Efficacy of transcranial direct current stimulation (tDCS) in reducing consumption in patients with alcohol use disorders: study protocol for a randomized controlled trial

Non-invasive brain stimulation for patients and healthy subjects: Current challenges and future perspectives

Non-invasive brain stimulation (NIBS) techniques have a rich historical background, yet their utilization has witnessed significant growth only recently. These techniques encompass transcranial electrical stimulation and transcranial magnetic stimulation, which were initially employed in neuroscience to explore the intricate relationship between the brain and behaviour. However, they are increasingly finding application in research contexts as a means to address various neurological, psychiatric, and neurodegenerative disorders. This article aims to fulfill two primary objectives. Firstly, it seeks to showcase the current state of the art in the clinical application of NIBS, highlighting how it can improve and complement existing treatments. Secondly, it provides a comprehensive overview of the utilization of NIBS in augmenting the brain function of healthy individuals, thereby enhancing their performance. Furthermore, the article delves into the points of convergence and divergence between these two techniques. It also addresses the existing challenges and future prospects associated with NIBS from ethical and research standpoints.

Identification of Novel Loci and Cross-Disorder Pleiotropy Through Multi-Ancestry Genome-Wide Analysis of Alcohol Use Disorder in Over One Million Individuals

Alcohol use disorder (AUD) is highly heritable and burdensome worldwide. Genome-wide association studies (GWASs) can provide new evidence regarding the aetiology of AUD. We report a multi-ancestry GWASs across diverse ancestries focusing on a narrow AUD phenotype, using novel statistical tools in a total sample of 1,041,450 individuals [102,079 cases; European, 75,583; African, 20,689 (mostly African-American); Hispanic American, 3,449; East Asian, 2,254; South Asian, 104; descent]. Cross-ancestry functional analyses were performed with European and African samples. Thirty-seven genome-wide significant loci were identified, of which seven were novel for AUD and six for other alcohol phenotypes. Loci were mapped to genes enriched for brain regions relevant for AUD (striatum, hypothalamus, and prefrontal cortex) and potential drug targets (GABAergic, dopaminergic and serotonergic neurons). African-specific analysis yielded a unique pattern of immune-related gene sets. Polygenic overlap and positive genetic correlations showed extensive shared genetic architecture between AUD and both mental and general medical phenotypes, suggesting they are not only complications of alcohol use but also share genetic liability with AUD. Leveraging a cross-ancestry approach allowed identification of novel genetic loci for AUD and underscores the value of multi-ancestry genetic studies. These findings advance our understanding of AUD risk and clinically-relevant comorbidities.

Frontal tDCS reduces alcohol relapse rates by increasing connections from left dorsolateral prefrontal cortex to addiction networks

BACKGROUND

Brain-based interventions are needed to address persistent relapse in alcohol use disorder (AUD). Neuroimaging evidence suggests higher frontal connectivity as well as higher within-network connectivity of theoretically defined addiction networks are associated with reduced relapse rates and extended abstinence during follow-up periods.

OBJECTIVE

/Hypothesis: A longitudinal randomized double-blind sham-controlled clinical trial investigated whether a non-invasive neuromodulation intervention delivered during early abstinence can (i) modulate connectivity of addiction networks supporting abstinence and (ii) improve relapse rates.

HYPOTHESES

Active transcranial direct current stimulation (tDCS) will (i) increase connectivity of addiction networks known to support abstinence and (ii) reduce relapse rates.

METHODS

Short-term abstinent AUD participants (n = 60) were assigned to 5 days of either active tDCS or sham during cognitive training. Causal discovery analysis (CDA) examined the directional influence from left dorsolateral prefrontal cortex (LDLPFC, stimulation site) to addiction networks that support abstinence.

RESULTS

Active tDCS had an effect on the average strength of CDA-determined connectivity from LDLPFC to the incentive salience and negative emotionality addiction networks - increasing in the active tDCS group only. Active tDCS had an effect on relapse rates following the intervention, with lower probability of relapse in the active tDCS vs. sham. Active tDCS showed an unexpected sex-dependent effect on relapse rates.

CONCLUSION

Our results suggest that LDLPFC stimulation delivered during early abstinence has an effect on addiction networks supporting abstinence and on relapse rates. The unexpected sex-dependent neuromodulation effects need to be further examined in larger clinical trials.

Efficacy of non-invasive brain stimulation interventions in reducing smoking frequency in patients with nicotine dependence: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

Nicotine is a highly addictive substance in tobacco products that dysregulates several neurotransmitters in the brain and impairs executive function. Non-invasive brain stimulation (NIBS) methods such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are promising treatments for nicotine dependence. We investigated the efficacy and acceptability of NIBS in managing smoking cessation through a systematic review and network meta-analysis (NMA).

METHODS

We conducted a systematic review to identify randomized controlled trials (RCTs) that investigated the efficacy of NIBS for smoking cessation. All pairwise meta-analyses and NMA procedures were conducted using random-effects and frequentist models. The co-primary outcomes were (1) the change in number of cigarettes smoked per day (change in frequency of smoking) in patients with nicotine dependence after NIBS and (2) acceptability (the dropout rate). The effect sizes for co-primary outcomes of change in frequency of smoking and acceptability were assessed according to standardized mean difference (SMD) and odds ratio, respectively.

RESULTS

Twelve RCTs with 710 participants (mean age: 44.2 years, 31.2% female) were included. Compared with the sham control, 10-Hz rTMS over the left dorsolateral prefrontal cortex (DLPFC) was associated with the largest changes in smoking frequency [SMD = -1.22, 95% confidence interval (95% CI) = -1.77 to -0.66]. The 2-mA bifrontal tDCS (SMD = -0.97, 95% CI = -1.32 to -0.62) and 10-Hz deep rTMS over the bilateral DLPFC with cue provocation (SMD = -0.77, 95% CI = -1.20 to -0.34) were associated with a significantly larger decrease in smoking frequency versus the sham. None of the investigated NIBSs was associated with dropout rates significantly different from those of the sham control groups.

CONCLUSION

Prefrontal non-invasive brain stimulation interventions appear to reduce the number of cigarettes smoked with good acceptability.

Application of Transcranial Direct Current Stimulation in Psychiatry

Transcranial direct current stimulation (tDCS) is a neuromodulation technique, which noninvasively alters cortical excitability via weak polarizing currents between two electrodes placed on the scalp. Since it is comparably easy to handle, cheap to use and relatively well tolerated, tDCS has gained increasing interest in recent years. Based on well-known behavioral effects, a number of clinical studies have been performed in populations including patients with major depressive disorder followed by schizophrenia and substance use disorders, in sum with heterogeneous results with respect to efficacy. Nevertheless, the potential of tDCS must not be underestimated since it could be further improved by systematically investigating the various stimulation parameters to eventually increase clinical efficacy. The present article briefly explains the underlying physiology of tDCS, summarizes typical stimulation protocols and then reviews clinical efficacy for various psychiatric disorders as well as prevalent adverse effects. Future developments include combined and more complex interactions of tDCS with pharmacological or psychotherapeutic interventions. In particular, using computational models to individualize stimulation protocols, considering state dependency and applying closed-loop technologies will pave the way for tDCS-based personalized interventions as well as the development of home treatment settings promoting the role of tDCS as an effective treatment option for patients with mental health problems.

Effects of tDCS on reward responsiveness and valuation in Parkinson's patients with impulse control disorders

Parkinson's disease (PD) patients with impulse control disorders (ICD) frequently report hypersensitivity to rewards. However, a few studies have explored the effectiveness of modulation techniques on symptoms experienced by these patients. In this study, we assessed the effect of anodal tDCS over the DLPFC on reward responsiveness and valuation in PD patients with ICD. 43 participants (15 PD patients with ICD, 13 PD without ICD, and 15 healthy matched controls) were asked to perform a reward-craving test employing both explicit (self-ratings of liking and wanting) and implicit (heart rate and skin conductance response) measures, as well as two temporal discounting tasks with food and money rewards. Each participant performed the experimental tasks during active anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC), anodal tDCS of the primary motor cortex (M1), and sham tDCS. Results showed increased wanting and a steeper temporal discounting of rewards in PD with ICD compared to the other groups. Moreover, we found that PD without ICD exhibit reduced liking for rewards. tDCS results capable to modulate the altered intensity of PD patients' liking, but not wanting and temporal discounting of rewards in PD patients with ICD. These findings confirm that alterations in reward responsiveness and valuation are characteristics of impulse control disorders in patients with PD but suggest that anodal tDCS over the left DLPFC is not capable to influence these processes. At the same time, they provide new insight into affective experience of rewards in PD.

A Frontal Neuropsychological Profile in Fitness to Drive

Traffic accidents are a global concern due to the elevated mortality rates of both drivers and pedestrians. The World Health Organization declared 2011-2020 as the Decade of Action for Road Safety, endorsing initiatives to reduce traffic-related deaths. Yet, despite these incentives, fatal accidents still occur. Different studies have linked deficits in executive functions to risky driving attitudes and crashes. The present study focuses on demographic, cognitive and personality factors, related to the prefrontal cortex, that are characteristic of drivers prone to risky behavior behind the wheel. The penalty Points System was used to classify drivers as "safe", with no point loss over a two-year period, or "risky", with full point loss during the same interval. A neuropsychological assessment of prefrontal cognitive functions was carried out on each group to identify variables associated with safe and risky behavior. Neuropsychological indexes were obtained from a continuous performance task without cue (Simple Attention), a continuous performance task with cue (Conditioned Attention), the Tower of Hanoi test and the Neurologically-related Changes in Personality Inventory (NECHAPI). A Discriminant Analysis (DA) found that education level, reaction times in Simple and Conditioned Attention, learning errors in the Tower of Hanoi and vulnerability in the personality test, best predicted whether drivers were likely to be in the safe or risky group. Finally, a cross-validation analysis performed on the same sample correctly classified 87.5% of the drivers. These data suggest that prefrontal dysfunction contributes to risky behavior behind the wheel. The inclusion of cognitive programs to identify and train drivers with this propensity could reduce risky driving, and consequently, save lives on the road.

History of Alcohol Consumption and HIV Status Related to Functional Connectivity Differences in the Brain During Working Memory Performance

BACKGROUND

Poorer working memory function has previously been associated with alcohol misuse, Human Immunodeficiency Virus (HIV) positive status, and risky behavior. Poorer working memory performance relates to alterations in specific brain networks.

OBJECTIVE

The current study examined if there was a relationship between brain networks involved in working memory and reported level of alcohol consumption during an individual's period of heaviest use. Furthermore, we examined whether HIV status and the interaction between HIV and alcohol consumption was associated with differences in these brain networks.

METHODS

Fifty adults, 26 of whom were HIV positive, engaged in an n-back working memory task (0-back and 2-back trials) administered in a magnetic resonance imaging (MRI) scanner. The Kreek- McHugh-Schluger-Kellogg (KMSK) scale of alcohol consumption was used to characterize an individual's period of heaviest use and correlates well with their risk for alcohol dependence. Connectivity analyses were conducted using data collected during n-back task.

RESULTS

Functional connectivity differences associated with greater alcohol consumption included negative connectivity, primarily from parietal attention networks to frontal networks. Greater alcohol consumption was also associated with positive connectivity from working memory nodes to the precuneus and paracingulate. HIV positive status was associated with more nodes of negative functional connectivity relative to alcohol consumption history alone, particularly in the frontoparietal networks. The HIV positive individuals with heavier drinking history related to negative fronto-parietal connectivity, along with positive connectivity from working memory nodes to mesolimbic regions.

CONCLUSION

Findings allow for a better understanding of brain networks affected by HIV and alcohol and may provide avenues for interventions.

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 (tDCS) modulates biometric and inflammatory parameters and anxiety-like behavior in obese rats

Obesity is a multifactorial disease associated with metabolic dysfunction and the prevention and treatment of obesity are often unsatisfactory. Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique that has proven promising in the treatment of eating disorders such as obesity. We investigate the effects of tDCS on locomotor and exploratory activities, anxiety-like and feeding behavior, and levels of brain-derived neurotrophic factor (BDNF), IL (interleukin)-10, IL-1β, and tumor necrosis factor-alpha (TNF-α) in the cerebral cortex of obese rats. A total of 40 adult male Wistar rats were used in our study. Animals were divided into groups of three or four animals per cage and allocated to four treatment groups: standard diet plus sham tDCS treatment (SDS), standard diet plus tDCS treatment (SDT), hypercaloric diet plus sham tDCS treatment (HDS), hypercaloric diet plus tDCS treatment (HDT). After 40 days on a hypercaloric diet and/or standard diet were to assessed the locomotor and exploratory activity and anxiety-like behavior to by the open field (OF) and elevated plus maze (EPM) tests respectively before and after exposure to tDCS treatment. The experimental groups were submitted to active or sham treatment tDCS during eight days. Palatable food consumption test (PFT) was performed 24 h after the last tDCS session under fasting and feeding conditions. Obese animals submitted to tDCS treatment showed a reduction in the Lee index, visceral adipose tissue weight, and food craving. In addition, bicephalic tDCS decreased the cerebral cortex levels of IL-1β and TNF-α in these animals. Exposure to a hypercaloric diet produced an anxiolytic effect, which was reversed by bicephalic tDCS treatment. These results suggest that, in accordance with studies in humans, bicephalic tDCS could modulate biometric and inflammatory parameters, as well as anxiety-like and feeding behavior, of rats subjected to the consumption of a hypercaloric diet.