Subjective and neural responses to intravenous alcohol in young adults with light and heavy drinking patterns

PET imaging in rat brain shows opposite effects of acute and chronic alcohol exposure on phosphodiesterase-4B, an indirect biomarker of cAMP activity

The cyclic adenosine monophosphate (cAMP) cascade is thought to play an important role in regulating alcohol-dependent behaviors, with potentially opposite effects following acute versus chronic administration. Phosphodiesterase 4 (PDE4) is the primary brain enzyme that metabolizes cAMP, thereby terminating its signal. Radioligand binding to PDE4 serves as an indirect biomarker of cAMP activity, as cAMP-protein kinase A (PKA)-mediated phosphorylation of PDE4 increases its affinity for radioligand binding ~10-fold. Of the four PDE4 subtypes, PDE4B polymorphisms are known to be strongly associated with alcohol and substance use disorders. This study imaged rats with the PDE4B-preferring positron emission tomography (PET) radioligand [18F]PF-06445974 following acute and chronic ethanol administration, aiming to explore the potential of PDE4B PET imaging for future human studies. Compared to the control group treated with saline, acute alcohol administration (i.p. ethanol 0.5 g/kg) significantly increased whole brain uptake of [18F]PF-06445974 as early as 30 minutes post-exposure. This effect persisted at 2 hours, peaked at 4 hours, and diminished at 6 hours and 24 hours post-exposure. In contrast, in a rat model of alcohol dependence, [18F]PF-06445974 brain uptake was significantly reduced at 5 hours post-exposure and was normalized by 3 days. This reduction may reflect long-term adaptation to repeated alcohol-induced activation of cAMP signaling with chronic exposure. Taken together, the results suggest that PET imaging of PDE4B in individuals with alcohol use disorder (AUD) should be considered in conjunction with ongoing trials of PDE4 inhibitors to treat alcohol withdrawal and reduce alcohol consumption.

Stress and substance use disorders: risk, relapse, and treatment outcomes

Stress has long been associated with substance misuse and substance use disorders (SUDs). The past two decades have seen a surge in research aimed at understanding the underlying mechanisms driving this association. This Review introduces a multilevel "adaptive stress response" framework, encompassing a stress baseline, acute reaction, and recovery with return-to-homeostasis phase that occurs at varying response times and across domains of analysis. It also discusses evidence showing the disruption of this adaptive stress response in the context of chronic and repeated stressors, trauma, adverse social and drug-related environments, as well as with acute and chronic drug misuse and with drug withdrawal and abstinence sequelae. Subjective, cognitive, peripheral, and neurobiological disruptions in the adaptive stress response phases and their link to inflexible, maladaptive coping; increased craving; relapse risk; and maintenance of drug intake are also presented. Finally, the prevention and treatment implications of targeting this "stress pathophysiology of addiction" are discussed, along with specific aspects that may be targeted in intervention development to rescue stress-related alterations in drug motivation and to improve SUD treatment outcomes.

The Continuing Challenges of Studying Parallel Behaviours in Humans and Animal Models

The use of animal models continues to be essential for carrying out research into clinical phenomena, including addiction. However, the complexity of the clinical condition inevitably means that even the best animal models are inadequate, and this may go some way to account for the apparent failures of discoveries from animal models, including the identification of potential novel therapies, to translate to the clinic. We argue here that it is overambitious and misguided in the first place to attempt to model complex, multifacetted human disorders such as addiction in animals, and especially in rodents, and that all too frequently "validity" of such models is limited to superficial similarities, referred to as "face validity", that reflect quite different underlying phenomena and biological processes from the clinical situation. Instead, a more profitable approach is to identify (a) well-defined intermediate human behavioural phenotypes that reflect defined, limited aspects of, or contributors to, the human clinical disorder, and (b) to develop animal models that are homologous with those discrete human behavioural phenotypes in terms of psychological processes, and underlying neurobiological mechanisms. Examples of past and continuing weaknesses and suggestions for more limited approaches that may allow better homology between the test animal and human condition are made.

Neural responses to reward, threat, and emotion regulation and transition to hazardous alcohol use

AIMS

Reward processing and regulation of emotions are thought to impact the development of addictive behaviors. In this study, we aimed to determine whether neural responses during reward anticipation, threat appraisal, emotion reactivity, and cognitive reappraisal predicted the transition from low-level to hazardous alcohol use over a 12-month period.

METHODS

Seventy-eight individuals aged 18-22 with low-level alcohol use [i.e. Alcohol Use Disorder Identification Test (AUDIT) score <7] at baseline were enrolled. They completed reward-based and emotion regulation tasks during magnetic resonance imaging to examine reward anticipation, emotional reactivity, cognitive reappraisal, and threat anticipation (in the nucleus accumbens, amygdala, superior frontal gyrus, and insula, respectively). Participants completed self-report measures at 3-, 6-, 9-, and 12-month follow-up time points to determine if they transitioned to hazardous use (as defined by AUDIT scores ≥8).

RESULTS

Of the 57 participants who completed follow-up, 14 (24.6%) transitioned to hazardous alcohol use. Higher baseline AUDIT scores were associated with greater odds of transitioning to hazardous use (odds ratio = 1.73, 95% confidence interval 1.13-2.66, P = .005). Brain activation to reward, threat, and emotion regulation was not associated with alcohol use. Of the neural variables, the amygdala response to negative imagery was numerically larger in young adults who transitioned to hazardous use (g = 0.31), but this effect was not significant.

CONCLUSIONS

Baseline drinking levels were significantly associated with the transition to hazardous alcohol use. Studies with larger samples and longer follow-up should test whether the amygdala response to negative emotional imagery can be used to indicate a future transition to hazardous alcohol use.

People who binge drink show neuroendocrine tolerance to alcohol cues that is associated with immediate and future drinking- results from a randomized clinical experiment

Neuroendocrine tolerance to alcohol, i.e., a blunted cortisol response to alcohol, has been linked to Ventromedial Prefrontal Cortex (VmPFC) alcohol cue reactivity and relapse risk in severe Alcohol Use Disorders (AUDs), but its role in the development of AUDs is not clear. Recent work suggests that blunted cortisol responses to alcohol cues in individuals who engage in binge drinking (BD) may play a role in motivation to consume larger amounts of alcohol, but the link between this dysregulated endocrine response and BD's neural responses to alcohol cues remains unclear. To examine this, two groups of participants were recruited based on their recent drinking history. Thirty-three BD and 31 non-binging, social drinkers (SD) were exposed to alcohol cues and water cues in two separate 7 T functional magnetic resonance imaging (fMRI) scans. Each scan was followed by the Alcohol Taste Test (ATT) of implicit motivation for alcohol and a post-experiment, one-month prospective measurement of their "real world" drinking behavior. During each scan session, blood plasma was collected repeatedly to examine the separate effects of alcohol cues and alcohol consumption on cortisol levels. Relative to water cues and SD, BD demonstrated blunted cortisol cue reactivity that was negatively associated with VmPFC cue reactivity. In BD, both blunted cortisol and greater VmPFC cue reactivity were related to immediate and future alcohol consumption in the month following the scans. Thus, neuroendocrine tolerance in BD may be associated with increased incentive salience of cues and contribute mechanistically to increased alcohol consumption seen in the development of AUDs.

Ventral prefrontal network response to alcohol in young adults with bipolar disorder: a within-subject randomized placebo-controlled alcohol administration study

Bipolar disorder co-occurs with alcohol use disorder at a rate 3-5 times higher than the general population. We recently reported that individuals with bipolar disorder differ in the positive stimulating and anxiolytic effects of alcohol compared with healthy peers. This study used a randomized, placebo-controlled, cross-over, within-subject alcohol administration design to investigate neurobiological mechanisms within ventral prefrontal cortical (vPFC) systems that may underlie altered sensitivity to alcohol in bipolar disorder (NCT04063384). Forty-seven young adults (n = 23 with bipolar disorder, 64% women) completed clinical assessment and two beverage administration sessions (alcohol and placebo, counter-balanced). Participants were dosed to 0.08 g% breath alcohol concentration during the alcohol condition and completed measures of subjective response to alcohol and an emotional processing fMRI task during the ascending limb. Timing during the placebo condition mirrored the alcohol session. Acute alcohol was associated with reduced functional connectivity between the insula - subcallosal cingulate cortex, and increased connectivity between the left nucleus accumbens - ventromedial PFC in bipolar disorder, but with no change in functional connectivity between these regions in healthy peers. Alcohol-related increases in nucleus accumbens - ventromedial PFC functional connectivity was associated with greater positive stimulating effects of alcohol in bipolar disorder and heavier recent alcohol use. Results suggest vPFC brain systems respond differently to acute alcohol during emotional processing in young adults with bipolar disorder compared with healthy peers, and that vPFC system responses relate to the subjective experience of intoxication and recent alcohol use.

Stimulant-like subjective effects of alcohol are not related to resting-state connectivity in healthy men

Individual differences in subjective, stimulant-like effects of alcohol are associated with the risk of developing alcohol use disorder. Specifically, individuals who experience more pronounced stimulant-like effects from alcohol are more likely to continue and escalate their usage. The neural basis for these individual differences in subjective response is not yet known. Using a within-subject design, 27 healthy male social drinkers completed three fMRI scans after ingesting a placebo, 0.4 and 0.8 g/kg alcohol, in a randomized order under double-blind conditions. Subjective stimulant effects of alcohol were assessed at regular intervals during each session. Seed-based and regional homogeneity analyses were conducted to evaluate changes in resting-state functional connectivity in relation to the stimulant effect of alcohol. Results indicated that 0.4 g/kg alcohol increased the connectivity to thalamus, and 0.8 g/kg alcohol decreased the connectivity to ventral anterior insula, primarily from the superior parietal lobule. Both doses reduced regional homogeneity in the superior parietal lobule but without an exact overlap with clusters showing connectivity changes in the seed-based analyses. The self-reported stimulant effect of alcohol was not significantly related to changes in seed-based connectivity or regional homogeneity. These findings suggest that alcohol-induced stimulation effects are not related to these indices of neural activity.

Blunted neural reward response to alcohol and greater alcohol motivation in binge drinkers in a randomized clinical experiment

BACKGROUND

Alcohol stimulates cerebral blood flow (CBF) in brain reward regions. However, neural processes that support sustained alcohol motivation after the first drink are not well understood.

METHODS

Using a novel placebo-controlled, randomized, crossover experiment, 27 individuals who binge drink (BD; 15 M, 12 F) and 25 social drinkers (SD; 15 M, 10 F) underwent a behavioral test of self-motivated alcohol consumption using an Alcohol Taste Test (ATT) involving alcoholic and nonalcoholic beer on separate days. The test was followed immediately by perfusion functional magnetic resonance imaging (fMRI). On both days, participants then engaged in a post-scan ATT with placebo beer to assess sustained alcohol self-motivation without active alcohol effects. Linear mixed effects models were used to examine the effects of drinking group on the placebo-controlled effect of initial alcohol motivation on brain perfusion (whole brain corrected p < 0.001, cluster corrected p < 0.025) and on the relationship between placebo-controlled brain perfusion and sustained alcohol motivation.

RESULTS

Initial alcohol self-motivation in the alcohol relative to placebo session led to markedly decreased activation in the medial orbitofrontal cortex (OFC) and the ventral striatum in BD relative to SD, indicative of neural reward tolerance. The BD group also showed an enhanced neural response in behavioral intention regions of the supplementary motor area (SMA) and inferior frontal gyrus (IFG) regions. Moreover, there was greater sustained alcohol motivation in BD than SD in the post-scan ATT in the alcohol relative to placebo session. Correspondingly, only in BD and only in the alcohol session, lower alcohol-induced OFC response correlated with concurrent sensitized SMA response, and each predicted the subsequent sustained higher alcohol motivation in the post-scan ATT.

CONCLUSIONS

Alcohol-related OFC tolerance may play an important role in sustained alcohol motivation. Furthermore, both specific alcohol-related neural reward tolerance and premotor sensitization responses may contribute to escalating alcohol motivation to drive excessive alcohol intake, even in individuals without alcohol use disorder.

Association of cerebellar and pre-motor cortex gray matter density with subjective intoxication and subjective response following acute alcohol intake

Acute alcohol intake produces subjective intoxication (SI) and response (SR; e.g., valanced stimulation and sedation), which has important implications for alcohol-related risk. Individuals who experience less SI may be more likely to engage in risky behaviors while drinking. Gray matter morphometry in brain regions underlying cognitive and affective processes may help to inform individual differences in subjective intoxication and response. The subjective effects of alcohol vary between limbs of the blood alcohol concentration (BAC) curve (i.e., whether BAC is rising or falling; acute tolerance). We examined the relationship between gray matter density (GMD) and SI/SR as a function of BAC limb. Healthy social drinkers (N = 89; 55 women) completed an alcohol challenge paradigm (target BAC = 0.08 g/dL) and structural magnetic resonance imaging (MRI). Participants completed measures of SR and SI on ascending and descending BAC limbs. Association between GMD and SI/SR on each limb were assessed using whole-brain, voxel-wise general linear models. GMD estimates were extracted from significant clusters. Differences in association of GMD and SI/SR between limbs were assessed using hierarchical regression. Significant associations of SI with GMD on the ascending limb were observed in the cerebellum. A significant association between SR and GMD on the descending limb were observed in the pre-motor cortex (BA6) and cerebellum. We identified common and unique associations among cerebellum and pre-central gyrus structures with SI and SR between BAC limbs. Functional imaging studies may further clarify unique dimensions of subjective alcohol effects linked to the observed structural associations.

Stress-related neuropeptide systems as targets for treatment of alcohol addiction: A clinical perspective

Alcohol use is a major cause of disability and death globally. These negative consequences disproportionately affect people who develop alcohol addiction, a chronic relapsing condition characterized by increased motivation to use alcohol, choice of alcohol over healthy, natural rewards, and continued use despite negative consequences. Available pharmacotherapies for alcohol addiction are few, have effect sizes in need of improvement, and remain infrequently prescribed. Research aimed at developing novel therapeutics has in large part focused on attenuating pleasurable or "rewarding" properties of alcohol, but this targets processes that primarily play a role as initiation factors. As clinical alcohol addiction develops, long-term changes in brain function result in a shift of affective homeostasis, and rewarding alcohol effects become progressively reduced. Instead, increased stress sensitivity and negative affective states emerge in the absence of alcohol and create powerful incentives for relapse and continued use through negative reinforcement, or "relief." Based on research in animal models, several neuropeptide systems have been proposed to play an important role in this shift, suggesting that these systems could be targeted by novel medications. Two mechanisms in this category, antagonism at corticotropin-releasing factor type 1, and neurokinin 1/substance P receptors, have been subject to initial evaluation in humans. A third, kappa-opioid receptor antagonism, has been evaluated in nicotine addiction and could soon be tested for alcohol. This paper discusses findings with these mechanisms to date, and their prospects as future targets for novel medications.

Neural underpinnings of expecting alcohol: Placebo alcohol administration alters nucleus accumbens resting state functional connectivity

BACKGROUND

Using balanced placebo designs, seminal alcohol administration research has shown individuals' beliefs about whether they have consumed alcohol, irrespective of the actual presence of alcohol, can determine level of alcohol consumption and impact social behavior. Despite the known effect of expecting alcohol on drinking behavior, few studies have used the placebo manipulation to directly investigate the neural underpinnings of the expectancy-related effects that occur following perceived alcohol consumption in humans. The present paper examined placebo responses in the laboratory to better understand the neural basis for the psychological phenomenon of expectancies.

METHODS

As part of a larger within-subjects study design, healthy young adults (N = 22, agemean+SD=23 +1) completed resting state fMRI scans and measures of subjective response before and after consuming placebo beverages. Effect of placebo beverage consumption (pre- versus post-beverage consumption) on functional connectivity within prefrontal cortical networks was examined using the CONN Toolbox. Relations between perceived subjective response to alcohol with functional connectivity response following placebo beverage consumption were examined.

RESULTS

Compared to pre-beverage scan, placebo beverage consumption was associated with increased positive functional connectivity between right nucleus accumbens - ventromedial prefrontal cortex and subcallosal cingulate cortex (pFDR<0.05). Subjective ratings of intoxication (i.e., feeling 'drunk') positively correlated with placebo beverage-related increases in nucleus accumbens - subcallosal cingulate cortex functional connectivity.

CONCLUSION

Results suggest placebo response to alcohol is associated with increased functional connectivity within a key reward network (nucleus accumbens - ventromedial prefrontal cortex and subcallosal cingulate cortex) and put forth a mechanism by which alcohol expectancies may contribute to the subjective experience of intoxication.

The Dopamine System in Mediating Alcohol Effects in Humans

Brain-imaging studies show that the development and maintenance of alcohol use disorder (AUD) is determined by a complex interaction of different neurotransmitter systems and multiple psychological factors. In this context, the dopaminergic reinforcement system appears to be of fundamental importance. We focus on the excitatory and depressant effects of acute versus chronic alcohol intake and its impact on dopaminergic neurotransmission. Furthermore, we describe alterations in dopaminergic neurotransmission as associated with symptoms of alcohol dependence. We specifically focus on neuroadaptations to chronic alcohol consumption and their effect on central processing of alcohol-associated and reward-related stimuli. Altered reward processing, complex conditioning processes, impaired reinforcement learning, and increased salience attribution to alcohol-associated stimuli enable alcohol cues to drive alcohol seeking and consumption. Finally, we will discuss how the neurobiological and neurochemical mechanisms of alcohol-associated alterations in reward processing and learning can interact with stress, cognition, and emotion processing.

Pharmacodynamic determinants of hangover: An intravenous alcohol self-administration study in non-dependent drinkers

Alcohol hangover refers to the combination of negative mental and physical symptoms that can be experienced after an episode of alcohol consumption, typically emerging as blood alcohol concentration (BAC) approaches zero. Hangover has been associated with heavy drinking and may be relevant in the transition to alcohol use disorder (AUD). Our aim was to examine hangover prevalence and associated symptoms following intravenous alcohol self-administration (IV-ASA), and to identify possible predictors of hangover in non-dependent drinkers. Ninety-five drinkers without AUD completed an IV-ASA session. Pharmacodynamic measures of alcohol consumption included peak and average breath alcohol concentrations. Subjective measures of alcohol response included the Drug Effects Questionnaire and Biphasic Effects of Alcohol Scale. The Alcohol Hangover Scale assessed hangover symptoms from the end of the session until the following morning. 78% of participants endorsed at least one hangover symptom following IV-ASA. There was no association between hangover scores and IV-ASA measures of alcohol consumption. Additional mediation and moderation analysis revealed that self-reported intoxication was a significant mediator of the relationship between recent drinking and hangover symptoms. Hangover symptoms may be an early marker of the relationship between subjective response to alcohol and heavy drinking for those with no prior history of AUD. In particular, the effects of hangover go beyond exposure to alcohol and the individual's subjective response to this exposure is associated with their experience of hangover. Future studies should further characterize the determinants of hangover across different populations of drinkers to better understand the risk for AUD and inform prevention methods.

Alcohol’s Negative Emotional Side: The Role of Stress Neurobiology in Alcohol Use Disorder

This article is part of a Festschrift commemorating the 50th anniversary of the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Established in 1970, first as part of the National Institute of Mental Health and later as an independent institute of the National Institutes of Health, NIAAA today is the world’s largest funding agency for alcohol research. In addition to its own intramural research program, NIAAA supports the entire spectrum of innovative basic, translational, and clinical research to advance the diagnosis, prevention, and treatment of alcohol use disorder and alcohol-related problems. To celebrate the anniversary, NIAAA hosted a 2-day symposium, “Alcohol Across the Lifespan: 50 Years of Evidence-Based Diagnosis, Prevention, and Treatment Research,” devoted to key topics within the field of alcohol research. This article is based on Dr. Sinha’s presentation at the event. NIAAA Director George F. Koob, Ph.D., serves as editor of the Festschrift.

Characterization of DREADD receptor expression and function in rhesus macaques trained to discriminate ethanol

Circuit manipulation has been a staple technique in neuroscience to identify how the brain functions to control complex behaviors. Chemogenetics, including designer receptors exclusively activated by designer drugs (DREADDs), have proven to be a powerful tool for the reversible modulation of discrete brain circuitry without the need for implantable devices, thereby making them especially useful in awake and unrestrained animals. This study used a DREADD approach to query the role of the nucleus accumbens (NAc) in mediating the interoceptive effects of 1.0 g/kg ethanol (i.g.) in rhesus monkeys (n = 7) using a drug discrimination procedure. After training, stereotaxic surgery was performed to introduce an AAV carrying the human muscarinic 4 receptor DREADD (hM4Di) bilaterally into the NAc. The hypothesis was that decreasing the output of the NAc by activation of hM4Di with the DREADD actuator, clozapine-n-oxide (CNO), would potentiate the discriminative stimulus effect of ethanol (i.e., a leftward shift the ethanol dose discrimination curve). The results showed individual variability shifts of the ethanol dose-response determination under DREADD activation. Characterization of the expression and function of hM4Di with MRI, immunohistochemical, and electrophysiological techniques found the selectivity of NAc transduction was proportional to behavioral effect. Specifically, the proportion of hM4Di expression restricted to the NAc was associated with the potency of the discriminative stimulus effects of ethanol. Together, these experiments highlight the NAc in mediating the interoceptive effects of ethanol, provide a framework for validation of chemogenetic tools in primates, and underscore the importance of robust within-subjects examination of DREADD expression for interpretation of behavioral findings.

Low versus high level of response to alcohol affects amygdala functional connectivity during processing of emotional stimuli

BACKGROUND

Low levels of response (low LR) to alcohol predict heavy drinking and alcohol problems. Functional magnetic resonance imaging (fMRI) studies of emotion processing have shown that low LR individuals exhibit lower activation in task-related brain regions following both placebo and alcohol administration, but these studies did not examine functional brain networks that might contribute to the phenomena. The current study expands upon the earlier results by evaluating whether functional connectivity differences between the amygdala and other brain regions modulated by emotional face processing are associated with LR. Based on prior findings, we hypothesized that low LR is related to lower functional connectivity in fronto-amygdalar functional circuits, which underlie the processing of emotional stimuli.

METHODS

Secondary analyses were conducted on data from a double-blind, placebo-controlled, within-subjects, cross-over study in 108 18-to-25-year-old low and high LR sex-matched pairs without alcohol use disorder at baseline. Participants performed modified emotional faces processing tasks after receiving placebo or approximately 0.7 ml/kg of ethanol. Psychophysiological interaction analyses examined functional connectivity between left and right amygdalae and related brain circuits using LR-by-alcohol general linear models. The data included 54 sex-matched pairs with 216 fMRI scans comprising alcohol and placebo conditions.

RESULTS

Compared with individuals with high LR, low LR subjects demonstrated lower functional connectivity between the amygdala and the frontal lobes, insula, and parietal regions, while processing angry and happy faces. Interactions showed lower connectivity following alcohol in low LR and higher connectivity in high LR groups.

CONCLUSIONS

Low LR individuals demonstrated lower functional connectivity in response both to placebo and a modest dose of ethanol. Attenuated connectivity among low LR individuals when processing emotional faces may contribute to an impaired ability to recognize alcohol intoxication in social situations and to appraise angry and happy emotions irrespective of whether alcohol is consumed.

Effects of Acute Drug Administration on Emotion: A Review of Pharmacological MRI Studies

Purpose of review

Many drug users claim to use drugs to cope with negative emotions, which may, in turn, result in persistent emotional blunting or anhedonia even when they are not using drugs. The purpose of this review is to describe the ways acute administration of psychoactive drugs impacts brain regions during emotion-related tasks, as a first step in understanding how drugs influence emotion processing in the brain.

Recent findings

Drugs have varying effects on neural responses to emotional stimuli. In general, alcohol, analgesics, and psychedelics reduce neural reactivity to negative emotional stimuli in the amygdala and other brain regions. Other drugs produce mixed effects: Stimulants such as caffeine and modafinil increase brain activation while viewing emotional stimuli, whereas MDMA decreases activation during presentation of negative images. The effects of cannabinoids (cannabidiol and THC) are mixed. There are also inconsistent findings on the associations between neural responses to emotional stimuli and subjective drug effects.

Summary

Consistent with the notion that individuals might use drugs non-medically to diminish the experience of negative emotions, several drugs of abuse decrease neural responses to negative stimuli in limbic brain regions. These neural actions may underlie the reported 'emotional blunting' of drugs, which may contribute to drug-seeking behavior. Future work is needed to examine these limbic responses in relation to self-reports of changes in affect, both during acute administration and after extended drug use.

Neural correlates of inhibitory control are associated with stimulant-like effects of alcohol

Poor inhibitory control and heightened feelings of stimulation after alcohol are two well-established risk factors for alcohol use disorder (AUD). Although these risk factors have traditionally been viewed as orthogonal, recent evidence suggests that the two are related and may share common neurobiological mechanisms. Here we examined the degree to which neural activity during inhibition was associated with subjective reports of stimulation following alcohol. To assess neural changes during inhibition, moderate alcohol drinkers performed a stop signal task during fMRI without drug. To assess subjective responses to alcohol they ingested alcohol (0.8 g/kg) or placebo beverages under double-blind conditions and provided subjective reports of stimulation and sedation. Feelings of stimulation following alcohol were inversely associated with activity in the supplementary motor area, insula, and middle frontal gyrus during inhibition (successful stop trials compared to go trials). Feelings of sedation did not correlate with brain activation. These results extend previous findings suggesting that poor inhibitory control is associated with more positive subjective responses to alcohol. These interrelated risk factors may contribute to susceptibility to future excessive alcohol use, and ultimately lead to neurobiological targets to prevent or treat AUD.

Subjective Responses to Alcohol in the Development and Maintenance of Alcohol Use Disorder

OBJECTIVE

Alcohol use disorder (AUD) remains an urgent public health problem. Longitudinal data are needed to clarify the role of acute subjective responses to alcohol in the development and maintenance of excessive drinking and AUD. The authors report on 10 years of repeated examination of acute alcohol responses in the Chicago Social Drinking Project.

METHODS

Young adult drinkers (N=190) participated in an initial alcohol challenge (0.8 g/kg of alcohol compared with placebo) that was repeated 5 and 10 years later. They were also assessed on drinking behavior and AUD symptoms at numerous intervals across the decade. Retention was high, as 184 of the 185 (99%) nondeceased active participants completed the 10-year follow-up, and 91% (163 of 179) of those eligible for alcohol consumption engaged in repeated laboratory testing during this interval.

RESULTS

At the end of the decade, 21% of participants met criteria for past-year AUD. Individuals who reported the greatest alcohol stimulation, liking, and wanting at the initial alcohol challenge were most likely to have developed AUD 10 years later. Further, alcohol-induced stimulation and wanting increased in reexamination testing among those with the highest AUD symptoms as the decade progressed.

CONCLUSIONS

Initial stimulant and rewarding effects of alcohol predicted heavy alcohol use, and the magnitude of these positive subjective effects increased over a 10-year period in those who developed AUD compared with those who did not develop the disorder. The findings demonstrate systematic changes in subjective responses to alcohol over time, providing an empirical basis for prevention, early intervention, and treatment strategies.

Hof P. Understanding Emotions: Origins and Roles of the Amygdala

Emotions arise from activations of specialized neuronal populations in several parts of the cerebral cortex, notably the anterior cingulate, insula, ventromedial prefrontal, and subcortical structures, such as the amygdala, ventral striatum, putamen, caudate nucleus, and ventral tegmental area. Feelings are conscious, emotional experiences of these activations that contribute to neuronal networks mediating thoughts, language, and behavior, thus enhancing the ability to predict, learn, and reappraise stimuli and situations in the environment based on previous experiences. Contemporary theories of emotion converge around the key role of the amygdala as the central subcortical emotional brain structure that constantly evaluates and integrates a variety of sensory information from the surroundings and assigns them appropriate values of emotional dimensions, such as valence, intensity, and approachability. The amygdala participates in the regulation of autonomic and endocrine functions, decision-making and adaptations of instinctive and motivational behaviors to changes in the environment through implicit associative learning, changes in short- and long-term synaptic plasticity, and activation of the fight-or-flight response via efferent projections from its central nucleus to cortical and subcortical structures.

Facial expression recognition: A meta-analytic review of theoretical models and neuroimaging evidence

Discrimination of facial expressions is an elementary function of the human brain. While the way emotions are represented in the brain has long been debated, common and specific neural representations in recognition of facial expressions are also complicated. To examine brain organizations and asymmetry on discrete and dimensional facial emotions, we conducted an activation likelihood estimation meta-analysis and meta-analytic connectivity modelling on 141 studies with a total of 3138 participants. We found consistent engagement of the amygdala and a common set of brain networks across discrete and dimensional emotions. The left-hemisphere dominance of the amygdala and AI across categories of facial expression, but category-specific lateralization of the vmPFC, suggesting a flexibly asymmetrical neural representations of facial expression recognition. These results converge to characteristic activation and connectivity patterns across discrete and dimensional emotion categories in recognition of facial expressions. Our findings provide the first quantitatively meta-analytic brain network-based evidence supportive of the psychological constructionist hypothesis in facial expression recognition.

Baclofen attenuates fMRI alcohol cue reactivity in treatment-seeking alcohol dependent individuals

RATIONALE

Baclofen has been shown to effect fMRI alcohol cue reactivity in alcohol dependence, but potential varying effects related to baclofen dose levels have not been examined.

OBJECTIVE

This study investigated whether baclofen attenuates craving and alcohol cue-elicited activation in alcohol-dependent treatment seekers, and the relationship between this response and clinical outcomes (Morley et al. 2018; Morley et al. 2013).

METHODS

Participants included 30 alcohol-dependent individuals who had received daily baclofen 30 mg (n = 11), 75 mg (n = 8) or placebo (n = 11) for at least 2 weeks. Using functional magnetic resonance imaging (fMRI), we examined alcohol cue-elicited neural activation during a visual alcohol cue reactivity task 120 min following treatment administration, and alcohol cue reactivity and percentage of heavy drinking days (% HDD) associations were assessed.

RESULTS

Both baclofen-treated groups reported fewer post-scan % HDD when compared to the placebo-treated group, but no subjective craving group differences were found. Increased alcohol cue-elicited activation was seen in placebo compared to the 75 mg/day baclofen participants in two clusters spanning prefrontal regions implicated in cue reactivity, chiefly frontal regions (i.e., frontal and precentral gyri, anterior cingulate cortex), but no observed alcohol cue reactivity differences between placebo and 30 mg/day baclofen groups. Post-scan % HDD was positively correlated with increased alcohol cue-elicited activation in a cluster encompassing the bilateral caudate nucleus and dorsal anterior cingulate cortex when comparing placebo versus 75 mg/day baclofen groups, and several clusters including prefrontal and mesolimbic regions when comparing placebo versus 30 mg/day baclofen groups.

CONCLUSIONS

Baclofen administration attenuates alcohol cue-elicited activation and reduced the association in baclofen-treated participants between increased activity in key drug cue reactivity regions and higher post-scan % HDD observed in placebo-treated participants, suggesting a dose-specific response effect that may lead to reduced heavy drinking in chronic alcohol-dependent individuals.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT01711125, https://clinicaltrials.gov/ct2/show /NCT01711125.

Acute effects of alcohol on resting-state functional connectivity in healthy young men

Alcohol abuse and dependence remain significant public health issues, and yet the brain circuits that are involved in the rewarding effects of alcohol are poorly understood. One promising way to study the effects of alcohol on neural activity is to examine its effects on functional connectivity between brain areas involved in reward and other functions. Here, we compared the effects of two doses of alcohol (0.4 and 0.8 g/kg) to placebo on resting-state functional connectivity in brain circuits related to reward in 19 healthy young men without histories of alcohol problems. The higher, but not the lower, dose of alcohol, significantly increased connectivity from reward-related regions to sensory and motor cortex, and between seeds associated with cognitive control. Contrary to expectation, alcohol did not significantly change connectivity for the ventral striatum at either dose. These findings reveal unrecognized effects of alcohol on connectivity from reward-related regions to visual and sensory cortical areas.

Acute rewarding and disinhibiting effects of alcohol as indicators of drinking habits

RATIONALE

Laboratory studies have reliably shown that heightened sensitivity to the rewarding effects of alcohol is associated with heavier drinking patterns. More recently, there has been research to suggest that heightened sensitivity to the disinhibiting effects of alcohol might also contribute to drinking habits. Most research on the acute effects of alcohol has focused on drinking magnitudes averaged across participants with little attention paid to how individual differences influence alcohol abuse potential. In large part, this is due to limited sample sizes in previous laboratory studies.

OBJECTIVES

This study overcomes previous limitations by testing the degree to which individual differences in acute sensitivity and tolerance to the rewarding and disinhibiting effects of alcohol relate to drinking behavior in a large sample size.

METHODS

Data from six laboratory studies were aggregated to comprise a sample of 181 adults. Participants' level of "liking" (the effects of alcohol) and disinhibition were assessed following 0.65 g/kg alcohol once during the ascending limb of the blood alcohol concentration (BAC) curve and again at the same BAC during the descending limb of the curve. The measures were also assessed following placebo.

RESULTS

Alcohol increased ratings of liking and behavioral disinhibition. Heavier drinking was associated with heightened sensitivity to liking on the ascending limb. Additionally, those who showed reduced acute tolerance to both disinhibition and liking were also heavier drinkers.

CONCLUSIONS

These data suggest that individual variability in liking the effects of alcohol and persistent disinhibition are key indicators of drinking habits.

Striatal activation to monetary reward is associated with alcohol reward sensitivity

One well-known phenotypic risk factor for the development of alcohol use disorder is sensitivity to the rewarding effects of alcohol. In the present study, we examined whether individuals who are sensitive to alcohol reward are also sensitive to nondrug rewards, thereby reflecting a broader individual difference risk factor. Specifically, we tested the hypothesis that subjective response to acute rewarding effects of alcohol would be related to neural activation during monetary reward receipt relative to loss (in the absence of alcohol). Community-recruited healthy young social drinkers (N = 58) completed four laboratory sessions in which they received alcohol (0.8 g/kg) and placebo in alternating order under double-blind conditions, providing self-report measures of subjective response to alcohol at regular intervals. At a separate visit 1-3 weeks later, they completed a reward-guessing game, the 'Doors' task, during fMRI in a drug-free state. Participants who reported greater motivation (i.e., wanting) to consume more alcohol after a single moderate dose of alcohol also exhibited greater neural activation in the bilateral ventral caudate and the nucleus accumbens during reward receipt relative to loss. Striatal activation was not related to other subjective ratings including alcohol-induced sedation, stimulation, or pleasure (i.e., feeling, liking). Our study is the first to show that measures of alcohol reward are related to neural indices of monetary reward in humans. These results support growing evidence that individual differences in responses to drug and nondrug reward are linked and together form a risk profile for drug use or abuse, particularly in young adults.

Neuroimaging reveals functionally distinct neuronal networks associated with high-level alcohol consumption in two genetic rat models

Human imaging data suggest that the motivational processes associated with alcohol reward are reflected in the patterns of neural activation after alcohol or alcohol-related cues. In animal models of alcohol drinking, however, the changes in brain activation during voluntary alcohol ingestion are poorly known. In order to improve the translational utility of animal models, we examined alcohol-induced functional brain activation in Alko Alcohol (AA) and Marchigian-Sardinian alcohol-preferring (msP) rats that drink voluntarily high levels of alcohol, but exhibit widely different neurochemical and behavioral traits cosegregated with alcohol preference. Brain imaging was performed using manganese-enhanced MRI (MEMRI), which is based on accumulation of Mn2+ ions in activated neurons, allowing the identification of functional neuronal networks recruited during specific behaviors in awake animals during a subsequent imaging session under anesthesia. MEMRI was performed following 4 weeks of voluntary alcohol drinking, using water drinking as the control. Despite similar levels of alcohol drinking, strikingly different alcohol-induced neuronal activity patterns were observed in AA and msP rats. Overall, functional activation in the AA rats was more widespread, involving large cortical areas and subcortical structures, such as the bed nucleus of the stria terminalis, preoptic area, hypothalamus, periaqueductal grey, and substantia nigra. In the msP rats, however, alcohol-related activation was largely confined to prefrontal cortical regions and insular cortex, and olfactory areas. Overlapping areas of activation found in both rat lines included the nucleus accumbens, prelimbic, orbital, and insular cortex. In conclusion, our data reveal strikingly different brain circuits associated with alcohol drinking in two genetically different rat lines and suggest innately different motivational and behavioral processes driving alcohol drinking. These findings have important implications for the use of these lines in translational alcohol research.

To Infuse or Ingest in Human Laboratory Alcohol Research

Human alcohol laboratory studies use two routes of alcohol administration: ingestion and infusion. The goal of this paper was to compare and contrast these alcohol administration methods. The work summarized in this report was the basis of a 2019 Research Society on Alcoholism Roundtable, "To Ingest or Infuse: A Comparison of Oral and Intravenous Alcohol Administration Methods for Human Alcohol Laboratory Designs." We review the methodological approaches of each and highlight strengths and weaknesses pertaining to different research questions. We summarize methodological considerations to aid researchers in choosing the most appropriate method for their inquiry, considering exposure variability, alcohol expectancy effects, safety, bandwidth, technical skills, documentation of alcohol exposure, experimental variety, ecological validity, and cost. Ingestion of alcohol remains a common and often a preferable, methodological practice in alcohol research. Nonetheless, the main problem with ingestion is that even the most careful calculation of dose and control of dosing procedures yields substantial and uncontrollable variability in the participants' brain exposures to alcohol. Infusion methodologies provide precise exposure control but are technically complex and may be limited in ecological validity. We suggest that alcohol ingestion research may not be the same thing as alcohol exposure research; investigators should be aware of the advantages and disadvantages that the choice between ingestion and infusion of alcohol invokes.

Evidence for incentive salience sensitization as a pathway to alcohol use disorder

The incentive salience sensitization (ISS) theory of addiction holds that addictive behavior stems from the ability of drugs to progressively sensitize the brain circuitry that mediates attribution of incentive salience (IS) to reward-predictive cues and its behavioral manifestations. In this article, we establish the plausibility of ISS as an etiological pathway to alcohol use disorder (AUD). We provide a comprehensive and critical review of evidence for: (1) the ability of alcohol to sensitize the brain circuitry of IS attribution and expression; and (2) attribution of IS to alcohol-predictive cues and its sensitization in humans and non-human animals. We point out gaps in the literature and how these might be addressed. We also highlight how individuals with different alcohol subjective response phenotypes may differ in susceptibility to ISS as a pathway to AUD. Finally, we discuss important implications of this neuropsychological mechanism in AUD for psychological and pharmacological interventions attempting to attenuate alcohol craving and cue reactivity.

The grey future: Overgenerality of emotional future thinking in alcohol-use disorders

BACKGROUND

While previous research has highlighted the overgenerality of future thinking in alcohol-use disorders (AUD), the emotional characteristics of future thinking were not taken into account. We therefore evaluated the ability to retrieve episodic (i.e., events that happened at a particular place and time and lasted for a day or less) emotional future events in AUD.

METHODS

We invited 36 participants with AUD and 40 control participants to imagine positive, negative and neutral future scenarios and analyzed these scenarios regarding their episodic characteristics (i.e., the ability of participants to imagine future events situated in time and space enriched with phenomenological details).

RESULTS

Analysis demonstrated lower episodic positive, negative and neutral future thinking in participants with AUD than in control participants. Participants with AUD also demonstrated lower episodic positive and negative future thinking compared to episodic neutral future thinking. Interestingly, high depression scores were associated with overgenerality of neutral, positive, and negative future thinking in AUD participants.

CONCLUSIONS

These findings demonstrate overgenerality of both positive and negative future thinking in AUD. This overgenerality may represent an avoidance strategy in which individuals with AUD may try to avoid the hopelessness and/or conflicts that may be activated when constructing future scenarios.

The effects of nalmefene on emotion processing in alcohol use disorder - A randomized, controlled fMRI study

Nalmefene is a µ- and δ-opioid receptor antagonist and a partial κ-opioid receptor agonist. The drug is suggested to reduce the craving for, and the consumption of alcohol effectively, also alleviating anxiety and anhedonia. The present fMRI study is the first to investigate the processing of emotions as a possible mechanism of action of nalmefene in humans. Fifteen non-treatment-seeking participants suffering from alcohol use disorder (AUD) (24-66 years; 5 females) finished this randomized, placebo controlled, double blind study. Following a cross over design, participants received either a single dose nalmefene or a placebo, with an interval of one week between sessions. Using fMRI, we investigated neural reactivity during the presentation of emotional faces picture sets. Additionally, we performed a visual dot-probe task to detect nalmefene's effects on attentional bias. We detected an increase in the response to emotional faces in the supramarginal gyrus, the angular gyrus as well as the putamen in the nalmefene vs. placebo condition. However, contradictory to our initial hypotheses, amygdala activation was not altered significantly in the placebo condition - a limitation, which might be associated with a lack of activation in the placebo condition maybe due to the small sample size. Attentional bias analyses revealed an interaction effect by trend, which was driven by a significant effect in a sub-analysis showing increased attentional shift towards happy compared to fearful facial expressions under nalmefene. Nalmefene increased brain activation in areas responsible for empathy, social cognition and behavior, which might help alleviating the reinforcing properties of alcohol.

Suggestibility is associated with alcohol self-administration, subjective alcohol effects, and self-reported drinking behavior

BACKGROUND

Suggestibility, defined as an individual's inclination to accept and internalize messages, has not been studied in relation to alcohol use. Peer conformity, a component of suggestibility, may be related to alcohol use, as peer groups show similarities in patterns of alcohol use. Few studies have assessed how suggestibility and peer conformity relate to alcohol self-administration or to reinforcing effects of alcohol.

AIMS

This study assessed whether suggestibility and peer conformity were associated with drinking behavior, alcohol self-administration, subjective response to alcohol, and drinking motives and expectancies.

METHODS

Study 1 participants were alcohol drinkers (n=20), who completed a laboratory study of free-access intravenous alcohol self-administration. Study 2 participants were adolescents and young adults, age 14-25 (n=150), with lifetime alcohol use. Participants completed surveys of suggestibility and drinking patterns (Study 1 and 2), subjective alcohol effects (Study 1 only), and alcohol motives and expectancies (Study 2 only).

RESULTS/OUTCOMES

In Study 1, participants with higher levels of suggestiblity self-administered more alcohol, and reported greater subjective alcohol effects. Peer conformity, though correlated with suggestibility, was not related to these measures. In Study 2, participants with higher suggestiblity reported more alcohol consumption, higher drinking motives and alcohol expectancies. Peer conformity was not related to alcohol consumption, but was related to coping and enhancement drinking motives, and all expectancies measures.

CONCLUSIONS/INTERPRETATION

Results indicate that suggestibility, beyond peer conformity, may be a critical factor to study when examining alcohol consumption behavior, and may provide insight into the development of alcohol use disorder.

Building better strategies to develop new medications in Alcohol Use Disorder: Learning from past success and failure to shape a brighter future

Alcohol Use Disorder (AUD) is a chronic disease that develops over the years. The complexity of the neurobiological processes contributing to the emergence of AUD and the neuroadaptive changes occurring during disease progression make it difficult to improve treatments. On the other hand, this complexity offers researchers the possibility to explore new targets. Over years of intense research several molecules were tested in AUD; in most cases, despite promising preclinical data, the clinical efficacy appeared insufficient to justify futher development. A prototypical example is that of corticotropin releasing factor type 1 receptor (CRF1R) antagonists that showed significant effectiveness in animal models of AUD but were largely ineffective in humans. The present article attempts to analyze the most recent venues in the development of new medications in AUD with a focus on the most promising drug targets under current exploration. Moreover, we delineate the importance of using a more integrated translational framework approach to correlate preclinical findings and early clinical data to enhance the probability to validate biological targets of interest.

Comparison of Subjective Responses to Oral and Intravenous Alcohol Administration Under Similar Systemic Exposures

BACKGROUND

Individuals perceive the effects of alcohol differently, and the variation is commonly used in research assessing the risk for developing an alcohol use disorder. Such research is supported by both oral and intravenous (IV) alcohol administration techniques, and any differences attributable to the route employed should be understood. Our objective was to test whether an individual's subjective responses to alcohol are similar when the breath alcohol concentration (BrAC) trajectory resulting from oral administration is matched by IV administration.

METHODS

We conducted a 2-session, within-subject study in 44 young adult, healthy, nondependent drinkers (22 females and 22 males). In the first session, subjects ingested a dose of alcohol which was individually calculated, on the basis of total body water, to yield a peak BrAC near 80 mg/dl, and the resulting BrAC trajectory was recorded. A few days later, subjects received an IV alcohol infusion rate profile, precomputed to replicate each individual's oral alcohol BrAC trajectory. In both sessions, we assessed 4 subjective responses to alcohol: SEDATION, SIMULATION, INTOXICATION, and HIGH; at baseline and frequently for 4 hours. We compared the individuals' baseline-corrected responses at peak BrAC and at half-peak BrAC on both the ascending and descending limbs. We also computed and compared Pearson-product moment correlations of responses by route of administration, the Mellanby measure of acute adaptation to alcohol, and the area under the entire response curve for each subjective response.

RESULTS

No significant differences in any measure could be attributed to the route of alcohol administration. Eleven of 12 response comparisons were significantly correlated across the routes of alcohol administration, with 9 surviving correction for multiple measures, as did the Mellanby effect and area under the response curve correlations.

CONCLUSIONS

The route of alcohol administration has a minimal effect on subjective responses to alcohol when an individual's BrAC exposure profiles are similar.

Striatal activity correlates with stimulant-like effects of alcohol in healthy volunteers

Individuals who experience greater stimulation and less sedation from alcohol are at increased risk for alcohol-related problems. However, little is known regarding the neurobiological mechanisms underlying subjective response to alcohol. The current study examined the degree to which alcohol-induced brain activation correlates with ratings of stimulation and sedation, using a within-subjects, double-blind, placebo-controlled design. Participants (N = 34 healthy adults with no history of alcohol use disorder) completed three sessions: a calibration session to determine the duration of infusion needed to bring the breath alcohol to 80 mg/dl for each subject, and two counterbalanced fMRI sessions with placebo and alcohol administration. During the fMRI sessions, participants underwent 50 min scans, which included a 10 min baseline period, the IV infusion period needed to bring breath alcohol concentration (BrAC) to a peak 80 mg/dl (on the alcohol session), followed by a post-peak decline period. Participants rated their subjective stimulation and sedation at regular intervals throughout the scan. A priori VOI analyses showed that the time course of stimulation correlated with BOLD signal in the striatum. The time course of sedation did not correlate with BOLD signal in any VOIs. There were no correlations in primary visual cortex, which served as a control. These findings are the first to show that alcohol effects in the striatum are linked to the positive, stimulant-like effects of the drug and advance our understanding of the neurobiological mechanisms underlying individual differences in subjective responses to alcohol, and more broadly, risk for alcohol use disorders.

Acute alcohol administration dampens central extended amygdala reactivity

Alcohol use is common, imposes a staggering burden on public health, and often resists treatment. The central extended amygdala (EAc)—including the bed nucleus of the stria terminalis (BST) and the central nucleus of the amygdala (Ce)—plays a key role in prominent neuroscientific models of alcohol drinking, but the relevance of these regions to acute alcohol consumption in humans remains poorly understood. Using a single-blind, randomized-groups design, multiband fMRI data were acquired from 49 social drinkers while they performed a well-established emotional faces paradigm after consuming either alcohol or placebo. Relative to placebo, alcohol significantly dampened reactivity to emotional faces in the BST. To rigorously assess potential regional differences in activation, data were extracted from unbiased, anatomically predefined regions of interest. Analyses revealed similar levels of dampening in the BST and Ce. In short, alcohol transiently reduces reactivity to emotional faces and it does so similarly across the two major divisions of the human EAc. These observations reinforce the translational relevance of addiction models derived from preclinical work in rodents and provide new insights into the neural systems most relevant to the consumption of alcohol and to the initial development of alcohol abuse in humans.

Amygdala-orbitofrontal functional connectivity mediates the relationship between sensation seeking and alcohol use among binge-drinking adults

BACKGROUND

Decreased amygdala-orbitofrontal cortex (OFC) neural functional connectivity (FC) positively predicts alcohol use among adolescents. Low amygdala-OFC FC is also associated with poor emotion regulation, a trait robustly linked to alcohol use. Thus, decreased amygdala-OFC connectivity may represent a risk factor for the development of alcohol use disorder (AUD) via impaired emotion regulation or reward processing. In this study, we examined amygdala-OFC FC among young adult binge drinkers at high risk for AUD. We also tested if amygdala-OFC FC mediates the relationship between externalizing personality traits and alcohol use.

METHODS

Healthy male and female (n = 39) binge drinkers completed a resting state fMRI scan and the Eysenck Impulsive Personality questionnaire. We utilized seed-based connectivity of the left and right amygdala to prefrontal regions as well as mediation analysis.

RESULTS

Individuals with higher weekly alcohol use displayed decreased right amygdala-OFC FC. Furthermore, high trait venturesomeness, but not impulsivness, was associated with decreased right amygdala-OFC FC. Finally, right amygdala-OFC FC mediated the relationship between trait venturesomeness and weekly drinking; individuals with high trait venturesomeness displayed decreased right amygdala-OFC FC, which in turn predicted greater weekly drinking.

CONCLUSIONS

Our findings corroborate and extend the adolescent literature by showing that decreased amygdala-OFC FC is associated with higher alcohol consumption among adults at elevated risk for AUD. This study also demonstrates for the first time that this neural profile reflects a tendency to sensation seeking. In sum, our findings suggest that amygdala-OFC FC may be an objective neural target for alcohol use prevention and intervention.

Facets of impulsivity and alcohol use: What role do emotions play?

Alcohol misuse is a major public concern. Impulsivity has been recognised as a significant risk factor predisposing for the initiation of alcohol use, continuation and excessive alcohol use. Evidence suggests that impulsivity is also a result of both acute alcohol intoxication and long-term alcohol abuse. The multifaceted character of impulsivity and the various ways of assessing it in humans and animal models, hampers the full understanding of how impulsivity relates to alcohol use and misuse. Therefore, in this review we evaluate recent developments in the field, trying to disentangle the contribution of different impulsivity subtypes as causes and effects of alcohol use. Moreover, we review a growing body of evidence, including brain imaging, suggesting the importance of emotional states in engaging in alcohol consumption, particularly in highly impulsive individuals. We also present recent insights into how emotional processing is manifested in alcoholism and binge drinking and suggest novel approaches to treatment and prevention opportunities which target emotional-regulation as well as emotional perception and insight.

A preliminary examination of the relation between neural sensitivity to reward and history of alcohol use disorder among adults with internalizing psychopathologies

Decreased reward responsiveness, as demonstrated utilizing the event-related potential (ERP) component the reward positivity (RewP), is an established correlate of internalizing psychopathologies (IPs), such as depressive and anxiety disorders. Although IPs are highly comorbid with alcohol use disorders (AUDs) and despite evidence that AUDs are also characterized by aberrant reward processing styles, no studies have examined how AUD history impacts the RewP among adults with IPs. The current preliminary study sought to examine this question in a sample of 65 adults with 1) current IPs (i.e., depression, social anxiety, and/or generalized anxiety, 2) current IPs with a history of an AUD (IP + Past AUD), and 3) no history of a DSM-IV disorder. Participants completed a guessing reward task while electroencephalogram (EEG) was recorded. Results indicated that participants in the IP group exhibited a more attenuated RewP relative to IP + Past AUD and healthy control individuals. Findings from this study highlight the importance of examining diagnostic subgroups among adults with anxiety and depressive disorders, and suggest that a history of AUD may enhance reward reactivity at the neural level in individuals with IPs.

Brain Functional Magnetic Resonance Imaging Cue-reactivity Can Predict Baclofen Response in Alcohol Use Disorders

Objective

Baclofen is a promising treatment for alcohol use disorders (AUD), although its clinical response in humans is mixed. The present study aimed at investigating the impact of baclofen treatment on cue-induced brain activation pattern and its relationship with relapse outcomes.

Methods

Twenty-three inpatients with AUD underwent a functional magnetic resonance imaging cue-reactivity task before beginning medication with baclofen and 2 weeks later. Twelve additional inpatients with AUD, who did not receive any anticraving medications, formed the control group. All subjects were prospectively followed up for 90 days post-discharge or until lapse to first alcohol use.

Results

Whole-brain linear mixed effects analysis revealed a significant group-by-time interaction with greater activation of the bilateral dorsolateral pre-frontal cortex and right anterior cingulate cortex (ACC) following baclofen treatment in comparison with the control group. Further, cox regression analysis revealed that increased activation of ACC and deactivation of insular cortex (IC) was associated with longer time to first alcohol use only in the baclofen treatment group but not in the control group.

Conclusion

This study provides preliminary evidence for the neural predictors of baclofen treatment response in AUD. Baclofen treatment in AUD was associated with changes in cue-reactivity at critical brain regions within the incentive-salience network. Importantly, baclofen treatment-related specific activation of regions involved in cognitive control (ACC) and deactivation of regions involved in reward anticipation (IC) prolonged the time to first alcohol drink.

Application of Research Domain Criteria to childhood and adolescent impulsive and addictive disorders: Implications for treatment

The Research Domain Criteria (RDoC) initiative provides a large-scale, dimensional framework for the integration of research findings across traditional diagnoses, with the long-term aim of improving existing psychiatric treatments. A neurodevelopmental perspective is essential to this endeavor. However, few papers synthesizing research findings across childhood and adolescent disorders exist. Here, we discuss how the RDoC framework may be applied to the study of childhood and adolescent impulsive and addictive disorders in order to improve neurodevelopmental understanding and to enhance treatment development. Given the large scope of RDoC, we focus on a single construct highly relevant to addictive and impulsive disorders - initial responsiveness to reward attainment. Findings from genetic, molecular, neuroimaging and other translational research methodologies are highlighted.

Acute calming effects of alcohol are associated with disruption of the salience network

The mood-altering properties of alcohol are a key motivation for drinking, and people commonly report that they drink alcohol to alleviate stress or to relax. To date, the neural processes associated with the self-reported calming effects of alcohol are not well understood. Existing data imply that alcohol may target and disrupt activity within anterior insula (aINS) and amygdala-based neural networks, which are regions implicated in threat detection and anxious responding. The aims of the current study were (1) to examine the acute effect of alcohol upon functional connectivity within aINS and amygdala circuits and (2) to assess relationships between alcohol effects on functional connectivity and self-reported subjective mood. Healthy men and women (N = 39) who reported regular binge drinking completed a within-subjects, double-blind, placebo-controlled pharmacological functional magnetic resonance imaging experiment with i.v. infusions of either alcohol or placebo. Infusion profiles were personalized for each participant and raised breath alcohol concentration to 80 mg percent. Before, during and after infusions, participants rated their subjective mood (stimulation, sedation and calm). Results showed that alcohol dampened functional connectivity between bilateral aINS seed-regions-of-interest and the dorsal anterior cingulate cortex (dACC), key nodes of the salience network. Additionally, the more that alcohol reduced right aINS-dACC functional connectivity, the calmer participants felt during alcohol administration. Alcohol had no effect on amygdala functional connectivity. These findings suggest that alcohol disrupts aINS-dACC functional connectivity, which may impair detection and appraisal of emotionally salient information and relate to acute relaxing effects of the drug.

Neurobiological Correlates and Predictors of Two Distinct Personality Trait Pathways to Escalated Alcohol Use

BACKGROUND

The delineation of the behavioral neurobiological mechanisms underlying the heterogeneous pathways for alcohol use disorders (AUDs) is ostensibly imperative for the development of more cost-effective treatments predicated on better understanding of this complex psychopathology.

METHODS

1) Forty-eight high anxiety sensitive (HAS) and high sensation seeking (HSS) psychopathology-free emerging adults (mean (SD) age: 20.4 (1.9) years) completed a Face Emotion Processing Task and a social stress paradigm (Montreal Imaging Stress Task) during functional magnetic resonance imaging sessions with and without alcohol ingestion (1ml/kg of 95% USP alcohol, p.o.). Drug and alcohol use was reassessed during follow-up interviews 2-3years later.

OUTCOMES

The effects of alcohol (versus placebo) ingestion depended upon the task and risk group. In response to negative (versus neutral) faces, alcohol diminished amygdala (AMYG) activations in HAS but not HSS subjects. In response to psychosocial evaluative stress, alcohol enhanced activations of the medial orbitofrontal cortex (mOFC), perigenual anterior cingulate cortex, and nucleus accumbens in HAS male subjects (HASMS), but decreased mOFC activity in HSS male subjects (HSSMS). At follow-up, a greater alcohol versus placebo differential for threat-related AMYG activations predicted escalating drinking and/or illicit drug use among HAS but not HSS participants, whereas a greater differential for mOFC activations during acute social stress predicted escalating substance use among HSS but not HAS participants.

INTERPRETATION

This double dissociation provides evidence of distinct neurobiological profiles in a priori identified personality trait-based risk groups for AUDs, and links these signatures to clinically relevant substance use outcomes at follow-up. AUD subtypes might benefit from motivationally and personality-specific ameliorative and preventative interventions.

Rat animal models for screening medications to treat alcohol use disorders

The purpose of this review is to present animal research models that can be used to screen and/or repurpose medications for the treatment of alcohol abuse and dependence. The focus will be on rats and in particular selectively bred rats. Brief introductions discuss various aspects of the clinical picture, which provide characteristics of individuals with alcohol use disorders (AUDs) to model in animals. Following this, multiple selectively bred rat lines will be described and evaluated in the context of animal models used to screen medications to treat AUDs. Next, common behavioral tests for drug efficacy will be discussed particularly as they relate to stages in the addiction cycle. Tables highlighting studies that have tested the effects of compounds using the respective techniques are included. Wherever possible the Tables are organized chronologically in ascending order to describe changes in the focus of research on AUDs over time. In general, high ethanol-consuming selectively bred rats have been used to test a wide range of compounds. Older studies usually followed neurobiological findings in the selected lines that supported an association with a propensity for high ethanol intake. Most of these tests evaluated the compound's effects on the maintenance of ethanol drinking. Very few compounds have been tested during ethanol-seeking and/or relapse and fewer still have assessed their effects during the acquisition of AUDs. Overall, while a substantial number of neurotransmitter and neuromodulatory system targets have been assessed; the roles of sex- and age-of-animal, as well as the acquisition of AUDs, ethanol-seeking and relapse continue to be factors and behaviors needing further study. This article is part of the Special Issue entitled "Alcoholism".

Neural mechanisms of sensitivity to peer information in young adult cannabis users

Though social influence is a critical factor in the initiation and maintenance of marijuana use, the neural correlates of influence in those who use marijuana are unknown. In this study, marijuana-using young adults (MJ; n = 20) and controls (CON; n = 23) performed a decision-making task in which they made a perceptual choice after viewing the choices of unknown peers via photographs, while they underwent functional magnetic resonance imaging scans. The MJ and CON groups did not show differences in the overall number of choices that agreed with versus opposed group influence, but only the MJ group showed reaction time slowing when deciding against group choices. Longer reaction times were associated with greater activation of frontal regions. The MJ goup, compared to CON, showed significantly greater activation in the caudate when presented with peer information. Across groups, caudate activation was associated with self-reported susceptibility to influence. These findings indicate that young adults who use MJ may exhibit increased effort when confronted with opposing peer influence, as well as exhibit greater responsivity of the caudate to social information. These results not only better define the neural basis of social decisions, but also suggest that marijuana use is associated with exaggerated neural activity during decision making that involves social information.

Low μ-Opioid Receptor Status in Alcohol Dependence Identified by Combined Positron Emission Tomography and Post-Mortem Brain Analysis

Blockade of the μ-opioid receptor (MOR) by naltrexone reduces relapse risk in a subpopulation of alcohol-dependent patients. Previous positron-emission-tomography (PET) studies using the MOR ligand [¹¹C]carfentanil have found increased MOR availability in abstinent alcoholics, which may reflect either increased MOR expression or lower endogenous ligand concentration. To differentiate between both effects, we investigated two cohorts of alcoholic subjects using either post-mortem or clinical PET analysis. Post-mortem brain tissue of alcohol-dependent subjects and controls (N=43/group) was quantitatively analyzed for MOR ([³H]DAMGO)-binding sites and OPRM1 mRNA in striatal regions. [¹¹C]carfentanil PET was performed in detoxified, medication free alcohol-dependent patients (N=38), followed by a randomized controlled study of naltrexone versus placebo and follow-up for 1 year (clinical trial number: NCT00317031). Because the functional OPRM1 variant rs1799971:A>G affects the ligand binding, allele carrier status was considered in the analyses. MOR-binding sites were reduced by 23-51% in post-mortem striatal tissue of alcoholics. In the PET study, a significant interaction of OPRM1 genotype, binding potential (BP_ND) for [¹¹C]carfentanil in the ventral striatum, and relapse risk was found. Particularly in G-allele carriers, lower striatal BP_ND was associated with a higher relapse risk. Interestingly, this effect was more pronounced in the naltrexone treatment group. Reduced MOR is interpreted as a neuroadaptation to an alcohol-induced release of endogenous ligands in patients with severe alcoholism. Low MOR availability may explain the ineffectiveness of naltrexone treatment in this subpopulation. Finally, low MOR-binding sites are proposed as a molecular marker for a negative disease course.

Brain responses to emotional salience and reward in alcohol use disorder

Heightened neural responsiveness of alcoholics to alcohol cues and social emotion may impede sobriety. To test mesocorticolimbic network responsivity, 10 (8 men) alcohol use disorder (AUD) patients sober for 3 weeks to 10 months and 11 (8 men) controls underwent fMRI whilst viewing pictures of alcohol and non-alcohol beverages and of emotional faces (happy, sad, angry). AUD and controls showed similarities in mesocorticolimbic activity: both groups activated fusiform for emotional faces and hippocampal and pallidum regions during alcohol picture processing. In AUD, less fusiform activity to emotional faces and more pallidum activity to alcohol pictures were associated with longer sobriety. Using graph theory-based network efficiency measures to specify the role of the mesocorticolimbic network nodes for emotion and reward in sober AUD revealed that the left hippocampus was less efficiently connected with the other task-activated network regions in AUD than controls when viewing emotional faces, while the pallidum was more efficiently connected when viewing alcohol beverages. Together our findings identified lower occipito-temporal sensitivity to emotional faces and enhanced striatal sensitivity to alcohol stimuli in AUD than controls. Considering the role of the striatum in encoding reward, its activation enhancement with longer sobriety may reflect adaptive neural changes in the first year of drinking cessation and mesocorticolimbic system vulnerability for encoding emotional salience and reward potentially affecting executive control ability and relapse propensity during abstinence.

Amygdala-orbitofrontal connectivity predicts alcohol use two years later: a longitudinal neuroimaging study on alcohol use in adolescence

This study tested the relation between cortical-subcortical functional connectivity and alcohol consumption in adolescents using an accelerated longitudinal design, as well as normative developmental patterns for these measures. Participants between ages 8 and 27 completed resting-state neuroimaging scans at two time points separated by two years (N = 274 at T1, N = 231 at T2). In addition, participants between ages 12 and 27 reported on recent and lifetime alcohol use (N = 193 at T1, N = 244 at T2). Resting-state connectivity analyses focused on amygdala-orbitofrontal connectivity given prior research linking reduced coupling between these regions to alcohol use. Mixed model analyses revealed that age had a cubic relationship with alcohol use, with little to no use in childhood, steep increases in adolescence and leveling off in adulthood. No age effects were found for amygdala-OFC connectivity. Prediction analyses showed that left amygdala-orbitofrontal connectivity at the first time point predicted recent and lifetime alcohol use two years later. There was no evidence for the reversed relation, suggesting that brain connectivity measures precede explorative risk-taking behavior in adolescence, possibly because decreased subcortical-frontal connectivity biases towards more explorative or risky behavior.