Transcranial direct current stimulation, implicit alcohol associations and craving

Previous research has shown that stimulation of the left dorsolateral prefrontal cortex (DLPFC) enhances working memory (e.g. in the n-back task), and reduces craving for cigarettes and alcohol. Stimulation of the right inferior frontal gyrus (IFG) improves response inhibition. The underlying mechanisms are not clearly understood, nor is it known whether IFG stimulation also reduces craving. Here, we compared effects of DLPFC, IFG, and sham stimulation on craving in heavy drinkers in a small sample (n=41). We also tested effects of tDCS on overcoming response biases due to associations between alcohol and valence and alcohol and approach, using implicit association tests (IATs). Mild craving was reduced after DLPFC stimulation. Categorization of valence attribute words in the IAT was faster after DLPFC stimulation. We conclude that DLPFC stimulation can reduce craving in heavy drinkers, but found no evidence for tDCS induced changes in alcohol biases, although low power necessitates caution

The effect of acute alcohol on motor-related EEG asymmetries during preparation of approach or avoid alcohol responses

Alcohol-approach tendencies have been associated with heavy drinking and play a role in the transition to alcohol abuse. Such cognitive biases might predict future alcohol use better under a low dose of alcohol. The aim of this prospective study was to investigate both the magnitude and the predictive power of alcohol-induced changes on approach-avoidance bias and bias-related cortical asymmetries during response preparation across heavy and light drinking adolescents. In heavy drinking adolescents greater approach-related asymmetry index in the beta-band was observed for soft-drink cues compared to alcohol ones and this increase was associated with increase in difficulty to regulate alcohol intake. Earlier findings demonstrated that young heavy drinkers hold both positive and negative implicit alcohol associations, reflecting an ambiguity towards alcohol. The increase in approach related beta-lateralization for soft-drink cues measured in this study may represent a compensatory effort for the weaker S-R mapping (approaching soft drink). The MRAA findings in this study may highlight a mechanism related to overcompensation due to ambivalent attitudes towards drinking in our heavy drinking sample who had greater problems to limit their alcohol intake compared to light drinkers. Moreover, a relatively strong approach soft-drink and weak approach alcohol reaction-time bias after alcohol predicted decreasing drinking; suggesting that the capacity to control the bias under alcohol could be a protective factor

Interventions aimed at automatic processes in addiction: considering necessary conditions for efficacy

Automatic processes related to addiction can be directly targeted in novel training paradigms. First studies have demonstrated that Cognitive Bias Modification (CBM) targeting approach biases can enhance treatment outcomes when added to regular treatment. However, the overall efficacy of CBM is debated. We argue that considering the modulating role of motivation and the mediating role of actual bias change are essential to drawing valid conclusions. Findings on mediating cognitive and neural mechanisms underlying clinical effects provide further sources of evidence on CBM. Taken together the literature supports the claim that cognitive bias change can improve clinical outcome, but that there are necessary conditions that must be met. Improved theoretical understanding of changing biases and new techniques such as neuromodulation may be needed to optimally apply CBM to help patients overcome addictive behavior

On the development of implicit and control processes in relation to substance use in adolescence

Adolescence is a period in which brain structures involved in motivation and cognitive control continue to develop and also a period in which many youth begin substance use. Dual-process models propose that, among substance users, implicit or automatically activated neurocognitive processes gain in relative influence on substance use behavior, while the influence of cognitive control or reflective processes weakens. There is evidence that a variety of implicit cognitive processes, such as attentional bias, biased action tendencies (approach bias), memory bias and at a neural level, cue reactivity, are associated with adolescent substance use. The impact of these implicit processes on the further development of addictive behaviors appears to depend on moderating factors, such as (premorbid) executive control functions. Clear negative effects of adolescent substance use on executive control functions generally have not been found using behavioral tasks, although some studies have identified subtle and specific effects on cognitive functioning

Alcohol homograph priming in alcohol-dependent inpatients

Item does not contain fulltextAim: Alcohol dependency is characterized by alcohol-related interpretation biases (IBs): Individuals with high levels of alcohol consumption generate more alcohol-related than alcohol-unrelated interpretations in response to ambiguous alcohol-related cues. However, a response bias could be an alternative account, meaning that individuals with high levels of alcohol consumption generate more alcohol-related IBs because of a greater baseline tendency to endorse alcohol-related responses. Methods: To test this alternative explanation, the present study employed a homograph-priming task, reliability of which was also examined. The sample included 577 clinically diagnosed alcohol-dependent inpatients and 61 control inpatients. Participants completed a homograph priming task (primes: homographs with and without an alcohol-related meaning, target words: alcohol and soft drinks) before commencing their behavioral cognitive treatment at a rehabilitation clinic. Results: Contrary to our expectations, we did not find an enhanced priming effect in alcohol-dependent inpatients. Moreover, there was no correlation between the priming score and levels of harmful drinking (AUDIT scores). Conclusions: The data provide limited support for the existence of alcohol-related IBs, possibly because of the low reliability of the priming task, the features of the task, and the study’s design.8 p

Rare genetic variants explain missing heritability in smoking

Common genetic variants explain less variation in complex phenotypes than inferred from family-based studies, and there is a debate on the source of this ‘missing heritability’. We investigated the contribution of rare genetic variants to tobacco use with whole-genome sequences from up to 26,257 unrelated individuals of European ancestries and 11,743 individuals of African ancestries. Across four smoking traits, single-nucleotide-polymorphism-based heritability (hSNP2) was estimated from 0.13 to 0.28 (s.e., 0.10–0.13) in European ancestries, with 35–74% of it attributable to rare variants with minor allele frequencies between 0.01% and 1%. These heritability estimates are 1.5–4 times higher than past estimates based on common variants alone and accounted for 60% to 100% of our pedigree-based estimates of narrow-sense heritability (hped2, 0.18–0.34). In the African ancestry samples, hSNP2 was estimated from 0.03 to 0.33 (s.e., 0.09–0.14) across the four smoking traits. These results suggest that rare variants are important contributors to the heritability of smoking

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWASs for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally diverse individuals (European, African, Asian, and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole-genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n = 109,122 individuals. We identified 59 sentinel variants (p < 5 × 10−9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated that the independent signals colocalized with cell-type-specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated that our TL polygenic trait scores (PTSs) were associated with an increased risk of cancer-related phenotypes