise, a smaller craving was observed in the exercise group than in the control group. Acute exercise also facilitated inhibition performance in the No-Go task. After exercise, the participants' accuracy, the N2d amplitudes, and the theta two band spectral power during the No-Go conditions were higher in the exercise group than in the control group. Interestingly, significant correlations between the changes in these sensitive measurements and the changes in cravings were observed.

Conclusions

This is the first empirical study to demonstrate that aerobic exercise may be efficacious for reducing heroin cravings and promoting inhibitory control among heroin addicts.

Atypical response inhibition and error processing in 22q11.2 Deletion Syndrome and schizophrenia: Towards neuromarkers of disease progression and risk

22q11.2 deletion syndrome (also known as DiGeorge syndrome or velo-cardio-facial syndrome) is characterized by increased vulnerability to neuropsychiatric symptoms, with approximately 30% of individuals with the deletion going on to develop schizophrenia. Clinically, deficits in executive function have been noted in this population, but the underlying neural processes are not well understood. Using a Go/No-Go response inhibition task in conjunction with high-density electrophysiological recordings (EEG), we sought to investigate the behavioral and neural dynamics of inhibition of a prepotent response (a critical component of executive function) in individuals with 22q11.2DS with and without psychotic symptoms, when compared to individuals with idiopathic schizophrenia and age-matched neurotypical controls. Twenty-eight participants diagnosed with 22q11.2DS (14-35 years old; 14 with at least one psychotic symptom), 15 individuals diagnosed with schizophrenia (18-63 years old) and two neurotypical control groups (one age-matched to the 22q11.2DS sample, the other age-matched to the schizophrenia sample) participated in this study. Analyses focused on the N2 and P3 no-go responses and error-related negativity (Ne) and positivity (Pe). Atypical inhibitory processing was shown behaviorally and by significantly reduced P3, Ne, and Pe responses in 22q11.2DS and schizophrenia. Interestingly, whereas P3 was only reduced in the presence of psychotic symptoms, Ne and Pe were equally reduced in schizophrenia and 22q11.2DS, regardless of the presence of symptoms. We argue that while P3 may be a marker of disease severity, Ne and Pe might be candidate markers of risk.

Anhedonic-like behavior and BDNF dysregulation following a single injection of cocaine during adolescence

We have previously demonstrated that a single exposure to cocaine during adolescence causes several behavioural and neurobiological changes, highlighting the unique vulnerability of this period of life. The purpose of our work was to investigate whether a single exposure to cocaine during brain development is sufficient to shape a negative emotional state in adolescent rats. A single injection of cocaine during adolescence followed by measurement of sucrose consumption, a measure of anhedonia, identifies two separate groups of rats, i.e. anhedonic (AN) and non anhedonic (NON-AN) rats. AN rats show reduced ability to synthesize, traffic and translate the neurotrophin BDNF at synaptic level, reduced activation of hippocampal BDNF signaling, reduced BDNF plasma levels and a steep rise of corticosterone secretion. Conversely, NON-AN rats exhibit reduced trafficking of BDNF while up-regulating hippocampal BDNF synthesis and stabilizing its downstream signaling with no changes of BDNF and corticosterone plasma levels. Adult rats exposed to cocaine showed no signs of anhedonia, an increase of BDNF both in hippocampus and plasma and decreased levels of corticosterone. In conclusion, our findings reveal a complex central and peripheral dysregulation of BDNF-related mechanisms that instead are preserved in NON-AN rats, suggesting that BDNF modulation dictates behavioural vulnerability vs. resiliency to cocaine-induced anhedonia, a profile uniquely restricted to adolescent rats.

Reduced response inhibition after exposure to drug-related cues in male heroin abstainers

RATIONALE

Deficits in response inhibition associated with heroin use could last several months after abstinence in heroin users, and their response inhibition can also be interfered with task-irrelevant drug-related cues. However, it is unclear whether exposure to drug-related cues affects subsequent response inhibition in heroin users following abstinence.

OBJECTIVES

The present study aimed to investigate how drug-related cues with different durations between stimulus presentations, referred to as stimulus onset asynchronies (SOAs), affect subsequent response inhibition in heroin abstainers (HAs) with different length of abstinence.

METHODS

Sixty-seven male HAs performed a modified Go/NoGo task in which a motor response to frequent Go targets and no response to rare NoGo targets were required and a Go or NoGo target was displayed after either a heroin-related or a neutral picture presented for the 200 ms and 600 ms SOAs.

RESULTS

The HAs responded significantly faster to Go targets following the neutral pictures for the 600 ms SOA compared to other conditions. They also made more commission errors following heroin-related pictures compared to neutral pictures regardless of the SOAs. The shorter-term HAs made more commission errors compared to the longer-term HAs following the 200 ms SOA, and it was only a trend when the SOA was 600 ms. Additionally, negative correlations between the duration of current abstinence and commission errors were observed following cues with the 200 ms SOA.

CONCLUSIONS

Impaired response inhibition in HAs can be improved through protracted drug abstinence. However, that effect can be reduced by exposure to drug-related cues, which may increase the risk of relapse.

Mobile Brain/Body Imaging of cognitive-motor impairment in multiple sclerosis: Deriving EEG-based neuro-markers during a dual-task walking study

OBJECTIVE

Individuals with a diagnosis of multiple sclerosis (MS) often present with cognitive and motor deficits, and thus the ability to perform tasks that rely on both domains may be particularly impaired. Yet, dual-task walking studies yield mixed results. Individual variance in the ability to cope with brain insult and mobilize additional brain resources may contribute to mixed findings.

METHODS

To test this hypothesis, we acquired event-related potentials (ERP) in individuals with MS and healthy controls (HCs) performing a Go/NoGo task while sitting (i.e., single task) or walking (i.e., dual-task) and looked at the relationship between task related modulation of the brain response and performance.

RESULTS

On the Go/NoGo task the MS group showed dual-task costs when walking, whereas HCs showed a dual-task benefit. Further, whereas the HC group showed modulation of the brain response as a function of task load, this was not the case in the MS group. Analysis for the pooled sample revealed a positive correlation between load-related ERP effects and dual-task performance.

CONCLUSIONS

These data suggest a neurophysiological marker of cognitive-motor dysfunction in MS.

SIGNIFICANCE

Understanding neural processes underlying dual-task walking will help identify objective brain measurements of real-world issues and may improve assessment of MS.

Forging Neuroimaging Targets for Recovery in Opioid Use Disorder

The United States is in the midst of an opioid epidemic and lacks a range of successful interventions to reduce this public health burden. Many individuals with opioid use disorder (OUD) consume drugs to relieve physical and/or emotional pain, a pattern that may increasingly result in death. The field of addiction research lacks a comprehensive understanding of physiological and neural mechanisms instantiating this cycle of Negative Reinforcement in OUD, resulting in limited interventions that successfully promote abstinence and recovery. Given the urgency of the opioid crisis, the present review highlights faulty brain circuitry and processes associated with OUD within the context of the Three-Stage Model of Addiction (1). This model underscores Negative Reinforcement processes as crucial to the maintenance and exacerbation of chronic substance use together with Binge/Intoxication and Preoccupation/Anticipation processes. This review focuses on cross-sectional as well as longitudinal studies of relapse and treatment outcome that employ magnetic resonance imaging (MRI), functional near-infrared spectroscopy (fNIRs), brain stimulation methods, and/or electroencephalography (EEG) explored in frequency and time domains (the latter measured by event-related potentials, or ERPs). We discuss strengths and limitations of this neuroimaging work with respect to study design and individual differences that may influence interpretation of findings (e.g., opioid use chronicity/recency, comorbid symptoms, and biological sex). Lastly, we translate gaps in the OUD literature, particularly with respect to Negative Reinforcement processes, into future research directions involving operant and classical conditioning involving aversion/stress. Overall, opioid-related stimuli may lessen their hold on frontocingulate mechanisms implicated in Preoccupation/Anticipation as a function of prolonged abstinence and that degree of frontocingulate impairment may predict treatment outcome. In addition, longitudinal studies suggest that brain stimulation/drug treatments and prolonged abstinence can change brain responses during Negative Reinforcement and Preoccupation/Anticipation to reduce salience of drug cues, which may attenuate further craving and relapse. Incorporating this neuroscience-derived knowledge with the Three-Stage Model of Addiction may offer a useful plan for delineating specific neurobiological targets for OUD treatment.

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.

Competing Motivations: Proactive Response Inhibition Toward Addiction-Related Stimuli in Quitting-Motivated Individuals

We examined whether addiction-related cues impact proactive inhibition (the restraint of actions in preparation for stopping) in individuals who are motivated to quit gambling or cannabis use. In Study 1, treatment-seeking individuals with cannabis use disorder and matched controls performed a stop-signal task that required them to inhibit categorizing cannabis or neutral pictures, and within varying levels of stop-signal probability. In Study 2, two groups of individuals, who applied to a voluntary self-exclusion program toward gambling, performed the stop-task following relaxation or gambling craving induction, with results compared to non-gamblers. Study 1 showed that despite being less efficient in proactive inhibition, individuals with cannabis use disorder exhibited heightened proactive inhibition toward cannabis cues. In Study 2, proactive inhibition toward gambling cues was heightened in gamblers after craving, but the degree of proactive adjustment decreased as a function of induced changes in gambling-related motivation. Present findings demonstrate that exposure to addiction-related cues can modulate proactive inhibition in individuals who are motivated to restrict their addictive behaviors.

Presumed structural and functional neural recovery after long-term abstinence from cocaine in male military veterans

Cumulative evidence suggests that cocaine use could alter the structure and function of different brain systems. However, the extent to which the altered brain structure and function possibly recover over time after cocaine abstinence remains less clear. The present study examines 39 male military veterans with different stages of cocaine addiction and long-term abstinence (from 1 year up to 30 years) and evaluates plausible changes in brain structure and function of specific brain regions that sub-serve addictions. These include the striatum that is involved in cocaine reward; the lateral prefrontal cortex (especially the dorsolateral PFC) that plays a major role in inhibitory control; the insula, which has been implicated in craving; and the medial orbitofrontal (OFC) and ventromedial prefrontal cortex (VMPFC) shown to play key roles in foresight and decision-making. The results suggest that there are differences in both brain structure (gray matter volume, GMV) and function between cocaine USERS and CONTROLS, with USERS showing plausible relative strengthening in neural systems for processing reward and craving, and relative weakening in neural systems involved in inhibitory control and decision-making. Examination of possible neural changes after abstinence suggests that presumed recovery occurs mostly in neural systems related to reward, craving, and inhibitory control, but to a lesser extent in neural systems related to decision-making. Given the limitations of the data in terms of a small sample size, as well as the lack of certainty about occasional use in the abstinent group, these results may be considered as preliminary. However, they are compelling in that they suggest that male military veterans cocaine USERS are indefinitely at a higher risk compared to CONTROLS for making lapses in judgment and decision-making leading to possible relapse, if reward salience and craving become more intense. Understanding the neurobiology of long-term cocaine abstinence in vulnerable populations and beyond could help devising better therapeutic strategies that prevent relapse.

Disrupted coupling of large-scale networks is associated with relapse behaviour in heroin-dependent men

BACKGROUND

It is unknown whether impaired coupling among 3 core large-scale brain networks (salience [SN], default mode [DMN] and executive control networks [ECN]) is associated with relapse behaviour in treated heroin-dependent patients.

METHODS

We conducted a prospective resting-state functional MRI study comparing the functional connectivity strength among healthy controls and heroin-dependent men who had either relapsed or were in early remission. Men were considered to be either relapsed or in early remission based on urine drug screens during a 3-month follow-up period. We also examined how the coupling of large-scale networks correlated with relapse behaviour among heroin-dependent men.

RESULTS

We included 20 controls and 50 heroin-dependent men (26 relapsed and 24 early remission) in our analyses. The relapsed men showed greater connectivity than the early remission and control groups between the dorsal anterior cingulate cortex (key node of the SN) and the dorsomedial prefrontal cortex (included in the DMN). The relapsed men and controls showed lower connectivity than the early remission group between the left dorsolateral prefrontal cortex (key node of the left ECN) and the dorsomedial prefrontal cortex. The percentage of positive urine drug screens positively correlated with the coupling between the dorsal anterior cingulate cortex and dorsomedial prefrontal cortex, but negatively correlated with the coupling between the left dorsolateral prefrontal cortex and dorsomedial prefrontal cortex.

LIMITATIONS

We examined deficits in only 3 core networks leading to relapse behaviour. Other networks may also contribute to relapse.

CONCLUSION

Greater coupling between the SN and DMN and lower coupling between the left ECN and DMN is associated with relapse behaviour. These findings may shed light on the development of new treatments for heroin addiction.

Reduction in N2 amplitude in response to deviant drug-related stimuli during a two-choice oddball task in long-term heroin abstainers

RATIONALE

Chronic heroin use can cause deficits in response inhibition, leading to a loss of control over drug use, particularly in the context of drug-related cues. Unfortunately, heightened incentive salience and motivational bias in response to drug-related cues may exist following abstinence from heroin use.

OBJECTIVES

The present study aimed to examine the effect of drug-related cues on response inhibition in long-term heroin abstainers.

METHODS

Sixteen long-term (8-24 months) male heroin abstainers and 16 male healthy controls completed a modified two-choice oddball paradigm, in which a neutral "chair" picture served as frequent standard stimuli; the neutral and drug-related pictures served as infrequent deviant stimuli of different conditions respectively. Event-related potentials were compared across groups and conditions.

RESULTS

Our results showed that heroin abstainers exhibited smaller N2d amplitude (deviant minus standard) in the drug cue condition compared to the neutral condition, due to smaller drug-cue deviant-N2 amplitude compared to neutral deviant-N2. Moreover, heroin abstainers had smaller N2d amplitude compared with the healthy controls in the drug cue condition, due to the heroin abstainers having reduced deviant-N2 amplitude compared to standard-N2 in the drug cue condition, which reversed in the healthy controls.

CONCLUSIONS

Our findings suggested that heroin addicts still show response inhibition deficits specifically for drug-related cues after longer-term abstinence. The inhibition-related N2 modulation for drug-related could be used as a novel electrophysiological index with clinical implications for assessing the risk of relapse and treatment outcome for heroin users.

Event-Related Potentials as Biomarkers of Behavior Change Mechanisms in Substance Use Disorder Treatment

Substance use disorders (SUDs) are one of the most prevalent psychiatric conditions and represent a significant public health concern. Substantial research has identified key processes related to reinforcement and cognition for the development and maintenance of SUDs, and these processes represent viable treatment targets for psychosocial and pharmacological interventions. Research on SUD treatments has suggested that most approaches are comparable in effectiveness. As a result, recent work has focused on delineating the underlying mechanisms of behavior change that drive SUD treatment outcome. Given the rapid fluctuations associated with the key neurocognitive processes associated with SUDs, high-temporal-resolution measures of human brain processing, namely event-related potentials (ERPs), are uniquely suited to expand our understanding of the underlying neural mechanisms of change during and after SUD treatment. The value of ERPs in the context of SUD treatment are discussed along with work demonstrating the predictive validity of ERPs as biomarkers of SUD treatment response. Example associations between multiple ERP components and psychosocial and/or pharmacological treatment outcome include the P3a and P3b (in response to neutral and substance-related cues), the attention-related negativities (e.g., N170, N200), the late positive potential, and the error-related negativity. Also addressed are limitations of the biomarker approach to underscore the need for research programs evaluating mechanisms of change. Finally, we emphasize the advantages of ERPs as indices of behavior change in SUD treatment and outline issues relevant for future directions in this context.

Assessment of inhibitory control in crack and/or cocaine users: a systematic review

OBJECTIVE

Impairments involving inhibitory control have been considered central deficits in drug users, but it appears that dysfunctions may be specific to users' drug of choice. This article aims to review recent findings on inhibitory control impairment in samples of crack and/or cocaine users.

METHODS

Searches were conducted on the PubMed, PsycINFO, and Web of Knowledge databases in two stages according to eligibility criteria. Initially, databases were searched and the titles and abstracts of results were analyzed and then selected articles were read in full. Inclusion criteria were: empirical articles written in English, Portuguese, or Spanish, published in the last ten years and involving the assessment of inhibitory control in crack and/or cocaine users.

RESULTS

The database searches returned a total of 3,796 titles, 56 of them were selected initially and then a further 20 were excluded. Thirty-six articles were included in this review. In 90% of the studies reviewed the presence of inhibitory control deficits was reported, verified by impaired cognitive processing and response monitoring, as well as high levels of impulsiveness, regardless of the pattern of crack and/or cocaine consumption (recreational or chronic). Former users showed high levels of impulsiveness even after long periods of abstinence.

CONCLUSIONS

Crack and/or cocaine users may have inhibitory control deficits, irrespective of different consumption patterns. High levels of impulsiveness can represent a factor of vulnerability to drug use and relapse.

Neural correlates of proactive and reactive motor response inhibition of gambling stimuli in frequent gamblers

We used functional magnetic resonance imaging to examine whether motivational-salient cues could exert a differential impact on proactive (the restrain of actions in preparation for stopping) and reactive (outright stopping) inhibition. Fourteen high-frequency poker players, and 14 matched non-gambler controls, performed a modified version of the stop-signal paradigm, which required participants to inhibit categorization of poker or neutral pictures. The probability that a stop-signal occurs (0%, 17%, 25%, 33%) was manipulated across blocks of trials, as indicated by the color of the computer screen. Behavioral analyses revealed that poker players were faster than controls in categorizing pictures across all levels of proactive motor response inhibition (go trials). Brain imaging analyses highlighted higher dorsal anterior cingulate cortex activation in poker players, as compared to controls, during reactive inhibition. These findings suggest that, due to their faster rates of stimulus discrimination, poker players might have recruited more cognitive resources than controls when required to stop their response (reactive inhibition). Nevertheless, no main effect of stimulus type was found, on either proactive or reactive inhibition. Additional studies are, therefore, needed in order to confirm that investigating the dynamics between reactive and proactive inhibition offers a discriminative analysis of inhibitory control toward motivational-salient cues.

Resting-State Neuroimaging and Neuropsychological Findings in Opioid Use Disorder during Abstinence: A Review

Dependence to opiates, including illicit heroin and prescription pain killers, and treatment of the opioid use disorder (OUD) have been longstanding problems over the world. Despite intense efforts to scientific investigation and public health care, treatment outcomes have not significantly improved for the past 50 years. One reason behind the continuing use of heroin worldwide despite such efforts is its highly addictive nature. Brain imaging studies over the past two decades have made significant contribution to the understanding of the addictive properties as to be due in part to biological processes, specifically those in the brain structure and function. Moreover, traditional clinical neuropsychology studies also contribute to the account in part for the treatment-refractory nature of the drug abuse. However, there is a gap between those studies, and the rates of relapse are still high. Thus, a multidisciplinary approach is needed to understand the fundamental neural mechanism of OUD. How does the brain of an OUD patient functionally and cognitively differ from others? This brief review is to compare and contrast the current literature on non-invasive resting state neuroimaging and clinical neuropsychological studies with the focus on the abstinence stage in OUD. The results show as follow:

Brain connectivity strength in the reward system, dysregulation of circuits associated with emotion and stress, enhanced beta and alpha power activity, and high impulsivity are induced by OUD.

Some recovery signs in cognition are demonstrated in OUD subjects after prolonged abstinence, but not in the subjects undergoing methadone treatment.

Normalization in the composition of brain oscillations especially in the temporal region is induced and restored by methadone treatment in roughly 6 months in mean duration for OUDs having a mean opioid-use history of 10 years.

We hope that the review provides valuable implications for clinical research and practice and paves a new insight into the future path to the identification of potential biomarkers and clinical outcome predictors in OUD in the domains of brain regions, functions, and behaviors.

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.

Alexithymia and Addiction: A Review and Preliminary Data Suggesting Neurobiological Links to Reward/Loss Processing

Alexithymia, characterized by impairments in emotional awareness, is common among individuals with substance use disorders. Research on alexithymia suggests that it is a trait that may contribute to substance dependence. This paper will review alexithymia as it relates to substance use and substance use disorders, considering its potential role in the maintenance and treatment of these disorders. We will then describe how neural correlates associated with alexithymia may shed light on how alexithymia relates to addiction. Finally, we present preliminary fMRI data that examines how alexithymia may relate to the neurobiological correlates of reward/loss processing in individuals with cocaine dependence. While preliminary, these findings suggest a role of alexithymia in reward anticipation in cocaine-dependent individuals.

Regulating task-monitoring systems in response to variable reward contingencies and outcomes in cocaine addicts

BACKGROUND

We investigated anticipatory and consummatory reward processing in cocaine addiction. In addition, we set out to assess whether task-monitoring systems were appropriately recalibrated in light of variable reward schedules. We also examined neural measures of task-monitoring and reward processing as a function of hedonic tone, since anhedonia is a vulnerability marker for addiction that is obviously germane in the context of reward processing.

METHOD

High-density event-related potentials were recorded while participants performed a speeded response task that systematically varied anticipated probabilities of reward receipt. The paradigm dissociated feedback regarding task success (or failure) from feedback regarding the value of reward (or loss), so that task-monitoring and reward processing could be examined in partial isolation. Twenty-three active cocaine abusers and 23 age-matched healthy controls participated.

RESULTS

Cocaine abusers showed amplified anticipatory responses to reward predictive cues, but crucially, these responses were not as strongly modulated by reward probability as in controls. Cocaine users also showed blunted responses to feedback about task success or failure and did not use this information to update predictions about reward. In turn, they showed clearly blunted responses to reward feedback. In controls and users, measures of anhedonia were associated with reward motivation. In cocaine users, anhedonia was also associated with diminished monitoring and reward feedback responses.

CONCLUSION

Findings imply that reward anticipation and monitoring deficiencies in addiction are associated with increased responsiveness to reward cues but impaired ability to predict reward in light of task contingencies, compounded by deficits in responding to actual reward outcomes.

Impulsivity in abstinent alcohol and polydrug dependence: a multidimensional approach

RATIONALE

Dependence on drugs and alcohol is associated with impaired impulse control, but deficits are rarely compared across individuals dependent on different substances using several measures within a single study.

OBJECTIVES

We investigated impulsivity in abstinent substance-dependent individuals (AbD) using three complementary techniques: self-report, neuropsychological and neuroimaging. We hypothesised that AbDs would show increased impulsivity across modalities, and that this would depend on length of abstinence.

METHODS

Data were collected from the ICCAM study: 57 control and 86 AbDs, comprising a group with a history of dependence on alcohol only (n = 27) and a group with history of dependence on multiple substances ("polydrug", n = 59). All participants completed self-report measures of impulsivity: Barratt Impulsiveness Scale, UPPS Impulsive Behaviour Scale, Behaviour Inhibition/Activation System and Obsessive-Compulsive Inventory. They also performed three behavioural tasks: Stop Signal, Intra-Extra Dimensional Set-Shift and Kirby Delay Discounting; and completed a Go/NoGo task during fMRI.

RESULTS

AbDs scored significantly higher than controls on self-report measures, but alcohol and polydrug dependent groups did not differ significantly from each other. Polydrug participants had significantly higher discounting scores than both controls and alcohol participants. There were no group differences on the other behavioural measures or on the fMRI measure.

CONCLUSIONS

The results suggest that the current set of self-report measures of impulsivity is more sensitive in abstinent individuals than the behavioural or fMRI measures of neuronal activity. This highlights the importance of developing behavioural measures to assess different, more relevant, aspects of impulsivity alongside corresponding cognitive challenges for fMRI.

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.

Electrophysiology for addiction medicine: From methodology to conceptualization of reward deficits

In the past decade, electroencephalographic research on addiction has employed passive viewing, oddball, inhibition, prediction, gambling, and reversal learning tasks to study how substance users neurally prioritize drug-related rewards at the expense of nondrug rewards. On the whole, findings across substances (alcohol, cannabis, cocaine, nicotine, opiates, gambling, and gaming) demonstrate impairments in the differentiation of monetary incentives and the inhibition of prepotent responses. Furthermore, exaggerated resources devoted to drug cues and attenuated processing of other types of pleasant emotional stimuli predict greater probability of future drug use. However, drug use recency, frequency, sensitivity, and insight all appear to be moderators of these effects. We argue that more longitudinal studies are warranted to determine the time course of reward processing as a function of development and chronicity.

Aberrant response inhibition and task switching in psychopathic individuals

Deficits in cognitive control have been considered a core dysfunction of psychopathy, responsible for disrupted self-control. We investigated cognitive control impairments, including difficulties with task switching, failure of response inhibition, and inability to adjust speed of responding. Participants included 16 subjects with psychopathic traits (Ps), and 22 healthy controls (HCs). We recorded behavioral responses during a Task Switching paradigm, a probe of flexible behavioral adaptation to changing contexts; and a Go/NoGo Task, which assesses response inhibition and indexes behavioral impulsivity. During task switching, Ps evidenced impairments shifting set when conflicting (incongruent) information was presented, but performed as well as HCs in the absence of such conflict. In addition, when they encountered these difficulties, they failed to adjust their speed of responding. Ps presented also with deficits in response inhibition, with many commission errors on the Go/NoGo Task. This study identified impairments in response inhibition and in set shifting in psychopathic individuals. When shifting set, they evidenced difficulties refocusing on a new task when it was incongruent with the previous task. These deficits interfere with regulation of ongoing behavior and disrupt self-regulation. Our findings suggest abnormal neural processing during suppression of inappropriate responses in psychopathic individuals.

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.

Effects of prior cocaine self-administration on cognitive performance in female cynomolgus monkeys

Cocaine use has been associated with cognitive impairments that may contribute to poor treatment outcomes. However, the degree to which these deficits extend into periods of abstinence has not been completely elucidated. This study tested whether prior experience self-administering cocaine affected acquisition of two cognitive tasks in 16 adult female cynomolgus monkeys. Seven monkeys had previously self-administered cocaine but had not had access to cocaine for 2 months at the start of this study. After monkeys were trained to respond on a touchscreen, associative learning and behavioral flexibility were assessed using a stimulus discrimination (SD) and reversal (SDR) task from the CANTAB battery. Performance on this task was monitored over the subsequent 3 months. Additionally, working memory was assessed with a delayed match-to-sample (DMS) task. Cocaine-naïve monkeys required fewer total trials and made fewer errors and omissions before acquiring the SD and SDR tasks compared with monkeys who had previously self-administered cocaine; two monkeys in the latter group did not acquire the task. However, this cognitive impairment dissipated over several months of exposure to the task. The number of sessions for touch training and delays required to establish a performance-based curve on the DMS task did not differ between groups. Results suggest that cocaine exposure can impair the ability to learn a novel task requiring behavioral inhibition and flexibility, even after an extended period of abstinence. However, this deficit did not extend to maintenance of the task or to acquisition of a working memory task.

The aging brain shows less flexible reallocation of cognitive resources during dual-task walking: A mobile brain/body imaging (MoBI) study

Aging is associated with reduced abilities to selectively allocate attention across multiple domains. This may be particularly problematic during everyday multitasking situations when cognitively demanding tasks are performed while walking. Due to previous limitations in neuroimaging technology, much remains unknown about the cortical mechanisms underlying resource allocation during locomotion. Here, we utilized an EEG-based mobile brain/body imaging (MoBI) technique that integrates high-density event-related potential (ERP) recordings with simultaneously acquired foot-force sensor data to monitor gait patterns and brain activity concurrently. To assess effects of motor load on cognition we evaluated young (N=17; mean age=27.2) and older adults (N=16; mean age=63.9) and compared behavioral and ERP measures associated with performing a Go/No-Go response inhibition task as participants sat stationary or walked on a treadmill. Stride time and variability were also measured during task performance and compared to stride parameters obtained without task performance, thereby assessing effects of cognitive load on gait. Results showed that older, but not young adults' accuracy dropped significantly when performing the inhibitory task while walking. Young adults revealed ERP modulations at relatively early (N2 amplitude reduction) and later (earlier P3 latency) stages within the processing stream as motor load increased while walking. In contrast, older adults' ERP modulations were limited to later processing stages (increased P3 amplitude) of the inhibitory network. The relative delay and attenuation of ERP modulations accompanied by behavioral costs in older participants might indicate an age-associated loss in flexible resource allocation across multiple tasks. Better understanding of the neural underpinnings of these age-related changes may lead to improved strategies to reduce fall risk and enhance mobility in aging.