Transition to substance use disorders: impulsivity for reward and learning from reward

The effect of reward learning on inhibitory control in internet gaming disorder: Evidence from behavioral and ERP

Reward dysregulation and deficits in inhibitory control significantly contribute to the development of internet gaming disorder (IGD). While prior research demonstrates that reward history influences individuals' inhibitory control, it remains unclear whether this effect extends to individuals with IGD. The primary aim of this study was to investigate whether individuals with IGD exhibit impairments in reward learning and whether prior reward learning influences their inhibitory control, using both behavioral and event-related potential (ERP) measures. This study first employed a probability selection task to examine potential impairments in reward learning among individuals with IGD. Next, a stop-signal task incorporating reward- and punishment-associated stimuli was used to further investigate the behavioral and electroencephalographic effects of prior reward learning on subsequent inhibitory control. Results revealed that during the reward-learning phase, the IGD group exhibited significantly longer response times than the control group in both the learning and transfer phases. Additionally, the feedback-related negativity amplitude in the IGD group was significantly lower than that in the control group. Conversely, the P3 wave amplitude induced by positive and negative feedback in the IGD group were significantly higher than in the control group. In the inhibitory control phase following reward learning, the Nogo-P3 wave amplitude in response to reward cues was significantly greater in the IGD group than in the control group. Moreover, within the IGD group, the Nogo-P3 wave amplitude evoked by reward cues was significantly larger than the amplitude evoked by loss cues. These findings suggest that reward learning is impaired in individuals with IGD and that stimuli with a prior reward history may compromise inhibitory control, potentially serving as a critical factor in addiction development in this population.

Higher alcohol use is associated with subsequent increased risk seeking toward gains: A longitudinal cohort study in young men

BACKGROUND

A higher propensity for impulsive and risky choices has often been reported in individuals with addiction, such as alcohol use disorder (AUD). Although domains of choice impulsivity, for example, temporal discounting, have been identified to predispose the development of hazardous alcohol use, research on altered decision making as a consequence of drinking is scarce. These may be particularly pronounced during periods of progressive brain development, such as young adulthood.

METHODS

This 3-year prospective study investigated the effects of alcohol use on changes in four decision-making domains in 18-year-old men (N = 130). We assessed temporal changes in discounting of delayed rewards, risk aversion for gains, risk seeking for losses, and loss aversion. By correlating three-year cumulative alcohol consumption and total binge drinking frequency with respective change scores, we aimed to explore the influences of drinking on altered development in different impulsive choice tendencies.

RESULTS

From ages 18 to 21, choice impulsivity in our moderately drinking cohort decreased significantly with respect to temporal discounting and risk aversion for gains, while risk seeking for losses and loss aversion did not change significantly. Importantly, higher cumulative alcohol intake and more binge drinking occasions over 3 years were associated with slower increases in risk aversion for gains, that is, the general trend for lower choice impulsivity was diminished. Such relationships were not found for temporal discounting, risk seeking for losses, or loss aversion.

CONCLUSIONS

Alcohol consumption in young adulthood is linked to stunted development of risk aversion for gains. Given that risk seeking for gains was previously identified as a risk factor for increasing alcohol intake, this relationship may reinforce a spiral of escalating consumption over time. The absence of similar findings in other decision-making domains suggests that drinking behavior and modifying factors interact differently across domains, rather than universally enhancing impulsive choice behavior.

Oxytocin differentially modulates reward system responses to social and non-social incentives

RATIONALE

Oxytocin has been shown to modulate behavior related to processing of monetary incentives and to regulate social and reproductive behavior, yet little is known about how oxytocin differentially influences neural responses to social and non-social incentives.

OBJECTIVES

We aimed to evaluate the effects of oxytocin administration on behavioral and neural responses to social and monetary incentives.

METHODS

Twenty-eight healthy adults (age 18-45 years) performed both monetary and social incentive tasks during blood oxygenation level dependent (BOLD) imaging. Intranasal oxytocin or placebo was administered before each scan using a double blind, randomized, cross-over design. Task performance and self-reported motivation and mood states were collected. Time-series analysis was conducted to assess the influence of oxytocin on the hemodynamic response in the ventral tegmental area and substantia nigra (VTA/SN) and nucleus accumbens (NAc).

RESULTS

Oxytocin demonstrated a multifaceted effect on VTA/SN and NAc when processing reward incentives, with it increasing BOLD response in VTA/SN and decreasing BOLD response in NAc during social incentive anticipation. A reversal of this was shown with decreased BOLD responses in the VTA/SN and increased BOLD response in the NAc during monetary incentive anticipation.

CONCLUSIONS

Our findings suggest a more nuanced purpose of oxytocin when evaluating reward incentive decision making. It is possible that while oxytocin does increase salience to rewards, that it is more important for cognitive control when determining short-term versus long-term benefits in rewards. Future studies should more closely examine the relationship between oxytocin and delay discounting.

Impulsivity facets and substance use involvement: insights from genomic structural equation modeling

BACKGROUND

Impulsivity is a multidimensional trait associated with substance use disorders (SUDs), but the relationship between distinct impulsivity facets and stages of substance use involvement remains unclear.

METHODS

We used genomic structural equation modeling and genome-wide association studies (N = 79,729-903,147) to examine the latent genetic architecture of nine impulsivity traits and seven substance use (SU) and SUD traits.

RESULTS

We found that the SU and SUD factors were strongly genetically inter-correlated (rG=0.77) but their associations with impulsivity facets differed. Lack of premeditation, negative and positive urgency were equally positively genetically correlated with both the SU (rG=.0.30-0.50) and SUD (rG=0.38-0.46) factors; sensation seeking was more strongly genetically correlated with the SU factor (rG=0.27 versus rG=0.10); delay discounting was more strongly genetically correlated with the SUD factor (rG=0.31 versus rG=0.21); and lack of perseverance was only weakly genetically correlated with the SU factor (rG=0.10). After controlling for the genetic correlation between SU/SUD, we found that lack of premeditation was independently genetically associated with both the SU (β=0.42) and SUD factors (β=0.21); sensation seeking and positive urgency were independently genetically associated with the SU factor (β=0.48, β=0.33, respectively); and negative urgency and delay discounting were independently genetically associated with the SUD factor (β=0.33, β=0.36, respectively).

CONCLUSIONS

Our findings show that specific impulsivity facets confer risk for distinct stages of substance use involvement, with potential implications for SUDs prevention and treatment.

Applications of Behavioral Economics and Neuroeconomics in Mental Health

Objective: The integration of behavioral economics and neuroeconomics into mental health offers innovative perspectives on understanding and addressing psychological disorders. This overview aims to synthesize current knowledge and explore the implications of these interdisciplinary approaches in the context of mental health. Method : In this narrative review, we summarized the current evidence regarding the applications of behavioral economics and neuroeconomics approaches in the field of mental health. Results: Behavioral economics and neuroeconomics provide valuable insights into the cognitive and emotional processes underlying mental health disorders, such as irrational decision-making, impulsivity, and self-control issues. Concepts such as loss aversion, temporal discounting, and framing effects inform the development of innovative interventions and policy initiatives. Behavioral economic interventions, including nudges, incentives, and commitment devices, show promise in promoting treatment adherence, reducing risky behaviors, and enhancing mental well-being. Neuroeconomics contributes by identifying neural markers predictive of treatment response and relapse risk, paving the way for personalized treatment approaches. Conclusion: The integration of behavioral economics and neuroeconomics into mental health research and practice holds significant potential for improving the understanding of psychological disorders and developing more effective, personalized interventions. Further research is needed to elucidate the mechanisms of action, optimize intervention strategies, and address ethical considerations associated with these approaches in mental health settings.

Problematic Substance Use in Depressed Youth: Associations with Suicidal Ideation and Suicide Attempt History

Objective: Depressed youth exhibit higher rates of suicidal behavior compared to healthy controls, with problematic substance use potentially intensifying this risk. Accordingly, this study aimed to examine the impact of comorbid depression and problematic substance use and its association with suicidality in youth populations. Methods: We examined differences in clinical features and demographic characteristics between 797 depressed youth ages 8-20 years with and without problematic substance use from the Texas Youth Depression and Suicide Research Network (TX-YDSRN). Additionally, to assess whether the effect of depression severity on suicidal ideation and suicide attempt history were influenced by problematic substance use, multivariable linear and logistic regression analyses were conducted. Results: Depressed youth with problematic substance use (versus those without) were significantly older, more likely to exhibit suicidal ideation and a history of suicide attempts and had significantly worse school functioning after controlling for age, sex, race, and ethnicity. Problematic substance use did not moderate the effect of depression severity on suicidal ideation or suicide attempt history. Conclusions: Findings shed light on the impact of problematic substance use in depressed youth which may allow for earlier and more specified intervention efforts aimed at identifying and targeting youth suicidality.

Factors associated with cognitive flexibility in people with opioid-use disorder: a pilot study

The ability to adapt to changing circumstances has strong survival value. Individuals with substance use disorders tend to get "stuck" over-responding to drug-reward signals and pursuing drugs despite negative consequences. A lack of flexibility may be tied to impairments in neurocognition, including learning, memory, and executive function. However, results are often mixed, potentially due to heterogeneity in factors such as mental health, personality traits, or prior adversity. This study aimed to identify which factors influence neurocognitive variations within the opioid use disorder (OUD) population. Based on prior literature, we hypothesized that individuals with OUD would show deficits (vs. controls) in one or more neurocognitive domains, and that these cognitive difficulties might be greater in individuals with other known contributors to impaired cognition. This pilot project included 32 individuals receiving medication for OUD and 15 non-substance using controls (NSC). Questionnaires assessed addiction and relapse risk factors, such as impulsiveness, social function, depressive symptoms, and childhood adversity. Neurocognitive performance was measured via the Penn Computerized Neurocognitive Battery (P-CNB), including tasks that probe attention, working memory, episodic memory, cognitive flexibility, and complex cognition, and was compared between the OUD and NSC groups. OUD participants (vs. NSCs) exhibited significantly lower performance on the conditional exclusion task (CET) (Accuracy: 1.11 vs. 2.38, p < 0.001) and the n-Back task (NBT) (F1 Scores: 83% vs. 95%, p < 0.001). Impulsiveness, social function, and depressive symptoms were highly inter-related; however, only higher impulsiveness (r = -.48, p = 0.006) and more social impairment (r = -.47, p = 0.007) significantly correlated with decreased CET (but not n-Back) performance. This pilot study suggests that working memory and cognitive flexibility are impaired in people with OUD and that impulsiveness and social function are key factors in cognitive flexibility impairments in people with OUD. These results may offer insights for larger-scale investigations and potential interventions to reduce relapse risk.

The Impact of Dexamphetamine Treatment for Obesity on Executive Function: A Double-Blind Randomised Controlled Pilot Study

BACKGROUND

Amphetamines increase dopamine levels in mid-brain regions which, in turn, impact top-down executive function. Repeated exposure is linked to substance use disorders. Nonetheless, amphetamines are used to manage attention-deficit/hyperactivity disorder (ADHD) and eating-related disorders. In ADHD, amphetamines upregulate a system characterised by low dopaminergic tone, assisting to improve executive function. A similar process might be at play with eating disorders; however, the effect of amphetamine treatment on executive function in this case has not been thoroughly considered.

METHODS

Participants (N = 52, Mage = 47.06, SD = 12.29) with a body mass index of 25-60 were randomised to treatment (6-week dexamphetamine titration) or control (placebo) groups. They completed an executive function measure-Barkley Deficits in Executive Functioning Scale (BDEFS-SF)-and response inhibition task-Stop-Signal Task (SST)-at Baseline, throughout titration, at Maintenance, and at Follow-up. Mixed effects models examined whether BDEFS-SF score or the SST variable, stop-signal reaction time (SSRT), changed across sessions as a function of treatment.

RESULTS

There was no effect of group (p = 0.440), but an effect of session (p = 0.024) on BDEFS-SF, with scores at Time 2 (p = 0.011, 95% CI [0.47, 3.49]) and Maintenance (p = 0.022, 95% CI [-4.89, -0.39]), respectively, higher and lower than other timepoints. There was no group by session interaction (p = 0.659). R2 (conditional) = 0.74; ICC = 0.73. There was an effect of group (p = 0.039) and session (p < 0.001) on SSRT, but no interaction (p = 0.707). Baseline SSRT was significantly longer than the mean of all subsequent timepoints (p < 0.001, 95% CI [16.29, 33.84]). R2 (conditional) = 0.47; ICC = 0.39.

CONCLUSIONS

There was no discernible impact of amphetamine treatment for obesity on executive function. Our results suggest some variation related to sample size and/or practice effects. Thus, while treatment appears unlikely to render individuals susceptible to substance use disorders, parallels with ADHD might be overstated.

Adolescent morphine exposure induced long-term cognitive impairment and prefrontal neurostructural abnormality in adulthood in male mice

Opioids abuse in adolescence is becoming a pressing public health issue. While evidence suggests that exposure to opioids during adolescence leads to lasting alterations in brain development, the long-term cognitive implications in adulthood remain uncertain. We developed a male mouse model of adolescent morphine exposure and used the 5-choice serial reaction time task (5-CSRTT), along with the open field, novel object recognition, Y maze and Barnes maze tests, to assess changes in cognitive behavior. We found that exposure to morphine during adolescence led to deficits in multidimensional cognitive functions in mice, including attention, information processing speed, and behavior inhibition. Notable, these impairments persisted into adulthood. Furthermore, the morphine-exposed mice exhibited decreased learning efficiency and spatial memory. Adolescent morphine exposure also induced significant and persistent morphological changes and synaptic abnormalities in medial prefrontal cortex (mPFC) neurons, which may be responsible for cognitive impairments in adulthood. Together, our study suggests that opioid exposure during adolescence profoundly affects cognitive development and emphasizes that opioid-induced disruption of neurons in adolescence may link mPFC-associated cognitive impairments in adulthood.

A Preliminary Investigation of a Conceptual Model Describing the Associations Between Childhood Maltreatment and Alcohol Use Problems

BACKGROUND/OBJECTIVES

Childhood maltreatment has been linked to numerous adverse outcomes in adulthood, including problem substance use. However, not all individuals exposed to childhood maltreatment develop substance use problems, indicating the role of other factors in influencing this outcome. Past work suggests that adverse early life experiences, including childhood maltreatment, lead to neurobiological changes in frontolimbic functions that, in turn, result in altered stress and reward responses, heightened impulsivity, affect dysregulation, and, ultimately, increased risk for maladaptive behaviors such as substance use. The aim of this preliminary investigation using cross-sectional data was to test associations between these factors in the relationship between childhood maltreatment and alcohol use problems in a sample of emerging adults.

METHODS

Emerging adults (18-30 years old) who identified as regular drinkers (i.e., drinking at least 2-4 times in the past month) were recruited from a crowd-sourcing platform (Prolific) as well as community samples. Participants completed online standardized questionnaires assessing reward sensitivity and responsiveness, impulsivity, emotion regulation, and alcohol consequences.

RESULTS

Path analyses demonstrated good fit for the data (SRMR = 0.057, RMSEA = 0.096, 90% CI [0.055, 0.142], CFI = 0.957). Childhood maltreatment was associated with reward responsiveness (β = -0.026, Z = -4.222, p < 0.001) and emotion dysregulation (β = 0.669, Z = 9.633, p < 0.001), which in turn was associated with urgency and, subsequently, alcohol consequences (β = 0.758, Z = 7.870, p < 0.001).

CONCLUSIONS

Although these findings are preliminary, the current study is one of the first to test a comprehensive model addressing the relationship between childhood maltreatment and alcohol use problems. The findings have the potential to inform treatment strategies that target motivation and goal-directed action for reducing and managing consequences associated with childhood maltreatment. Future research should test the model using longitudinal data to address the limitations of a cross-sectional study and assess temporal associations between constructs.

Extended ambulatory assessment of executive function: within-person reliability of working memory and inhibitory control tasks

INTRODUCTION

Ambulatory assessment of executive function - particularly in the form working memory (WM) - is increasingly common. Few studies to date, however, have also incorporated ambulatory measures of inhibitory control. Critically, the extended within-person reliability of ambulatory tasks tapping each of these constructs has been largely overlooked.

METHOD

Participants (N = 283, Mage = 23.74 years, SD = 9.04) received notifications every 3 days (for 4 weeks) to undertake ambulatory assessment versions of the n-Back and Stop-Signal Tasks (SST) via the smartphone application CheckCog. Within-person reliability of these measures was explored.

RESULTS

Compliance ranged from 66% (for eight sessions) to 89% (for four sessions). Our results reveal significant changes in performance within the first two sessions for both the n-Back and SST, with performance remaining largely consistent across the remaining (two to eight) sessions. In terms of test-retest reliability, the ICC (C, 1) values ranged from .29 to .68 on the n-Back (with overall accuracy being .51) and .31-.73 on the SST (with stop-signal reaction time being .53).

CONCLUSION

The results of the current study contribute to the literature by demonstrating the reliability of brief measures of executive function - in the form of inhibitory control and WM - delivered using smartphones in participants' natural environments. Based on our findings, the CheckCog app reliability tracks baseline systematic changes in WM and response inhibition across multiple time points and for an extended period in healthy individuals.

Implications of Impulsivity on Criminal Behavior in Individuals With Substance Use Disorder

OBJECTIVE

Our aim was to analyze the association between criminal behavior and impulsivity in individuals with drug addiction and investigate whether impulsiveness mediates the relationship between drug use severity and legal problems.

METHODS

This cross-sectional study included 773 men diagnosed with addiction (295 alcohol users and 478 users of crack/polysubstance) while undergoing addiction treatment. The BIS-11 and ASI-6 were applied to assess impulsivity, criminal behavior, and drug use.

RESULTS

The prevalence of criminal behavior was 41.7% (n = 123) in alcohol users and 64.9% (n = 310) in users of crack/polysubstance. Earlier use of different substances and higher impulsivity scores were observed in individuals with criminal history. Mediation analyses revealed that impulsiveness acts as a mediator factor between substance use and criminal behavior, enhancing the severity of legal problems.

CONCLUSION

Our findings can help in deciding on tailored treatment strategies, focusing not only on substance use, but also on the prevention of social problems, criminality, and impulsivity.

Patient, supporter and primary healthcare professional perspectives on health risks in over 16s with attention deficit hyperactivity disorder (ADHD) in England: a national survey study

BACKGROUND

Current research suggests that people with attention deficit hyperactivity disorder (ADHD) are at higher risk of physical and mental health disorders. This study aimed to explore these health risks in ADHD from the perspectives of multiple stakeholders.

METHODS

This study forms part of the 'Managing young people with ADHD in Primary care (MAP) study'. A survey developed by the study team was distributed to over 16 year olds with ADHD, their supporters, primary healthcare professionals and health commissioners across England, via social media and through patient/clinical networks (September-October 2022). This survey contained two questions on health risks. Question one asked about views on health risks in ADHD (free text). Question two asked about advice given (options list and free text). Descriptive statistics summarised responses to questions one and two, and qualitative analysis (reflexive thematic analysis) was used to explore free text responses from question one.

RESULTS

782 participants responded to the MAP survey. Of these, 206 healthcare professionals, 157 people with ADHD and 88 supporters answered question one. The most mentioned perceived risks were substance misuse, sleep disorders, weight management and smoking. More people with ADHD reported disordered eating as a health risk (n = 32) than healthcare professionals (n = 5). Generated themes included perceived health risks, impact of living with ADHD, lack of adequate healthcare, and need for ADHD awareness. In respect to advice given (question two), based on responses from 258 professionals, 162 people with ADHD and 100 supporters, the most common advice discussed in consultation was mental health (n = 149, n = 50 and n = 17 respectively). High numbers of respondents reported not giving/receiving advice on wider health (n = 38, n = 88 and n = 61 respectively).

CONCLUSIONS

Findings demonstrate that respondents perceived a range of physical and mental health risks posed by ADHD. These related to difficulties with activities of daily living, as well as healthcare interactions and the impact of core features of ADHD (e.g. impulsivity, emotional dysregulation). These risks are not currently explicitly addressed in United Kingdom national guidance on ADHD. More work is needed to examine and address the broader health outcomes of people with ADHD.

Dysfunctional feedback processing in male methamphetamine abusers: Evidence from neurophysiological and computational approaches

Methamphetamine use disorder (MUD) as a major public health risk is associated with dysfunctional neural feedback processing. Although dysfunctional feedback processing in people who are substance dependent has been explored in several behavioral, computational, and electrocortical studies, this mechanism in MUDs requires to be well understood. Furthermore, the current understanding of latent components of their behavior such as learning speed and exploration-exploitation dilemma is still limited. In addition, the association between the latent cognitive components and the related neural mechanisms also needs to be explored. Therefore, in this study, the underlying neurocognitive mechanisms of feedback processing of such impairment, and age/gender-matched healthy controls are evaluated within a probabilistic learning task with rewards and punishments. Mathematical modeling results based on the Q-learning paradigm suggested that MUDs show less sensitivity in distinguishing optimal options. Additionally, it may be worth noting that MUDs exhibited a slight decrease in their ability to learn from negative feedback compared to healthy controls. Also through the lens of underlying neural mechanisms, MUDs showed lower theta power at the medial-frontal areas while responding to negative feedback. However, other EEG measures of reinforcement learning including feedback-related negativity, parietal-P300, and activity flow from the medial frontal to lateral prefrontal regions, remained intact in MUDs. On the other hand, the elimination of the linkage between value sensitivity and medial-frontal theta activity in MUDs was observed. The observed dysfunction could be due to the adverse effects of methamphetamine on the cortico-striatal dopamine circuit, which is reflected in the anterior cingulate cortex activity as the most likely region responsible for efficient behavior adjustment. These findings could help us to pave the way toward tailored therapeutic approaches.

Rewiring the future: drugs abused in adolescence may predispose to mental illness in adult life by altering dopamine axon growth

Adolescence is a period of increased exploration and novelty-seeking, which includes new social behaviors, as well as drug experimentation, often spurred on by peer pressure. This is unfortunate, as the immature state of the adolescent brain makes it particularly susceptible to the negative developmental impact of drug use. During adolescence, dopamine terminals, which have migrated from the ventral tegmental area, pause in the nucleus accumbens, before segregating by either forming local connections or growing towards the prefrontal cortex (PFC). This developmentally late and lengthy process renders adolescent dopamine axon pathfinding vulnerable to disruption by substance use. Indeed, exposure to stimulant drugs in adolescent male mice, but not females, triggers dopamine axons to mistarget the nucleus accumbens and to grow ectopically to the PFC. Some evidence suggests that at this novel site, the functional organization of the ectopic dopamine axons mirrors that of the intended target. The structural rewiring dysregulates local synaptic connectivity, leading to poor impulse control ability, deficits of which are a core symptom of substance-use disorders. In the present commentary, we argue that different substances of abuse induce dopamine mistargeting events with the off-target trajectory prescribed by the type of drug, leading to psychiatric outcomes later in life.

The mediating effect of attentional impulsivity between mindfulness and problematic smartphone use

OBJECTIVE

Problematic smartphone use has been linked to lower levels of mindfulness, impaired attentional function, and higher impulsivity. This study aimed to identify the psychological mechanisms of problematic smartphone use by exploring the relationship between addictive smartphone use, mindfulness, attentional function and impulsivity.

METHODS

Ninety participants were evaluated with the smartphone addiction proneness scale and classified into the problematic smartphone use group (n = 42; 24 women; mean age: 27.6 ± 7.2 years) or normal use group (n = 48; 22 women; mean age: 30.1 ± 5.7 years). All participants completed self-report questionnaires evaluating their trait impulsivity and mindfulness and attention tests that assessed selective, sustained and divided attention. We compared the variables between the groups and explored the relationship between mindfulness, attentional function, impulsivity and addictive smartphone use through mediation analysis.

RESULTS

The problematic smartphone use group showed higher trait impulsivity and lower mindfulness than the normal use group. There were no significant group differences in performance on attention tests. Levels of addictive smartphone use were significantly correlated with higher levels of trait impulsivity and lower levels of mindfulness, but not with performance on attention tests. Mediation analysis showed that acting with awareness, an aspect of mindfulness, reduces the degree of addictive smartphone use through attentional impulsivity, one of the trait impulsivity.

CONCLUSION

Acting without sufficient awareness could influence addictive smartphone use by mediating attentional impulsivity. This supports that executive control deficits, reflected in high attentional impulsivity, contribute to problematic smartphone use. Our findings imply that mindfulness-based interventions can enhance executive control over smartphone use by promoting awareness.

More widespread and rigid neuronal representation of reward expectation underlies impulsive choices

Impulsive choices prioritize smaller, more immediate rewards over larger, delayed, or potentially uncertain rewards. Impulsive choices are a critical aspect of substance use disorders and maladaptive decision-making across the lifespan. Here, we sought to understand the neuronal underpinnings of expected reward and risk estimation on a trial-by-trial basis during impulsive choices. To do so, we acquired electrical recordings from the human brain while participants carried out a risky decision-making task designed to measure choice impulsivity. Behaviorally, we found a reward-accuracy tradeoff, whereby more impulsive choosers were more accurate at the task, opting for a more immediate reward while compromising overall task performance. We then examined how neuronal populations across frontal, temporal, and limbic brain regions parametrically encoded reinforcement learning model variables, namely reward and risk expectation and surprise, across trials. We found more widespread representations of reward value expectation and prediction error in more impulsive choosers, whereas less impulsive choosers preferentially represented risk expectation. A regional analysis of reward and risk encoding highlighted the anterior cingulate cortex for value expectation, the anterior insula for risk expectation and surprise, and distinct regional encoding between impulsivity groups. Beyond describing trial-by-trial population neuronal representations of reward and risk variables, these results suggest impaired inhibitory control and model-free learning underpinnings of impulsive choice. These findings shed light on neural processes underlying reinforced learning and decision-making in uncertain environments and how these processes may function in psychiatric disorders.

Neural correlates of model-based behavior in internet gaming disorder and alcohol use disorder

Background

An imbalance between model-based and model-free decision-making systems is a common feature in addictive disorders. However, little is known about whether similar decision-making deficits appear in internet gaming disorder (IGD). This study compared neurocognitive features associated with model-based and model-free systems in IGD and alcohol use disorder (AUD).

Method

Participants diagnosed with IGD (n = 22) and AUD (n = 22), and healthy controls (n = 30) performed the two-stage task inside the functional magnetic resonance imaging (fMRI) scanner. We used computational modeling and hierarchical Bayesian analysis to provide a mechanistic account of their choice behavior. Then, we performed a model-based fMRI analysis and functional connectivity analysis to identify neural correlates of the decision-making processes in each group.

Results

The computational modeling results showed similar levels of model-based behavior in the IGD and AUD groups. However, we observed distinct neural correlates of the model-based reward prediction error (RPE) between the two groups. The IGD group exhibited insula-specific activation associated with model-based RPE, while the AUD group showed prefrontal activation, particularly in the orbitofrontal cortex and superior frontal gyrus. Furthermore, individuals with IGD demonstrated hyper-connectivity between the insula and brain regions in the salience network in the context of model-based RPE.

Discussion and Conclusions

The findings suggest potential differences in the neurobiological mechanisms underlying model-based behavior in IGD and AUD, albeit shared cognitive features observed in computational modeling analysis. As the first neuroimaging study to compare IGD and AUD in terms of the model-based system, this study provides novel insights into distinct decision-making processes in IGD.

Psychosocial Correlates of Motivation for Abstinence Among People Who Used Drugs After Community Rehabilitation Treatment in China: A Structural Equation Modelling

Background

Enhancing abstinence motivation of drugs is an effective strategy for the rehabilitation of people who used drugs and prevention of drug use relapse. However, little is known about its risk and protective factors. This study aimed to examine the potential intrapersonal (ie, impulsivity, depression, anxiety, sleep quality) and interpersonal factors (ie, perceived social support) of abstinence motivation among people who completed the community rehabilitation treatment.

Methods

A total of 222 participants (mean age = 43; male = 89.2%) were recruited from eleven communities located in Wenzhou, China. Data were collected using a self-reported questionnaire in counselling room settings between April and June 2021.

Results

The proportions of participants with depression, anxiety, and poor sleep quality were 38.8%, 19.5%, and 21.2%, respectively. Age and family history of physical disease were significant background factors of abstinence motivation. Impulsivity, depressive symptoms, anxiety symptoms, and poor quality of sleep were negatively associated with abstinence motivation. Perceived social support from family and important others was positively associated with abstinence motivation. Structural equation modeling fitted the data well in which impulsivity and perceived social support were both associated with abstinence motivation indirectly through mental health problems.

Conclusion

The identified psychosocial factors should be addressed in community rehabilitation treatment and follow-up service to enhance abstinence motivation and the long-term effectiveness of the treatment.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

Understanding patch foraging strategies across development

Patch foraging is a near-ubiquitous behaviour across the animal kingdom and characterises many decision-making domains encountered by humans. We review how a disposition to explore in adolescence may reflect the evolutionary conditions under which hunter-gatherers foraged for resources. We propose that neurocomputational mechanisms responsible for reward processing, learning, and cognitive control facilitate the transition from exploratory strategies in adolescence to exploitative strategies in adulthood - where individuals capitalise on known resources. This developmental transition may be disrupted by psychopathology, as there is emerging evidence of biases in explore/exploit choices in mental health problems. Explore/exploit choices may be an informative marker for mental health across development and future research should consider this feature of decision-making as a target for clinical intervention.

Action initiation and punishment learning differ from childhood to adolescence while reward learning remains stable

Theoretical and empirical accounts suggest that adolescence is associated with heightened reward learning and impulsivity. Experimental tasks and computational models that can dissociate reward learning from the tendency to initiate actions impulsively (action initiation bias) are thus critical to characterise the mechanisms that drive developmental differences. However, existing work has rarely quantified both learning ability and action initiation, or it has relied on small samples. Here, using computational modelling of a learning task collected from a large sample (N = 742, 9-18 years, 11 countries), we test differences in reward and punishment learning and action initiation from childhood to adolescence. Computational modelling reveals that whilst punishment learning rates increase with age, reward learning remains stable. In parallel, action initiation biases decrease with age. Results are similar when considering pubertal stage instead of chronological age. We conclude that heightened reward responsivity in adolescence can reflect differences in action initiation rather than enhanced reward learning.

An altered reward system characterizes chronic migraine with medication overuse headache

BACKGROUND

Medication overuse headache shares several characteristics with substance use disorders. However, key features of substance use disorders such as increased impulsivity and alterations in reward processing remain little explored in medication overuse headache.

METHODS

Temporal discounting and impulsive decision making behavior and the associated brain mechanisms were assessed in 26 chronic migraine patients with medication overuse headache and in 28 healthy controls. Regions-of-interest analyses were first performed for task-related regions, namely the ventral striatum and the ventromedial and dorsomedial prefrontal cortices. Resting-state functional connectivity between these regions were then explored. An additional 27 chronic migraine patients without medication overuse headache were included for comparison in the latter analysis.

RESULTS

Patients with medication overuse headache showed steeper temporal discounting behavior than healthy controls. They also showed weaker subjective value representations in the dorsomedial prefrontal cortex, when accepting larger delayed rewards, and in ventral striatum and ventromedial prefrontal cortex, when accepting the smaller immediate reward. Resting-state functional connectivity was reduced among the valuation regions when comparing patients with medication overuse headache to the other two control groups.

CONCLUSIONS

Patients with medication overuse headache were characterized by altered processing and dysconnectivity in the reward system during intertemporal choices and in the resting-state.

Disrupted functional connectivity of the brain reward system in substance use problems: A meta-analysis of functional neuroimaging studies

Extensive literature suggests that the brain reward system is crucial in understanding the neurobiology of substance use disorders. However, evidence of reliable deficits in functional connectivity across studies on substance use problems remains limited. Therefore, a voxel-wise seed-based meta-analysis using brain regions of the reward system as seeds of interest was conducted on 96 studies representing 5757 subjects with substance use problems. The ventromedial prefrontal cortex exhibited hyperconnectivity with the ventral striatum and hypoconnectivity with the amygdala and hippocampus. The executive striatum showed hyperconnectivity with the motor thalamus and dorsolateral prefrontal cortex and hypoconnectivity with the anterior cingulate cortex and anterior insula. Finally, the limbic striatum was found to be hyperconnected to the orbitofrontal cortex and hypoconnected to the precuneus compared with healthy subjects. The current study provided meta-analytical evidence of deficient functional connectivity between brain regions of the reward system and cortico-striato-thalamocortical loops in addiction. These results are consistent with deficits in motivation and habit formation occurring in addiction, and they highlight alterations in brain regions involved in socio-emotional processing and attention salience.

Investigating predictors of problematic alcohol, cannabis, and nicotine use among legal users of all three substances

BACKGROUND

The three most used substances-alcohol, cannabis, and nicotine-are frequently concurrently. Use of each substance has been connected to an increased probability of use of the other substances, and the problematic use of each substance has been linked to demographic factors, substance use factors, and personality. However, little is known about which risk factors are most important for consumers of all three substances. This study examined the extent to which various factors are associated with dependence on alcohol, cannabis, and/or nicotine in users of all three substances.

METHODS

516 Canadian adults with past month use of alcohol, cannabis, and nicotine completed online surveys querying their demographics, personality, substance use history, and levels substance dependence. Hierarchical linear regressions were used to determine which factors best predicted levels of dependence on each substance.

RESULTS

Alcohol dependence was associated with levels of cannabis and nicotine dependence, and impulsivity, with 44.9% of variance explained. Cannabis dependence was predicted by alcohol and nicotine dependence levels, impulsivity, and the age of onset of cannabis use, with 47.6% of variance explained. Nicotine dependence was best predicted by alcohol and cannabis dependence levels, impulsivity, and dual use of cigarettes and e-cigarettes, with 19.9% of variance explained.

CONCLUSIONS

Alcohol dependence, cannabis dependence, and impulsivity were the strongest predictors for dependence on each of the substances. A strong relationship between alcohol and cannabis dependence was evident, warranting further research.

Prospective Memory, Sustained Attention and Response Inhibition in Poly-Substance Users Stable on Methadone Maintenance Treatment

Background: Prospective memory and response inhibition are interrelated constructs, though studied separately in the drug addiction literature. Also, although sustained attention underlies response inhibition, its role in the relation between these functions has been largely neglected. The limited research on the cognitive effects of methadone-maintenance treatment (MMT) further stresses the importance of investigating these effects. Objective: Therefore, the current study focused on possible effects of MMT combined with long-term drug abuse on all these functions. Thirty five long term opiate/poly-substance users in MMT and thirty four drug-free controls were screened for socioeconomic status, anxiety, depression and general, non-verbal intelligence and then tested on a self-report measure of prospective memory and on the Go/No-Go task. Results: Compared to controls, the MMT group scored worse in all functions assessed. Prospective memory scores were also negatively related to Go/NoGo accuracy scores. Conclusion: As predicted, (a) the MMT participants show impairments in prospective memory, sustained attention and response inhibition and (b) prospective memory, response inhibition and sustained attention are related constructs. The results of this study could inform current rehabilitation and relapse prevention cognitive training practices.

Contrasting effects of DOI and lisuride on impulsive decision-making in delay discounting task

RATIONALE

The 5-HT2A receptor is the major target of classic hallucinogens. Both DOI (2,5-dimethoxy-4-iodoamphetamine) and lisuride act at 5-HT2A receptors, and lisuride shares comparable affinity with DOI and acts as a partial agonist at 5-HT2A receptors. However, not like DOI, lisuride lacks hallucinogenic properties. Impulsive decision-making refers to the preference for an immediate small reinforcer (SR) over a delayed large reinforcer (LR).

OBJECTIVES

The current study aims to compare the effects of DOI and lisuride on impulsive decision-making and further to investigate the possible receptor mechanisms responsible for the actions of the two drugs.

METHODS

Impulsive decision-making was evaluated in male Sprague-Dawley rats by the percentage of choice for the LR in delay discounting task (DDT). Delay to the LR changed in an ascending order (0, 4, 8, 16, and 32 s) across one session.

RESULTS

DOI (0.5 and 1.0 mg/kg) increased impulsive decision-making, and the effects of DOI (1.0 mg/kg) were blocked by the 5-HT2A receptor antagonist ketanserin (1.0 mg/kg) rather than the 5-HT2C receptor antagonist SB-242084 (1.0 mg/kg). Contrarily, lisuride (0.1, 0.3, and 0.5 mg/kg) decreased impulsive decision-making. The effects of lisuride (0.3 mg/kg) were not antagonized by ketanserin (1.0 mg/kg), selective 5-HT1A antagonist WAY-100635 (1.0 mg/kg), or selective dopamine D4 receptor antagonist L-745870 (1.0 mg/kg) but were attenuated by the selective dopamine D2/D3 receptor antagonist tiapride (40 mg/kg).

CONCLUSIONS

DOI and lisuride have contrasting effects on impulsive decision-making via distinct receptors. DOI-induced increase of impulsivity is mediated by the 5-HT2A receptor, while lisuride-induced inhibition of impulsivity is regulated by the dopamine D2/D3 receptor.

Differential expression of miR-1249-3p and miR-34b-5p between vulnerable and resilient phenotypes of cocaine addiction

Cocaine addiction is a complex brain disorder involving long-term alterations that lead to loss of control over drug seeking. The transition from recreational use to pathological consumption is different in each individual, depending on the interaction between environmental and genetic factors. Epigenetic mechanisms are ideal candidates to study psychiatric disorders triggered by these interactions, maintaining persistent malfunctions in specific brain regions. Here we aim to study brain-region-specific epigenetic signatures following exposure to cocaine in a mouse model of addiction to this drug. Extreme subpopulations of vulnerable and resilient phenotypes were selected to identify miRNA signatures for differential vulnerability to cocaine addiction. We used an operant model of intravenous cocaine self-administration to evaluate addictive-like behaviour in rodents based on the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition criteria to diagnose substance use disorders. After cocaine self-administration, we performed miRNA profiling to compare two extreme subpopulations of mice classified as resilient and vulnerable to cocaine addiction. We found that mmu-miR-34b-5p was downregulated in the nucleus accumbens of vulnerable mice with high motivation for cocaine. On the other hand, mmu-miR-1249-3p was downregulated on vulnerable mice with high levels of motor disinhibition. The elucidation of the epigenetic profile related to vulnerability to cocaine addiction is expected to help find novel biomarkers that could facilitate the interventions to battle this devastating disorder.

Age differences in the behavioural economics of cannabis use: Do adolescents and adults differ on demand for cannabis and discounting of future reward?

BACKGROUND

Adolescence is a period of psychological and neural development in which harms associated with cannabis use may be heightened. We hypothesised that adolescent who use cannabis (adolescentsWUC) would have steeper delay discounting (preference for immediate over future rewards) and greater demand (relative valuation) for cannabis than adults who use cannabis (adultsWUC).

METHODS

This cross-sectional study, part of the 'CannTeen' project, compared adultsWUC (n = 71, 26-29 years old) and adolescentsWUC (n = 76, 16-17 years old), and gender- and age-matched adolescent (n = 63) and adult (n = 64) controls. AdolescentsWUC and adultsWUC used cannabis 1-7 days/week and were matched on cannabis use frequency (4 days/week). The Monetary Choice Questionnaire assessed delay discounting. A modified Marijuana Purchase Task (MPT) assessed cannabis demand in adolescentsWUC and adultsWUC. The MPT yielded five indices: intensity (amount of cannabis used at zero cost), O_max (total peak expenditure), P_max (price at peak expenditure), breakpoint (cost at which cannabis demand is suppressed to zero) and elasticity (degree to which cannabis use decreases with increasing price). Analyses were adjusted for covariates of gender, socioeconomic status, other illicit drug use.

RESULTS

Both adolescentsWUC and adultsWUC had steeper delay discounting than controls (F, (1,254)= 9.13, p = 0.003, η_p²= 0.04), with no significant age effect or interaction. AdolescentsWUC showed higher intensity (F, (1,138)= 9.76, p = 0.002, η_p²= 0.07) and lower elasticity (F, (1,138)= 15.25, p < 0.001, η_p²= 0.10) than adultsWUC. There were no significant differences in P_max, O_max or breakpoint.

CONCLUSION

Individuals who use cannabis prefer immediate rewards more than controls. AdolescentsWUC, compared to adultsWUC, may be in a high-risk category with diminished sensitivity to cannabis price increases and a greater consumption of cannabis when it is free.

Intersection between social inequality and emotion regulation on emerging adult cannabis use

Emerging adulthood (EA; ages 18-25) is characterized by socioemotional and neurodevelopmental challenges. Cannabis is a widely used substance among EAs, and hazardous use may increase risk for sustained use patterns and related health consequences. Research shows differential increases in hazardous use by objective as well as subjective measures of social inequality, with more concerning trajectories for youth with greater experiences of social inequality. Learning how to flexibly monitor and modify emotions in proactive ways (i.e., emotion regulation) is a central developmental task navigated during the EA window. Challenges to and with emotion regulation processes can contribute to the emergence of mental health symptoms during EA, including hazardous cannabis use. In this perspective, we highlight emotion dysregulation and social inequality as two critical factors that interact to either buffer against or exacerbate cannabis use during the EA period, noting critical gaps in the literature that merit additional research. We recommend novel methods and longitudinal designs to help clarify how dynamic cognition-emotion interplay predicts trajectories of negative emotional experiences and cannabis use in EA.

The Ventral Tegmental Area and Nucleus Accumbens as Circadian Oscillators: Implications for Drug Abuse and Substance Use Disorders

Circadian rhythms convergently evolved to allow for optimal synchronization of individuals’ physiological and behavioral processes with the Earth’s 24-h periodic cycling of environmental light and temperature. Whereas the suprachiasmatic nucleus (SCN) is considered the primary pacemaker of the mammalian circadian system, many extra-SCN oscillatory brain regions have been identified to not only exhibit sustainable rhythms in circadian molecular clock function, but also rhythms in overall region activity/function and mediated behaviors. In this review, we present the most recent evidence for the ventral tegmental area (VTA) and nucleus accumbens (NAc) to serve as extra-SCN oscillators and highlight studies that illustrate the functional significance of the VTA’s and NAc’s inherent circadian properties as they relate to reward-processing, drug abuse, and vulnerability to develop substance use disorders (SUDs).

Addressing methodological issues in a study of impulsivity and vulnerability for transition to alcohol use disorder

BACKGROUND

Heightened behavioral impulsivity has been advocated as a preexisting risk factor for the development of alcohol use disorder (AUD). Nonetheless, studies investigating impulsivity in adolescent/young adult at-risk drinkers-who are at increased risk of developing AUD-report mixed findings. This may be due to methodological limitations related to definitions of at-risk drinking, the retrospective assessment of alcohol intake, and/or the relatively modest sample size of some studies.

METHODS

Healthy individuals (N = 814, M_age  = 22.50) completed online surveys and a measure of choice impulsivity. Of these, a number of participants also undertook an online measure of response inhibition (n = 627, M_age  = 22.66), and a further subgroup submitted real-time alcohol consumption information for a period of 21 days using an app (n = 543, M_age  = 22.96). Differences in behavioral impulsivity were assessed as a function of various at-risk alcohol intake categories. Hierarchical multiple regression was employed to determine whether impulsivity predicted alcohol use in the form of a continuous index comprising variables related to intake and consequences of use.

RESULTS

Significantly greater impulsivity was not evident in heavy, standard binge, high binge, harmful, or hazardous alcohol drinkers as compared to controls, regardless of the criteria employed to categorize these at-risk drinkers. Neither choice impulsivity nor reduced response inhibition significantly predicted the alcohol use index.

CONCLUSIONS

While results could be attributed to the online nature of this research, it is possible that more sensitive measures of behavioral impulsivity are required when assessing nondependent drinkers.

Disentangling substance use and related problems: urgency predicts substance-related problems beyond the degree of use

BACKGROUND

Substance use disorders are reliably associated with high impulsivity and sensation seeking. Importantly, both precede problematic substance use, implicating them as risk factors. Individuals with substance use disorders show variable degrees of substance use (combined quantity and frequency) and substance-related problems and differ in both aspects from healthy controls. Dimensional research has indicated differential associations of impulsivity-related traits as well as sensation seeking with the degree of substance use and substance-related problems. The current study aimed to clarify whether impulsivity-related traits and sensation seeking predict substance-related problems above and beyond the degree of substance use and are thus specifically linked to problems, the dimension that characterizes substance use disorders.

METHOD

We assessed impulsivity-related traits and sensation seeking using self-report, as well as delay discounting, a behavioral indicator of impulsivity, in a sample of 258 substance-using adults.

RESULTS

Sensation seeking and impulsivity-related traits significantly predicted the degree of substance use, with sensation seeking explaining the largest portion of variance. In contrast, self-reported impulsivity, in particular when experiencing negative emotions (urgency), but not sensation seeking or delay discounting, predicted substance-related problems when controlling for the degree of substance use.

CONCLUSIONS

This suggests that urgency, but not sensation seeking, may be specifically linked to substance-related problems and thus especially relevant for substance use disorders. Taken together, this study underlines the necessity to assess and control for the degree of substance use in risk factor research concerning substance-related problems. Thus, it may inform future research improving targeted prevention and therapy.

The phenotype of recovery V: Does delay discounting predict the perceived risk of relapse among individuals in recovery from alcohol and drug use disorders

BACKGROUND

Substance use recovery is a dynamic process. Relapse, often part of the recovery process, is a persistent problem for individuals seeking freedom from their harmful substance use and has become a focus of research on the improvement of recovery outcomes. Delay discounting is associated with substance use disorder severity, both its negative outcomes and the propensity to relapse. However, the association between delay discounting and perceived risk of relapse as measured by the Alcohol Warning of Relapse Questionnaire has not previously been examined in a population of individuals in long-term recovery from substance misuse.

METHODS

In this study, using data collected from the International Quit and Recovery Registry, we investigated the association between delay discounting, self-reported time in recovery, and perceived risk of relapse. Data from 193 individuals self-reporting to be in recovery from harmful substance use were included in the study.

RESULTS

Delay discounting rates were significantly negatively associated with length of recovery (p = 0.036) and positively with perceived risk of relapse (p = 0.027) even after controlling for age, gender, education, marital status, ethnicity, race, primary substance, and length in the registry. Moreover, a mediation analysis using Hayes' methods revealed that the association between the length of recovery and perceived relapse risk was partially mediated by delay discounting, accounting for 21.2% of the effect.

CONCLUSIONS

Our finding supports previous characterizations of delay discounting as a candidate behavioral marker of substance misuse and may help to identify individuals at higher perceived risk of relapse in an extended recovery population.

Impaired Learning From Errors and Punishments and Maladaptive Avoidance-General Mechanisms Underlying Self-Regulation Disorders?

Self-regulation (SR) is an important human function that relates to quality of life in multiple domains including mental health. Previous studies have found important correlates of low SR including impulsivity and poor emotional regulation; however, underpinnings of low SR are incompletely understood. Individuals low in SR frequently engage in maladaptive behaviors (substance abuse, procrastination, etc.) despite negative consequences. This phenomenon suggests that impaired learning from errors and punishments may be important mechanisms underlying low SR. Consistently, previous studies observed impaired error processing in a wide spectrum of individuals with low SR and impaired learning from errors and punishments in SR-related disorders. We also note a possible role for poor emotional regulation and refer to concepts suggesting that engaging in maladaptive behaviors may serve as short term emotion regulation strategies aimed at avoiding or alleviating negative affect. We speculate on transdiagnostic factors underlying poor SR. We propose that impaired error processing (possibly related to striatal functioning) may prevent subjects with low SR from learning from errors and punishments and thus learning better SR skills or tendencies. Additionally, impaired coping in emotionally challenging situations, possibly related to prefrontal-cortical functioning, may lead to maladaptive avoidance. Moreover, maladaptive behaviors may be reinforced by the temporary decreases in negative affect and rewarding values of behaviors. Given existing knowledge gaps, we call for more extensive research and describe possible directions and challenges for future studies.

Early environmental enrichment and impoverishment differentially affect addiction-related behavioral traits, cocaine-taking, and dopamine D2/3 receptor signaling in a rat model of vulnerability to drug abuse

RATIONALE

Risk factors for drug addiction include genetics, environment, and behavioral traits such as impulsivity and novelty preference (NP), which have been related to deficits in striatal dopamine (DA) D_2/3-receptors (D_2/3R) and heightened amphetamine (AMPH)-induced DA release. However, the influence of the early rearing environment on these behavioral and neurochemical variables is not clear.

OBJECTIVES

We investigated the influence of early rearing environment on striatal D_2/3R availabilities and AMPH-induced DA release in relation to impulsivity, NP, and propensity to drug self-administration (SA) in "addiction-prone" Roman high- (RHA) and "addiction-resistant" Roman low-avoidance (RLA) rats.

METHODS

Animals were reared post-weaning in either environmental enrichment (EE) or impoverishment (EI) and were assessed at adulthood for impulsivity, NP, and propensity to cocaine SA. EE and EI rats were also scanned using single-photon emission computed tomography to concurrently measure in vivo striatal D_2/3R availability and AMPH-induced DA release.

RESULTS

EE vs. EI was associated with heightened impulsivity and a lack of NP in both rat lines. Higher dorsal striatal D_2/3R densities were found in RHA EE and higher AMPH-induced DA release in RLA EE. Both impulsivity and NP were negatively correlated to dorsal striatal D_2/3R availabilities and positively correlated with AMPH-induced DA release in EI but not in EE. EE vs. EI was related to a faster rate of cocaine intake and elevated active timeout responses in RHAs.

CONCLUSION

Our results suggest non-monotonic, environment-dependent, relationships between impulsivity, NP, and D_2/3R-mediated signaling, and suggest that EI vs. EE may decrease the reinforcing effects of psychostimulants in predisposed individuals.

Lack of Premeditation Predicts Aberrant Behaviors Related to Prescription Opioids in Patients with Chronic Pain: A Cross-Sectional Study

OBJECTIVE

In light of the opioid epidemic, there is a need to identify factors that predict aberrant opioid behaviors including misuse and abuse. Impulsivity has been extensively studied in addiction literature, but not in the context of opioid misuse. Hence, this study aimed to identify which of the impulsivity facets (negative urgency, positive urgency, sensation seeking, lack of perseverance, and lack of premeditation) would predict current aberrant opioid-related behaviors in patients with chronic pain.

METHODS

Data were collected through an online survey from patients with chronic pain who visited a tertiary pain clinic. Patients were predominately female (74%), middle aged (M = 55 years), and White/Caucasian (84%). Upon consent, they completed a series of surveys including UPPS-P Impulsive Behavior Scale, the Current Opioid misuse Measure, Pain Catastrophizing Scale, PROMIS-anxiety, depression, and physical function, and a 0-10 numerical pain rating scale. Ordinal regression analyses were conducted to test study hypotheses.

RESULTS

Contrary to expectations, only lack of premeditation predicted higher odds of aberrant opioid-related behaviors in the past 30 days, after controlling for known covariates, and explained 26% of variance. Interestingly, lack of premeditation together with pain catastrophizing as a covariate explained 56% of the variance in aberrant opioid-related behaviors.

DISCUSSION

The current study is the first to identify a potential role of lack of premeditation as an impulsivity facet predicting aberrant opioid-related behaviors among patients with chronic pain.

Representation of the observer's predicted outcome value in mirror and nonmirror neurons of macaque F5 ventral premotor cortex

In the search for the function of mirror neurons, a previous study reported that F5 mirror neuron responses are modulated by the value that the observing monkey associates with the grasped object. Yet we do not know whether mirror neurons are modulated by the expected reward value for the observer or also by other variables, which are causally dependent on value (e.g., motivation, attention directed at the observed action, arousal). To clarify this, we trained two rhesus macaques to observe a grasping action on an object kept constant, followed by four fully predictable outcomes of different values (2 outcomes with positive and 2 with negative emotional valence). We found a consistent order in population activity of both mirror and nonmirror neurons that matches the order of the value of this predicted outcome but that does not match the order of the above-mentioned value-dependent variables. These variables were inferred from the probability not to abort a trial, saccade latency, modulation of eye position during action observation, heart rate, and pupil size. Moreover, we found subpopulations of neurons tuned to each of the four predicted outcome values. Multidimensional scaling revealed equal normalized distances of 0.25 between the two positive and between the two negative outcomes suggesting the representation of a relative value, scaled to the task setting. We conclude that F5 mirror neurons and nonmirror neurons represent the observer's predicted outcome value, which in the case of mirror neurons may be transferred to the observed object or action.NEW & NOTEWORTHY Both the populations of F5 mirror neurons and nonmirror neurons represent the predicted value of an outcome resulting from the observation of a grasping action. Value-dependent motivation, arousal, and attention directed at the observed action do not provide a better explanation for this representation. The population activity's metric suggests an optimal scaling of value representation to task setting.