The orbital prefrontal cortex and drug addiction in laboratory animals and humans

Prelimbic cortex is involved in the regulation of morphine-induced conditioned place preference in both resistant and sensitive mice

A primary behavioral pathology in drug addiction is the overpowering motivational strength and decreased ability to control the desire to obtain drugs, which shows some variation between different individuals. Here, using a morphine-induced conditioned place preference (CPP) model with footshock, we found that mice exhibited significant individual differences in morphine-induced addiction. Despite the consequences of footshock, a small percentage of mice (24%) still showed stable morphine preference, demonstrating resistant to punishment. The majority of mice (76%) were relatively sensitive to punishment and showed termination of morphine preference. As a region of advanced cognitive function in the mammalian brain, the medial prefrontal cortex (mPFC) is involved in regulating drug-induced addictive behaviors. We found that activating the pyramidal neurons in the prelimbic cortex (PrL) could effectively reverse morphine-induced CPP in resistant mice, and inhibiting pyramidal neurons in the PrL could promote morphine-induced CPP in sensitive mice. To further explore the differences between resistant and sensitive mice, we analyzed the differences in gene expression in their PrL regions through RNA-seq analysis. The results showed that compared to sensitive mice, the significantly downregulated differentially expressed genes (DEGs), such as Panx2, Tcf7l2, Htr2c, Htr5a, Orai3, Slc24a4 and Cacnb2, in resistant mice were mainly involved in synaptic formation and neurodevelopment. We speculated that there may be defects in the neuronal system of resistant mice, and caused they are more prone to morphine-induced CPP. These findings are likely to contribute to research in gene therapy, and they may also serve as potential therapeutic targets for drug addiction.

Prior cocaine use diminishes encoding of latent information by orbitofrontal, but not medial, prefrontal ensembles

Maladaptive decision-making is a hallmark of substance use disorders (SUDs), though how drugs of abuse alter neural representations supporting adaptive behavior remains poorly understood. Past studies show that the orbitofrontal (OFC) and prelimbic (PL) cortices are important for decision-making, tracking both task-relevant and latent information. However, previous studies have focused on how drugs of abuse impact the firing rates of individual units. More work at the ensemble level is necessary to accurately characterize potential drug-induced changes. Using single-unit recordings in rats during a multidimensional decision-making task and then applying population- and ensemble-level analyses, we show that prior use of cocaine altered the strength and structure of task-relevant and latent representations in the OFC, changes relatable to suboptimal decision-making in this and perhaps other settings. These data expand our understanding of the neuropathological underpinnings of maladaptive decision-making in SUDs, potentially enabling enhanced future treatment strategies.

The Role of Unawareness, Volition, and Neural Hyperconnectivity in Alcohol Use Disorder: A Functional Magnetic Resonance Imaging Study

BACKGROUND

Automated alcohol craving and habitual alcohol consumption characterize the later stages of alcohol use disorder (AUD). This study reanalyzed previously collected functional neuroimaging data in combination with the Craving Automated Scale for Alcohol (CAS-A) questionnaire to investigate the neural correlates and brain networks underlying automated drinking characterized by unawareness and nonvolition.

METHODS

We assessed 49 abstinent male patients with AUD and 36 male healthy control participants during a functional magnetic resonance imaging-based alcohol cue-reactivity task. We performed whole-brain analyses examining the associations between CAS-A scores and other clinical instruments and neural activation patterns in the alcohol versus neutral contrast. Furthermore, we performed psychophysiological interaction analyses to assess the functional connectivity between predefined seed regions and other brain areas.

RESULTS

In patients with AUD, higher CAS-A scores correlated with greater activation in dorsal striatal, pallidal, and prefrontal regions, including frontal white matter, and with lower activation in visual and motor processing regions. Between-group psychophysiological interaction analyses showed extensive connectivity between the seed regions inferior frontal gyrus and angular gyrus and several frontal, parietal, and temporal brain regions in AUD versus healthy control participants.

CONCLUSIONS

The present study applied a new lens to previously acquired alcohol cue-reactivity functional magnetic resonance imaging data by correlating neural activation patterns with clinical CAS-A scores to elucidate potential neural correlates of automated alcohol craving and habitual alcohol consumption. Our results support previous findings showing that alcohol addiction is associated with hyperactivation in habit-processing regions, with hypoactivation in areas mediating motor and attention processing, and with general hyperconnectivity.

Effects of Acute Moderate- and High-Intensity Aerobic Exercise on Oxygenation in Prefrontal Cortex of Male Methamphetamine-Dependent Patients

The aim of this study was to explore the influence of different intensities of acute aerobic exercise on brain activation in male methamphetamine (MA)-dependent patients during exercise. Twenty MA-dependent patients were divided randomly into two groups participating in 35 min of either moderate- or high-intensity aerobic exercise. Functional near-infrared spectral imaging (fNIRS) was used to detect hemodynamic changes in prefrontal cortex during the main 25-min exercise stage. The results revealed that high-intensity acute aerobic exercise aroused more cerebral oxygenation changes in the prefrontal cortex and left dorsolateral prefrontal cortex during exercise as compared with moderate-intensity exercise. Furthermore, there was a stronger positive connection observed between orbital frontal cortex and left dorsolateral prefrontal cortex in the high-intensity group than in the moderate-intensity group. Together these results suggest that for submaximal exercise intensities, high-intensity exercise may bring more benefits to male MA-dependent patients than moderate-intensity.

Relative salience signaling within a thalamo-orbitofrontal circuit governs learning rate

Learning to predict rewards is essential for the sustained fitness of animals. Contemporary views suggest that such learning is driven by a reward prediction error (RPE)-the difference between received and predicted rewards. The magnitude of learning induced by an RPE is proportional to the product of the RPE and a learning rate. Here we demonstrate using two-photon calcium imaging and optogenetics in mice that certain functionally distinct subpopulations of ventral/medial orbitofrontal cortex (vmOFC) neurons signal learning rate control. Consistent with learning rate control, trial-by-trial fluctuations in vmOFC activity positively correlate with behavioral updating when the RPE is positive, and negatively correlates with behavioral updating when the RPE is negative. Learning rate is affected by many variables including the salience of a reward. We found that the average reward response of these neurons signals the relative salience of a reward, because it decreases after reward prediction learning or the introduction of another highly salient aversive stimulus. The relative salience signaling in vmOFC is sculpted by medial thalamic inputs. These results support emerging theoretical views that prefrontal cortex encodes and controls learning parameters.

A neural substrate of compulsive alcohol use

Alcohol intake remains controlled in a majority of users but becomes "compulsive," i.e., continues despite adverse consequences, in a minority who develop alcohol addiction. Here, using a footshock-punished alcohol self-administration procedure, we screened a large population of outbred rats to identify those showing compulsivity operationalized as punishment-resistant self-administration. Using unsupervised clustering, we found that this behavior emerged as a stable trait in a subpopulation of rats and was associated with activity of a brain network that included central nucleus of the amygdala (CeA). Activity of PKCδ+ inhibitory neurons in the lateral subdivision of CeA (CeL) accounted for ~75% of variance in punishment-resistant alcohol taking. Activity-dependent tagging, followed by chemogenetic inhibition of neurons activated during punishment-resistant self-administration, suppressed alcohol taking, as did a virally mediated shRNA knockdown of PKCδ in CeA. These findings identify a previously unknown mechanism for a core element of alcohol addiction and point to a novel candidate therapeutic target.

Neural Substrates and Circuits of Drug Addiction

Drug addiction is a chronic relapsing disorder, and a significant amount of research has been devoted to understand the factors that contribute to the development, loss of control, and persistence of compulsive addictive behaviors. In this review, we provide an overview of various theories of addiction to drugs of abuse and the neurobiology involved in elements of the addiction cycle. Specific focus is devoted to the role of the mesolimbic pathway in acute drug reinforcement and occasional drug use, the role of the mesocortical pathway and associated areas (e.g., the dorsal striatum) in escalation/dependence, and the contribution of these pathways and associated circuits to conditioned responses, drug craving, and loss of behavioral control that may underlie drug relapse. By enhancing the understanding of the neurobiological factors that mediate drug addiction, continued preclinical and clinical research will aid in the development of novel therapeutic interventions that can serve as effective long-term treatment strategies for drug-dependent individuals.

Novel circuit biomarker of impulsivity and craving in male heroin-dependent individuals

INTRODUCTION

The striatum mediates reward processing in addiction, and previous fMRI (functional Magnetic Resonance Imaging) studies have revealed abnormal striatofrontal functional connectivity in heroin addiction. However, little is known about whether there is abnormal structural connectivity of the striatal circuit in heroin addiction. This study investigated the structural connectivity of striatal circuits in abstinent heroin-dependent individuals (HDIs) without methadone treatment.

METHODS

Forty-three (age: 38.8 ± 7.1) male HDIs and twenty-one (age: 42.4 ± 7.9) matched healthy controls underwent high-resolution T1 and whole-brain diffusion tensor imaging (64 directions) magnetic resonance imaging. Connectivity-based seed classification probabilistic tractography was used to detect the tract strengths of striatal circuits with 10 a priori target masks. Tract strengths were compared between groups and correlated with impulsivity behavior, evaluated using the Barratt Impulsivity Scale (BIS), and craving, measured on visual analogue scale (VAS).

RESULTS

HDIs showed significantly weaker tract strength of the left striatum-medial orbitofrontal cortex (mOFC) (Bonferroni corrected, p < 0.05/20 = 0.0025) and significantly higher BIS total, attention, motor, and non-planning scores (Bonferroni corrected, p < 0.05/4 = 0.0125) than controls. In HDIs, negative correlations were observed between the left striatum- mOFC tract strengths and the BIS total, attention and non-planning scores (r₁=-0.410, p₁ = 0.005; r₂=-0.432, p₂ = 0.003; r₃=-0.506, p₃<0.001) and between the right striatum-posterior cingulate cortex (PCC) tract strengths and craving scores (r=-0.433, p = 0.009) in HDIs.

CONCLUSION

HDIs displayed decreased structural connectivity of the striatum-mOFC circuit and higher impulsivity. Higher impulsive behavior was associated with decreased left striatal circuit connectivity. These findings suggest that the striatal circuit tract strengths might be a novel potential biomarker in heroin and, potentially, general opioid addiction.

Predicting relapse in patients with severe alcohol use disorder: The role of alcohol insight and implicit alcohol associations

Low insight is reported as a risk factor for relapse among patients treated for alcohol use disorders. However, to date, little is known on why patients with low insight are at higher risk for relapse. In this study, we tested the hypothesis that an implicit preference for alcohol over abstinence predicts relapse in patients with low, but not high, alcohol insight. Participants consisted of 77 patients who had received treatment for severe alcohol use disorder in a hospital in France. During hospitalization, they completed a self-report measure of insight and an implicit association test to assess implicit preference for alcohol over abstinence. The primary outcome was relapse assessed one month after discharge. Control variables were gender, age, cognitive deficit, anxiety, depression, craving, and impulsivity. Data were analysed using logistic regression analysis. After adjusting for demographic and clinical variables, relapse was predicted by the interaction between insight and implicit preference for alcohol but not by their main effects alone. Implicit preference for alcohol predicted relapse among patients with relatively low insight, but not among those with relatively high insight. These findings suggest that patients with low insight and strong implicit preference for alcohol are at a higher risk of relapse. Clinicians may therefore focus on and tailor specific interventions to prevent relapse in this vulnerable and at-risk population.

Orbitofrontal Cortex Encodes Preference for Alcohol

Orbitofrontal cortex (OFC) plays a key role in representation and regulation of reward value, preference, and seeking. OFC function is disrupted in drug use and dependence, but its specific role in alcohol use disorders has not been thoroughly studied. In alcohol-dependent humans OFC activity is increased by alcohol cue presentation. Ethanol (EtOH) also alters OFC neuron excitability in vitro, and OFC manipulation influences EtOH seeking and drinking in rodents.

Orbitofrontal cortex (OFC) plays a key role in representation and regulation of reward value, preference, and seeking. OFC function is disrupted in drug use and dependence, but its specific role in alcohol use disorders has not been thoroughly studied. In alcohol-dependent humans OFC activity is increased by alcohol cue presentation. Ethanol (EtOH) also alters OFC neuron excitability in vitro, and OFC manipulation influences EtOH seeking and drinking in rodents. To understand the relationship between OFC function and individual alcohol use, we recorded OFC neuron activity in rats during EtOH self-administration, characterizing the neural correlates of individual preference for alcohol. After one month of intermittent access to 20% EtOH, male Long–Evans rats were trained to self-administer 20% EtOH, 10% EtOH, and 15% sucrose. OFC neuronal activity was recorded and associated with task performance and EtOH preference. Rats segregated into high and low EtOH drinkers based on homecage consumption and operant seeking of 20% EtOH. Motivation for 10% EtOH and sucrose was equally high in both groups. OFC neuronal activity was robustly increased or decreased during sucrose and EtOH seeking and consumption, and strength of changes in OFC activity was directly associated with individual preference for 20% EtOH. EtOH-associated OFC activity was more similar to sucrose-associated activity in high versus low EtOH drinkers. The results show that OFC neurons are activated during alcohol seeking based on individual preference, supporting this brain region as a potential substrate for alcohol motivation that may be dysregulated in alcohol misuse.

Selective impact of lateral orbitofrontal cortex inactivation on reinstatement of alcohol seeking in male Long-Evans rats

The orbitofrontal cortex (OFC) plays a fundamental role in motivated behavior and decision-making. In humans, OFC structure and function is significantly disrupted in drug using and dependent individuals, including those exhibiting chronic alcohol use and alcoholism. In animal models, the OFC has been shown to significantly influence the seeking of non-alcohol drugs of abuse. However direct investigations of the OFC during alcohol seeking and use have been more limited. In the studies reported here, we inactivated lateral (lOFC) or medial OFC (mOFC) subregions in rats during multiple stages of alcohol seeking. After one month of intermittent access to homecage 20% ethanol (EtOH), rats were trained to self-administer EtOH under an FR3 schedule and implanted with cannulae directed to lOFC or mOFC. We inactivated OFC subregions with baclofen/muscimol during EtOH self-administration, extinction, cue-induced reinstatement, and progressive ratio testing to broadly characterize the influence of these subregions on alcohol seeking. There were no significant effects of mOFC or lOFC inactivation during FR3 self-administration, extinction, or progressive ratio self-administration. However, lOFC, and not mOFC, inactivation significantly decreased cue-induced reinstatement of EtOH seeking. These findings contribute new information to the specific impact of OFC manipulation on operant alcohol seeking, support previous studies investigating the role of OFC in seeking and consumption of alcohol and other drugs of abuse, and indicate a specific role for lOFC vs. mOFC in reinstatement.

Cognitive control and reward/loss processing in Internet gaming disorder: Results from a comparison with recreational Internet game-users

Although playing of Internet games may lead to Internet gaming disorder (IGD), most game-users do not develop problems and only a relatively small subset experiences IGD. Game playing may have positive health associations, whereas IGD has been repeatedly associated with negative health measures, and it is thus important to understand differences between individuals with IGD, recreational (non-problematic) game use (RGU) and non-/low-frequency game use (NLFGU). Individuals with IGD have shown differences in neural activations from non-gamers, yet few studies have examined neural differences between individuals with IGD, RGU and NLFGU. Eighteen individuals with IGD, 21 with RGU and 19 with NFLGU performed a color-word Stroop task and a guessing task assessing reward/loss processing. Behavioral and functional imaging data were collected and compared between groups. RGU and NLFGU subjects showed lower Stroop effects as compared with those with IGD. RGU subjects as compared to those with IGD demonstrated less frontal cortical activation brain activation during Stroop performance. During the guessing task, RGU subjects showed greater cortico-striatal activations than IGD subjects during processing of winning outcomes and greater frontal brain during processing of losing outcomes. Findings suggest that RGU as compared with IGD subjects show greater executive control and greater activations of brain regions implicated in motivational processes during reward processing and greater cortical activations during loss processing. These findings suggest neural and behavioral features distinguishing RGU from IGD and mechanisms by which RGU may be motivated to play online games frequently yet avoid developing IGD.

Dysfunctional default mode network and executive control network in people with Internet gaming disorder: Independent component analysis under a probability discounting task

Background

The present study identified the neural mechanism of risky decision-making in Internet gaming disorder (IGD) under a probability discounting task.

Methods

Independent component analysis was used on the functional magnetic resonance imaging data from 19 IGD subjects (22.2 ± 3.08 years) and 21 healthy controls (HC, 22.8 ± 3.5 years).

Results

For the behavioral results, IGD subjects prefer the risky to the fixed options and showed shorter reaction time compared to HC. For the imaging results, the IGD subjects showed higher task-related activity in default mode network (DMN) and less engagement in the executive control network (ECN) than HC when making the risky decisions. Also, we found the activities of DMN correlate negatively with the reaction time and the ECN correlate positively with the probability discounting rates.

Conclusions

The results suggest that people with IGD show altered modulation in DMN and deficit in executive control function, which might be the reason for why the IGD subjects continue to play online games despite the potential negative consequences.

Sex differences in resting-state cerebral activity alterations in internet gaming disorder

Although evidence has shown that the prevalence rates of Internet gaming disorder (IGD) differ between males and females, few studies have examined whether such sex differences extend to brain function. This study aimed to explore the sex differences in resting-state cerebral activity alterations in IGD. Thirty male participants with IGD (IGDm), 23 female participants with IGD (IGDf), and 30 male and 22 female age-matched healthy controls (HC) underwent resting-state functional MRI. Maps of the amplitude of low-frequency fluctuation (ALFF) and functional connectivity (FC) were constructed. A two-factor ANCOVA model was performed, with sex and diagnosis as the between-subject factors. Then, post hoc pair-wise comparisons were performed using two-sample t-tests within the interaction masks. The Barratt Impulsiveness Scale-11 (BIS-11) was used to assess the behavioral inhibition function. We found that the ALFF values in the orbital part of the left superior frontal gyrus (SFG) were lower in IGDm than in HCm, which were negatively correlated with BIS-11 scores. IGDm also demonstrated lower connectivity between the orbital part of the left SFG and the posterior cingulate cortex (PCC), the right angular gyrus, and the right dorsolateral prefrontal cortex than HCm. Furthermore, IGDm had lower seed connectivity between the orbital part of the left SFG and the PCC than ICDf. Our findings suggest that (1) the altered ALFF values in the orbital part of the left SFG represent a clinically relevant biomarker for the behavioral inhibition function of IGDm; (2) IGD may interact with sex-specific patterns of FC in male and female subjects.

mTORC1 in the orbitofrontal cortex promotes habitual alcohol seeking

The mechanistic target of rapamycin complex 1 (mTORC1) plays an important role in dendritic translation and in learning and memory. We previously showed that heavy alcohol use activates mTORC1 in the orbitofrontal cortex (OFC) of rodents (Laguesse et al., 2017a). Here, we set out to determine the consequences of alcohol-dependent mTORC1 activation in the OFC. We found that inhibition of mTORC1 activity in the OFC attenuates alcohol seeking and restores sensitivity to outcome devaluation in rats that habitually seek alcohol. In contrast, habitual responding for sucrose was unaltered by mTORC1 inhibition, suggesting that mTORC1’s role in habitual behavior is specific to alcohol. We further show that inhibition of GluN2B in the OFC attenuates alcohol-dependent mTORC1 activation, alcohol seeking and habitual responding for alcohol. Together, these data suggest that the GluN2B/mTORC1 axis in the OFC drives alcohol seeking and habit.

Altered motor, anxiety-related and attentional task performance at baseline associate with multiple gene copies of the vesicular acetylcholine transporter and related protein overexpression in ChAT::Cre+ rats

Transgenic rodents expressing Cre recombinase cell specifically are used for exploring mechanisms regulating behavior, including those mediated by cholinergic signaling. However, it was recently reported that transgenic mice overexpressing a bacterial artificial chromosome containing choline acetyltransferase (ChAT) gene, for synthesizing the neurotransmitter acetylcholine, present with multiple vesicular acetylcholine transporter (VAChT) gene copies, resulting in altered cholinergic tone and accompanying behavioral abnormalities. Since ChAT::Cre+ rats, used increasingly for understanding the biological basis of CNS disorders, utilize the mouse ChAT promotor to control Cre recombinase expression, we assessed for similar genotypical and phenotypical differences in such rats compared to wild-type siblings. The rats were assessed for mouse VAChT copy number, VAChT protein expression levels and for sustained attention, response control and anxiety. Rats were also subjected to a contextual fear conditioning paradigm using an unconditional fear-inducing stimulus (electrical foot shocks), with blood samples taken at baseline, the fear acquisition phase and retention testing, for measuring blood plasma markers of hypothalamic-pituitary-adrenal gland (HPA)-axis activity. ChAT::Cre+ rats expressed multiple mouse VAChT gene copies, resulting in significantly higher VAChT protein expression, revealed anxiolytic behavior, hyperlocomotion and deficits in tasks requiring sustained attention. The HPA-axis was intact, with unaltered circulatory levels of acute stress-induced corticosterone, leptin and glucose. Our findings, therefore, reveal that in ChAT::Cre+ rats, VAChT overexpression associates with significant alterations of certain cognitive, motor and affective functions. Although highly useful as an experimental tool, it is essential to consider the potential effects of altered cholinergic transmission on baseline behavior in ChAT::Cre rats.

Withdrawal from escalated cocaine self-administration impairs reversal learning by disrupting the effects of negative feedback on reward exploitation: a behavioral and computational analysis

Addiction is regarded as a disorder of inflexible choice with behavior dominated by immediate positive rewards over longer-term negative outcomes. However, the psychological mechanisms underlying the effects of self-administered drugs on behavioral flexibility are not well understood. To investigate whether drug exposure causes asymmetric effects on positive and negative outcomes we used a reversal learning procedure to assess how reward contingencies are utilized to guide behavior in rats previously exposed to intravenous cocaine self-administration (SA). Twenty-four rats were screened for anxiety in an open field prior to acquisition of cocaine SA over six daily sessions with subsequent long-access cocaine SA for 7 days. Control rats (n = 24) were trained to lever-press for food under a yoked schedule of reinforcement. Higher rates of cocaine SA were predicted by increased anxiety and preceded impaired reversal learning, expressed by a decrease in lose-shift as opposed to win-stay probability. A model-free reinforcement learning algorithm revealed that rats with high, but not low cocaine escalation failed to exploit previous reward learning and were more likely to repeat the same response as the previous trial. Eight-day withdrawal from high cocaine escalation was associated, respectively, with increased and decreased dopamine receptor D2 (DRD2) and serotonin receptor 2C (HTR2C) expression in the ventral striatum compared with controls. Dopamine receptor D1 (DRD1) expression was also significantly reduced in the orbitofrontal cortex of high cocaine-escalating rats. These findings indicate that withdrawal from escalated cocaine SA disrupts how negative feedback is used to guide goal-directed behavior for natural reinforcers and that trait anxiety may be a latent variable underlying this interaction.

Reward

Neurons throughout frontal cortex show robust responses to rewards, but a challenge is determining the specific function served by these different reward signals. Most neuropsychiatric disorders involve dysfunction of circuits between frontal cortex and subcortical structures, such as the striatum. There are multiple frontostriatal loops, and different neuropsychiatric disorders involve different loops to greater or lesser extents. Understanding the role of reward in each of these different circuits is a necessary step in developing novel treatments for these disorders. This chapter summarizes the recent literature that has identified the role of reward in different subregions of the frontal cortex. Orbitofrontal cortex integrates information about multiple aspects of expected rewards in order to derive their value, which can then be used to decide between alternative potential rewards. Neurons in anterior cingulate cortex encode the difference between the expected reward and the actual outcome. This information is useful for learning, since it can ensure that behavior changes when the outcome was not anticipated. Reward also affects signals in lateral prefrontal cortex related to attention and response selection, ensuring that behaviors are optimally prioritized. Finally, the chapter discusses how reward signals contribute to social processing and autonomic control.

Brain response features during forced break could predict subsequent recovery in internet gaming disorder: A longitudinal study

Although internet gaming disorder (IGD) is associated with negative health measures, individuals may recover without professional intervention. Exploring neural features associated with natural recovery may provide insights into how best to promote health among people with IGD. Seventy-nine IGD subjects were scanned when they were performing cue-craving tasks before and after gaming was interrupted with a forced break. After one year, 20 individuals no longer met IGD criteria and were considered recovered. We compared brain responses in cue-craving tasks between these 20 recovered IGD subjects and 20 matched IGD subjects still meeting criteria at one year (persistent IGD). Recovered IGD subjects showed lower dorsolateral prefrontal cortex (DLPFC) activation than persistent IGD subjects to gaming cues at both pre- and post-gaming times. Significant group-by-time interactions were found in the bilateral DLPFC and insula, and these involved relatively decreased DLPFC and increased insula activation in the persistent IGD group during the forced break. Relatively decreased DLPFC activity and increased insula activity in response to gaming cues following recent gaming may underlie persistence of gaming. These findings suggest that executive control and interoceptive processing warrant additional study in understanding recovery from IGD.

Noradrenergic terminals are the primary source of α2-adrenoceptor mediated dopamine release in the medial prefrontal cortex

In various psychiatric disorders, deficits in dopaminergic activity in the prefrontal cortex (PFC) are implicated. Treatments involving selective augmentation of dopaminergic activity in the PFC primarily depend on the inhibition of α₂-adrenoreceptors singly or in combination with the inhibition of the norepinephrine transporter (NET). We aimed to clarify the relative contribution of dopamine (DA) release from noradrenergic and dopaminergic terminals to DA output induced by blockade of α₂-adrenoreceptors and NET. To this end, we assessed whether central noradrenergic denervation modified catecholamine output in the medial PFC (mPFC) of rats elicited by atipamezole (an α₂-adrenoreceptor antagonist), nisoxetine (an NET inhibitor), or their combination. Intraventricular administration of anti-dopamine-beta-hydroxylase-saporin (aDBH) caused a loss of DBH-positive fibers in the mPFC and almost total depletion of tissue and extracellular NE level; however, it did not reduce tissue DA level but increased extracellular DA level by 70% in the mPFC. Because noradrenergic denervation should have caused a loss of NET and reduced NE level at α₂-adrenoceptors, the actual effect of an aDBH-induced lesion on DA output elicited by blockade of α₂-adrenoceptors and NET was evaluated by comparing denervated and control rats following blockade of α₂-adrenoceptors and NET with atipamezole and nisoxetine, respectively. In the control rats, extracellular NE and DA levels increased by approximately 150% each with 3 mg/kg atipamezole; 450% and 230%, respectively, with 3 mg/kg nisoxetine; and 2100% and 600%, respectively, with combined atipamezole and nisoxetine. In the denervated rats, consistent with the loss of NET, nisoxetine failed to modify extracellular DA level, whereas atipamezole, despite the lack of NE-induced stimulation of α₂-adrenoceptors, increased extracellular DA level by approximately 30%. Overall, these results suggest that atipamezole-induced DA release mainly originated from noradrenergic terminals, possibly through the inhibition of α₂-autoreceptors. Furthermore, while systemic and local administration of the α₂-adrenoceptor agonist clonidine into the mPFC of the controls rats reduced extracellular NE level by 80% and 60%, respectively, and extracellular DA level by 50% and 60%, respectively, it failed to reduce DA output in the denervated rats, consistent with the loss of α₂-autoreceptors. To eliminate the possibility that denervation reduced DA release potential via the effects at dopaminergic terminals in the mPFC, the effect of systemic administration of the D₂-DA antagonist raclopride (0.5 mg/kg IP) on DA output was analyzed. In the control rats, raclopride was found to be ineffective when administered alone, but it increased extracellular DA level by 380% following NET inhibition with nisoxetine. In the denervated rats, as expected due to the loss of NET, raclopride-alone or with nisoxetine-increased DA release to approximately the same level as that observed in the control rats after NET inhibition. Overall, these results suggest that noradrenergic terminals in the mPFC are the primary source of DA released by blockade of α₂-adrenoreceptors and NET and that α₂-autoreceptors, and not α₂-heteroreceptors, mediate DA output induced by α₂-adrenoceptor blockade.

The cellular basis of fetal endoplasmic reticulum stress and oxidative stress in drug-induced neurodevelopmental deficits

Prenatal substance exposure is a growing public health concern worldwide. Although the opioid crisis remains one of the most prevalent addiction problems in our society, abuse of cocaine, methamphetamines, and other illicit drugs, particularly amongst pregnant women, are nonetheless significant and widespread. Evidence demonstrates prenatal drug exposure can affect fetal brain development and thus can have long-lasting impact on neurobehavioral and cognitive performance later in life. In this review, we highlight research examining the most prevalent drugs of abuse and their effects on brain development with a focus on endoplasmic reticulum stress and oxidative stress signaling pathways. A thorough exploration of drug-induced cellular stress mechanisms during prenatal brain development may provide insight into therapeutic interventions to combat effects of prenatal drug exposure.

Gender-related functional connectivity and craving during gaming and immediate abstinence during a mandatory break: Implications for development and progression of internet gaming disorder

BACKGROUND

Although males more frequently develop Internet gaming disorder (IGD) as compared with females, few studies have examined gender-related neurocognitive differences in IGD. TASK AND DESIGN: fMRI and subjective data were collected from 119 subjects (IGD, male 29, female 25; recreational game use (RGU), male 34, female 31) when they were actively playing games and during a forced mandatory break. Analyses investigating effects of group (IGD, RGU) and gender (male, female) on the functional connectivity (FC) of executive control and reward systems linked to the dorsolateral prefrontal cortex (DLPFC) and striatum, respectively, were performed. Correlations between FC and subjective craving measures were also calculated.

RESULTS

Gaming-group-by-gender interactions were observed. During gaming in males but not in females, the FC between the DLPFC and superior frontal gyrus was relatively decreased, and that between the striatum and thalamus was relatively increased. During the mandatory break, changes in the FC between DLPFC and superior frontal gyrus and the FC between the striatum and thalamus varied by gender with greater RGU-IGD differences observed in females. Significant correlations between FC and self-reported craving were observed.

CONCLUSIONS

During both gaming and a forced mandatory break, brain regions implicated in executive control and reward processing showed changes in FC that varied by gender. Brain regions implicated in executive control showed differential FC in males during gaming, and FC during the forced mandatory break appeared relevant to both genders, and perhaps particularly for females. The findings suggest possible neural mechanisms for why males appear more likely to develop IGD, and why it may be particularly difficult for individuals with IGD to cease gaming.

Vitamin B12 Levels in Methamphetamine Addicts

Objective: It has been established that reduced vitamin B12 serum levels are associated with cognitive decline and mental illness. The chronic use of methamphetamine (MA), which is a highly addictive drug, can induce cognitive impairment and psychopathological symptoms. There are few studies addressing the association of MA with vitamin B12 serum levels. This study examined whether the serum levels of B12 are associated with MA addiction.

Methods: Serum vitamin B12, homocysteine (Hcy), glucose and triglyceride concentrations were measured in 123 MA addicts and 108 controls. In addition, data were collected on their age, marital status, level of education and Body Mass Index (BMI) for all participants. In the patient group, the data for each subject were collected using the Fagerstrom Test for Nicotine Dependence (FTND), the Alcohol Use Disorders Identification Test (AUDIT), and a drug use history, which included the age of onset, total duration of MA use, the number of relapses and addiction severity.

Results: Our results showed that MA addicts had lower vitamin B12 levels (p < 0.05) than those of healthy controls, but Hcy levels were not significantly different between the two groups (p > 0.05). Serum B12 levels were negatively correlated with the number of relapses in the MA group. Furthermore, binary logistics regression analysis indicated that the B12 was an influencing factor contributing to addiction severity.

Conclusion: The findings of this study suggest that some MA addicts might have vitamin B12 deficiency, and serum B12 levels may be involved in the prognosis of MA addiction.

Orbitofrontal gray matter deficits as marker of Internet gaming disorder: converging evidence from a cross-sectional and prospective longitudinal design

Internet gaming disorder represents a growing health issue. Core symptoms include unsuccessful attempts to control the addictive patterns of behavior and continued use despite negative consequences indicating a loss of regulatory control. Previous studies revealed brain structural deficits in prefrontal regions subserving regulatory control in individuals with excessive Internet use. However, because of the cross-sectional nature of these studies, it remains unknown whether the observed brain structural deficits preceded the onset of excessive Internet use. Against this background, the present study combined a cross-sectional and longitudinal design to determine the consequences of excessive online video gaming. Forty-one subjects with a history of excessive Internet gaming and 78 gaming-naive subjects were enrolled in the present study. To determine effects of Internet gaming on brain structure, gaming-naive subjects were randomly assigned to 6 weeks of daily Internet gaming (training group) or a non-gaming condition (training control group). At study inclusion, excessive Internet gamers demonstrated lower right orbitofrontal gray matter volume compared with Internet gaming-naive subjects. Within the Internet gamers, a lower gray matter volume in this region was associated with higher online video gaming addiction severity. Longitudinal analysis revealed initial evidence that left orbitofrontal gray matter volume decreased during the training period in the training group as well as in the group of excessive gamers. Together, the present findings suggest an important role of the orbitofrontal cortex in the development of Internet addiction with a direct association between excessive engagement in online gaming and structural deficits in this brain region.

The role of the orbitofrontal cortex in alcohol use, abuse, and dependence

One of the major functions of the orbitofrontal cortex (OFC) is to promote flexible motivated behavior. It is no surprise, therefore, that recent work has demonstrated a prominent impact of chronic drug use on the OFC and a potential role for OFC disruption in drug abuse and addiction. Among drugs of abuse, the use of alcohol is particularly salient with respect to OFC function. Although a number of studies in humans have implicated OFC dysregulation in alcohol use disorders, animal models investigating the association between OFC and alcohol use are only beginning to be developed, and there is still a great deal to be revealed. The goal of this review is to consider what is currently known regarding the role of the OFC in alcohol use and dependence. I will first provide a brief, general overview of current views of OFC function and its contributions to drug seeking and addiction. I will then discuss research to date related to the OFC and alcohol use, both in human clinical populations and in non-human models. Finally I will consider issues and strategies to guide future study that may identify this brain region as a key player in the transition from moderated to problematic alcohol use and dependence.

Gender-related differences in cue-elicited cravings in Internet gaming disorder: The effects of deprivation

BACKGROUND

Online gaming has become a popular leisure activity, in which males more frequently develop Internet gaming disorder (IGD) compared to females. However, gender-related neurocognitive differences have largely not been systematically investigated in IGD.

METHODS

Cue-elicited-craving tasks were performed before game playing and immediately after deprivation operationalized as a forced break from gaming when the Internet was disconnected. Ninety-nine subjects with IGD (27 males and 22 females) or recreational game use (RGU; 27 males and 23 females) provided functional MRI and subjective data. Analyses investigating effects of group (IGD and RGU) × gender (male and female) at different times (pre-gaming, post-gaming, and post-pre) on cue-elicited craving and brain responses were performed. Correlations between brain responses and subjective measures were calculated.

RESULTS

In pre-, post-, and post-pre tests, significant gender-by-group interactions (p < .001, cluster size > 15 voxels) were observed in the left dorsolateral prefrontal cortex (DLPFC). Further analyses of the DLPFC cluster showed that in post-pre comparisons, results were related to less engagement of the DLPFC in IGD, especially in females. In addition, at post-test, significant interactions were observed in the caudate, as females with IGD showed greater activation as compared to those with RGU.

DISCUSSION

The results raise the possibility that women with RGU may show better executive control than men when facing gaming cues, which may provide resiliency against developing IGD; however, once they develop IGD, their gaming may impair their executive control and enhance their cravings for gaming, which may make it more difficult to quit gaming.

Cortical thickness and volume abnormalities in Internet gaming disorder: Evidence from comparison of recreational Internet game users

Although online gaming may lead to Internet gaming disorder (IGD), most players are recreational game users (RGUs) who do not develop IGD. Thus far, little is known about brain structural abnormalities in IGD subjects relative to RGUs. The inclusion of RGUs as a control group could minimize the potential effects of gaming experience and gaming-related cue familiarity on the neural mechanism of IGD subjects. In this study, structural magnetic resonance imaging data were acquired from 38 IGD subjects and 66 RGUs with comparable age, gender, and educational level. Group differences in cortical thickness and volume were analyzed using the FreeSurfer software. Correlations between cortical changes and addiction severity were calculated for both groups. Compared with the RGU group, the IGD group showed significantly decreased cortical thickness in the left lateral orbitofrontal cortex, inferior parietal lobule, bilateral cuneus, precentral gyrus, and right middle temporal gyrus. Moreover, significantly reduced cortical volume was observed in the left superior temporal gyrus and right supramarginal gyrus in the IGD group. Whole-brain correlational analysis indicated different correlations between the two groups. The brain regions that showed group differences were considered to be involved in cognitive control, decision making, and reward/loss processing. These functions may serve as potential mechanisms that explain why IGD individuals experience negative outcomes in frequent game playing.

Inactivation of nucleus reuniens impairs spatial working memory and behavioral flexibility in the rat

The hippocampal formation (HF) and medial prefrontal cortex (mPFC) play critical roles in spatial working memory (SWM). The nucleus reuniens (RE) of the ventral midline thalamus is an important anatomical link between the HF and mPFC, and as such is crucially involved in SWM functions that recruit both structures. Little is known, however, regarding the role of RE in other behaviors mediated by this circuit. In the present study, we examined the role of RE in spatial working memory and executive functioning following reversible inactivation of RE with either muscimol or procaine. Rats were implanted with an indwelling cannula targeting RE and trained in a delayed nonmatch to sample spatial alternation T-maze task. For the task, sample and choice runs were separated by moderate or long delays (30, 60, and 120 s). Following asymptotic performance, rats were tested following infusions of drug or vehicle. Muscimol infused into RE impaired SWM at all delays, whereby procaine only impaired performance at the longest delays. Furthermore, RE inactivation with muscimol produced a failure in win-shift strategy as well as severe spatial perseveration, whereby rats persistently made re-entries into incorrect arms during correction trials, despite the absence of reward. This demonstrated marked changes in behavioral flexibility and response strategy. These results strengthen the role of nucleus reuniens as a pivotal link between hippocampus and prefrontal cortex in cognitive and executive functions and suggest that nucleus reuniens may be a potential target in the treatment of CNS disorders such as schizophrenia, attention deficit hyperactivity disorder, addiction, and obsessive-compulsive disorder, whose symptoms are defined by hippocampal-prefrontal dysfunctions.

Modeling human methamphetamine use patterns in mice: chronic and binge methamphetamine exposure, reward function and neurochemistry

Different methamphetamine use patterns in human subjects may contribute to inconsistent findings regarding the effects of methamphetamine abuse on brain and behavior. The present study investigated whether human-derived chronic and binge methamphetamine use patterns have differential effects on reward and neurochemistry in mice. Brain reward function in mice was evaluated during acute/prolonged withdrawal, and in response to methamphetamine challenge using the intracranial self-stimulation procedure. Brain dopaminergic, serotonergic and glutamatergic neurochemistry was determined with high-performance liquid chromatography. Chronic and binge regimens induced withdrawal-related decreases in reward function that were more severe during the binge regimen during cycles 1-2. Despite large differences in methamphetamine dose, both regimens induced similar reward deficits during cycles 3-4. Neither methamphetamine regimen led to persistent alterations in the sensitivity to the reward-enhancing effects of acute methamphetamine challenge. The binge regimen severely depleted striatal dopamine levels and increased brain glutamine levels. The chronic regimen had milder effects on striatal dopamine levels and altered cortical dopamine and serotonin levels. This work highlights that the magnitude of acute/prolonged withdrawal may not reflect amount or frequency of methamphetamine intake. In contrast, the array of underlying neurochemical alterations was methamphetamine regimen dependent. Thus, stratifying methamphetamine-dependent individuals based on use pattern may help to cater therapeutic interventions more appropriately by targeting use pattern-specific neurotransmitter systems.

Neurobiological Correlates in Internet Gaming Disorder: A Systematic Literature Review

Internet Gaming Disorder (IGD) is a potential mental disorder currently included in the third section of the latest (fifth) edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-5) as a condition that requires additional research to be included in the main manual. Although research efforts in the area have increased, there is a continuing debate about the respective criteria to use as well as the status of the condition as mental health concern. Rather than using diagnostic criteria which are based on subjective symptom experience, the National Institute of Mental Health advocates the use of Research Domain Criteria (RDoC) which may support classifying mental disorders based on dimensions of observable behavior and neurobiological measures because mental disorders are viewed as biological disorders that involve brain circuits that implicate specific domains of cognition, emotion, and behavior. Consequently, IGD should be classified on its underlying neurobiology, as well as its subjective symptom experience. Therefore, the aim of this paper is to review the neurobiological correlates involved in IGD based on the current literature base. Altogether, 853 studies on the neurobiological correlates were identified on ProQuest (in the following scholarly databases: ProQuest Psychology Journals, PsycARTICLES, PsycINFO, Applied Social Sciences Index and Abstracts, and ERIC) and on MEDLINE, with the application of the exclusion criteria resulting in reviewing a total of 27 studies, using fMRI, rsfMRI, VBM, PET, and EEG methods. The results indicate there are significant neurobiological differences between healthy controls and individuals with IGD. The included studies suggest that compared to healthy controls, gaming addicts have poorer response-inhibition and emotion regulation, impaired prefrontal cortex (PFC) functioning and cognitive control, poorer working memory and decision-making capabilities, decreased visual and auditory functioning, and a deficiency in their neuronal reward system, similar to those found in individuals with substance-related addictions. This suggests both substance-related addictions and behavioral addictions share common predisposing factors and may be part of an addiction syndrome. Future research should focus on replicating the reported findings in different cultural contexts, in support of a neurobiological basis of classifying IGD and related disorders.

Modulation of salience network intranetwork resting state functional connectivity in women with chronic migraine

Objective To investigate the intranetwork resting state fMRI connectivity within the Salience Network of chronic migraine with and without medication overuse headache. Methods We compared 351 pairs of intranetwork connectivity in chronic migraine (n = 13) and chronic migraine with medication overuse headache (n = 16) compared to matched controls, and between each chronic migraine subgroup. Results Compared to controls, 17 pairs of intranetwork connections in chronic migraine and 27 pairs in chronic migraine with medication overuse headache were decreased. When comparing chronic migraine with medication overuse headache versus chronic migraine, connectivity between bilateral extended amygdala, and between paracingulate to right ventral tegmental area/substantia nigra were decreased in chronic migraine (chronic migraine < chronic migraine with medication overuse headache). Connectivity between left dorsolateral prefrontal cortex to bilateral ventral striatum/pallidum, to bilateral dorsal anterior cingulate cortex; left anterior prefrontal cortex to contralateral orbitofrontal insula; and left ventral striatum/pallidum to ipsilateral supplementary motor area (SMA)/preSMA were decreased in chronic migraine with medication overuse headache (chronic migraine with medication overuse headache < chronic migraine). Conclusion Both chronic migraine subgroups had shared intranetwork connectivity abnormality, however, each subgroup had unique pattern of disruption within the salience network. The results suggest that the aberrant assignment of salience to external and internal stimuli plays an important role in chronic migraine and chronic migraine with medication overuse headache interictally, mostly involving mesolimbic pathways (especially bilateral extended amygdala) in chronic migraine, and prefrontal-subcortical limbic pathways in chronic migraine with medication overuse headache.

Overlapping Risky Decision-Making and Olfactory Processing Ability in HIV-Infected Individuals

OBJECTIVE

Given neuroimaging evidences of overlap in the circuitries for decision-making and olfactory processing, we examined the hypothesis that impairment in psychophysical tasks of olfaction would independently predict poor performances on Iowa Gambling Task (IGT), a laboratory task that closely mimics real-life decision-making, in a US cohort of HIV-infected (HIV+) individuals.

METHOD

IGT and psychophysical tasks of olfaction were administered to a Washington DC-based cohort of largely African American HIV+ subjects (N=100), and to a small number of demographically-matched non-HIV healthy controls (N=43) from a different study. Constructs of olfactory ability and decision-making were examined through confirmatory factor analysis (CFA). Structural equation models (SEMs) were used to evaluate the validity of the path relationship between these two constructs.

RESULT

The 100 HIV+ participants (56% female; 96% African Americans; median age = 48 years) had median CD4 count of 576 cells/μl and median HIV RNA viral load <48 copies per milliliter. Majority of HIV+ participants performed randomly throughout the course of IGT tasks, and failed to demonstrate a learning curve. Confirmatory factor analysis provided support for a unidimensional factor underlying poor performances on IGT. Nomological validity for correlations between olfactory ability and IGT performance was confirmed through SEM. Finally, factor scores of olfactory ability and IGT performance strongly predicted 6 months history of drug use, while olfaction additionally predicted hallucinogen use.

CONCLUSION

This study suggests that combination of simple, office-based tasks of olfaction and decision-making may identify those HIV+ individuals who are more prone to risky decision-making. This finding may have significant clinical, public health value if joint impairments in olfaction and IGT task correlates with more decreased activity in brain regions relevant to decision-making.

Neurobiological findings related to Internet use disorders

In the last 10 years, numerous neurobiological studies have been conducted on Internet addiction or Internet use disorder. Various neurobiological research methods - such as magnetic resonance imaging; nuclear imaging modalities, including positron emission tomography and single photon emission computed tomography; molecular genetics; and neurophysiologic methods - have made it possible to discover structural or functional impairments in the brains of individuals with Internet use disorder. Specifically, Internet use disorder is associated with structural or functional impairment in the orbitofrontal cortex, dorsolateral prefrontal cortex, anterior cingulate cortex, and posterior cingulate cortex. These regions are associated with the processing of reward, motivation, memory, and cognitive control. Early neurobiological research results in this area indicated that Internet use disorder shares many similarities with substance use disorders, including, to a certain extent, a shared pathophysiology. However, recent studies suggest that differences in biological and psychological markers exist between Internet use disorder and substance use disorders. Further research is required for a better understanding of the pathophysiology of Internet use disorder.

A neuronal activation correlate in striatum and prefrontal cortex of prolonged cocaine intake

Maladaptive changes in the involvement of striatal and frontal cortical regions in drug use are thought to underlie the progression to habitual drug use and loss of cognitive control over drug intake that occur with accumulating drug experience. The present experiments focus on changes in neuronal activity in these regions associated with short-term (10 days) and long-term (60 days) self-administration of cocaine. Quantitative in situ hybridization for the immediate early gene Mkp1 was combined with statistical parametric mapping to assess the distribution of neuronal activity. We hypothesized that neuronal activity in striatum would increase in its dorsal part and that activity in frontal cortex would decrease with prolonged cocaine self-administration experience. Expression of Mkp1 was profoundly increased after cocaine self-administration, and the magnitude of this effect was greater after short-term compared to long-term self-administration. Increased neuronal activity was seen in both dorsal and ventral sectors of the striatum after 10 days exposure to cocaine. However, enhanced activity was restricted to dorsomedial and dorsocentral striatum after 60 days cocaine self-administration. In virtually all medial prefrontal and most orbitofrontal areas, increased expression of Mkp1 was observed after 10 days of cocaine taking, whereas after 60 days, enhanced expression was restricted to caudal parts of medial prefrontal and caudomedial parts of orbitofrontal cortex. Our data reveal functional changes in cellular activity in striatum and frontal cortex with increasing cocaine self-administration experience. These changes might reflect the neural processes that underlie the descent from recreational drug taking to compulsive cocaine use.

Changes of quality of life and cognitive function in individuals with Internet gaming disorder: A 6-month follow-up

Internet gaming disorder (IGD) contributes to poor quality of life (QOL) and cognitive dysfunction and is increasingly recognized as a social problem in various countries. However, no evidence exists to determine whether QOL and cognitive dysfunction stabilize after appropriate management. The present study addressed improvement in QOL and cognitive functioning associated with changes in addiction symptoms following outpatient management for IGD. A total of 84 young males (IGD group: N = 44, mean age: 19.159 ± 5.216 years; healthy control group: N = 40, mean age: 21.375 ± 6.307 years) participated in this study. We administered self-report questionnaires at baseline to assess clinical and psychological characteristics, and conducted traditional and computerized neuropsychological tests. Nineteen patients with IGD completed follow-up tests in the same manner after 6 months of outpatient treatment, which included pharmacotherapy with selective serotonin reuptake inhibitors. A baseline comparison of patients with IGD against the healthy control group showed that the IGD patients had more symptoms of depression and anxiety, higher degrees of impulsiveness and anger/aggression, higher levels of distress, poorer QOL, and impaired response inhibition. After 6 months of treatment, patients with IGD showed significant improvements in the severity of IGD, as well as in QOL, response inhibition, and executive functioning. Additionally, a stepwise multiple regression analysis revealed a favorable prognosis for IGD patients with low working memory functioning and high executive functioning at baseline. These results provide evidence regarding longitudinal changes in QOL and cognitive function following psychiatric intervention for IGD. Furthermore, it appears that response inhibition may be an objective state marker underlying the pathophysiology of IGD.

From mother to child: orbitofrontal cortex gyrification and changes of drinking behaviour during adolescence

Adolescence is a common time for initiation of alcohol use and alcohol use disorders. Importantly, the neuro-anatomical foundation for later alcohol-related problems may already manifest pre-natally, particularly due to smoking and alcohol consumption during pregnancy. In this context, cortical gyrification is an interesting marker of neuronal development but has not been investigated as a risk factor for adolescent alcohol use. On magnetic resonance imaging scans of 595 14-year-old adolescents from the IMAGEN sample, we computed whole-brain mean curvature indices to predict change in alcohol-related problems over the following 2 years. Change of alcohol use-related problems was significantly predicted from mean curvature in left orbitofrontal cortex (OFC). Less gyrification of OFC was associated with an increase in alcohol use-related problems over the next 2 years. Moreover, lower gyrification in left OFC was related to pre-natal alcohol exposure, whereas maternal smoking during pregnancy had no effect. Current alcohol use-related problems of the biological mother had no effect on offsprings' OFC gyrification or drinking behaviour. The data support the idea that alcohol consumption during pregnancy mediates the development of neuro-anatomical phenotypes, which in turn constitute a risk factor for increasing problems due to alcohol consumption in a vulnerable stage of life. Maternal smoking during pregnancy or current maternal alcohol/nicotine consumption had no significant effect. The OFC mediates behaviours known to be disturbed in addiction, namely impulse control and reward processing. The results stress the importance of pre-natal alcohol exposure for later increases in alcohol use-related problems, mediated by structural brain characteristics.

Sufficiency of Mesolimbic Dopamine Neuron Stimulation for the Progression to Addiction

The factors causing the transition from recreational drug consumption to addiction remain largely unknown. It has not been tested whether dopamine (DA) is sufficient to trigger this process. Here we use optogenetic self-stimulation of DA neurons of the ventral tegmental area (VTA) to selectively mimic the defining commonality of addictive drugs. All mice readily acquired self-stimulation. After weeks of abstinence, cue-induced relapse was observed in parallel with a potentiation of excitatory afferents onto D1 receptor-expressing neurons of the nucleus accumbens (NAc). When the mice had to endure a mild electric foot shock to obtain a stimulation, some stopped while others persevered. The resistance to punishment was associated with enhanced neural activity in the orbitofrontal cortex (OFC) while chemogenetic inhibition of the OFC reduced compulsivity. Together, these results show that stimulating VTA DA neurons induces behavioral and cellular hallmarks of addiction, indicating sufficiency for the induction and progression of the disease.

Association of exposure to neighborhood drug activity, neurobehavioral traits, and marijuana use among at-risk African American females

INTRODUCTION

Theories of relative deprivation suggest African Americans in disadvantaged communities are at increased risk for drug use. This increased risk may be due, in part, to exposure to drugs and drug subcultures. Given the significance of the prefrontal cortex (PFC) functioning in yielding behavior that is strategically guided rather than reactive to environmental demands, it is important to examine the relationship between PFC functioning, neighborhood drug activity and substance use among African Americans residing in high risk communities.

METHODS

A sample of 120 young adult African American females was recruited from high-risk neighborhoods. Each completed the modified version of the neighborhood environment scale, a neurobehavioral assessment designed to measure apathy, behavioral disinhibition and executive dysfunction, and provided a urine sample that was tested for the presence of psychoactive drugs.

RESULTS

Logistic regression analyses indicated that females with higher scores on behavioral disinhibition were 2.6 times more likely to test positive for marijuana (95%CI = 1.02, 6.57). Neither apathy nor executive dysfunction was related to marijuana use. No relationship emerged between neighborhood drug activity and marijuana use.

CONCLUSIONS

Among the neurobehavioral traits considered only behavioral disinhibition was associated with marijuana use, suggesting that different neurobehavioral domains may be uniquely related to marijuana use. For females living in high risk environments, the extent to which they are able to control impulses may provide some protection against marijuana use. Future studies focused on the moderating effects of behavioral disinhibition on the association of exposure to risk environments and marijuana use may prove beneficial. Further, the study adds to the small base of literature supporting the Frontal Systems Behavior Scale as a brief assessment to evaluate frontally-mediated neurobehavioral traits relevant to substance use. However, future studies aimed at examining the influence of neighborhood drug activity might benefit from more precise measures of exposure to neighborhood drug activity. More research to replicate and expand on the present findings is warranted.

Effects of prior cocaine versus morphine or heroin self-administration on extinction learning driven by overexpectation versus omission of reward

BACKGROUND

Addiction is characterized by an inability to stop using drugs, despite adverse consequences. One contributing factor to this compulsive drug taking could be the impact of drug use on the ability to extinguish drug seeking after changes in expected outcomes. Here, we compared effects of cocaine, morphine, and heroin self-administration on two forms of extinction learning: standard extinction driven by reward omission and extinction driven by reward overexpectation.

METHODS

In experiment 1, we trained rats to self-administer cocaine, morphine, or sucrose for 3 hours per day (limited access). In experiment 2, we trained rats to self-administer heroin or sucrose for 12 hours per day (extended access). Three weeks later, we trained the rats to associate several cues with palatable food reward, after which we assessed extinction of the learned Pavlovian response, first by pairing two cues together in the overexpectation procedure and later by omitting the food reward.

RESULTS

Rats trained under limited access conditions to self-administer sucrose or morphine demonstrated normal extinction in response to both overexpectation and reward omission, whereas cocaine-experienced rats or rats trained to self-administer heroin under extended access conditions exhibited normal extinction in response to reward omission but failed to show extinction in response to overexpectation.

CONCLUSIONS

Here we show that cocaine and heroin can induce long-lasting deficits in the ability to extinguish reward seeking. These deficits were not observed in a standard extinction procedure but instead only affected extinction learning driven by a more complex phenomenon of overexpectation.

Molecular and functional imaging of internet addiction

Maladaptive use of the Internet results in Internet addiction (IA), which is associated with various negative consequences. Molecular and functional imaging techniques have been increasingly used for analysis of neurobiological changes and neurochemical correlates of IA. This review summarizes molecular and functional imaging findings on neurobiological mechanisms of IA, focusing on magnetic resonance imaging (MRI) and nuclear imaging modalities including positron emission tomography (PET) and single photon emission computed tomography (SPECT). MRI studies demonstrate that structural changes in frontal cortex are associated with functional abnormalities in Internet addicted subjects. Nuclear imaging findings indicate that IA is associated with dysfunction of the brain dopaminergic systems. Abnormal dopamine regulation of the prefrontal cortex (PFC) could underlie the enhanced motivational value and uncontrolled behavior over Internet overuse in addicted subjects. Further investigations are needed to determine specific changes in the Internet addictive brain, as well as their implications for behavior and cognition.

Imbalanced functional link between executive control network and reward network explain the online-game seeking behaviors in Internet gaming disorder

Literatures have shown that Internet gaming disorder (IGD) subjects show impaired executive control and enhanced reward sensitivities than healthy controls. However, how these two networks jointly affect the valuation process and drive IGD subjects' online-game-seeking behaviors remains unknown. Thirty-five IGD and 36 healthy controls underwent a resting-states scan in the MRI scanner. Functional connectivity (FC) was examined within control and reward network seeds regions, respectively. Nucleus accumbens (NAcc) was selected as the node to find the interactions between these two networks. IGD subjects show decreased FC in the executive control network and increased FC in the reward network when comparing with the healthy controls. When examining the correlations between the NAcc and the executive control/reward networks, the link between the NAcc - executive control network is negatively related with the link between NAcc - reward network. The changes (decrease/increase) in IGD subjects' brain synchrony in control/reward networks suggest the inefficient/overly processing within neural circuitry underlying these processes. The inverse proportion between control network and reward network in IGD suggest that impairments in executive control lead to inefficient inhibition of enhanced cravings to excessive online game playing. This might shed light on the mechanistic understanding of IGD.

Decreased functional connectivity in an executive control network is related to impaired executive function in Internet gaming disorder

BACKGROUND

Resting brain spontaneous neural activities across cortical regions have been correlated with specific functional properties in psychiatric groups. Individuals with Internet gaming disorder (IGD) demonstrate impaired executive control. Thus, it is important to examine executive control networks (ECNs) during resting states and their relationships to executive control during task performance.

METHODS

Thirty-five IGD and 36 healthy control participants underwent a resting-state fMRI scan and performed a Stroop task inside and outside of the MRI scanner. Correlations between Stroop effect and functional connectivity among ECN regions of interest (ROIs) were calculated within and between groups.

RESULTS

IGD subjects show lower functional connectivity in ECNs than do HC participants during resting state; functional-connectivity measures in ECNs were negatively correlated with Stroop effect and positively correlated with brain activations in executive-control regions across groups. Within groups, negative trends were found between Stroop effect and functional connectivity in ECNs in IGD and HC groups, separately; positive trends were found between functional connectivity in ECNs and brain activations in Stroop task in IGD and HC groups, separately.

CONCLUSIONS

Higher functional connectivity in ECNs may underlie better executive control and may provide resilience with respect to IGD. Lower functional connectivity in ECNs may represent an important feature in understanding and treating IGD.

Altered brain activation during response inhibition and error processing in subjects with Internet gaming disorder: a functional magnetic imaging study

The aim of the present study was to evaluate the impulsivity and brain correlates of response inhibition and error processing among subjects with Internet gaming disorder (IGD). We evaluated the response inhibition and error processing by functional magnetic resonance imaging (fMRI) in subjects with IGD and controls. Twenty-six men with IGD for at least 2 years and 23 controls with no history of IGD were recruited as the IGD and control groups, respectively. All subjects performed the event-related designed Go/No-go task under fMRI and completed questionnaires related to Internet addiction and impulsivity. The IGD group exhibited a higher score for impulsivity than the control group. The IGD group also exhibited higher brain activation when processing response inhibition over the left orbital frontal lobe and bilateral caudate nucleus than controls. Both the IGD and control groups exhibited activation of the insula and anterior cingulate cortex during error processing. The activation over the right insula was lower in the subjects with IGD than the control group. Our results support the fact that the fronto-striatal network involved in response inhibition, and the salience network, anchored by the anterior cingulate and insula, contributes to error processing. Further, adults with IGD have impaired insular function in error processing and greater activation of the fronto-striatal network in order to maintain their response inhibition performance.

A cognitive-behavioral model of Internet gaming disorder: theoretical underpinnings and clinical implications

Cognitive contributions to the behaviors observed in substance and non-substance addictions have been investigated and characterized. Based on models of drug addictions and the extant literature on Internet gaming disorder (IGD), we propose a cognitive-behavioral model for conceptualizing IGD. The model focuses on three domains and their roles in addictive behaviors. The three domains include motivational drives related to reward-seeking and stress-reduction, behavioral control relating to executive inhibition, and decision-making that involves weighing the pros and cons of engaging in motivated behaviors. Based on this model, we propose how behavioral therapies might target these domains in the treatment of IGD.

Alpha 2A adrenergic receptor agonist, guanfacine, attenuates cocaine-related impairments of inhibitory response control and working memory in animal models

There is considerable evidence that centrally acting α2A adrenergic receptor agonists can attenuate impairments in executive function that result from dysfunction of the prefrontal cortex. Such positive effects resulted in the recent approval by the United States Food and Drug Administration (FDA) of the α2A agonists clonidine and guanfacine for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD), but also suggest that they could have beneficial effects in substance abuse disorders and other neuropsychiatric conditions. The purpose of this study was to evaluate guanfacine for its ability to attenuate behavioral alterations associated with acute cocaine exposure in rats trained to perform a task of sustained attention, the five choice serial reaction time task (5C-SRTT) and monkeys trained to perform a task of working/short term memory, the delayed match to sample (DMTS) task. In the rodent 5C-SRTT acute intraperitoneal (i.p.) administration of cocaine (3.5-15.0mg/kg) did not affect accuracy, but was associated with dose-dependent increases in premature responses and timeout responses. Guanfacine (0.1-1.0mg/kgi.p.) dose-dependently decreased premature responses and timeout responses associated with cocaine and it attenuated similar deficits in inhibitory response control observed in a variable ITI version of the 5C-SRTT. In the DMTS task in monkeys, acute intramuscular (i.m.) administration of cocaine (4.0mg/kg) was associated with impairments in accuracy at long delay intervals, an effect that was attenuated by guanfacine (0.4mg/kg). These animal studies suggest that guanfacine may have therapeutic potential for treating impairments of executive function that are associated with the abuse of cocaine.