Development of stimulus material for research in alcohol use disorders

Positive affect amplifies integration within episodic memories in the laboratory and the real world

Emotional events hold a privileged place in our memories, differing in accuracy and structure from memories for neutral experiences. Although much work has focused on the pronounced differences in memory for negative experiences, there is growing evidence that positive events may lead to more holistic, or integrated, memories. However, it is unclear whether these affect-driven changes in memory structure, which have been found in highly controlled laboratory environments, extend to real-world episodic memories. We ran experiments that assessed memory for experiences created in the laboratory (Experiment 1) and, using smartphones, memories for everyday experiences (Experiment 2). We complement these design innovations with a novel analysis approach to model memory accuracy and integration in both settings. Consistent with past findings, emotional events were subjectively remembered more strongly. These studies also revealed that features of more positive events were indeed more integrated within memory, both in the laboratory and the real world. These effects were specific to participants' emotional responses to the events during encoding rather than general emotional states at the time of retrieval, and reflected a general increase in integration between multiple memory features. Together, these results demonstrate robust differences in memory for positive events, introduce a novel measure of memory integration, and highlight the importance of assessing the impact of emotion on memory beyond the laboratory.

Hippocampal Mechanisms Support Cortisol-Induced Memory Enhancements

Stress can powerfully influence episodic memory, often enhancing memory encoding for emotionally salient information. These stress-induced memory enhancements stand at odds with demonstrations that stress and the stress-related hormone cortisol can negatively affect the hippocampus, a brain region important for episodic memory encoding. To resolve this apparent conflict and determine whether and how the hippocampus supports memory encoding under cortisol, we combined behavioral assays of associative memory, high-resolution fMRI, and pharmacological manipulation of cortisol in a within-participant, double-blinded procedure (in both sexes). Behaviorally, hydrocortisone promoted the encoding of subjectively arousing, positive associative memories. Neurally, hydrocortisone led to enhanced functional connectivity between hippocampal subregions, which predicted subsequent memory enhancements for emotional associations. Cortisol also modified the relationship between hippocampal representations and associative memory: whereas hippocampal signatures of distinctiveness predicted memory under placebo, relative integration predicted memory under cortisol. Together, these data provide novel evidence that the human hippocampus contains the necessary machinery to support emotional associative memory enhancements under cortisol.SIGNIFICANCE STATEMENT Our daily lives are filled with stressful events, which powerfully shape the way we form episodic memories. For example, stress and stress-related hormones can enhance our memory for emotional events. However, the mechanisms underlying these memory benefits are unclear. In the current study, we combined functional neuroimaging, behavioral tests of memory, and double-blind, placebo-controlled hydrocortisone administration to uncover the effects of the stress-related hormone cortisol on the function of the human hippocampus, a brain region important for episodic memory. We identified novel ways in which cortisol can enhance hippocampal function to promote emotional memories, highlighting the adaptive role of cortisol in shaping memory formation.

Alcohol-specific inhibition training in patients with alcohol use disorder: a multi-centre, double-blind randomized clinical trial examining drinking outcome and working mechanisms

AIMS

For the first time, to our knowledge, in a clinical sample with alcohol use disorder (AUD), this study compared the effects of two versions of alcohol-specific inhibition training (Alc-IT) on drinking outcomes and on experimental parameters assessing two possible working mechanisms: stimulus devaluation and inhibitory enhancement.

DESIGN

Multi-centre, double-blind, three-arm clinical RCT with 3-, 6- and 12-month follow-up comparing standard Alc-IT, improved Alc-IT and an active control condition.

SETTING

Three specialized AUD treatment centres in Switzerland.

PARTICIPANTS

A total of 242 detoxified, recently abstinent patients with severe AUD (18-60 years; 29.8% female).

INTERVENTION AND COMPARATOR

Both interventions [standard Alc-IT (n = 84) and improved Alc-IT (n = 79)] and the comparator [unspecific inhibition training (n = 79)] consisted of six sessions of a modified inhibitory task (Go/NoGo task) with alcohol-related and neutral stimuli. Both versions of Alc-IT required response inhibition in alcohol-related trials but differed in Go/NoGo ratios (standard: 50/50; improved: 75/25), with improved Alc-IT posing higher inhibitory demands. The control condition, an unspecific inhibition training, featured alcohol-related pictures in Go as well as NoGo trials.

MEASUREMENTS

The primary outcome, percentage of days abstinent, was assessed at 3-month follow-up with a time-line follow-back interview.

FINDINGS

The group receiving improved Alc-IT showed a significantly higher percentage of days abstinent at 3-month follow-up compared with the control group [γ_control  = 74.30; γ_improved  = 85.78; β = 11.48, 95% confidence interval (CI) = 2.57, 20.40, P = 0.012, adjusted r²  = 0.062], while for standard Alc-IT no effect significantly different from zero was detected (γ_standard  = 70.95; β = -3.35, 95% CI = -12.20, 5.50, P = 0.457, adjusted r²  = -0.04).

CONCLUSIONS

Alcohol-specific inhibition training with high inhibitory demands increased days abstinent at 3-month follow-up in patients with severe alcohol use disorder. Such an improved, inhibitory-demanding, alcohol-specific inhibition training outperformed the standard version of alcohol-specific inhibition training, suggesting an inhibitory working mechanism.

Hippocampal mechanisms support cortisol-induced memory enhancements

Stress can powerfully influence episodic memory, often enhancing memory encoding for emotionally salient information. These stress-induced memory enhancements stand at odds with demonstrations that stress and the stress-related hormone cortisol can negatively affect the hippocampus, a brain region important for episodic memory encoding. To resolve this apparent conflict and determine whether and how the hippocampus supports memory encoding under cortisol, we combined behavioral assays of associative memory, high-resolution functional magnetic resonance imaging (fMRI), and pharmacological manipulation of cortisol in a within-participant, double-blinded procedure. Hydrocortisone led to enhanced functional connectivity between hippocampal subregions, which predicted subsequent memory enhancements for emotional information. Cortisol also modified the relationship between hippocampal representations and memory: whereas hippocampal signatures of distinctiveness predicted memory under placebo, relative integration predicted memory under cortisol. Together, these data provide novel evidence that the human hippocampus contains the necessary machinery to support emotional memory enhancements under stress.

Using Imagination to Integrate Contextual Effects in a Cue-Reactivity Paradigm in Patients with Alcohol Use Disorder: A Functional Magnetic Resonance Imaging Pilot Study

INTRODUCTION

In individuals with alcohol use disorder (AUD), the brain areas underlying cue-induced reactions (e.g., cingulum, striatum, thalamus) and altered activation of these regions have been identified by functional neuroimaging. Neuronal responses to a complex alcohol-related context are yet to investigate. To better understand contextual effects as well as the interplay of cue-induced neural reactions and context exposure, the present study implemented an imagination procedure during functional magnetic resonance imaging (fMRI).

METHODS

Thirteen patients with AUD and 13 healthy controls completed two rounds of a cue-reactivity paradigm inside an MRI scanner. Two individualized imagination tasks were conducted before each of the two cue reactivity tasks. A 2 (group) × 2 (imagination) × 2 (picture-type) analysis of variance (ANOVA) was performed.

RESULTS

The ANOVA revealed a main effect for imagination with higher activation in bilateral thalamus and right caudate nucleus and an interaction effect between imagination and group in right thalamus and left caudate nucleus, due to the patient group reacting stronger during alcohol-related imagination. These structures are involved in relaying sensory information and habit learning. No main or interaction effects of picture type were observed.

CONCLUSIONS

These results support the view that context effects alter the neural responses in thalamus and nucleus caudatus in patients with AUD, and that imagination tasks are suited to incorporate contextual influences in neurophysiological research designs. Future research needs to investigate whether the failure to observe a picture-type effect was due to limited statistical power and omission to individualize picture set, or whether an imagination procedure interferes with the evocation of picture-type effects.

Pictures Library of Smoking Cravings: Development and Verification of Smokers and Non-smokers

Background: The cue-induced craving by addiction related materials is commonly employed in addiction research; however, no existing standardized picture database based on the expectation model of craving has been developed. We prepared and validated a Pictures Library of Smoking Cravings (PLSC) in this study. Methods: We captured pictures 366 smoking and 406 control pictures (matched in content). We selected 109 smoking pictures and 115 control pictures and asked participants to provide ratings of craving, familiarity, valence, and arousal induced in them. Participants were divided into three groups: non-smokers (n = 211), light smokers (n = 504), and heavy smokers (n = 101). Results: The results showed that smoking pictures evoked a greater craving, familiarity, and arousal than control pictures in smokers (ps < 0.01). In addition, craving caused by smoking pictures was positively associated with the Fagerström test for nicotine dependence score in dependent smokers. Conclusions: Overall, the contemporary results showed that PLSC is effective and can be used in smoking-related studies.

Deficient processing of alcohol cues in the addicted brain: Evidence from event-related potential microstates

OBJECTIVE

Patients with alcohol use disorder (AUD) show altered brain responses to alcohol cues as compared to healthy controls. Event-related potential (ERP) studies mostly focus on the P3, which is usually diminished in AUD patients. The few studies that have investigated earlier components have yielded inconsistent results. The present study aimed at identifying the onset of impaired alcohol cue processing in AUD patients, as well as the association between neurophysiological processing and subjective craving.

METHODS

A sample of 15 inpatients with AUD and 15 healthy controls completed a cue reactivity task with alcohol-related, neutral, and scrambled pictures. Multichannel-EEG was recorded from 70 scalp electrodes, and ERP microstates were analyzed.

RESULTS

Patients displayed impaired neurophysiological processing, as indexed by a weaker P3 and a weaker, insensitive P1. The blunted P1 was associated with higher subjective craving.

CONCLUSIONS

Impaired alcohol cue processing in AUD emerges early, at the stage of sensory processing. Such deficient initial processing seems crucial to understanding cue reactivity processes in the brain and in the subjective experience of craving.

SIGNIFICANCE

The results highlight the importance of investigating early ERP components preceding the P3, and contribute to the debate on the onset of information-processing dysfunction in the addicted brain.

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.

Wake Forest Alcohol Imagery Set: Development and Validation of a Large Standardized Alcohol Imagery Dataset

BACKGROUND

The study of alcohol use frequency utilizes alcohol-related cue imagery. Although a number of alcohol-image databases currently exist, they have several limitations: Many are not publicly available, some use stock images or clip art rather than real photographs, several eliminate any photographs displaying brand information, and predominantly they contain relatively few images. The aim of this project was to develop a large, open-access database of alcohol-related cue images, containing photographs with and without brand information, taken in real-world environments, with images in a variety of orientations and dimensions.

METHODS

The study collected 1,650 images voluntarily from the larger community, to capture photographs with a wide range of content, environments, and relation to alcohol. All images were then rated on scales of valence, arousal, and relation to alcohol by 1,008 Amazon Mechanical Turk workers, using classical emotion validation methods based on the International Affective Picture System (IAPS). Survey respondents were screened with the Alcohol Use Disorders Identification Test (AUDIT), and Cronbach's alpha scores were calculated to determine the interrater reliability of scores across the whole sample, and within low-risk, moderate-risk, and high-risk drinkers for each rating domain. Univariate ANOVAs were run to determine differences in ratings across drinking groups.

RESULTS

All Cronbach's alpha scores indicated high interrater reliability within the whole sample, and across drinking severity groups. Tukey's HSD post hoc results indicated greater arousal and affect in response to image viewing in moderate- and high-risk drinkers, and higher relation-to-alcohol ratings in low-risk drinkers. All images had categorization tags assigned by members of the study team.

CONCLUSIONS

The established imagery set includes 1,650 alcohol-related images, rated on scales of valence, arousal, and relation to alcohol, and categorized by type of alcohol depicted. The imagery database will be available for open-access download and use through Google Photos.

Interactive Effects of Naturalistic Drinking Context and Alcohol Sensitivity on Neural Alcohol Cue-Reactivity Responses

BACKGROUND

Considerable evidence indicates that a low level of subjective response to alcohol's acute effects (i.e., low sensitivity) is associated with enhanced risk for alcohol use disorder (AUD). Recent work suggests that the highest risk response profile consists of blunted sensitivity to alcohol's sedation-like effects, coupled with enhanced sensitivity to alcohol's stimulation-like effects (i.e., differential sensitivity). A largely separate body of work indicates that enhanced reactivity to alcohol-related cues is associated with increased AUD risk.

AIMS

The current research examined the extent to which variability in alcohol response phenotypes is associated with enhanced P3 event-related potential (ERP) responses to alcohol-related pictures (ACR-P3), and whether this reactivity varies according to depicted drinking contexts.

METHODS

Eighty young adults (aged 18 to 33 years) completed a self-report measure of alcohol sensitivity (the Alcohol Sensitivity Questionnaire) and viewed images depicting drinking in naturalistic contexts, alcohol and nonalcohol beverages in isolation (devoid of naturalistic drinking context), and neutral nonbeverage control images while ERPs were recorded.

RESULTS

Results indicated that blunted sensitivity to alcohol's sedative-like effects was differentially associated with enhanced ACR-P3 but reduced P3 reactivity to nonalcohol cues. Variation in sensitivity to alcohol's stimulant-like effects was not associated with differential ACR-P3. Contrary to predictions, these effects were not potentiated by drinking contexts.

CONCLUSIONS

The current results replicate and extend previous work linking low alcohol sensitivity with enhanced incentive salience for alcohol-related cues and suggest that cues depicting drinking contexts are less likely to differentiate high-risk from low-risk drinkers.

Learning to resist the urge: a double-blind, randomized controlled trial investigating alcohol-specific inhibition training in abstinent patients with alcohol use disorder

Background

Alcohol use disorder (AUD) leads to a significant individual and societal burden. To achieve higher therapy success rates, therapeutic interventions still need to be improved. Most current neuroscientific conceptualizations of AUD focus on the imbalance between an enhanced automatic reaction to alcohol cues and impaired inhibition. Complementary to traditional relapse prevention strategies, novel computerized training interventions aim to directly alter these processes. This study tests a computerized alcohol-specific inhibition training in a large clinical sample and investigates its effects on behavioral, experimental and neurophysiological outcomes. It also analyzes whether variations in inhibition difficulty and/or endogenous cortisol levels during training impact these effects.

Methods

This is a double-blind, randomized controlled trial (RCT) with 246 inpatients with AUD participating. After baseline assessment, participants are randomly assigned to one of three computerized Go-NoGo-based inhibition training interventions (two alcohol-specific versions with different Go/NoGo ratios, or neutral control training) and one of two intervention times (morning/afternoon), resulting in six study arms. All patients perform six training sessions within 2 weeks. Endogenous cortisol is measured in 80 patients before and after the first training session. Inhibitory control and implicit associations towards alcohol are assessed pre and post training, at which point electroencephalography (EEG) is additionally measured in 60 patients. Patients’ alcohol consumption and relevant psychological constructs (e.g., craving, self-efficacy, treatment motivation) are measured at discharge and at 3-, 6- and 12-month follow-ups. Fifty healthy participants are assessed (20 with EEG) at one time point as a healthy control group.

Discussion

This study investigates the effects of a computerized, alcohol-specific inhibition training for the first time in patients with AUD. Results should give insight into the effectiveness of this potential add-on to standard AUD treatment, including proximal and distal measures and effects on behavioral, experimental and neurophysiological measures. Information about working mechanisms and potential optimizations of this training are gathered through variations regarding difficulty of inhibition training and training time. This study may thus contribute to a deepened understanding of AUD and the improvement of its evidence-based treatment.

Trial registration

ClinicalTrials.gov, ID: NCT02968537. Registered on 18 November 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3505-2) contains supplementary material, which is available to authorized users.

The Galician Beverage Picture Set (GBPS): A standardized database of alcohol and non-alcohol images

BACKGROUND

The available picture sets in alcohol research are scarce and display a number of limitations, including poor picture quality, limited number of stimuli and absence of non-alcohol and/or real-life images. In the present study, we developed the Galician Beverage Picture Set (GBPS), a database of high-quality alcohol and non-alcohol pictures embedded in real-life scenarios.

METHODS

A total of 201 college students (∼59% females) were assessed by the Alcohol Use Disorders Identification Test, ∼54% being characterized as no/low drinkers (N/LDs) and ∼46% as risky drinkers (RDs). The GBPS included six types of beverages: beer, wine, liquor (alcoholic drinks); water, juice, milk (non-alcoholic drinks). Additionally, two subcategories were considered: orientation (landscape, portrait) and number of people (0, 1, ≥2 people). Participants rated the images for valence, arousal and visual complexity. Objective measures of brightness and color and recognition rates were also assessed. Internal consistency was estimated using Cronbach's alpha coefficient.

RESULTS

There was a high degree of internal consistency within each category (alcoholic and non-alcoholic drinks) for valence, arousal and visual complexity scores. A mixed-model ANOVA revealed that RDs rated alcohol pictures as more pleasant and arousing than N/LDs. Conversely, N/LDs displayed greater valence and arousal ratings than RDs for non-alcohol pictures.

CONCLUSIONS

The GBPS provides normative data on affective (valence/arousal), perceptual (visual complexity) and physical (brightness/color) values for a large number of images that may be useful for alcohol-related research. Differences in subjective assessments between N/LDs and RDs support the picture set's suitability for studies in young drinkers.

Development of stimulus material for research in alcohol use disorders

The availability of appropriate stimulus material is a key concern for an experimental approach to research on alcohol use disorders (AUDs). A large number of such stimuli are necessary to evoke relevant alcohol-related associations. We report the development of a large stimulus database consisting of 457 pictures of alcoholic beverages and 398 pictures of neutral objects. These stimuli were rated by 18 inpatients hospitalized due to severe AUD and 18 healthy controls along four dimensions: arousal, valence, alcohol-relatedness, and craving. Physical parameters of the pictures were assessed. After outlier removal, 831 stimuli that were characterized as either alcohol-related or neutral were retained in the final stimulus pool. Alcohol-related pictures (versus neutral pictures) evoked higher arousal, more craving and were judged to have higher alcohol-relatedness and a more negative valence. Group comparisons indicated that in patients, neutral pictures evoked more craving and had higher alcohol-relatedness than they did in controls. Physical parameters such as visual complexity, luminance, and color were extracted from these pictures, and extreme values were normalized to minimize mean differences between alcoholic and neutral stimuli. The pictures met the qualitative requirements for (neurophysiological) research. A data file containing rating values and physical parameters will be provided upon request.