Neurobiological mechanisms of control in alcohol use disorder - moving towards mechanism-based non-invasive brain stimulation treatments

The ReCoDe addiction research consortium: Losing and regaining control over drug intake-Findings and future perspectives

Substance use disorders (SUDs) are seen as a continuum ranging from goal-directed and hedonic drug use to loss of control over drug intake with aversive consequences for mental and physical health and social functioning. The main goals of our interdisciplinary German collaborative research centre on Losing and Regaining Control over Drug Intake (ReCoDe) are (i) to study triggers (drug cues, stressors, drug priming) and modifying factors (age, gender, physical activity, cognitive functions, childhood adversity, social factors, such as loneliness and social contact/interaction) that longitudinally modulate the trajectories of losing and regaining control over drug consumption under real-life conditions. (ii) To study underlying behavioural, cognitive and neurobiological mechanisms of disease trajectories and drug-related behaviours and (iii) to provide non-invasive mechanism-based interventions. These goals are achieved by: (A) using innovative mHealth (mobile health) tools to longitudinally monitor the effects of triggers and modifying factors on drug consumption patterns in real life in a cohort of 900 patients with alcohol use disorder. This approach will be complemented by animal models of addiction with 24/7 automated behavioural monitoring across an entire disease trajectory; i.e. from a naïve state to a drug-taking state to an addiction or resilience-like state. (B) The identification and, if applicable, computational modelling of key molecular, neurobiological and psychological mechanisms (e.g., reduced cognitive flexibility) mediating the effects of such triggers and modifying factors on disease trajectories. (C) Developing and testing non-invasive interventions (e.g., Just-In-Time-Adaptive-Interventions (JITAIs), various non-invasive brain stimulations (NIBS), individualized physical activity) that specifically target the underlying mechanisms for regaining control over drug intake. Here, we will report on the most important results of the first funding period and outline our future research strategy.

Making decisions one drink at a time and the "just one drink" effect: A fuzzy-trace theory model of harmful drinking

BACKGROUND

Understanding the decision factors that drive harmful alcohol use among young adults is of practical and theoretical importance. We apply fuzzy-trace theory (FTT) to investigate a potential danger that may arise from the arguably correct notion that a single drink carries no meaningful risk. Decisions that are mentally represented as one drink at a time could contribute to excessive drinking.

METHODS

College students (N = 351) made a series of decisions to take or decline eight hypothetical drinks presented one at a time. Outcome measures included each decision, recent alcohol consumption (weekly drinks, peak blood alcohol content, and binges), and alcohol-related harms (scores on the Brief Young Adult Alcohol Consequences Questionnaire and Alcohol Use Disorders Identification Test). Linear regression models predicted each outcome from sex, perceived risk of a single drink, perceived risk of heavy drinking, perceived consequences of drinking, and general health-related risk sensitivity.

RESULTS

Consistent with FTT, decisions to have a first drink and up to four additional drinks in short succession were each associated with lower perceived risk of one drink-a "just-one drink" effect-independent of perceived risks of heavy drinking, perceived consequences of drinking, and general risk sensitivity. Similarly, all measures of recent alcohol consumption and consequent harms were associated with perceived risk of one drink. Participants reporting "zero risk" of a single drink had worse outcomes on all measures than those reporting at least "low risk."

CONCLUSIONS

Results are consistent with the theoretically informed premise that consumption decisions are typically made one drink at a time rather than by deciding the total number of drinks to be consumed in a sitting. When decisions about alcohol use proceed one drink at a time, a perception of zero risk in a single drink may contribute to heavy drinking.

Regaining control over opioid use? The potential application of auricular transcutaneous vagus nerve stimulation to improve opioid treatment in China

Opioid use disorder (OUD) is a critical problem in China and is accompanied by depression and deficits in cognitive control. In China, the most successful intervention for OUD is the community drug rehabilitation where methadone maintenance treatment (MMT) plays a key role. Even though methadone for the treatment of OUD can be helpful, it can cause severe somatic side-effects, which limit its effectivity. Even worse, it can have detrimental effects on cognitive control, which is crucial to regain control over drug intake. Here, we consider the potential use of auricular transcutaneous vagus nerve stimulation (atVNS) as an addition to MMT for opioid withdrawal treatment. Compared to other non-invasive brain stimulation methods, atVNS also targets the locus coeruleus (LC) important for noradrenaline (NA) synthesis. NA is an essential neurotransmitter impacted in opioid withdrawal and also critically involved in cognitive control processes. Its ADD-ON to MMT might be a useful mean to improve mood and enhance cognitive control processes impacted in OUD. We discuss the translational advantages of atVNS in China such as the cultural acceptance of the modality of treatment similar to electroacupuncture. Additionally, the wearability of the ear electrode and at-home self-administration without intense medical supervision makes of atVNS a useful tool to enhance clinical and cognitive outcomes especially in everyday life situation. We discuss how atVNS can be integrated in tele-medical health approaches allowing that innovative treatments can widely be disseminated and continued even in situations of restricted medical access.

Alcohol Cue Processing in Co-Occurring Bipolar Disorder and Alcohol Use Disorder

Importance

Reward circuitry dysfunction is a candidate mechanism of co-occurring bipolar disorder and alcohol use disorder (BD + AUD) that remains understudied. This functional magnetic resonance imaging (fMRI) research represents the first evaluation of alcohol cue reward processing in BD + AUD.

Objective

To determine how alcohol cue processing in individuals with BD + AUD may be distinct from that of individuals with AUD or BD alone.

Design, Setting, and Participants

This cross-sectional case-control study (April 2013-June 2018) followed a 2 × 2 factorial design and included individuals with BD + AUD, AUD alone, BD alone, and healthy controls. A well-validated visual alcohol cue reactivity fMRI paradigm was administered to eligible participants following their demonstration of 1 week or more of abstinence from alcohol and drugs assessed via serial biomarker testing. Study procedures were completed at the Medical University of South Carolina. Analysis took place between June and August 2022.

Main Outcomes and Measures

Past-week mood symptoms were rated by clinicians using the Montgomery-Åsberg Depression Rating Scale and Young Mania Rating Scale. The Alcohol Dependence Scale, Obsessive-Compulsive Drinking Scale, and Barratt Impulsiveness Scale were included questionnaires. Functional MRI whole-brain data were analyzed along with percent signal change within a priori regions of interest located in the ventral striatum, dorsal striatum, and ventromedial prefrontal cortex. Exploratory analyses of associations between cue reactivity and select behavioral correlates (alcohol craving, impulsivity, maximum number of alcohol drinks on a single occasion, and days since last alcohol drink) were also performed.

Results

Of 112 participants, 28 (25.0%) had BD + AUD, 26 (23.2%) had AUD alone, 31 (27.7%) had BD alone, and 27 (24.1%) were healthy controls. The mean (SD) age was 38.7 (11.6) years, 50 (45.5%) were female, 33 (30%) were smokers, and 37 (34.9%) reported recent alcohol consumption. Whole-brain analyses revealed a BD × AUD interaction (F = 10.64; P = .001; η2 = 0.09) within a cluster spanning portions of the right inferior frontal gyrus and insula. Region of interest analyses revealed a main association of BD (F = 8.02; P = .006; η2 = 0.07) within the dorsal striatum. In each instance, individuals with BD + AUD exhibited reduced activation compared with all other groups who did not significantly differ from one another. These hypoactivations were associated with increased impulsivity and obsessive-compulsive alcohol craving exclusively among individuals with BD + AUD.

Conclusion and Relevance

The findings of this study suggest conceptualizing reward dysfunction in BD + AUD by the potential interaction between blunted reward responsivity and deficient inhibitory control may help guide treatment development strategies. To this end, reduced right inferior frontal gyrus and insula alcohol cue reactivity represents a novel candidate biomarker of BD + AUD that may respond to pharmacological interventions targeting impulsivity-related neural mechanisms for improved executive control.

On the Role of Stimulus-Response Context in Inhibitory Control in Alcohol Use Disorder

The behavioral and neural dynamics of response inhibition deficits in alcohol use disorder (AUD) are still largely unclear, despite them possibly being key to the mechanistic understanding of the disorder. Our study investigated the effect of automatic vs. controlled processing during response inhibition in participants with mild-to-moderate AUD and matched healthy controls. For this, a Simon Nogo task was combined with EEG signal decomposition, multivariate pattern analysis (MVPA), and source localization methods. The final sample comprised n = 59 (32♂) AUD participants and n = 64 (28♂) control participants. Compared with the control group, AUD participants showed overall better response inhibition performance. Furthermore, the AUD group was less influenced by the modulatory effect of automatic vs. controlled processes during response inhibition (i.e., had a smaller Simon Nogo effect). The neurophysiological data revealed that the reduced Simon Nogo effect in the AUD group was associated with reduced activation differences between congruent and incongruent Nogo trials in the inferior and middle frontal gyrus. Notably, the drinking frequency (but not the number of AUD criteria we had used to distinguish groups) predicted the extent of the Simon Nogo effect. We suggest that the counterintuitive advantage of participants with mild-to-moderate AUD over those in the control group could be explained by the allostatic model of drinking effects.