Brain activation during craving for alcohol measured by positron emission tomography

Trying to forget alcohol: Brain mechanisms underlying memory suppression in young binge drinkers

People are able to voluntarily suppress unwanted thoughts or memories, a phenomenon known as suppression-induced forgetting or memory suppression. Despite harmful alcohol use, such as binge drinking, has been linked to impaired inhibitory control (IC) and augmented alcohol-cue reactivity, no study to date has assessed memory inhibition abilities towards alcohol-related cues in binge drinkers (BDs). Thus, the present preregistered study aimed to evaluate the behavioral and neurofunctional mechanisms associated with memory inhibition, specifically those related to the suppression of alcohol-related memories, in young BDs. For this purpose, electroencephalographic activity was recorded in eighty-two college students aged between 18 and 24 years old from the University of Minho (50% females; 40 non/low-drinkers [N/LDS] and 42 BDs) while they performed the Think/No-Think Alcohol task. Brain functional connectivity (FC) was calculated using the phase locking value and, subsequently, a dynamic seed-based analysis was conducted to explore the FC patterns between IC and memory networks. Comparatively to N/LDs, BDs exhibited decreased alpha-band FC between the anterior cingulate cortex and the left fusiform gyrus during attempts to suppress non-alcohol memories, accompanied by unsuccessful forgetting of those memories. Conversely, BDs displayed augmented gamma-band FC between the IC network and memory regions -i.e., hippocampus, parahippocampus and fusiform gyrus- during suppression of alcohol-related memories. Inhibitory abnormalities in BDs may lead to hypoconnectivity between IC and memory networks and deficient suppression of non-alcohol-related memories. However, while suppressing highly salient and reward-predicting stimuli, such as alcohol-related memories, BDs display a hyperconnectivity pattern between IC and memory networks, likely due to their augmented attention towards intrusive alcoholic memories and the attempts to compensate for potential underlying IC deficits. These findings hold important implications for alcohol research and treatment, as they open up new avenues for reducing alcohol use by shifting the focus to empowering suppression/control over alcohol-related memories. CLINICAL TRIAL REGISTRATION: [http://www.ClinicalTrials.gov], identifier [NCT05237414].

Efficacy of tDCS on craving in patients of alcohol dependence syndrome: A single-blind, sham-controlled trial

Background

Craving is attributed as one of the main reasons for relapse in alcohol dependence syndrome. Neurostimulation techniques targeting craving in substance use disorders are being researched. Neuroimaging has shown dorsolateral prefrontal cortex (DLPFC) as one of the potential targets responsible for craving, with frontal dysfunction being quintessential in alcohol use disorder. Evidence suggests that stimulation of DLPFC with low-dose current can help in reducing craving.

Objectives

To study the effectiveness of transcranial direct current stimulation (tDCS) on craving in patients with alcohol dependence syndrome.

Materials and Methods

We performed a single-blind, sham-controlled study involving 76 patients with alcohol dependence syndrome (according to ICD-10 DCR). Participants with Clinical Institute of Withdrawal Assessment in Alcohol Withdrawal (CIWA-Ar) scores less than 10, not on any anti-craving medications were included in the study. Patients were allocated to active and sham tDCS groups in a ratio of 1:1. Such that 38 patients received active, and 38 patients sham tDCS stimulations; with anode as right DLPFC and cathode as left DLPFC receiving 2 mA current (twice daily session, total of 10 sessions). The Alcohol Craving Questionnaire (ACQ-NOW) was administered to measure the severity of alcohol craving at baseline and after the last tDCS session.

Results

Our study showed a significant reduction in craving in the Post-tDCS, ACQ-NOW scores as compared to sham tDCS. There was a significant reduction in the compulsivity and emotionality domain of craving after tDCS. The effect size for treatment with time interaction was (0.58).

Conclusions

tDCS was superior to sham in reducing caving in patients with alcohol dependence syndrome.

Targeting cravings in substance addiction with transcranial direct current stimulation: insights from a meta-analysis of sham-controlled trials

Addiction is a substantial health concern; craving-the core symptom of addiction-is strongly associated with relapse. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that reduces cravings by altering cortical excitability and connectivity in brain regions. This systematic review and meta-analysis was conducted (following the PRISMA guidelines) to evaluate the efficacy of tDCS in reducing cravings for substances. Our analysis included 43 randomized, sham-controlled trials involving 1,095 and 913 participants receiving tDCS and sham stimulation, respectively. We analyzed the changes in craving scores and found that tDCS led to a moderate reduction in cravings compared with the sham effects. This effect was particularly pronounced when bilateral stimulation was used, the anodal electrode was placed on the right dorsolateral prefrontal cortex, current intensities ranged from 1.5 to 2 mA, stimulation sessions lasted 20 minutes, and the electrodes size was ≥35 cm². Notably, tDCS effectively reduced cravings for opioids, methamphetamine, cocaine, and tobacco but not for alcohol or cannabis. Our findings indicate tDCS as a promising, noninvasive, and low-risk intervention for reducing cravings for opioids, methamphetamine, cocaine, and tobacco. Additional studies are warranted to refine stimulation parameters and evaluate the long-term efficacy of tDCS in managing substance cravings.

Chemogenetic Perturbation of the Posterior But Not Anterior Cerebellum Reduces Voluntary Ethanol Consumption

The cerebellum communicates with brain areas critically involved in control of goal-directed behaviors including the prefrontal and orbitofrontal cortices and midbrain and basal ganglia structures. In particular, the posterior cerebellum is important for cognitive flexibility and has been implicated in alcohol and drug-related memory. We hypothesized that the cerebellum, through its multiple connections to reward-related brain circuitry, regulates alcohol consumption. To test this, we expressed inhibitory designer receptors exclusively activated by designer drugs (DREADDs) in molecular layer interneurons (MLIs) in anterior (IV-V) or posterior (VI-VIII) cerebellar lobules of male and female mice and activated them during alcohol drinking sessions. In a home-cage drinking paradigm, alcohol consumption was significantly decreased by clozapine-N-oxide (CNO) or deschloroclozapine (DCZ) administration in male mice expressing DREADDs in posterior but not anterior lobules. CNO/DCZ injections did not affect drinking in DREADD expressing female mice or in male mice expressing the control vector. Activation of DREADDs expressed in anterior or posterior lobules had no effect on sucrose or quinine consumption in male or female mice. During operant self-administration sessions, DCZ decreased the number of licks and bouts in male but not female mice expressing DREADDs in posterior lobules with no effect in control vector mice. Performance on an accelerated rotarod was unaffected by chemogenetic manipulation while distance traveled in the open field was decreased by DREADD activation in anterior but not posterior lobules. These results indicate that neuronal activity within the posterior cerebellar cortex plays an important role in the control of alcohol consumption in male mice.

Putting forward a model for the role of the cerebellum in cocaine-induced pavlovian memory

Substance Use Disorder (SUD) involves emotional, cognitive, and motivational dysfunction. Long-lasting molecular and structural changes in brain regions functionally and anatomically linked to the cerebellum, such as the prefrontal cortex, amygdala, hippocampus, basal ganglia, and ventral tegmental area, are characteristic of SUD. Direct and indirect reciprocal connectivity between the cerebellum and these brain regions can explain cerebellar roles in Pavlovian and reinforcement learning, fear memory, and executive functions. It is increasingly clear that the cerebellum modulates brain functions altered in SUD and other neuropsychiatric disorders that exhibit comorbidity with SUD. In the present manuscript, we review and discuss this evidence and present new research exploring the role of the cerebellum in cocaine-induced conditioned memory using chemogenetic tools (designer receptor exclusively activated by designer drug, DREADDs). Our preliminary data showed that inactivation of a region that includes the interposed and lateral deep cerebellar nuclei reduces the facilitating effect of a posterior vermis lesion on cocaine-induced preference conditioning. These findings support our previous research and suggest that posterior vermis damage may increase drug impact on the addiction circuitry by regulating activity in the DCN. However, they raise further questions that will also be discussed.

How Should Transcranial Direct Current Stimulation be Used in Populations With Severe Alcohol Use Disorder? A Clinically Oriented Systematic Review

Background and rationale. Severe alcohol use disorder (SAUD) is a major public health concern, given its massive individual, interpersonal, and societal consequences. The available prevention and treatment programs have proven limited effectiveness, as relapse rates are still high in this clinical population. Developing effective interventions reducing the appearance and persistence of SAUD thus constitutes an experimental and clinical priority. Among the new therapeutic approaches, there is a growing interest for noninvasive neuromodulation techniques, and particularly for transcranial direct current stimulation (tDCS) as an adjunctive treatment in neuropsychiatric disorders, including SAUD. Methods. We propose a systematic review, based on preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, evaluating the available evidence on the effectiveness of tDCS to improve clinical interventions in SAUD. Results. We provide an integrative overview of studies applying tDCS in clinical populations with SAUD, together with a standardized methodological quality assessment. We show that the currently available data remain inconsistent. Some data suggested that tDCS can (1) reduce craving, relapse or alcohol-cue reactivity and (2) improve cognitive control and inhibition. However, other studies did not observe any beneficial effect of tDCS in SAUD. Conclusions. Capitalizing on the identified strengths and shortcomings of available results, we present evidence-based clinical guidelines to integrate tDCS in current clinical settings and to combine it with neurocognitive training.

Alcohol use and interoception - A narrative review

Interoception, defined as the ability to perceive and interpret body signals, may play an important role in alcohol use disorder (AUD). Earlier studies suggested an association between interoception impairment and known risk factors for AUD (e.g., alexithymia, emotion dysregulation, impulsivity, pain). Neurobiological studies show that the neurotoxicity of alcohol affects various elements of the interoceptive system (especially the insula) at structural and functional levels, with differential short/long term impacts. Conversely, primary interoceptive impairments may promote alcohol consumption and foster the evolution towards addiction. Despite convincing evidence demonstrating that interoception impairment may be an important contributor to the development and course of AUD, only a few studies directly evaluated interoceptive abilities in AUD. The research shows that interoceptive accuracy, the objective component of interoception, is lower in AUD individuals, and is correlated with craving and emotion dysregulation. Interoceptive sensibility is in turn higher in AUD individuals compared to healthy controls. Moreover, there is evidence that therapy focused on improving the ability to sense signals from the body in addiction treatment is effective. However, important methodological limitations in interoceptive measures persist, and it is therefore necessary to further investigate the associations between interoception and AUD.

The influence of perceived stress and self-control on efficacy of repeated transcranial direct current stimulation in non-treatment-seeking smokers

INTRODUCTION

Transcranial direct current stimulation (tDCS) has recently been raising interest in its therapeutic impact on tobacco use disorder. This study investigates the effects of repeated frontal tDCS (anode: F3, cathode: F4) on cigarette consumption, craving and executive functions.

MATERIAL AND METHODS

In a randomized sham-controlled trial, 24 individuals received active (2.0 mA) and 20 individuals received sham stimulation (0.3 mA) for 20 min on five consecutive days. The participants indicated their tobacco cravings, answered questionnaires and completed neuropsychological tasks at various time points throughout the study. Carbon monoxide (CO) levels and the daily numbers of consumed cigarettes were recorded.

RESULTS

Both intervention groups experienced a significant decrease in the daily number of smoked cigarettes, CO levels, and craving after the stimulation, however, there were no improvements in executive functions. These results did not differ significantly between both intervention groups. Additionally, in the active group, a higher level of perceived stress and a lower level of self-control were linked to a lower cigarette consumption, respectively a higher reduction of the level of CO.

CONCLUSION

This study does not support the hypotheses that tDCS reduces cigarette consumption, attenuates substance craving, or improves executive functions beyond the placebo effect. Our subgroup analysis suggests that high levels of perceived stress and low self-control may be predictors for a successful reduction in cigarette consumption. Furthermore, the placebo effect might be rather high for light smokers, whereas heavy smokers seem to benefit more from the specific effects of tDCS.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03691805.

The synergistic effect between interoceptive accuracy and alcohol use disorder status on pain sensitivity

BACKGROUND

Interoceptive accuracy and pain sensitivity are both risk factors in the development of alcohol use disorder (AUD). However, the synergistic association between these two factors has not been investigated in an AUD sample. Therefore, the aim of the current study was to investigate whether the association between interoceptive accuracy and sensitivity to pain differed across AUD status.

METHODS

The study group included 165 individuals diagnosed with AUD (88.1% men) and 110 healthy controls (HCs; 74.5% men). Interoceptive accuracy was assessed with the Schandry Task. The Pain Sensitivity Questionnaire was utilized to measure sensitivity to pain. Anxiety, biological sex, and age were included as covariates in a model examining the role of AUD status as a moderator in the association between interoceptive accuracy and pain sensitivity.

RESULTS

A significant interaction was found between interoceptive accuracy and AUD status (b = -4.580, 95% CI = [-8.137, -1.022], p = 0.012, ΔR² = 0.032). Findings indicate that interoceptive accuracy was negatively associated with pain sensitivity among individuals with AUD, while there was a trend for an opposite association among healthy controls.

CONCLUSION

We hypothesize that persistent alcohol drinking may contribute to disruption of the normative association between interoception and pain. Future studies should be conducted to develop knowledge on this association and to investigate its possible therapeutic significance and implications.

Non-invasive Brain Stimulation for Alcohol Use Disorders: State of the Art and Future Directions

Alcohol use disorders remain one of the leading causes of mortality and morbidity across the world, yet despite this impact, there are few treatment options for patients suffering from these disorders. To this end, non-invasive brain stimulation, most commonly utilizing technologies including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has recently emerged as promising potential treatments for alcohol use disorders. Enthusiasm for these interventions is fueled by their non-invasive nature, generally favorable safety profile, and ability to target and modulate brain regions implicated in substance use disorders. In this paper, we describe the underlying principles behind these commonly used stimulation technologies, summarize existing experiments and randomized controlled trials, and provide an integrative summary with suggestions for future areas of research. Currently available data generally supports the use of non-invasive brain stimulation as a near-term treatment for alcohol use disorder, with important caveats regarding the use of stimulation in this patient population.

Transcranial Direct Current Stimulation on Opium Craving, Depression, and Anxiety: A Preliminary Study

OBJECTIVES

Transcranial direct current stimulation can be effective in reducing the craving for food, alcohol, and methamphetamine. Because its effects have not been tested on patients with opium use disorder, we investigated its efficacy when it is combined with a standard methadone maintenance therapy protocol.

METHODS

We carried out a pretest-posttest control group method to evaluate the effect of transcranial direct current stimulation at the dorsolateral prefrontal cortex (right anodal/left cathodal) on opium craving, depression, and anxiety symptoms. We considered opium craving as a primary outcome as well as depression and anxiety symptoms as secondary outcomes. Sixty participants with opium use disorder were randomly assigned into 3 groups (n = 20 for each group): (1) an active transcranial direct current stimulation with methadone maintenance treatment (active tDCS group), (2) sham transcranial direct current stimulation with methadone maintenance treatment (sham tDCS group), and (3) only methadone maintenance treatment (methadone maintenance treatment group). All participants completed the Desire for Drug Questionnaire, Obsessive-Compulsive Drug Use Scale, Beck Depression Inventory II, and Beck Anxiety Inventory a week before and a week after the treatment. The outcomes were assessed by independent assessors who were blind to the treatment conditions.

RESULTS

The active tDCS group had a significant reduction in opium craving, depression, and anxiety symptoms compared with the other 2 groups.

CONCLUSIONS

Our results provide a preliminary support for using the transcranial direct current stimulation along with methadone maintenance therapy in the treatment of patients with opium use disorder.

Posterior Cingulate Cortical Response to Active Avoidance Mediates the Relationship between Punishment Sensitivity and Problem Drinking

Many people drink to alleviate negative affect, reflecting an avoidance strategy which can lead to alcohol misuse. Individuals with heightened sensitivity to punishment (SP) are especially susceptible to problem drinking via this maladaptive coping mechanism. As imaging studies have largely focused on sensation-seeking traits and approach behavior, the neural substrates underlying behavioral avoidance as well as their relationship with punishment sensitivity and alcohol use remain unclear. Here, we examined in humans the cerebral correlates of response inhibition to avoid a penalty in relation to both problem drinking and SP, as evaluated by the Alcohol Use Disorders Identification Test and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, respectively. Seventy nondependent female and male drinkers performed a reward go/no-go task with approximately two-thirds go and one-third no-go trials. Correct go and no-go responses were rewarded, and incorrect responses were punished. The results showed that SP and Alcohol Use Disorders Identification Test scores were both positively correlated with brain activations during response inhibition, and these activations overlapped in the posterior cingulate cortex (PCC). Thus, the PCC may represent a shared neural substrate for avoidance, punishment sensitivity, and problem drinking. Mediation analyses further suggested that PCC response to avoidance completely and bidirectionally mediated the relationship between SP and hazardous alcohol use. These findings substantiated the role of the PCC in behavioral avoidance and its link to problem drinking in punishment-sensitive nondependent drinkers.SIGNIFICANCE STATEMENT Many people drink to alleviate negative affect, reflecting an avoidance strategy that can lead to alcohol misuse. Individuals with heightened punishment sensitivity (SP) trait are particularly vulnerable to this maladaptive coping mechanism. The current study examined the neural substrates underlying behavioral avoidance and their relationship with SP and problem drinking. Using a reward go/no-go task, we showed both SP and drinking severity were positively correlated with the posterior cingulate cortex (PCC) activation during action inhibition. Thus, the PCC may represent a shared neural substrate for avoidance behavior, punishment sensitivity, and problem drinking. Further, PCC response to avoidance mediated the relationship between SP and alcohol use. These findings substantiated the neural processes linking avoidance tendency to alcohol misuse in punishment-sensitive drinkers.

Effect of transcranial direct current stimulation on the number of smoked cigarettes in tobacco smokers

BACKGROUND

Recent studies reported that transcranial direct current stimulation (tDCS) applied over the dorsolateral prefrontal cortex (DLPFC) reduced craving and cigarette smoking. We aimed to evaluate whether 3 sessions of tDCS over the DLPFC modulate cigarette smoking which is a critical factor in tobacco smokers.

METHODS

In a double-blinded, sham-controlled, parallel experimental study, 22 participants who wished to quit smoking received tDCS with the cathodal over the right DLPFC and anodal over the left DLPFC based on the 10-20 EEG international system (F4, F3) at an intensity of 1.5 mA for 20 minutes during three consecutive days. For sham stimulation, the electrodes placement was the same as for the active stimulation.

RESULTS

For the short time interval (8 days after the end of the tDCS regimen), the number of smoked cigarettes was reduced similarly in the active and sham groups (p < 0.001). Also, at the long time-interval (4 months after the end of the tDCS regimen) as compared to pre-tDCS, there was no significant difference in the number of smoked cigarettes in the active (p = 0.806) or the sham (p = 0.573) groups. Overall, there were no statistically significant differences between the active and sham tDCS groups on cigarette smoking.

CONCLUSION

These findings suggested that 3 sessions of tDCS over the right and left DLPFC may reduce number of smoked cigarettes for short-time period but might not be significantly more effective than sham to decrease cigarette smoking.

Add-on high frequency deep transcranial magnetic stimulation (dTMS) to bilateral prefrontal cortex in depressive episodes of patients with major depressive disorder, bipolar disorder I, and major depressive with alcohol use disorders

BACKGROUND

Dorsolateral prefrontal cortex (DLPFC) is critically involved in mood and alcohol use disorders.

OBJECTIVE

We aimed to investigate the safety of intervention with add-on bilateral prefrontal high-frequency deep transcranial magnetic stimulation (dTMS) and between-group differences in treatment response in patients with different types of depressive episodes, including major depressive episodes in the course of major depressive disorder (MDD), bipolar disorder, type I (BD-I), and MDD with alcohol use disorder (MDAUD).

METHODS

We conducted a 6-month open-label study, involving 82 patients with DSM-5 Depressive Episode. Of these, 41 had diagnosis of MDD, 20 BD-I, and 21 MDAUD. All patients received standard drug treatment and add-on dTMS over the bilateral DLPFC with left prevalence for four weeks, with five sessions in each week. We rated mood state with the Hamilton Depression Rating Scale (HDRS) at baseline, one-month, and six-month follow-up visits.

RESULTS

Mean total HDRS scores dropped from 22.8 (SD = 5.9) at baseline to 10.4 (SD = 3.6) at 1 month, to 10.0 (SD = 4.5) at 6 months, while response/remission were 70.73% (N = 58) and 19.51% (N = 16) at 1 month and 76.83% (N = 63) and 32.93% (27) at 6 months, respectively, with no between-group differences. No patient experienced any side effects.

CONCLUSIONS

High-frequency DLPFC dTMS was well tolerated and did not significantly differ on improvement of depression in MDD, BD-I, and MDAUD.

Binge drinking differentially affects cortical and subcortical microstructure

Young adult binge drinkers represent a model for endophenotypic risk factors for alcohol misuse and early exposure to repeated binge cycles. Chronic or harmful alcohol use leads to neurochemical, structural and morphological neuroplastic changes, particularly in regions associated with reward processing and motivation. We investigated neural microstructure in 28 binge drinkers compared with 38 matched healthy controls. We used a recently developed diffusion magnetic resonance imaging acquisition and analysis, which uses three‐compartment modelling (of intracellular, extracellular and cerebrospinal fluid) to determine brain tissue microstructure features including neurite density and orientation dispersion index (ODI). Binge drinkers had reduced ODI, a proxy of neurite complexity, in frontal cortical grey matter and increased ODI in parietal grey matter. Neurite density was higher in cortical white matter in adjacent regions of lower ODI in binge drinkers. Furthermore, binge drinkers had higher ventral striatal grey matter ODI that was positively correlated with binge score. Healthy volunteers showed no such relationships. We demonstrate disturbed dendritic complexity of higher‐order prefrontal and parietal regions, along with higher dendritic complexity of a subcortical region known to mediate reward‐related motivation. The findings illustrate novel microstructural abnormalities that may reflect an infnce of alcohol bingeing on critical neurodevelopmental processes in an at‐risk young adult group.

Recreational concentrations of alcohol enhance synaptic inhibition of cerebellar unipolar brush cells via pre- and postsynaptic mechanisms

Variation in cerebellar sensitivity to alcohol/ethanol (EtOH) is a heritable trait associated with alcohol use disorder in humans and high EtOH consumption in rodents, but the underlying mechanisms are poorly understood. A recently identified cellular substrate of cerebellar sensitivity to EtOH, the GABAergic system of cerebellar granule cells (GCs), shows divergent responses to EtOH paralleling EtOH consumption and motor impairment phenotype. Although GCs are the dominant afferent integrator in the cerebellum, such integration is shared by unipolar brush cells (UBCs) in vestibulocerebellar lobes. UBCs receive both GABAergic and glycinergic inhibition, both of which may mediate diverse neurological effects of EtOH. Therefore, the impact of recreational concentrations of EtOH (~10-50 mM) on GABA_A receptor (GABA_AR)- and glycine receptor (GlyR)-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) of UBCs in cerebellar slices was characterized. Sprague-Dawley rat (SDR) UBCs exhibited sIPSCs mediated by GABA_ARs, GlyRs, or both, and EtOH dose-dependently (10, 26, 52 mM) increased their frequency and amplitude. EtOH increased the frequency of glycinergic and GABAergic sIPSCs and selectively enhanced the amplitude of glycinergic sIPSCs. This GlyR-specific enhancement of sIPSC amplitude resulted from EtOH actions at presynaptic Golgi cells and via protein kinase C-dependent direct actions on postsynaptic GlyRs. The magnitude of EtOH-induced increases in UBC sIPSC activity varied across SDRs and two lines of mice, in parallel with their respective alcohol consumption/motor impairment phenotypes. These data indicate that Golgi cell-to-UBC inhibitory synapses are targets of EtOH, which acts at pre- and postsynaptic sites, via Golgi cell excitation and direct GlyR enhancement.NEW & NOTEWORTHY Genetic variability in cerebellar alcohol/ethanol sensitivity (ethanol-induced ataxia) predicts ethanol consumption phenotype in rodents and humans, but the cellular and molecular mechanisms underlying genetic differences are largely unknown. Here it is demonstrated that recreational concentrations of alcohol (10-30 mM) enhance glycinergic and GABAergic inhibition of unipolar brush cells through increases in glycine/GABA release and postsynaptic enhancement of glycine receptor-mediated responses. Ethanol effects varied across rodent genotypes parallel to ethanol consumption and motor sensitivity phenotype.

The cerebellum in drug craving

Craving has been considered one of the core features of addiction. It can be defined as the urge or conscious desire to use a drug elicited by the drug itself, drug-associated cues or stressors. Craving plays a major role in relapse, even after prolonged periods of abstinence, as well as in the maintenance of drug seeking in non-abstinent addicts. The circuitry of craving includes medial parts of the prefrontal cortex, ventral striatal zones, ventral tegmental area, ventral pallidum, and limbic regions. Interestingly, the cerebellum shows reciprocal loops with many of these areas. The cerebellum has been linked traditionally to motor functions but increasing evidence indicates that this part of the brain is also involved in functions related to cognition, prediction, learning, and memory. Moreover, the functional neuroimaging studies that have addressed the study of craving in humans repeatedly demonstrate cerebellar activation when craving is elicited by the presentation of drug-related cues. However, the role of cerebellar activity in these craving episodes remains unknown. Therefore, the main goal of this review is to provide a brief update on craving studies and the traditional neural basis of this phenomenon, and then discuss and propose a hypothesis for the function of the cerebellum in craving episodes.

Neuromodulation for Addiction by Transcranial Direct Current Stimulation: Opportunities and Challenges

The field of neuromodulation encompasses a wide spectrum of interventional technologies that modify the pathological activity within the nervous system to achieve a therapeutic effect. Therapy, including transcranial direct current stimulation, has shown promising results across a range of neurological and neuropsychiatric disorders. This article reviews the state-of-the-art of neuromodulation for addiction and discusses the opportunities and challenges available for clinicians and researchers interested in advancing the neuromodulation therapy. A neuromodulation-based approach for addiction has the advantage that the effects might be immediate and selective to the dysfunction. If an alteration in the mechanisms of brain plasticity indeed represents the proximal cause for nicotine-associated cognitive decline and is a critical contributor to the early pathogenesis of addiction, novel interventions that forestall the development of symptoms might be possible.

Elevated Glutamate Levels in the Left Dorsolateral Prefrontal Cortex Are Associated with Higher Cravings for Alcohol

BACKGROUND

Quantifying craving longitudinally during the course of withdrawal, early abstinence, and relapse is essential for optimal management of alcohol use disorder (AUD). In an effort to identify biological correlates of craving, we used proton magnetic resonance spectroscopy (1H-MRS) to investigate the correlation between craving and glutamate levels in the left dorsolateral prefrontal cortex (LDLPFC) of patients with AUD.

METHODS

Participants underwent 1H-MRS of the LDLPFC with 2-dimensional J-resolved (2DJ) averaged PRESS. MRS data were processed with LCModel and cerebrospinal fluid (CSF)-corrected to generate metabolite concentrations. The Penn Alcohol Craving Scale (PACS) and the 30-day time line follow-back (TLFB 30) were used to quantify craving for alcohol and drinking patterns, respectively.

RESULTS

There was a statistically significant positive correlation between CSF-corrected glutamate ([Glu]) levels and PACS scores (n = 14; p = 0.005). When PACS scores were dichotomized (< or ≥median = 16), [Glu] levels were significantly higher in the high- versus low-craving group (p = 0.007). In addition, there was a significant negative correlation between CSF-corrected N-acetyl aspartic acid ([NAA]) levels and mean number of drinks per drinking day in the past month (n = 13; TLFB 30; p = 0.012). When mean TLFB 30 was dichotomized (< or ≥median = 7.86), [NAA] levels were significantly lower in subjects that consumed more alcoholic beverages. There was no significant correlation between [Glu] and [NAA] levels with other measures of drinking behavior and or depression symptom severity.

CONCLUSIONS

While limited by small sample size, these data suggest that glutamate levels in LDLPFC are associated with alcohol craving intensity in patients with AUD. Further study with larger sample size is needed to replicate this finding and evaluate the merits of glutamate spectroscopy as a biological correlate of alcohol craving intensity and a guide to treatment interventions.

Locally Estimated Hemodynamic Response Function and Activation Detection Sensitivity in Heroin-Cue Reactivity Study

Introduction:

A fixed hemodynamic response function (HRF) is commonly used for functional magnetic resonance imaging (fMRI) analysis. However, HRF may vary from region to region and subject to subject. We investigated the effect of locally estimated HRF (in functionally homogenous parcels) on activation detection sensitivity in a heroin cue reactivity study.

Methods:

We proposed a novel exploratory method for brain parcellation based on a probabilistic model to segregate the brain into spatially connected and functionally homogeneous components. Then, we estimated HRF and detected activated regions in response to an experimental task in each parcel using a joint detection estimation (JDE) method. We compared the proposed JDE method with the general linear model (GLM) that uses a fixed HRF and is implemented in FEAT (as a part of FMRIB Software Library, version 4.1).

Results:

1) Regions detected by JDE are larger than those detected by fixed HRF, 2) In group analysis, JDE found areas of activation not detected by fixed HRF. It detected drug craving a priori “regions-of-interest” in the limbic lobe (anterior cingulate cortex [ACC], posterior cingulate cortex [PCC] and cingulate gyrus), basal ganglia, especially striatum (putamen and head of caudate), and cerebellum in addition to the areas detected by the fixed HRF method, 3) JDE obtained higher Z-values of local maxima compared to those obtained by fixed HRF.

Conclusion:

In our study of heroin cue reactivity, our proposed method (that estimates HRF locally) outperformed the conventional GLM that uses a fixed HRF.

Neuroimaging in alcohol-use disorders: clinical implications and future directions

Advances in clinical research have led to significant alterations in diagnostic criteria for alcohol-use disorders (AUD). Neuroimaging techniques are now being called upon to shed light on the validity and clinical utility of diagnostic criteria. For example, craving has recently been added to the diagnostic criteria of AUD based mainly on neurobiological research. In addition to understanding the nuances of the craving process, neuroimaging techniques are helping determine the biological factors that contribute to the onset and maintenance of the disorder and offer insight into the mechanisms underlying treatment. The purpose of this review is to provide a clinically relevant summary of the neuroimaging research that has impacted our understanding of the etiology, treatment and recovery in AUD.

Antidepressant effectiveness of deep Transcranial Magnetic Stimulation (dTMS) in patients with Major Depressive Disorder (MDD) with or without Alcohol Use Disorders (AUDs): a 6-month, open label, follow-up study

INTRODUCTION

Co-occurrence of Major Depressive (MDD) and Alcohol Use Disorders (AUDs) is frequent, causing more burden than each disorder separately. Since the dorsolateral prefrontal cortex (DLPFC) is critically involved in both mood and reward and dysfunctional in both conditions, we aimed to evaluate the effects of dTMS stimulation of bilateral DLPFC with left prevalence in patients with MDD with or without concomitant AUD.

METHODS

Twelve MDD patients and 11 with concomitant MDD and AUD (MDD+AUD) received 20 dTMS sessions. Clinical status was assessed through the Hamilton Depression Rating Scale (HDRS) and the Clinical Global Impressions severity scale (CGIs), craving through the Obsessive Compulsive Drinking Scale (OCDS) in MDD+AUD, and functioning with the Global Assessment of Functioning (GAF).

RESULTS

There were no significant differences between the two groups in sociodemographic (age, sex, years of education and duration of illness) and baseline clinical characteristics, including scores on assessment scales. Per cent drops on HDRS and CGIs scores at the end of the sessions were respectively 62.6% and 78.2% for MDD+AUD, and 55.2% and 67.1% for MDD (p<0.001). HDRS, CGIs and GAF scores remained significantly improved after the 6-month follow-up. HDRS scores dropped significantly earlier in MDD+AUD than in MDD LIMITATIONS: The small sample size and factors inherent to site and background treatment may have affected results.

CONCLUSIONS

High frequency bilateral DLPFC dTMS with left preference was well tolerated and effective in patients with MDD, with or without AUD. The antidepressant effect of dTMS is not affected by alcohol abuse in patients with depressive episodes. The potential use of dTMS for mood modulation as an adjunct to treatment in patients with a depressive episode, with or without alcohol abuse, deserves further investigation.

Add-on deep transcranial magnetic stimulation (dTMS) in patients with dysthymic disorder comorbid with alcohol use disorder: a comparison with standard treatment

OBJECTIVES

Dorsolateral prefrontal cortex (DLPFC) is dysfunctional in mood and substance use disorders. We predicted higher efficacy for add-on bilateral prefrontal high-frequency deep transcranial magnetic stimulation (dTMS), compared with standard drug treatment (SDT) in patients with dysthymic disorder (DD)/alcohol use disorder (AUD) comorbidity.

METHODS

We carried-out a 6-month open-label study involving 20 abstinent patients with DSM-IV-TR AUD comorbid with previously developed DD. Ten patients received SDT for AUD with add-on bilateral dTMS (dTMS-AO) over the DLPFC, while another 10 received SDT alone. We rated alcohol craving with the Obsessive Compulsive Drinking Scale (OCDS), depression with the Hamilton Depression Rating Scale (HDRS), clinical status with the Clinical Global Impressions scale (CGI), and global functioning with the Global Assessment of Functioning (GAF).

RESULTS

At the end of the 20-session dTMS period (or an equivalent period in the SDT group), craving scores and depressive symptoms in the dTMS-AO group dropped significantly more than in the SDT group (P < 0.001 and P < 0.02, respectively).

CONCLUSIONS

High frequency bilateral DLPFC dTMS with left preference was well tolerated and found to be effective as add-on in AUD. The potential of dTMS for reducing craving in substance use disorder patients deserves to be further investigated.

Alterations in brain connectivity in three sub-regions of the anterior cingulate cortex in heroin-dependent individuals: Evidence from resting state fMRI

Previous studies that utilized task-based approaches have demonstrated that the chronic use of heroin is associated with altered activity of the anterior cingulate cortex (ACC). However, few studies have focused on examining the variation in resting-state functional connectivity in heroin-dependent individuals, which might help further understanding the mechanisms underlying heroin addiction. Due to the structural and functional heterogeneity of the ACC, we systematically mapped the resting-state functional connectivity patterns of three sub-regions of the ACC in heroin-dependent individuals, wondered whether the partition of three sub-regions of the ACC is feasible in heroin-dependent individuals, and identified how heroin affected the correlated activities among three sub-regions of the ACC using resting-state functional magnetic resonance imaging (fMRI). In the present study, fMRI data were acquired from 21 heroin-dependent individuals (Her group) and 15 non-addicted controls (CN group). Compared to controls, there were reduced functional connectivities in the dorsal ACC (dACC) and rostral ACC (rACC) networks with different areas of the dorsal striatum (the caudate and the putamen) in the Her group. Meanwhile, there exhibited an inverted alteration of pattern for orbital frontal cortex (OFC) and superior frontal gyrus (SFG) in the functional connectivity network with the dACC and subcallosal ACC (sACC), and a different alteration of the cerebellum and the amygdala in the functional connectivity network with the rACC and the sACC. In addition, we also found reduced connectivities between dACC and rACC, as well as reduced connectivities between sACC and dACC. Our findings of variations of functional connectivities in three sub-regions of ACC in Her group implied that these sub-regions of the ACC together with other key brain areas (such as dorsal striatum, OFC, SFG, cerebellum, amygdale, etc.) might potentially play independent and/or overlapping roles in heroin addiction, which might indicate the potential direction of future research.

Functional role for mouse cerebellar NO/cGMP/KATP pathway in ethanol-induced ataxia

BACKGROUND

We have previously shown that brain adenosine A1 receptors and nitric oxide (NO) play an important role in ethanol (EtOH)-induced cerebellar ataxia (EICA) through glutamate/NO/cGMP pathway. I now report possible modulation of EICA by the cerebellar NO/cGMP/K(ATP) pathway.

METHODS

EICA was evaluated by Rotorod in CD-1 male mice. All drugs (K(ATP) activators pinacidil, 0.05, 0.1, 0.5 nmol; minoxidil, 0.01, 0.1, 1.0 pmol; antagonists glipizide/glibenclamide, 0.01, 0.05, 0.1 nmol; NO donor l-arginine, 20 nmol; NOS inhibitors [iNOS] inhibitor L-NAME, 50 nmol; glutamate, 1.5 nmol; adenosine A1 receptor agonist N(6) -cyclohexyladenosine [CHA], 6, 12 pmol; antagonist DPCPX, 0.1 or 0.4 nmol) were given by direct intracerebellar microinfusion via stereotaxically implanted guide cannulas, except EtOH (2 g/kg, i.p.).

RESULTS

Pinacidil and minoxidil dose-dependently accentuated, whereas glipizide and glibenclamide markedly attenuated EICA, indicating tonic participation of K(ATP) channels. Glipizide abolished the pinacidil potentiation of EICA, which confirmed both drugs acted via K(ATP) channels. A possible link between K(ATP) channels and glutamate/NO pathway was suggested when (i) CHA (12 pmol) totally abolished l-arginine-induced attenuation of EICA; (ii) L-NAME abolished l-arginine-induced attenuation of EICA associated with further increase in EICA; and (iii) the combined l-arginine and glutamate infusion virtually abolished EICA. Also, whereas CHA abolished glibenclamide-induced attenuation and potentiated pinacidil/minoxidil-induced accentuation of EICA, the effects of DPCPX were just the opposite to those of CHA.

CONCLUSIONS

The results with CHA therefore suggest a functional link between K(ATP) and A1 receptors and between K(ATP) and glutamate/NO and as an extension may involve participation of NO/cGMP/K(ATP) pathway in EICA.

Cerebellar networks with the cerebral cortex and basal ganglia

The dominant view of cerebellar function has been that it is exclusively concerned with motor control and coordination. Recent findings from neuroanatomical, behavioral, and imaging studies have profoundly changed this view. Neuroanatomical studies using virus transneuronal tracers have demonstrated that cerebellar output reaches vast areas of the neocortex, including regions of prefrontal and posterior parietal cortex. Furthermore, it has recently become clear that the cerebellum is reciprocally connected with the basal ganglia, which suggests that the two subcortical structures are part of a densely interconnected network. Taken together, these findings elucidate the neuroanatomical substrate for cerebellar involvement in non-motor functions mediated by the prefrontal and posterior parietal cortex, as well as in processes traditionally associated with the basal ganglia.

Chronic cigarette smoking in alcohol dependence: associations with cortical thickness and N-acetylaspartate levels in the extended brain reward system

Chronic smoking in alcohol dependence is associated with abnormalities in brain morphology and metabolite levels in large lobar regions (e.g. frontal lobe). Here, we evaluated if these abnormalities are specifically apparent in several cortical and select subcortical components of the extended brain reward system (BRS), a network that is critically involved in the development and maintenance of all forms of addictive disorders. We studied 33 non-smoking and 43 smoking alcohol-dependent individuals (ALC) with 1 week of abstinence and 42 non-smoking Controls. At 1.5 Tesla, we obtained regional measures of cortical thickness and N-acetylaspartate (NAA; a surrogate marker of neuronal integrity) concentration in major components of the BRS as well as the corresponding measures throughout the cortex. Smoking ALC and non-smoking ALC demonstrated decreased thickness compared with Controls in the dorsolateral prefrontal cortex (DLPFC), insula, orbitofrontal cortex (OFC), the total BRS, total frontal cortex and global cortex. Smoking ALC had significantly decreased thickness compared to non-smoking ALC in the ACC, insula, the total BRS and total frontal cortex. Smoking ALC had also lower NAA concentrations than both non-smoking ALC and Controls in the DLPFC, insula, superior corona radiata and the total BRS. Alcohol consumption and common medical and psychiatric co-morbidities did not mediate differences between smoking and non-smoking ALC. This dual modality magnetic resonance (MR) study indicated that chronic smoking in ALC was associated with significant cortical thinning and NAA abnormalities in anterior brain regions that are implicated in the development and maintenance of addictive disorders.

Functional neuroimaging studies of alcohol cue reactivity: a quantitative meta-analysis and systematic review

A comprehensive understanding of the neurobiology of alcohol cue reactivity is critical in identifying the neuropathology of alcohol use disorders (AUD) and developing treatments that may attenuate alcohol craving and reduce relapse risk. Functional neuroimaging studies have identified many brain areas in which alcohol cues elicit activation. However, extant studies have included relatively small numbers of cases, with AUD of varying severity, and have employed many different cue paradigms. We used activation likelihood estimation, a quantitative, coordinate-based meta-analytic method, to analyze the brain areas activated by alcohol-related cues across studies, and to examine whether these areas were differentially activated between cases and controls. Secondarily, we reviewed correlations between behavioral measures and cue-elicited activation, as well as treatment effects on such activation. Data analyzed were from 28 studies of 679 cases and 174 controls. Among cases, alcohol cues elicited robust activation of limbic and prefrontal regions, including ventral striatum, anterior cingulate and ventromedial prefrontal cortex. As compared to controls, cases demonstrated greater activation of parietal and temporal regions, including posterior cingulate, precuneus and superior temporal gyrus. Cue-elicited activation of ventral striatum was most frequently correlated with behavioral measures and most frequently reduced by treatment, but these results were often derived from region-of-interest analyses that interrogated only limbic regions. These findings support long-standing theories of mesolimbic involvement in alcohol cue processing, but suggest that cue-elicited activation of other brain areas may more clearly differentiate cases from controls. Prevention and treatment for AUD should consider interventions that may reduce cue-elicited activation of these areas.

Tonic modulatory role of mouse cerebellar α- and β-adrenergic receptors in the expression of ethanol-induced ataxia: role of AC-cAMP

To further study neurochemical basis of ethanol-induced ataxia (EIA), we investigated role of cerebellar α and β-adrenergic receptors. Male CD-1 mice received intracerebellar microinfusion of adrenergic drugs to evaluate their effect on EIA (2g/kg; ip) by Rotorod. Isoproterenol, phenylephrine (4, 8, 16 ng each), methoxamine (8 ng), and atenolol (2, 4, 8 ng), propranolol (4, 8, 16 ng), markedly attenuated and accentuated, respectively, EIA indicating the tonic nature of modulation. The attenuation of EIA by isoproterenol is β(1)-receptor mediated because it is blocked by atenolol. Tonic β(1) modulation is functionally correlated with EIA potentiation by atenolol and propranolol. The prazosin-induced attenuation of EIA, initially thought of α(1)-receptor mediated, appeared instead β(1)-receptor modulated because of: (i) blockade by atenolol; and (ii) phosphodiesterase inhibition by prazosin. The phenylephrine/methoxamine-induced attenuation of EIA seems paradoxical as the response is similar to antagonist prazosin. However, functionally the attenuation seems β(1) receptor-mediated since atenolol blocked it but prazosin did not. Also norepinephrine (NE) attenuated EIA that was inhibited by atenolol suggesting role of β(1) receptors. Similarly yohimbine and rauwolscine attenuated EIA that indicates α(2)-receptor modulation associated with stimulation of AC-cAMP pathway. The results of study support the hypothesis that attenuation and potentiation of EIA is mediated by activation and inhibition of AC-cAMP pathway, respectively, in agreement with our previous reports, via direct and/or indirect activation of β-receptor.

An fMRI investigation of cerebellar function during verbal working memory in methadone maintenance patients

Working memory is impaired in opioid-dependent individuals, yet the neural underpinnings of working memory in this population are largely unknown. Previous studies in healthy adults have demonstrated that working memory is supported by a network of brain regions that includes a cerebro-cerebellar circuit. The cerebellum, in particular, may be important for inner speech mechanisms that assist verbal working memory. This study used functional magnetic resonance imaging to examine brain activity associated with working memory in five opioid-dependent, methadone-maintained patients and five matched, healthy controls. An item recognition task was administered in two conditions: (1) a low working memory load "match" condition in which participants determined whether target letters presented at the beginning of the trial matched a probe item, and (2) a high working memory load "manipulation" condition in which participants counted two alphabetical letters forward of each of the targets and determined whether either of these new items matched a probe item. Response times and accuracy scores were not significantly different between the groups. FMRI analyses indicated that, in association with higher working memory load ("manipulation" condition), the patient group exhibited hyperactivity in the superior and inferior cerebellum and amygdala relative to that of controls. At a more liberal statistical threshold, patients exhibited hypoactivity in the left prefrontal and medial frontal/pre-SMA regions. These results indicate that verbal working memory in opioid-dependent individuals involves a disrupted cerebro-cerebellar circuit and shed light on the neuroanatomical basis of working memory impairments in this population.

Efficacy of add-on deep transcranial magnetic stimulation in comorbid alcohol dependence and dysthymic disorder: three case reports

BACKGROUND

Craving for alcohol is associated with abnormal activation in the dorsolateral prefrontal cortex. Deep transcranial magnetic stimulation (dTMS) has shown promise in the treatment of depression. There are few treatment options for treatment-resistant dysthymic disorder comorbid with alcohol use disorder.

OBJECTIVE

To investigate the possible anticraving efficacy of bilateral dorsolateral prefrontal cortex high-frequency dTMS in 3 patients with comorbid long-term DSM-IV-TR dysthymic disorder and alcohol use disorder.

METHOD

Three patients with alcohol use disorder with dysthymic disorder in their detoxification phase (abstaining for > 1 month) underwent twenty 20-minute sessions of 20 Hz dTMS over the dorsolateral prefrontal cortex over 28 days between 2011 and 2012. Alcohol craving was rated with the Obsessive Compulsive Drinking Scale and depressive symptoms with the Hamilton Depression Rating Scale.

RESULTS

All 3 patients responded unsatisfactorily to initial intravenous antidepressant and antianxiety combinations but responded after 10 dTMS sessions, improving on both anxiety-depressive symptoms and craving. This improvement enabled us to reduce antidepressant dosages after dTMS cycle completion.

DISCUSSION

High-frequency bilateral dorsolateral prefrontal cortex dTMS with left prevalence was found to produce significant anticraving effects in alcohol use disorder comorbid with dysthymic disorder. The potential of dTMS for reducing craving in patients with substance use disorder deserves to be further investigated.

Brain grey matter deficits in smokers: focus on the cerebellum

Structural cerebral deficiencies in smokers have been well characterized by morphometric investigations focussing on cortical and subcortical structures. Although the role of the cerebellum is increasingly noted in mental and addiction disorders, no reports exist regarding cerebellar alterations in smokers employing a methodology specifically designed to assess the cerebellar morphology. We acquired high-resolution MRI scans from 33 heavy smokers and 22 never-smokers and used a voxel-based morphometry (VBM) approach utilizing the Spatially Unbiased Infratentorial (SUIT) toolbox (Diedrichsen 2006) to provide an optimized and fine-grained exploration of cerebellar structural alterations associated with smoking. Relative to never-smokers, smokers showed significant reductions of grey matter volume in the right cerebellum Crus I. The grey matter volume in Crus I correlated negatively with the amount of nicotine dependence as assessed by means of the Fagerström scale. Since Crus I has been identified as the cognitive division of the cerebellum, the structural deficit may in part mediate cognitive deficits previously reported in smokers. Of note, the dependence-related magnitude of the volume deficit may support the notion that the cerebellum is substantially involved in core mechanisms of drug dependence.

Striatal involvement in human alcoholism and alcohol consumption, and withdrawal in animal models

BACKGROUND

Different regions of the striatum may have distinct roles in acute intoxication, alcohol seeking, dependence, and withdrawal.

METHODS

The recent advances are reviewed and discussed in our understanding of the role of the dorsolateral striatum (DLS), dorsomedial striatum (DMS), and ventral striatum in behavioral responses to alcohol, including alcohol craving in abstinent alcoholics, and alcohol consumption and withdrawal in rat, mouse, and nonhuman primate models.

RESULTS

Reduced neuronal activity as well as dysfunctional connectivity between the ventral striatum and the dorsolateral prefrontal cortex is associated with alcohol craving and impairment of new learning processes in abstinent alcoholics. Within the DLS of mice and nonhuman primates withdrawn from alcohol after chronic exposure, glutamatergic transmission in striatal projection neurons is increased, while GABAergic transmission is decreased. Glutamatergic transmission in DMS projection neurons is also increased in ethanol withdrawn rats. Ex vivo or in vivo ethanol exposure and withdrawal causes a long-lasting increase in NR2B subunit-containing NMDA receptor activity in the DMS, contributing to ethanol drinking. Analyses of neuronal activation associated with alcohol withdrawal and site-directed lesions in mice implicate the rostroventral caudate putamen, a ventrolateral segment of the DMS, in genetically determined differences in risk for alcohol withdrawal involved in physical association of the multi-PDZ domain protein, MPDZ, with 5-HT(2C) receptors and/or NR2B.

CONCLUSIONS

Alterations of dopaminergic, glutamatergic, and GABAergic signaling within different regions of the striatum by alcohol is critical for alcohol craving, consumption, dependence, and withdrawal in humans and animal models.

Alternative splicing of AMPA subunits in prefrontal cortical fields of cynomolgus monkeys following chronic ethanol self-administration

Functional impairment of the orbital and medial prefrontal cortex underlies deficits in executive control that characterize addictive disorders, including alcohol addiction. Previous studies indicate that alcohol alters glutamate neurotransmission and one substrate of these effects may be through the reconfiguration of the subunits constituting ionotropic glutamate receptor (iGluR) complexes. Glutamatergic transmission is integral to cortico-cortical and cortico-subcortical communication and alcohol-induced changes in the abundance of the receptor subunits and/or their splice variants may result in critical functional impairments of prefrontal cortex in alcohol dependence. To this end, the effects of chronic ethanol self-administration on glutamate receptor ionotropic AMPA (GRIA) subunit variant and kainate (GRIK) subunit mRNA expression were studied in the orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (DLPFC), and anterior cingulate cortex (ACC) of male cynomolgus monkeys. In DLPFC, total AMPA splice variant expression and total kainate receptor subunit expression were significantly decreased in alcohol drinking monkeys. Expression levels of GRIA3 flip and flop and GRIA4 flop mRNAs in this region were positively correlated with daily ethanol intake and blood ethanol concentrations (BEC) averaged over the 6 months prior to necropsy. In OFC, AMPA subunit splice variant expression was reduced in the alcohol treated group. GRIA2 flop mRNA levels in this region were positively correlated with daily ethanol intake and BEC averaged over the 6 months prior to necropsy. Results from these studies provide further evidence of transcriptional regulation of iGluR subunits in the primate brain following chronic alcohol self-administration. Additional studies examining the cellular localization of such effects in the framework of primate prefrontal cortical circuitry are warranted.

Sustained antagonism of acute ethanol-induced ataxia following microinfusion of cyclic AMP and cpt-cAMP in the mouse cerebellum

Ataxia is a conspicuous physical manifestation of alcohol consumption in humans and laboratory animals. Previously we reported possible involvement of cAMP in ethanol-induced ataxia. We now report a sustained antagonism of ataxia due to multiple ethanol injections following intracerebellar (ICB) cAMP or cpt-cAMP microinfusion. Adenylyl cyclase drugs cAMP, cpt-cAMP, Sp-cAMP, Rp-cAMP, adenosine A₁ agonist, N⁶-cyclohexyladenosine (CHA) and GABA(A) agonist muscimol were directly microinfused into the cerebellum of CD-1 male mice to evaluate their effect on ethanol (2 g/kg; i.p.) ataxia. Drug microinfusions were made via stereotaxically implanted stainless steel guide cannulas. Rotorod was used to evaluate the ethanol's ataxic response. Intracerebellar cAMP (0.1, 1, 10 fmol) or cpt-cAMP (0.5, 1, 2 fmol) 60 min before ethanol treatment, dose-dependently attenuated ethanol-induced ataxia in general agreement with previous observations. Intracerebellar microinfusion of cAMP (100 fmol) or cpt-cAMP (2 fmol) produced a sustained attenuation of ataxia following ethanol administration at 1, 4, 7 and 25 h or 31 h post-cAMP/cpt-cAMP microinfusion. At 31 h post-cAMP, the ataxic response of ethanol reappeared. Additionally, marked antagonism to the accentuation of ethanol-induced ataxia by adenosine A₁ and GABA(A) agonists, CHA (34 pmol) and muscimol (88 pmol), respectively, was noted 24h after cAMP and cpt-cAMP treatment. This indicated possible participation of AC/cAMP/PKA signaling in the co-modulation of ethanol-induced ataxia by A₁ adenosinergic and GABAergic systems. No change in normal motor coordination was noted when cAMP or cpt-cAMP microinfusion was followed by saline. Finally, Rp-cAMP (PKA inhibitor, 22 pmol) accentuated ethanol-induced ataxia and antagonized its attenuation by cAMP whereas Sp-cAMP (PKA activator, 22 pmol) produced just the opposite effects, further indicating participation of cAMP-dependent PKA downstream. Overall, the results support a role of AC/cAMP/PKA signaling in the expression of ethanol-induced ataxia and its co-modulation by adenosine A₁ and GABA(A) receptors.

Appetite at high altitude: an fMRI study on the impact of prolonged high-altitude residence on gustatory neural processing

Regulation of food intake is very important for health. It has been reported that people have decreased appetite at high altitude (HA). The current study recruited long-term HA residents to participate in an fMRI experiment which involved food craving. Result shows that the HA group showed decreased activation in the neural circuit for food craving, accompanied by decreased activation in regions for cognitive control and increased activation in regions for emotional processing. Such results also reflect the decreased gray matter volume and the hypometabolism mechanism under prolonged hypoxia stress at HA.

Neuromodulation of decision-making in the addictive brain

Noninvasive brain stimulation of the dorsolateral prefrontal cortex with repetitive transcranial magnetic stimulation and transcranial direct current stimulation can modify decision-making behaviors in healthy subjects. The same type of noninvasive brain stimulation can suppress drug craving in substance user patients, who often display impaired decision-making behaviors. We discuss the implications of these studies for the cognitive neurosciences and their translational applications to the treatment of addictions. We propose a neurocognitive model that can account for our findings and suggests a promising therapeutic role of brain stimulation in the treatment of substance abuse and addictive behavior disorders.

Rostroventral caudate putamen involvement in ethanol withdrawal is influenced by a chromosome 4 locus

Physiological dependence and associated withdrawal episodes are thought to constitute a motivational force that sustains alcohol use and abuse and may contribute to relapse in dependent individuals. Although no animal model duplicates alcoholism, models for specific factors, like withdrawal, are useful for identifying potential genetic and neural determinants of liability in humans. Previously, we identified a quantitative trait locus (QTL) and gene (Mpdz, which encodes the multi-PDZ domain protein) on chromosome 4 with a large effect on alcohol withdrawal in mice. Using congenic mice that confirm this QTL and c-Fos expression as a high-resolution marker of neuronal activation, we report that congenic mice show significantly less neuronal activity associated with alcohol withdrawal in the rostroventral caudate putamen (rvCP), but not other parts of the striatum, compared with background strain mice. Moreover, bilateral rvCP lesions significantly increase alcohol withdrawal severity. Using retrograde (fluorogold) and anterograde (Texas Red conjugated dextran amine) tract tracing, we found that ∼25% of c-Fos immunoreactive rvCP neurons project to caudolateral substantia nigra pars reticulata (clSNr), which we previously found is crucially involved in withdrawal following acute and repeated alcohol exposure. Our results expand upon work suggesting that this QTL impacts alcohol withdrawal via basal ganglia circuitry associated with limbic function, and indicate that an rvCP-clSNr projection plays a critical role. Given the growing body of evidence that the syntenic region of human chromosome 9p and human MPDZ gene are associated with alcohol abuse, our results may facilitate research on alcohol dependence and associated withdrawal in clinical populations.

Harsh corporal punishment is associated with increased T2 relaxation time in dopamine-rich regions

Harsh corporal punishment (HCP) was defined as frequent parental administration of corporal punishment (CP) for discipline, with occasional use of objects such as straps, or paddles. CP is linked to increased risk for depression and substance abuse. We examine whether long-term exposure to HCP acts as sub-traumatic stressor that contributes to brain alterations, particularly in dopaminergic pathways, which may mediate their increased vulnerability to drug and alcohol abuse. Nineteen young adults who experienced early HCP but no other forms of maltreatment and twenty-three comparable controls were studied. T2 relaxation time (T2-RT) measurements were performed with an echo planar imaging TE stepping technique and T2 maps were calculated and analyzed voxel-by-voxel to locate regional T2-RT differences between groups. Previous studies indicated that T2-RT provides an indirect index of resting cerebral blood volume. Region of interest (ROI) analyses were also conducted in caudate, putamen, nucleus accumbens, anterior cingulate cortex, dorsolateral prefrontal cortex, thalamus, globus pallidus and cerebellar hemispheres. Voxel-based relaxometry showed that HCP was associated with increased T2-RT in right caudate and putamen. ROI analyses also revealed increased T2-RT in dorsolateral prefrontal cortex, substantia nigra, thalamus and accumbens but not globus pallidus or cerebellum. There were significant associations between T2-RT measures in dopamine target regions and use of drugs and alcohol, and memory performance. Alteration in the paramagnetic or hemodynamic properties of dopaminergic cell body and projection regions were observed in subjects with HCP, and these findings may relate to their increased risk for drug and alcohol abuse.

Metabolite levels in the brain reward pathway discriminate those who remain abstinent from those who resume hazardous alcohol consumption after treatment for alcohol dependence

OBJECTIVE

This study compared baseline metabolite levels in components of the brain reward system among individuals who remained abstinent and those who resumed hazardous alcohol consumption after treatment for alcohol dependence.

METHOD

Fifty-one treatment-seeking alcohol-dependent individuals (abstinent for approximately 7 days [SD = 3]) and 26 light-drinking nonsmoking controls completed 1.5-T proton magnetic resonance spectroscopic imaging, yielding regional concentrations of N-acetylaspartate, choline-containing compounds, creatine-containing compounds, and myoinositol. Metabolite levels were obtained in the following component of the brain reward system: dorsolateral prefrontal cortex, anterior cingulate cortex, insula, superior corona radiata, and cerebellar vermis. Alcohol-dependent participants were followed over a 12-month period after baseline study (i.e., at 7 days of abstinence [SD = 3]) and were classified as abstainers (no alcohol consumption; n = 18) and resumers (any alcohol consumption; n = 33) at follow-up. Baseline metabolite levels in abstainers and resumers and light-drinking nonsmoking controls were compared in the above regions of interest.

RESULTS

Resumers demonstrated significantly lower baseline N-acetylaspartate concentrations than light-drinking nonsmoking controls and abstainers in all regions of interest. Resumers also exhibited lower creatine-containing-compound concentrations than abstainers in the dorsolateral prefrontal cortex, superior corona radiata, and cerebellar vermis. Abstainers did not differ from light-drinking nonsmoking controls on baseline metabolite concentrations in any region of interest.

CONCLUSIONS

The significantly decreased N-acetylaspartate and creatine-containing-compound concentrations in resumers suggest compromised neuronal integrity and abnormalities in cellular bioenergetics in major neocortical components and white-matter interconnectivity of the brain reward pathway. The lack of metabolite differences between abstainers and light-drinking nonsmoking controls suggests premorbid factors potentially contributed to the baseline brain metabolite abnormalities observed in resumers.

Behavioral and biological indicators of impulsivity in the development of alcohol use, problems, and disorders

Alcohol use disorders (AUDs) are a devastating public health problem. The construct of impulsivity is biologically based and heritable, and its various dimensions are relevant for understanding alcohol use. The goal of the current manuscript is to review recent behavioral and biological research examining various dimensions of impulsivity and their relation to AUDs from risk for initial use through dependence and relapse. Moreover, we also highlight key psychological variables including affective processes as they relate to current use and early indications of alcohol problems, as well as psychopathology, violence, and aggression in relation to AUDs. Each section includes a critical summary and we conclude the review with future directions focused on issues relevant to measurement, causality, and intervention. Throughout the review, we attempt to be as specific as possible about the dimensions of impulsivity being referenced, while attempting to draw parallels and highlighting differences as the existing literature allows.

Ethanol self-administration modulation of NMDA receptor subunit and related synaptic protein mRNA expression in prefrontal cortical fields in cynomolgus monkeys

BACKGROUND

Functional impairment of the orbital and medial prefrontal cortex underlies deficits in executive control that characterize addictive disorders, including alcohol addiction. Previous studies indicate that alcohol alters glutamate neurotransmission and one substrate of these effects may be through the reconfiguration of the subunits constituting ionotropic glutamate receptor (iGluR) complexes. Glutamatergic transmission is integral to cortico-cortical and cortico-subcortical communication, and alcohol-induced changes in the abundance of the receptor subunits and/or their splice variants may result in critical functional impairments of prefrontal cortex in the alcohol-addicted state.

METHODS AND RESULTS

The effects of chronic ethanol self-administration on glutamate receptor ionotropic NMDA (GRIN), as well as GRIN1 splice variant mRNA expression was studied in the orbitofrontal cortex (OFC; Area 13), dorsolateral prefrontal cortex (DLPFC; Area 46) and anterior cingulate cortex (ACC; Area 24) of male cynomolgus monkeys. Chronic ethanol self-administration resulted in significant changes in the expression of NMDA subunit mRNA expression in the DLPFC and OFC, but not the ACC. In DLPFC, the overall expression of NMDA subunits was significantly decreased in ethanol treated monkeys. Slight but significant changes were observed for synaptic associated protein 102 kD (SAP102) and neuronal nitric oxide synthase (nNOS) mRNAs. In OFC, the NMDAR1 variant GRIN1-1 was reduced while GRIN1-2 was increased. Furthermore, no significant changes in GFAP protein levels were observed in either the DLPFC or OFC.

CONCLUSION

Results from these studies provide the first demonstration of posttranscriptional regulation of iGluR subunits in the primate brain following long-term ethanol self-administration. Furthermore, changes in these transcripts do not appear to reflect changes in glial activation or loss. Further studies examining the expression and cellular localization of subunit proteins and receptor pharmacology would shed more light on the findings reported here.

The cerebellum is involved in reward-based reversal learning

The cerebellum has recently been discussed in terms of a possible involvement in reward-based associative learning. To clarify the cerebellar contribution, eight patients with focal vascular lesions of the cerebellum and a group of 24 healthy subjects matched for age and IQ were compared on a range of different probabilistic outcome-based associative learning tasks, assessing acquisition, reversal, cognitive transfer, and generalization as well as the effect of reward magnitude. Cerebellar patients showed intact acquisition of stimulus contingencies, while reward-based reversal learning was significantly impaired. In addition, the patients showed slower acquisition of new stimulus contingencies in a second reward-based learning task, which might reflect reduced carry-over effects. Reward magnitude affected learning only during initial acquisition, with better learning on trials with high rewards in patients and control subjects. Overall, the findings suggest that the cerebellum is implicated in reversal learning as a dissociable component of reward-based learning.

Altered impulse control in alcohol dependence: neural measures of stop signal performance

BACKGROUND

Altered impulse control has been implicated in the shaping of habitual alcohol use and eventual alcohol dependence. We sought to identify the neural correlates of altered impulse control in 24 abstinent patients with alcohol dependence (PAD), as compared to 24 demographics matched healthy control subjects (HC). In particular, we examined the processes of risk taking and cognitive control as the neural endophenotypes of alcohol dependence.

METHODS

To this end, functional magnetic resonance imaging (fMRI) was conducted during a stop signal task (SST), in which a procedure was used to elicit errors in the participants. The paradigm allowed trial-by-trial evaluation of response inhibition, error processing, and post-error behavioral adjustment. Furthermore, by imposing on the subjects to be both fast and accurate, the SST also introduced a distinct element of risk, which participants may or may not avert during the task. Brain imaging data were analyzed with Statistical Parametric Mapping in covariance analyses accounting for group disparity in general performance.

RESULTS

The results showed that, compared to HC, PAD demonstrated longer go trial reaction time (RT) and higher stop success rate (SS%). HC and PAD were indistinguishable in stop signal reaction time (SSRT) and post-error slowing (PES). In a covariance analysis accounting for go trial RT and SS%, HC showed greater activity in the left dorsolateral prefrontal cortex than PAD, when subjects with short and long SSRT were contrasted. By comparing PAD and HC directly during stop errors (SE), as contrasted with SS, we observed greater activity in PAD in bilateral visual and frontal cortices. Compared to HC, PAD showed less activation of the right dorsolateral prefrontal cortex during PES, an index of post-error behavioral adjustment. Furthermore, PAD who showed higher alcohol urge at the time of the fMRI were particularly impaired in dorsolateral prefrontal activation, as compared to those with lower alcohol urge. Finally, compared to HC subjects, PAD showed less activity in cortical and subcortical structures including putamen, insula, and amygdala during risk-taking decisions in the SST.

CONCLUSION

These preliminary results provided evidence for altered neural processing during impulse control in PAD. These findings may provide a useful neural signature in the evaluation of treatment outcomes and development of novel pharmacotherapy for alcohol dependence.

Prefrontal cortex modulation using transcranial DC stimulation reduces alcohol craving: a double-blind, sham-controlled study

BACKGROUND

Functional neuroimaging studies have shown that specific brain areas are associated with alcohol craving including the dorsolateral prefrontal cortex (DLPFC). We tested whether modulation of DLPFC using transcranial direct current stimulation (tDCS) could alter alcohol craving in patients with alcohol dependence while being exposed to alcohol cues.

METHODS

We performed a randomized sham-controlled study in which 13 subjects received sham and active bilateral tDCS delivered to DLPFC (anodal left/cathodal right and anodal right/cathodal left). For sham stimulation, the electrodes were placed at the same positions as in active stimulation; however, the stimulator was turned off after 30s of stimulation. Subjects were presented videos depicting alcohol consumption to increase alcohol craving.

RESULTS

Our results showed that both anodal left/cathodal right and anodal right/cathodal left significantly decreased alcohol craving compared to sham stimulation (p<0.0001). In addition, we found that following treatment, craving could not be further increased by alcohol cues.

CONCLUSIONS

Our findings showed that tDCS treatment to DLPFC can reduce alcohol craving. These findings extend the results of previous studies using noninvasive brain stimulation to reduce craving in humans. Given the relatively rapid suppressive effect of tDCS and the highly fluctuating nature of alcohol craving, this technique may prove to be a valuable treatment strategy within the clinical setting.