Modulation of smoking and decision-making behaviors with transcranial direct current stimulation in tobacco smokers: a preliminary study

Transcranial direct current stimulation combined with a brief intervention for smoking cessation: a randomized double-blind clinical trial

Non-invasive brain stimulation methods are currently being evaluated for treatment of addictive disorders. Some evidence indicates that modulating left and right prefrontal brain activity by transcranial direct current stimulation (tDCS) can reduce craving and relapse rates in tobacco addiction. Therefore, this study investigated the effects of active and sham tDCS as an add-on treatment to a standardized brief intervention for smoking cessation. This randomized, double-blind study included 36 participants (22 women and 14 men) with nicotine dependence according to ICD-10 criteria. At five visits on alternate days, participants underwent a 20-min active or sham tDCS over the left dorsolateral prefrontal cortex and subsequently participated in a 10-min brief intervention for smoking cessation. Patients were followed up after 3 months. On each treatment day and at follow-up, abstinence was assessed as the smoking status nonsmoker and craving was assessed with the German version of the Questionnaire on Smoking Urges. At each visit, the number of cigarettes smoked per day was recorded and carbon monoxide in expired air and cotinine in saliva were measured. At follow-up, a study-specific questionnaire was used to assess tobacco use. All 36 participants completed the treatment sessions, but one participant in each group was lost to follow-up. Abstinence rates were not significantly different between the groups at any of the study visits, but craving was significantly lower in the active group at tDCS session 5 compared with session 1. tDCS combined with a brief intervention may support smoking cessation, but studies need to evaluate whether longer and more intensive treatment can achieve significant, sustainable effects.

Transcranial random noise stimulation (tRNS) improves hot and cold executive functions in children with attention deficit-hyperactivity disorder (ADHD)

Children with attention deficit-hyperactivity disorder (ADHD) have impaired hot and cold executive functions, which is thought to be related to impaired ventromedial and dorsolateral prefrontal cortex (vmPFC and dlPFC) functions. The present study aimed to assess the impact concurrent stimulation of dlPFC and vmPFC through transcranial random noise stimulation (tRNS), a non-invasive brain stimulation tool which enhances cortical excitability via application of alternating sinusoidal currents with random frequencies and amplitudes over the respective target regions on hot and cold executive functions. Eighteen children with ADHD received real and sham tRNS over the left dlPFC and the right vmPFC in two sessions with one week interval. The participants performed Circle Tracing, Go/No-Go, Wisconsin Card Sorting, and Balloon Analogue Risk Tasks during stimulation in each session. The results showed improved ongoing inhibition, prepotent inhibition, working memory, and decision making, but not set-shifting performance, during real, as compared to sham stimulation. This indicates that simultaneous stimulation of the dlPFC and the vmPFC improves hot and cold executive functions in children with ADHD.

A systematic review and meta-analysis of neuromodulation therapies for substance use disorders

While pharmacological, behavioral and psychosocial treatments are available for substance use disorders (SUDs), they are not always effective or well-tolerated. Neuromodulation (NM) methods, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) and deep brain stimulation (DBS) may address SUDs by targeting addiction neurocircuitry. We evaluated the efficacy of NM to improve behavioral outcomes in SUDs. A systematic literature search was performed on MEDLINE, PsychINFO, and PubMed databases and a list of search terms for four key concepts (SUD, rTMS, tDCS, DBS) was applied. Ninety-four studies were identified that examined the effects of rTMS, tDCS, and DBS on substance use outcomes (e.g., craving, consumption, and relapse) amongst individuals with SUDs including alcohol, tobacco, cannabis, stimulants, and opioids. Meta-analyses were performed for alcohol and tobacco studies using rTMS and tDCS. We found that rTMS reduced substance use and craving, as indicated by medium to large effect sizes (Hedge's g > 0.5). Results were most encouraging when multiple stimulation sessions were applied, and the left dorsolateral prefrontal cortex (DLPFC) was targeted. tDCS also produced medium effect sizes for drug use and craving, though they were highly variable and less robust than rTMS; right anodal DLPFC stimulation appeared to be most efficacious. DBS studies were typically small, uncontrolled studies, but showed promise in reducing misuse of multiple substances. NM may be promising for the treatment of SUDs. Future studies should determine underlying neural mechanisms of NM, and further evaluate extended treatment durations, accelerated administration protocols and long-term outcomes with biochemical verification of substance use.

The effect of bipolar bihemispheric tDCS on executive function and working memory abilities

Introduction

Cognitive functioning is central to the ability to learn, problem solve, remember, and use information in a rapid and accurate manner and cognitive abilities are fundamental for communication, autonomy, and quality of life. Transcranial electric stimulation (tES) is a very promising tool shown to improve various motor and cognitive functions. When applied as a direct current stimulus (transcranial direct current stimulation; tDCS) over the dorsolateral pre-frontal cortex (DLPFC), this form of neurostimulation has mixed results regarding its ability to slow cognitive deterioration and potentially enhance cognitive functioning, requiring further investigation. This study set out to comprehensively investigate the effect that anodal and cathodal bipolar bihemispheric tDCS have on executive function and working memory abilities.

Methods

72 healthy young adults were recruited, and each participant was randomly allocated to either a control group (CON), a placebo group (SHAM) or one of two neurostimulation groups (Anodal; A-STIM and Cathodal; C-STIM). All participants undertook cognitive tests (Stroop & N Back) before and after a 30-minute stimulation/ sham/ control protocol.

Results

Overall, our results add further evidence that tDCS may not be as efficacious for enhancing cognitive functioning as it has been shown to be for enhancing motor learning when applied over M1. We also provide evidence that the effect of neurostimulation on cognitive functioning may be moderated by sex, with males demonstrating a benefit from both anodal and cathodal stimulation when considering performance on simple attention trial types within the Stroop task.

Discussion

Considering this finding, we propose a new avenue for tDCS research, that the potential that sex may moderate the efficacy of neurostimulation on cognitive functioning.

Are we really targeting and stimulating DLPFC by placing transcranial electrical stimulation (tES) electrodes over F3/F4?

In many clinical trials involving transcranial electrical stimulation (tES), target electrodes are typically placed over DLPFC with the assumption that this will primarily stimulate the underlying brain region. However, our study aimed to evaluate the electric fields (EF) that are actually delivered and identify prefrontal regions that may be inadvertently targeted in DLPFC tES. Head models were generated from the Human Connectome Project database's T1 + T2-weighted MRIs of 80 healthy adults. Two common DLPFC montages were simulated; symmetric-F4/F3, and asymmetric-F4/Fp1. Averaged EF was extracted from (1) the center of the target electrode (F4), and (2) the top 1% of voxels showing the strongest EF in individualized EF maps. Interindividual variabilities were quantified with the standard deviation of EF peak location/value. Similar steps were repeated with 66 participants with methamphetamine use disorder (MUDs) as an independent clinical population. In healthy adults, the group-level location of EF peaks was situated in the medial-frontopolar, and the individualized EF peaks were positioned in a cube with a volume of 29 cm3 /46 cm3 (symmetric/asymmetric montages). EFs in the frontopolar area were significantly higher than EF "under" the target electrode in both symmetric (peak: 0.41 ± 0.06, F4:0.22 ± 0.04) and asymmetric (peak: 0.38 ± 0.04, F4:0.2 ± 0.04) montages (Heges'g > 0.7). Similar results with slight between-group differences were found in MUDs. We highlighted that in common DLPFC tES montages, in addition to interindividual/intergroup variability, the frontopolar received the highest EFs rather than DLPFC as the main target. We specifically recommended considering the potential involvement of the frontopolar area as a mechanism underlying the effectiveness of DLPFC tES protocols.

Methylphenidate is more effective to improve inhibitory control and working memory compared to tDCS in children and adolescents with attention deficit/hyperactivity disorder: a proof-of-concept study

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is characterized by an inappropriate, pervasive and persistent pattern of inattention, hyperactivity, and/or impulsivity and associated with substantial functional impairment. Despite considerable advances in the understanding and management of ADHD, some patients do not respond well to methylphenidate (MPH), the first-choice pharmacological treatment. Over the past decades, among non-invasive brain stimulation techniques, transcranial direct current stimulation (tDCS) has proven to be an effective and safe technique to improve behavior and cognition in children with neurodevelopmental disorders, including ADHD, by modifying cortical excitability. However, the effect of tDCS has never been directly compared with that of the MPH. The present randomized sham-controlled trial evaluated the effect of a single session of anodal tDCS compared with the administration of a single dose of MPH in children and adolescents with ADHD.

Methods

After completing baseline assessment (T0), 26 children and adolescents with ADHD were exposed to 3 conditions with a 24-h interval-sessions: (A) a single session of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC); (B) a single session of sham tDCS over the left DLPFC; (C) a single dose of MPH.

Results

Our results showed that after administering a single dose of MPH, children and adolescents with ADHD improved inhibitory control and visual-spatial WM compared with baseline, anodal, and sham tDCS. However, a single session of active tDCS over the left DLPFC was not effective compared with either baseline or sham tDCS.

Discussion

In conclusion, our protocol in ADHD involving a single tDCS session did not demonstrate consistent improvements in neurocognitive features compared with baseline, sham tDCS, or single MPH administration. Different protocols need to be developed to further test the effectiveness of tDCS in improving ADHD symptoms.

Transcranial Direct Current Stimulation in Nicotine Use: Nursing Implications for Patient Outcomes

ABSTRACT

Tobacco use is a leading cause of cancer, cardiovascular and respiratory disease, and preventable death in the United States. The brains of individuals with nicotine dependence are characterized by damaged mesolimbic pathways in the medial portion of the limbic and frontal lobes, creating positive reinforcing mechanisms. Transcranial direct current stimulation (tDCS) targets this neuroadaptation to improve smokers' nicotine-related outcomes, such as craving and smoking behavior, by depolarizing or hyperpolarizing the neurons of the brain. Recent literature reported promising outcomes in smokers after tDCS treatment interventions. tDCS has great potential for clinical nursing research for tobacco control given its multiple methodological advantages and few disadvantages. Nurse researchers can consider individualized and home-based tDCS interventions for community-based tobacco control research and may need to consider objective outcome measures (e.g., cotinine in urine) and addiction-related cognitive variables (e.g., self-regulation). Users of electronic nicotine delivery systems also need to be considered as participants in tDCS interventions. Additional considerations for nursing research are discussed.

Effects of psychoeducation combined with transcranial direct current stimulation on reducing cigarette craving and consumption in male smokers

Psychoeducation (PE) has been widely used in smoking interventions, but its long-term effects are limited. Recent studies have reported that, in some fields, a combination of transcranial direct current stimulation (tDCS) and cognitive training (e.g., working memory tasks) may improve cognitive outcomes; thus, we aimed to investigate whether such a combined intervention has a better effect than a PE intervention for reducing smoking cravings and cigarette consumption. In Exp. 1, 19 male smokers received four types of interventions at one-week intervals. In each session, participants were presented with audio PE (or control) while receiving 2-mA active (or sham) tDCS of the dorsolateral prefrontal cortex (DLPFC). In Exp. 2, 48 male smokers were randomized into four experimental groups (PE + Active, Control + Active, PE + Sham, or Control + Sham). Each participant received one type of five-day intervention (i.e., watching a five-minute PE/Control video twice while receiving 2-mA active/sham tDCS) and was followed up for one week. The results showed (a) an enhancement effect of tDCS on PE's ability to reduce cigarette consumption; (b) that repeated PE has a cumulative effect on reducing both craving and cigarette consumption during the intervention period; and (c) that, compared with PE alone, PE combined with tDCS is capable of helping participants maintain a low intake of cigarettes over one week. These findings suggest that repeated interventions of PE combined with tDCS may be effective in reducing smoking consumption and that further studies are warranted to confirm its application.

Transcranial direct current stimulation alters the process of reward processing in children with ADHD: Evidence from cognitive modeling

BACKGROUND

The ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) are the neural underpinnings of reward processing, which is impaired in individuals with attention deficit hyperactivity disorder (ADHD). In the present study, we aimed to explore the impact of the vmPFC and the dlPFC regulation on reward processing.

METHODS

Twenty-six children with ADHD performed the balloon analogue risk-taking task (BART) and chocolate delay discounting task (CDDT) during five different sessions of transcranial direct current stimulation (tDCS), separated by a one-week interval: anodal left dlPFC/cathodal right vmPFC, the reversed electrode positioning, anodal left dlPFC stimulation with extracranial return electrode, anodal right vmPFC stimulation with extracranial return electrodes, and sham stimulation. Four-parameter and constant-sensitivity models were used to model the data.

RESULTS

In the BART, anodal dlPFC/cathodal vmPFC stimulation facilitated conservative decision making, anodal tDCS over dlPFC with extracranial return electrode increased positive beliefs about the explosion of a balloon, and anodal vmPFC/cathodal dlPFC stimulation reduced ongoing learning in the process of decision making. In the CDDT, anodal vmPFC stimulation with extracranial return electrode decreased impatience in the process of the task.

CONCLUSION

These results suggest a role of the left dlPFC and right vmPFC in the outcome of decision making and the process of risky decision making and delay discounting.

Brain stimulation therapeutics

This chapter covers how repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) presently affects smoking cessation. 14 human studies have examined the efficacy of rTMS on cue craving, cigarette consumption, or smoking cessation using a variety of different coils, locations, and treatment parameters. These studies included 7 randomized-controlled trials (RCT) and 7 experimental studies. Most studies (12/14) reported that rTMS reduced cue-induced craving, 5 showed that it decreased cigarette consumption, and 3/4 reported that multiple sessions of rTMS increased the quit rate. In contrast to rTMS, tDCS has 6 RCT studies, of which only 2 studies reported that tDCS reduced craving, and only 1 reported that it reduced cigarette consumption. Three studies failed to find an effect of tDCS on cravings. No tDCS studies reported changing quitting rates in people who smoke. Despite the early positive results of tDCS on nicotine dependence symptoms, 2 larger RCTs recently failed to find a therapeutic effect of tDCS for smoking cessation. In conclusion, rTMS studies demonstrate that multiple sessions help quit smoking, and it has gained FDA approval for that purpose. However, more studies are needed to examine the effect of tDCS with different treatment parameters.

Effects of Transcranial Electrical Stimulation on Gambling and Gaming: A Systematic Review of Studies on Healthy Controls, Participants with Gambling/Gaming Disorder, and Substance Use Disorder

Gambling disorder (GD) and internet gaming disorder (IGD) are formally recognized behavioral addictions with a rapidly growing prevalence and limited treatment options. Recently, transcranial electrical stimulation (tES) techniques have emerged as potentially promising interventions for improving treatment outcomes by ameliorating cognitive functions implicated in addictive behaviors. To systematize the current state of evidence and better understand whether and how tES can influence gambling and gaming-related cognitive processes, we conducted a PRISMA-guided systematic review of the literature, focusing on tES effects on gaming and gambling in a diverse range of population samples, including healthy participants, participants with GD and IGD, as well as participants with substance abuse addictions. Following the literature search in three bibliographic databases (PubMed, Web of Science, and Scopus), 40 publications were included in this review, with 26 conducted on healthy participants, 6 focusing on GD and IGD patients, and 8 including participants with other addictions. Most of the studies targeted the dorsolateral prefrontal cortex, using transcranial direct current stimulation (tDCS), and assessed the effects on cognition, using gaming and gambling computerized cognitive tasks measuring risk taking and decision making, e.g., balloon analogue risk task, Iowa gambling task, Cambridge gambling task, etc. The results indicated that tES could change gambling and gaming task performances and positively influence GD and IGD symptoms, with 70% of studies showing neuromodulatory effects. However, the results varied considerably depending on the stimulation parameters, sample characteristics, as well as outcome measures used. We discuss the sources of this variability and provide further directions for the use of tES in the context of GD and IGD treatment.

Machine learning with neuroimaging biomarkers: Application in the diagnosis and prediction of drug addiction

Drug abuse is a serious problem worldwide. Owing to intermittent intake of certain substances and the early inconspicuous clinical symptoms, this brings huge challenges for timely diagnosing addiction status and preventing substance use disorders (SUDs). As a non-invasive technique, neuroimaging can capture neurobiological signatures of abnormality in multiple brain regions caused by drug consumption in each clinical stage, like parenchymal morphology alteration as well as aberrant functional activity and connectivity of cerebral areas, making it realizable to diagnosis, prediction and even preemptive therapy of addiction. Machine learning (ML) algorithms primarily used for classification have been extensively applied in analysing medical imaging datasets. Significant neurobiological characteristics employed and revealed by classifiers were used to diagnose addictive states and predict initiation and vulnerability to drug usage, treatment abstinence, relapse and resilience of addicts and the risk of SUD. In this review, we summarize application of ML methods in neuroimaging focusing on addicts' diagnosis of clinical status and risk prediction and elucidate the discriminative neurobiological features from brain electrophysiological, morphological and functional perspectives that contribute most to the classifier, finally highlighting the auxiliary role of ML in addiction treatment.

A critical perspective on updating drug memories through the integration of memory editing and brain stimulation

Addiction is a persistent, recurring condition characterized by repeated relapses despite the desire to control drug use or maintain sobriety. The attainment of abstinence is hindered by persistent maladaptive drug-associated memories, which drive drug-seeking and use behavior. This article examines the preliminary evidence supporting the combination of non-invasive brain stimulation (NIBS) techniques and memory editing (or reconsolidation) interventions as add-on forms of treatment for individuals with substance-related disorders (SUD). Studies have shown that NIBS can modestly reduce drug use and craving through improved cognitive control or other undetermined reasons. Memory reconsolidation, a process by which a previously consolidated memory trace can be made labile again, can potentially erase or significantly weaken SUD memories underpinning craving and the propensity for relapse. This approach conveys enthusiasm while also emphasizing the importance of managing boundary conditions and null results for interventions found on fear memory reconsolidation. Recent studies, which align with the state-dependency and activity-selectivity hypotheses, have shown that the combination of NIBS and behavioral interventions holds promise for treating SUD by reducing self-reported and physiological aspects of craving. Effective long-term outcomes for this procedure require better identification of critical memories, a deeper understanding of the brain mechanisms underlying SUD and memory reconsolidation and overcoming any boundary conditions of destabilized memories. This will enable the procedure to be personalized to the unique needs of individual patients.

Transcranial direct current stimulation of the frontal-parietal-temporal brain areas reduces cigarette consumption in abstinent heroin users

Transcranial direct current stimulation (tDCS) has been demonstrated to modulate neural activity and related brain functions. In clinical studies, tDCS has been shown to reduce craving in various substance use disorders including cocaine, heroin and nicotine. Our previous report suggested that cathodal tDCS on the frontal-parietal-temporal (FPT) brain areas reduced cigarette consumption in moderate smokers. However, whether it is effective in smokers with history of drug use is unknown. This study investigated the effects of bilateral FPT areas cathodal tDCS on smokers with history of heroin use. 22 abstinent heroin users were recruited and randomly assigned to sham group and tDCS group. The sham group received 30 s tDCS treatment and tDCS group received normal tDCS (one trial of 20 min, 1 mA, cathodal electrodes were placed bilaterally on the FPT areas). The average of daily cigarettes consumption was recorded for the week before the tDCS and the following day after tDCS. In addition, pupil light reflex was measured right before and after tDCS treatment. One trial of tDCS stimulation significantly reduced daily cigarette consumption in smokers who had heroin use history. This reducing effect was also observed in heavy smokers. In addition, this effect on cigarette consumption lasted at least 48 h after the stimulation. Furthermore, it has been shown that opiates decrease pupillary size in humans, we found detectable changes of the dynamic pupil light reflex after bilateral tDCS stimulation. These findings suggest that FPT cathodal tDCS may be an effective approach to reduce cigarette craving in heroin users.

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.

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex for Treatment of Neuropsychiatric Disorders

Background

The dorsolateral prefrontal cortex (DLPFC) is a key node of the frontal cognitive circuit. It is involved in executive control and many cognitive processes. Abnormal activities of DLPFC are likely associated with many psychiatric diseases. Modulation of DLPFC may have potential beneficial effects in many neural and psychiatric diseases. One of the widely used non-invasive neuromodulation technique is called transcranial direct current stimulation (or tDCS), which is a portable and affordable brain stimulation approach that uses direct electrical currents to modulate brain functions.

Objective

This review aims to discuss the results from the past two decades which have shown that tDCS can relieve clinical symptoms in various neurological and psychiatric diseases.

Methods

Here, we performed searches on PubMed to collect clinical and preclinical studies that using tDCS as neuromodulation technique, DLPFC as the stimulation target in treating neuropsychiatric disorders. We summarized the stimulation sites, stimulation parameters, and the overall effects in these studies.

Results

Overall, tDCS stimulation of DLPFC could alleviate the clinical symptoms of schizophrenia, depression, drug addiction, attention deficit hyperactivity disorder and other mental disorders.

Conclusion

The stimulation parameters used in these studies were different from each other. The lasting effect of stimulation was also not consistent. Nevertheless, DLPFC is a promising target for non-invasive stimulation in many psychiatric disorders. TDCS is a safe and affordable neuromodulation approach that has potential clinical uses. Larger clinical studies will be needed to determine the optimal stimulation parameters in each condition.

Reducing craving and consumption in individuals with drug addiction, obesity or overeating through neuromodulation intervention: a systematic review and meta-analysis of its follow-up effects

BACKGROUND AND AIMS

Non-invasive brain stimulation has shown potential in clinical applications aiming at reducing craving and consumption levels in individuals with drug addiction or overeating behaviour. However, it is unclear whether these intervention effects are maintained over time. This study aimed to measure the immediate, short- and long-term effects of excitatory transcranial direct current stimulation (tDCS) and high-frequency repetitive transcranial magnetic stimulation (rTMS) targeting at dorsolateral prefrontal cortex (dlPFC) in people with drug addiction or overeating.

METHODS

A systematic review and random effects meta-analysis. We included 20 articles (total of 22 studies using randomized controlled trials: 3 alcohol dependence, 3 drug dependence, 12 smoking, 4 overeating; total: 720 participants) from January 2000 to June 2020, which reported at least one follow-up assessment of craving, consumption or abstinence levels after the intervention. We compared effects of active versus sham stimulation immediately after the intervention and at the last follow-up assessment, as compared with baseline.

RESULTS

Excitatory neuromodulation of dlPFC activity reduced craving and consumption immediately after the intervention (craving: g = 0.734, CI = 0.447-1.021, P < 0.001; consumption: g = 0.527, CI = 0.309-0.745; P < 0.001), as well as during short-, mid- and long-term abstinence (craving: g = 0.677, CI = 0.440-0.914, P < 0.001; consumption: g = 0.445, CI = 0.245-0.645, P < 0.001; abstinence levels: g = 0.698, CI = 0.433-0.963, P < 0.001; average time of follow-up: 84 ± 83 days after last stimulation). Additional analysis demonstrated that the intervention effects were sustained in all populations studied (food, nicotine, alcohol or drug abuse) and with both stimulation techniques used (rTMS, tDCS). Interventions targeting at the left (vs right) hemisphere may be more effective.

CONCLUSIONS

Excitatory neuromodulation targeting the dorsolateral prefrontal cortex appears to lead to a sustained reduction of craving and consumption in individuals with addiction or overeating behaviour.

Mini-review: When neurostimulation joins cognitive-behavioral therapy. On the need of combining evidence-based treatments for addiction disorders

Substance and behavioral addiction is a global health problem related to cognitive functioning and emotional responses like top-down control and craving. The present review discusses the role of non-invasive brain stimulation (NIBS) and cognitive-behavioral therapy (CBT) as evidence-based treatments for addiction disorders. The discussion spans between several evidence for both therapies, also considering the difference and heterogeneity among clinical protocols. Nowadays, literature is consistent in indicating the neurostimulation of the prefrontal cortex as effective for different kinds of addiction, corroborating the evidence that they rely on a common network in the brain. Likewise, within the CBT studies it is possible to observe a wide range of interventions that are overall effective in regulating the executive functions associated with addiction disorders. Nevertheless, the integration of NIBS and CBT in addictions has been scarcely considered in literature so far. For this reason, the present article is meant to foster empirical research in this field by highlighting the findings supporting these evidence-based interventions, both as stand-alone and integrated treatments. To this aim, psychological and neurophysiological mechanisms of NIBS and CBT in addictions are reviewed, and the rationale of their integration discussed. In particular, as evidence suggest these treatments affect top-down and bottom-up processes in different ways, with NIBS reducing craving and CBT boosting motivation and coping, we suggest their combination might better target the different components of addiction to promote abstinence.

The Effects of a Single Transcranial Direct Current Stimulation Session on Impulsivity and Risk Among a Sample of Adult Recreational Cannabis Users

Individuals with substance use disorders exhibit risk-taking behaviors, potentially leading to negative consequences and difficulty maintaining recovery. Non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS) have yielded mixed effects on risk-taking among healthy controls. Given the importance of risk-taking behaviors among substance-using samples, this study aimed to examine the effects of tDCS on risk-taking among a sample of adults using cannabis. Using a double-blind design, 27 cannabis users [M(SD) age = 32.48 (1.99), 41% female] were randomized, receiving one session of active or sham tDCS over the bilateral dorsolateral prefrontal cortex (dlPFC). Stimulation parameters closely followed prior studies with anodal right dlPFC and cathodal left dlPFC stimulation. Risk-taking-assessed via a modified Cambridge Gambling Task-was measured before and during tDCS. Delay and probability discounting tasks were assessed before and after stimulation. No significant effects of stimulation on risk-taking behavior were found. However, participants chose the less risky option ∼86% of the trials before stimulation which potentially contributed to ceiling effects. These results contradict one prior study showing increased risk-taking among cannabis users following tDCS. There was a significant increase in delay discounting of a $1000 delayed reward during stimulation for the sham group only, but no significant effects for probability discounting. The current study adds to conflicting and inconclusive literature on tDCS and cognition among substance-using samples. In conclusion, results suggest the ineffectiveness of single session dlPFC tDCS using an established stimulation protocol on risk-taking, although ceiling effects at baseline may have also prevented behavior change following tDCS.

Efficacy of repetitive transcranial magnetic stimulation (rTMS) for reducing consumption in patients with alcohol use disorders (ALCOSTIM): study protocol for a randomized controlled trial

Background

The number of people with an alcohol use disorder (AUD) was recently estimated to be 63.5 million worldwide. The global burden of disease and injury attributable to alcohol is considerable: about 3 million deaths, namely one in 20, were caused by alcohol in 2015. At the same time, AUD remains seriously undertreated.

In this context, alternative or adjunctive therapies such as brain stimulation could play an important role. The early results of studies using repetitive transcranial magnetic stimulation (rTMS) suggest that stimulations delivered to the dorsolateral prefrontal cortex significantly reduce cravings and improve decision-making processes in various addictive disorders. We therefore hypothesize that rTMS could lead to a decrease in alcohol consumption in patients with AUD.

Methods/design

We report the protocol of a randomized, double-blind, placebo-controlled, parallel-group trial to evaluate the efficacy of rTMS on alcohol reduction in individuals diagnosed with AUD. The study will be conducted in 2 centers in France. Altogether, 144 subjects older than 18 years and diagnosed with AUD will be randomized to receive 5 consecutive twice-daily sessions of either active or sham rTMS (10 Hz over the right DLPFC, 2000 pulses per day). The main outcomes of the study will be changes in alcohol consumption within the 4 weeks after the rTMS sessions. Secondary outcome measures will include changes in alcohol consumption within the 24 weeks, alcohol cravings, clinical and biological improvements, effects on mood and quality of life, and cognitive and safety assessments, and, for smokers, an assessment of the effects of rTMS on tobacco consumption.

Discussion

Several studies have observed a beneficial effect of rTMS on substance use disorders by reducing craving, impulsivity, and risk-taking behavior and suggest that rTMS may be a promising treatment in addiction. However, to date, no studies have included sufficiently large samples and sufficient follow-up to confirm this hypothesis. The results from this large randomized controlled trial will give a better overview of the therapeutic potential of rTMS in AUD.

Trial registration

ClinicalTrials.gov NCT04773691. Registered on 26 February 2021

https://clinicaltrials.gov/ct2/show/NCT04773691?term=trojak&draw=2&rank=5.

Transcranial direct current stimulation (tDCS) reduces motivation to drink ethanol and reacquisition of ethanol self-administration in female mice

Transcranial direct current stimulation (tDCS) is an emerging noninvasive brain neuromodulation technique aimed at relieving symptoms associated with psychiatric disorders, including addiction. The goal of the present study was to better identify which phase of alcohol-related behavior (hedonic effect, behavioral sensitization, self-administration, or motivation to obtain the drug) might be modulated by repeated anodal tDCS over the frontal cortex (0.2 mA, 20 min, twice a day for 5 consecutive days), using female mice as a model. Our data showed that tDCS did not modulate the hedonic effects of ethanol as assessed by a conditioned place preference test (CPP) or the expression of ethanol-induced behavioral sensitization. Interestingly, tDCS robustly reduced reacquisition of ethanol consumption (50% decrease) following extinction of self-administration in an operant paradigm. Furthermore, tDCS significantly decreased motivation to drink ethanol on a progressive ratio schedule (30% decrease). Taken together, our results show a dissociation between the effects of tDCS on “liking” (hedonic aspect; no effect in the CPP) and “wanting” (motivation; decreased consumption on a progressive ratio schedule). Our tDCS procedure in rodents will allow us to better understand its mechanisms of action in order to accelerate its use as a complementary and innovative tool to help alcohol-dependent patients maintain abstinence or reduce ethanol intake.

Transcranial Electrical Stimulation for Psychiatric Disorders in Adults: A Primer

Transcranial electrical stimulation (tES) comprises noninvasive neuromodulation techniques that deliver low-amplitude electrical currents to targeted brain regions with the goal of modifying neural activities. Expanding evidence from the past decade, specifically using transcranial direct current simulation and transcranial alternating current stimulation, presents promising applications of tES as a treatment for psychiatric disorders. In this review, the authors discuss the basic technical aspects and mechanisms of action of tES in the context of clinical research and practice and review available evidence for its clinical use, efficacy, and safety. They also review recent advancements in use of tES for the treatment of depressive disorders, schizophrenia, substance use disorders, and obsessive-compulsive disorder. Findings largely support growing evidence for the safety and efficacy of tES in the treatment of patients with resistance to existing treatment options, particularly demonstrating promising treatment outcomes for depressive disorders. Future directions of tES research for optimal application in clinical settings are discussed, including the growing home-based, patient-friendly methods and the potential pairing with existing pharmacological or psychotherapeutic treatments for enhanced outcomes. Finally, neuroimaging advancements may provide more specific mapping of brain networks, aiming at more precise tES therapeutic targeting in the treatment of psychiatric disorders.

The neurobiology of drug addiction: cross-species insights into the dysfunction and recovery of the prefrontal cortex

A growing preclinical and clinical body of work on the effects of chronic drug use and drug addiction has extended the scope of inquiry from the putative reward-related subcortical mechanisms to higher-order executive functions as regulated by the prefrontal cortex. Here we review the neuroimaging evidence in humans and non-human primates to demonstrate the involvement of the prefrontal cortex in emotional, cognitive, and behavioral alterations in drug addiction, with particular attention to the impaired response inhibition and salience attribution (iRISA) framework. In support of iRISA, functional and structural neuroimaging studies document a role for the prefrontal cortex in assigning excessive salience to drug over non-drug-related processes with concomitant lapses in self-control, and deficits in reward-related decision-making and insight into illness. Importantly, converging insights from human and non-human primate studies suggest a causal relationship between drug addiction and prefrontal insult, indicating that chronic drug use causes the prefrontal cortex damage that underlies iRISA while changes with abstinence and recovery with treatment suggest plasticity of these same brain regions and functions. We further dissect the overlapping and distinct characteristics of drug classes, potential biomarkers that inform vulnerability and resilience, and advancements in cutting-edge psychological and neuromodulatory treatment strategies, providing a comprehensive landscape of the human and non-human primate drug addiction literature as it relates to the prefrontal cortex.

Noninvasive Brain Stimulation for Nicotine Dependence in Schizophrenia: A Mini Review

Individuals with schizophrenia are 10 times more likely to have a tobacco use disorder than the general population. Up to 80% of those with schizophrenia smoke tobacco regularly, a prevalence three-times that of the general population. Despite the striking prevalence of tobacco use in schizophrenia, current treatments are not tailored to the pathophysiology of this population. There is growing support for use of noninvasive brain stimulation (NIBS) to treat substance use disorders (SUDs), particularly for tobacco use in neurotypical smokers. NIBS interventions targeting the dorsolateral prefrontal cortex have been effective for nicotine dependence in control populations-so much so that transcranial magnetic stimulation is now FDA-approved for smoking cessation. However, this has not borne out in the studies using this approach in schizophrenia. We performed a literature search to identify articles using NIBS for the treatment of nicotine dependence in people with schizophrenia, which identified six studies. These studies yielded mixed results. Is it possible that nicotine has a unique effect in schizophrenia that is different than its effect in neurotypical smokers? Individuals with schizophrenia may receive additional benefit from nicotine's pro-cognitive effects than control populations and may use nicotine to improve brain network abnormalities from their illness. Therefore, clinical trials of NIBS interventions should test a schizophrenia-specific target for smoking cessation. We propose a generalized approach whereby schizophrenia-specific brain circuitry related to SUDs is be identified and then targeted with NIBS interventions.

Noninvasive brain stimulation of addiction: one target for all?

Noninvasive brain stimulation includes repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), and emerges as a prospective approach for addiction treatment in clinical practices. The dorsolateral prefrontal cortex (DLPFC) is regarded as the most effective stimulation target, giving its important position in controlling cue-elicited drug craving and initiating drug abuse. In this paper, through literature searches (e.g. Pubmed, Google Scholar), 34 studies (2003-2021) were identified examining the effect of rTMS, tDCS on cravings, and consumption of substance use disorders, including tobacco, alcohol, opioids, and stimulants. We summarize the main methods, designs, and effects of rTMS or tDCS that are delivered to the DLPFC on different types of addiction. We conclude that targeting DLPFC might be effective for all types of drug addiction.

Transcranial direct current stimulation of the prefrontal cortex reduces cigarette craving in not motivated to quit smokers: A randomized, sham-controlled study

Transcranial direct current stimulation (tDCS) over the dorsolaterateral prefrontal cortex (DLPFC) has been indicated as a promising treatment for several addictions, while its contribution for smoking cessation was less investigated. In particular, the role of motivation to quit and the nicotine dependence level as possible mediators of tDCS effect needs to be deepened. In the present study, we recruited twenty smokers who did not look for a treatment to quit: most of them presented a mild level of nicotine addiction, and they were randomly assigned to active or sham group for receiving bilateral tDCS over the DLPFC. tDCS was provided for five consecutive days with anode over the right hemisphere: in the first and the last day the craving level was evaluated through a specific evoking procedure, and the daily cigarette consumption was recorded. Results showed that the active tDCS decreased by about 50% the cigarette craving, while the number of cigarettes smoked remained unchanged and no differences emerged in the sham group. The present study indicates the tDCS of the DLPFC as a possible treatment for smoking addiction because of its effectiveness in reducing craving. Further, as we recruited smokers with no motivation to quit, and the nicotine dependence level was a moderator of the tDCS effect, we suggest that its efficacy might be even greater in the severe smokers looking for a treatment.

Bilateral transcranial direct current stimulation attenuated symptoms of alcohol use disorder: A systematic review and meta-analysis

BACKGROUND

Alcohol use disorder is one of the common substance use disorders leading to mental and health problems. Despite the potential positive effects of transcranial direct current stimulation (tDCS) on symptoms of various substance use disorder, how specific tDCS protocols effectively influence on individuals with alcohol use disorder is still controversial. This systematic review and meta-analysis investigated beneficial effects of tDCS on symptoms of alcohol use disorder.

METHOD

Eighteen total studies met our inclusion criteria, and we used 25 total comparisons from the qualified studies for the data synthesis. We estimated effect sizes by quantifying changes in alcohol craving and consumption between active tDCS protocol and sham groups. In addition, three moderator variable analyses determined whether tDCS effects on symptoms of alcohol use disorder were different based on (a) bilateral versus unilateral tDCS protocols, (b) specific targeted regions, and (c) multiple sessions versus single session of tDCS protocols.

RESULTS

Random-effects model meta-analysis revealed small positive tDCS effects on alcohol craving and consumption. Specifically, bilateral tDCS protocols significantly reduced alcohol craving, and further anodal tDCS on right dorsolateral prefrontal cortex (DLPFC) and cathodal tDCS on left DLPFC revealed significant positive effects. The multiple sessions of tDCS protocols showed better effects on reducing alcohol craving.

CONCLUSIONS

The current findings suggested that bilateral tDCS protocols including anodal tDCS on right DLPFC and cathodal tDCS on left DLPFC with multiple sessions may effectively improve tDCS effects on symptoms of alcohol use disorder.

Reduce Depression and Anxiety in Methadone Users with Transcranial Direct Current Stimulation

Background: Research shows that transcranial direct current stimulation is effective in reducing depression and anxiety. Objectives: This research is aimed at reducing depression and anxiety in methadone users with transcranial direct current stimulation. Methods: This study is a randomized clinical trial with a pretest-posttest. The sample of this study was 60 methadone users who had severe depression and anxiety. Participants were allocated to two experimental (n = 30) and control groups (n = 30). The two regions, F3 (cathode) and F4 (anode) were stimulated with a current of 2 mA for 20 minutes in 10 sessions. Participants were assessed before and after stimulation with Beck’s depression inventory and Berger’s anxiety test. Results: Data analysis showed that tDCS reduced the symptoms of depression and anxiety in methadone users (P < 0.01). Conclusions: It seems that the method of tDCS can reduce the severity of symptoms of depression and anxiety. Therefore, it can be claimed that this intervention can be considered by experts as a complementary intervention along with other psychological and pharmacological treatments.

A double-blind sham-controlled phase 1 clinical trial of tDCS of the dorsolateral prefrontal cortex in cocaine inpatients: Craving, sleepiness, and contemplation to change

Impaired inhibitory control accompanied by enhanced salience attributed to drug-related cues, both associated with function of the dorsolateral prefrontal cortex (dlPFC), are hallmarks of drug addiction, contributing to worse symptomatology including craving. dlPFC modulation with transcranial direct current stimulation (tDCS) previously showed craving reduction in inpatients with cocaine use disorder (CUD). Our study aimed at assessing feasibility of a longer tDCS protocol in CUD (15 versus the common five/10 sessions) and replicability of previous results. In a randomized double-blind sham-controlled protocol, 17 inpatients with CUD were assigned to either a real-tDCS (right anodal/left cathodal) or a sham-tDCS condition for 15 sessions. Following the previous report, primary outcome measures were self-reported craving, anxiety, depression, and quality of life. Secondary measures included sleepiness, readiness to change drug use, and affect. We also assessed cognitive function including impulsivity. An 88% retention rate demonstrated feasibility. Partially supporting the previous results, there was a trend for self-reported craving to decrease in the real-tDCS group more than the sham-group, an effect that would reach significance with 15 subjects per group. Quality of life and impulsivity improved over time in treatment in both groups. Daytime sleepiness and readiness to change drug use showed significant Group × Time interactions whereby improvements were noted only in the real-tDCS group. One-month follow-up suggested transient effects of tDCS on sleepiness and craving. These preliminary results suggest the need for including more subjects to show a unique effect of real-tDCS on craving and examine the duration of this effect. After replication in larger sample sizes, increased vigilance and motivation to change drug use in the real-tDCS group may suggest fortification of dlPFC-supported executive functions.

Transcranial magnetic stimulation and neuroimaging for cocaine use disorder: Review and future directions

Background: Cocaine use disorder (CUD) is a public health problem with limited treatment options and a significant relapse rate. Neuroimaging studies have identified abnormal functional connectivity in individuals with substance use disorders. Neuromodulation has been proposed to target this altered neurocircuitry. Combining TMS with neuroimaging has the potential to inform identification of biomarkers, diagnosis, and treatment.Objectives: We review the literature of transcranial magnetic stimulation (TMS) with neuroimaging for CUD and outline a research path forward whereby TMS can be used to identify brain network features as diagnostic or prognostic biomarkers for treatment.Methods: We reviewed the literature for primary research studies of TMS with neuroimaging for CUD. We searched PubMed using search terms of "cocaine," "transcranial magnetic stimulation," and "neuroimaging." Identified studies were screened by title and abstract. Full-text studies were reviewed for inclusion.Results: In our initial search, we identified 73 studies. Six studies met our inclusion criteria. These studies used rTMS (n = 3) and single or paired pulse TMS (n = 3) and included a total of 289 participants. All studies used fMRI as the neuroimaging modality. The most common outcome measure was craving and cue-reactivity (n = 3).Conclusion: The literature combining TMS with neuroimaging is small and heterogeneous. We propose that combining TMS with neuroimaging will accelerate our understanding of substance use disorder neurobiology and treatment. Once network biomarkers of substance use have been identified, TMS can be used to manipulate the dysfunctional circuits in order to identify a causal relationship between connectivity and psychopathology.

Reduced risk-taking behavior during frontal oscillatory theta band neurostimulation

BACKGROUND

Most of our decisions involve a certain degree of risk regarding the outcomes of our choices. People vary in the way they make decisions, resulting in different levels of risk-taking behavior. These differences have been linked to prefrontal theta band activity. However, a direct functional relationship between prefrontal theta band activity and risk-taking has not yet been demonstrated.

OBJECTIVE

We used noninvasive brain stimulation to test the functional relevance of prefrontal oscillatory theta activity for the regulatory control of risk-taking behavior.

METHODS

In a within-subject experiment, 31 healthy participants received theta (6.5 Hertz [Hz]), gamma (40 Hz), and sham transcranial alternating current stimulation (tACS) over the left prefrontal cortex (lPFC). During stimulation, participants completed a task assessing their risk-taking behavior as well as response times and sensitivity to value and outcome probabilities. Electroencephalography (EEG) was recorded before and immediately after stimulation to investigate possible long-lasting stimulation effects.

RESULTS

Theta band, but not gamma band or sham, tACS led to a significant reduction in risk-taking behavior, indicating a frequency-specific effect of prefrontal brain stimulation on the modulation of risk-taking behavior. Moreover, theta band stimulation led to increased response times and decreased sensitivity to reward values. EEG data analyses did not show an offline increase in power in the stimulated frequencies after the stimulation protocol.

CONCLUSION

These findings provide direct empirical evidence for the effects of prefrontal theta band stimulation on behavioral risk-taking regulation.

The transcranial direct current stimulation over prefrontal cortex combined with the cognitive training reduced the cue-induced craving in female individuals with methamphetamine use disorder: A randomized controlled trial

BACKGROUND

Craving and cognitive deficits are potential treatment targets for methamphetamine use disorder (MUD). Previous studies implied that transcranial direct current stimulation (tDCS) and cognitive training respectively improve these symptoms, but the combined effect is unknown. In this study, we investigated the combined effects of tDCS over dorsolateral prefrontal cortex (DLPFC) and computerized cognitive addiction therapy (CCAT) on cue-induced craving and cognitive functions among female individuals with MUD.

METHODS

Seventy-five patients with MUD were randomly assigned to three groups: CCAT + tDCS group, CCAT + sham tDCS group and the control group. The former two groups received 20 sessions of cognitive training combined 1.5 mA active/sham tDCS over DLPFC (20min/session, 5times/week), while the control group received usual care which includes routine medical care, health education, physical exercises and psychological support related to relapse prevention. The cue-induced craving and cognitive functions were tested at the baseline, the end of 2nd week and 4th week.

RESULTS

The CCAT + tDCS group showed a significant reduction in cue-induced craving after 4-week intervention. Moreover, the craving score of the real CCAT + tDCS group was significantly lower than that of the CCAT + sham tDCS group and that of the control group at the end of 4th week. A significant improvement in accuracy of TWOB task was only observed in the CCAT + tDCS group at the end of 4th week when compared to baseline. Unexpectedly, participants who received CCAT plus active or sham tDCS did not change their discounting, whereas those in the control group performed more impulsively over time.

CONCLUSIONS

The study found that the intervention of tDCS over DLPFC combined with CCAT may have potential benefit in improving treatment outcome in patients with MUD. More research is needed to explore the underlying mechanism.

The two-way relationship between nicotine and cortical activity: a systematic review of neurobiological and treatment aspects

Nicotine intake and cortical activity are closely related, as they can influence each other. Nicotine is implicated in the induction and modification of cortical plasticity and excitability, whereas a change on cortical plasticity and excitability can also lead to a modification of the smoking behaviour of an individual. The aim of this systematic review was, on the one hand, to evaluate the effects of nicotinergic modulation on cortical excitability and plasticity, and, on the other hand, to assess if modifying the brain's excitability and plasticity could influence one's smoking behaviour. Two systematic literature searches in the PubMed/MEDLINE and PsycINFO databases were conducted. Studies focusing either on the impact of nicotinergic modulation on cortical activity or the treatment effect of non-invasive brain stimulation techniques (NIBS) on smoking behaviour were included. A total of 22 studies for the first systematic search and 35 studies for the second one were included after full-text screening. Nicotine's effect on cortical activity appeared to depend on smoking status of the individual. While deprived smokers seem to generally profit from nicotine consumption in terms of cortical excitability and plasticity, the contrary was true for non-smokers. Regarding the questions of how changes in cortical excitability can influence smoking behaviour, a trend points towards NIBS being a potential intervention technique for smoking cessation.

[Transcranial direct current stimulation in neurology and psychiatry]

Transcranial direct current stimulation (tDCS) is a non-invasive method of modulating brain excitability by low intensity direct current. At present, there are numerous studies of tDCS application in various mental and neurological diseases. In this review, the data of tDCS efficiency in the treatment of different disorders are presented and the recommendations on using this method in clinical practice are given.

Efficacy of single-session transcranial direct current stimulation on addiction-related inhibitory control and craving: a randomized trial in males with Internet gaming disorder

BACKGROUND

Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (dlPFC) may reduce substance use and other addictive behaviours. However, the cognitive mechanisms that underpin such effects remain unclear. Impaired inhibitory control linked to hypoactivation of the prefrontal cortex may allow craving-related motivations to lead to compulsive addictive behaviours. However, very few studies have examined whether increasing the activation of the dlPFC via anodal tDCS could enhance inhibitory control over addiction-related distractors. The current study aimed to enrich empirical evidence related to this issue.

METHODS

Thirty-three males with Internet gaming disorder underwent active (1.5 mA for 20 minutes) and sham tDCS 1 week apart, in randomized order. We assessed inhibitory control over gaming-related distractors and craving pre- and post-stimulation.

RESULTS

Relative to sham treatment, active tDCS reduced interference from gaming-related (versus non-gaming) distractors and attenuated background craving, but did not affect cue-induced craving.

LIMITATIONS

This study was limited by its relatively small sample size and the fact that it lacked assessments of tDCS effects on addictive behaviour. Future tDCS studies with multiple sessions in larger samples are warranted to examine the effects on addictive behaviours of alterations in addiction-related inhibitory control.

CONCLUSION

These findings demonstrate that stimulation of the dlPFC influences inhibitory control over addiction-related cues and addiction-related motivation. This is the first empirical study to suggest that enhanced inhibitory control may be a cognitive mechanism underlying the effects of tDCS on addictions like Internet gaming disorder. Our finding of attenuated background craving replicated previous tDCS studies. Intriguingly, our finding of distinct tDCS effects on 2 forms of craving suggests that they may have disparate underlying mechanisms or differential sensitivity to tDCS.

CLINICAL TRIALS #

NCT03352973.

Multi-session electrical neuromodulation effects on craving, relapse and cognitive functions in cocaine use disorder: A randomized, sham-controlled tDCS study

BACKGROUND

The use of transcranial Direct Current Stimulation (tDCS) has previously shown promising results for reducing craving in cocaine use disorder. In this study we further explored the potential of tDCS as add-on intervention in the treatment of cocaine use disorder.

METHODS

In a randomized, placebo-controlled, between subject study, we applied tDCS bilaterally with the anodal electrode targeting the right dorsolateral prefrontal cortex (DLPFC; https://clinicaltrials.gov/ct2/show/NCT03025321). Patients with cocaine use disorder were allocated to ten sessions of either active tDCS (n = 29) or sham (n = 30) on five consecutive days. Inhibitory control and risky decision-making were measured via a Go-NoGo task and a two-choice gambling task, respectively, each at baseline, one day after all tDCS sessions and after three months. Relapse at follow-up and craving were also assessed.

RESULTS

There was no significant effect of active tDCS on the number of cocaine use days and craving. Relapse was frequent among patients who had received either active or sham tDCS (48.0 % and 69.2 %, respectively), despite an overall decrease in craving during the first two weeks of treatment. No effects were found on cognitive functions. An exploratory analysis for crack cocaine use only revealed that relapse rates were significantly reduced after active tDCS (n = 17) as compared to sham (n = 19).

CONCLUSIONS

No beneficial effects of tDCS on number of cocaine use days, craving and cognitive functions were found in the present study, but somewhat promising results were obtained regarding relapse rates among crack-cocaine users specifically. Further research is required to determine the efficacy of tDCS as a complementary treatment in cocaine use disorder.

Eye tracking of smoking-related stimuli in tobacco use disorder: A proof-of-concept study combining attention bias modification with alpha-transcranial alternating current stimulation

BACKGROUND

Tobacco use disorder (TUD) is characterized by the presence of an attentional bias (AB) towards smoking-related stimuli. We investigated whether combining an AB modification paradigm (ABM) with transcranial alternating current stimulation (tACS) applied over the dorsolateral prefrontal cortex (DLPFC) reduces the AB towards smoking-related stimuli, as well as craving level and impulsive choices.

METHODS

In a sham-controlled, crossover preliminary study, 19 subjects with TUD received two stimulation arms: 1) active tACS (10 Hz, 2 mA, 30 min) combined with ABM and 2) sham tACS combined with ABM, in a randomized order, separated by one week. AB towards smoking cues during passive observation of smoking and neutral cues was assessed with an eye-tracking device and reactions times at a visual-probe task. Craving level was measured with the Questionnaire of Smoking Urges. Impulsive choices were assessed with the delay discounting task.

RESULTS

Active tACS combined with ABM reduced the amount of time spent looking at smoking-related pictures (p = 0.03), prevented the increase of self-reported desire to smoke (p = 0.026), and reduced the proportion of impulsive choices (p = 0.049), compared to sham tACS combined with ABM. No significant effects were reported on other craving dimensions and on AB based on reaction times.

CONCLUSIONS

These preliminary findings suggest that combining tACS with ABM may help smokers who wish to quit by reducing the desire to smoke, attention to smoking-cues, and impulsive decision-making.

A Meta-Analysis of Transcranial Direct Current Stimulation on Substance and Food Craving: What Effect Do Modulators Have?

Substance addiction and food addiction are significant social problems worldwide. In previous studies of substance addiction, transcranial direct current stimulation (tDCS) has been used to influence craving of substance or food. However, the reported effects are not always consistent due to inconsistent experimental settings. The way modulators influence the effect of tDCS on substance addiction is worth exploring. This meta-analysis was conducted to estimate the effect size of tDCS on substance and food craving and to investigate the influence of potential modulators. We systemically identified and reviewed studies on substance/food craving using tDCS that were published between January 2008 to January 2020. A total of 32 eligible studies were identified. Hedges' g was computed as an indicator of the effect of tDCS and some potential moderators (substance type, stimulation sites, current intensities, number of sessions, duration of stimulation, and study design) were examined using subgroup analysis. Random effects analysis revealed a total medium effect size [Hedges' g = 0.536, 95% confidence interval (CI): 0.389-0.683, after adjusting Hedges' g = 0.416, 95% CI: 0.262-0.570] preferring active over sham stimulation to reduce craving. A significant difference was observed between the number of sessions (repeated stimulation was better than single stimulation). The duration of stimulation may have a positive influence on the effects of tDCS. No other significant differences were found in other subgroups analysis. In conclusion, our results provided evidence that tDCS can be an effective way to reduce craving of substance or food, and longer multiple stimulus durations in all can more effectively reduce craving; however, the influences of modulators still need be to be examined in depth in future.

No effect of repetitive tDCS on daily smoking behaviour in light smokers: A placebo controlled EMA study

Introduction

The effectiveness of repetitive transcranial Direct Current Stimulation (tDCS) on reducing smoking behaviour has been studied with mixed results. Smoking behaviour is influenced by affect and context, therefore we choose to use mobile ecological momentary assessments (EMA) to measure changes in smoking behaviour after tDCS.

Methods

In a randomized, placebo-controlled, between subject study, we applied tDCS bilaterally with the anodal electrode targeting the right DLPFC (https://clinicaltrials.gov/ct2/show/NCT03027687). Smokers were allocated to six sessions of either active tDCS (n = 35) or sham tDCS (n = 36) and received two sessions on three different days in one week. They were asked to keep track of their daily cigarette consumption, craving and affect in an application on their mobile phones for three months starting one week before the first tDCS session.

Results

Number of smoked cigarettes a day progressively decreased up to one week after the last tDCS session in both conditions. Active treatment had no additional effect on cigarette consumption, craving and affect.

Conclusions

In this exploratory study, repetitive bilateral tDCS over the DLPFC had no effect on daily smoking behaviour. Future research needs to investigate how motivation to quit smoking and the number of tDCS sessions affect the efficacy of repetitive tDCS.

Can transcranial direct current stimulation (tDCS) improve impulsivity in healthy and psychiatric adult populations? A systematic review

Impulsivity is a multidimensional phenomenon that remains hard to define. It compounds the core pathological construct of many neuropsychiatric illnesses, and despite its close relation to suicide risk, it currently has no specific treatment. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique whose application results in cognitive function improvement, both in healthy and psychiatric populations. Following PRISMA recommendations, a systematic review of the literature concerning tDCS's effects on impulsive behaviour was performed using the PubMed database. The research was based on the combination of the keyword 'tDCS' with 'impulsivity', 'response inhibition', 'risk-taking', 'planning', 'delay discounting' or 'craving'. The initial search yielded 309 articles, 92 of which were included. Seventy-four papers demonstrated improvement in task performance related to impulsivity in both healthy and clinical adult populations. However, results were often inconsistent. The conditions associated with improvement, such as tDCS parameters and other aspects that may influence tDCS's outcomes, are discussed. The overall effects of tDCS on impulsivity are promising. Yet further research is required to develop a more comprehensive understanding of impulsivity, allowing for a more accurate assessment of its behavioural outcomes as well as a definition of tDCS therapeutic protocols for impulsive disorders.

Supervised transcranial direct current stimulation (tDCS) at home: A guide for clinical research and practice

BACKGROUND

Transcranial direct current stimulation (tDCS) is a method of noninvasive neuromodulation and potential therapeutic tool to improve functioning and relieve symptoms across a range of central and peripheral nervous system conditions. Evidence suggests that the effects of tDCS are cumulative with consecutive daily applications needed to achieve clinically meaningful effects. Therefore, there is growing interest in delivering tDCS away from the clinic or research facility, usually at home.

OBJECTIVE

To provide a comprehensive guide to operationalize safe and responsible use of tDCS in home settings for both investigative and clinical use.

METHODS

Providing treatment at home can improve access and compliance by decreasing the burden of time and travel for patients and their caregivers, as well as to reach those in remote locations and/or living with more advanced disabilities.

RESULTS

To date, methodological approaches for at-home tDCS delivery have varied. After implementing the first basic guidelines for at-home tDCS in clinical trials, this work describes a comprehensive guide for facilitating safe and responsible use of tDCS in home settings enabling access for repeated administration over time.

CONCLUSION

These guidelines provide a reference and standard for practice when employing the use of tDCS outside of the clinic setting.

Transcranial Direct Current Stimulation Applied to the Dorsolateral and Ventromedial Prefrontal Cortices in Smokers Modifies Cognitive Circuits Implicated in the Nicotine Withdrawal Syndrome

BACKGROUND

The nicotine withdrawal syndrome remains a major impediment to smoking cessation. Cognitive and affective disturbances are associated with altered connectivity within and between the executive control network, default mode network (DMN), and salience network. We hypothesized that functional activity in cognitive control networks, and downstream amygdala circuits, would be modified by application of transcranial direct current stimulation (tDCS) to the left (L) dorsolateral prefrontal cortex (dlPFC, executive control network) and right (R) ventromedial prefrontal cortex (vmPFC, DMN).

METHODS

A total of 15 smokers (7 women) and 28 matched nonsmokers (14 women) participated in a randomized, sham-controlled, double-blind, exploratory crossover study of 3 tDCS conditions: anodal-(L)dlPFC/cathodal-(R)vmPFC, reversed polarity, and sham. Cognitive tasks probed withdrawal-related constructs (error monitoring, working memory, amygdalar reactivity), while simultaneous functional magnetic resonance imaging measured brain activity. We assessed tDCS impact on trait (nonsmokers vs. sated smokers) and state (sated vs. abstinent) smoking aspects.

RESULTS

Single-session, anodal-(L)dlPFC/cathodal-(R)vmPFC tDCS enhanced deactivation of DMN nodes during the working memory task and strengthened anterior cingulate cortex activity during the error-monitoring task. Smokers were more responsive to tDCS-induced DMN deactivation when sated (vs. withdrawn) and displayed greater cingulate activity during error monitoring than nonsmokers. Nicotine withdrawal reduced task engagement and attention and reduced suppression of DMN nodes.

CONCLUSIONS

Cognitive circuit dysregulation associated with nicotine withdrawal may be modifiable by anodal tDCS applied to L-dlPFC and cathodal tDCS applied to R-vmPFC. tDCS may have stronger effects as a complement to existing therapies, such as nicotine replacement, owing to possible enhanced plasticity in the sated state.

Transcranial Direct Current Stimulation to Improve the Dysfunction of Descending Pain Modulatory System Related to Opioids in Chronic Non-cancer Pain: An Integrative Review of Neurobiology and Meta-Analysis

Background: Opioid long-term therapy can produce tolerance, opioid-induced hyperalgesia (OIH), and it induces dysfunction in pain descending pain inhibitory system (DPIS). Objectives: This integrative review with meta-analysis aimed: (i) To discuss the potential mechanisms involved in analgesic tolerance and opioid-induced hyperalgesia (OIH). (ii) To examine how the opioid can affect the function of DPIS. (ii) To show evidence about the tDCS as an approach to treat acute and chronic pain. (iii) To discuss the effect of tDCS on DPIS and how it can counter-regulate the OIH. (iv) To draw perspectives for the future about the tDCS effects as an approach to improve the dysfunction in the DPIS in chronic non-cancer pain. Methods: Relevant published randomized clinical trials (RCT) comparing active (irrespective of the stimulation protocol) to sham tDCS for treating chronic non-cancer pain were identified, and risk of bias was assessed. We searched trials in PubMed, EMBASE and Cochrane trials databases. tDCS protocols accepted were application in areas of the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), or occipital area. Results: Fifty-nine studies were fully reviewed, and 24 with moderate to the high-quality methodology were included. tDCS improved chronic pain with a moderate effect size [pooled standardized mean difference; -0.66; 95% confidence interval (CI) -0.91 to -0.41]. On average, active protocols led to 27.26% less pain at the end of treatment compared to sham [95% CI; 15.89-32.90%]. Protocol varied in terms of anodal or cathodal stimulation, areas of stimulation (M1 and DLPFC the most common), number of sessions (from 5 to 20) and current intensity (from 1 to 2 mA). The time of application was 20 min in 92% of protocols. Conclusion: In comparison with sham stimulation, tDCS demonstrated a superior effect in reducing chronic pain conditions. They give perspectives that the top-down neuromodulator effects of tDCS are a promising approach to improve management in refractory chronic not-cancer related pain and to enhance dysfunctional neuronal circuitries involved in the DPIS and other pain dimensions and improve pain control with a therapeutic opioid-free. However, further studies are needed to determine individualized protocols according to a biopsychosocial perspective.

The Effects of Transcranial Direct Current Stimulation of Dorsolateral Prefrontal Cortex on Reduction of Craving in Daily and Social Smokers

Objective: Tobacco smoking is an addictive behavior with many psychological side effects, and many smokers are unable to quit it. Despite various treatments for smoking cessation, there is an urgent need to develop and utilize a noninvasive technique with high efficacy. This study aimed to determine the effects of transcranial direct current stimulation (tDCS) of dorsolateral prefrontal cortex (DLPFC) on reduction of craving in daily and social smokers. Method : This pretest-posttest quasi-experimental study, in which the participants were randomly assigned into sham and active groups, was performed on 40 daily and social smokers. Stimulation was delivered over the left DLPFC at a 2 m/A during 10 twenty-minute sessions for 5 weeks. The participants filled out the Desire for Drug questionnaire (DDQ) before and after intervention. Analysis of covariance was used for data analysis. Results: A significant decrease was found in the number of cigarette smoking in both daily and social smokers compared to the sham group. Moreover, the results indicated that anodal tDCS on F3 and Cathodal tDCS on F4 has significant effects on nicotine craving (P < 0/000). Conclusion: The results of the present study showed that the current tDCS of DLPFC decreases the craving of smoking. This noninvasive brain stimulation technique targeted at DLPFC area may be a promising method for reducing and treating smoking craving.

Transcranial Direct Current Stimulation Over Dorsolateral Prefrontal Cortex Modulates Risk-Attitude in Motor Decision-Making

Humans often face situations requiring a decision about where to throw an object or when to respond to a stimulus under risk. Several behavioral studies have shown that such motor decisions can be suboptimal, which results from a cognitive bias toward risk-seeking behavior. However, brain regions involved in risk-attitude of motor decision-making remain unclear. Here, we investigated the role of the dorsolateral prefrontal cortex (DLPFC) in risky motor decisions using transcranial direct current stimulation (tDCS). The experiment comprised a selective timing task requiring participants to make a continuous decision about the timing of their response under the risk of no rewards. The participants performed this task twice in a day: before and while receiving either anodal stimulation over the right DLPFC with cathodal stimulation over the left DLPFC (20 min, 2 mA), cathodal stimulation over the right DLPFC with anodal stimulation over the left DLPFC, or sham stimulation. In line with previous studies, their strategies before the stimulation were biased toward risk-seeking. During anodal stimulation over right DLPFC with cathodal stimulation over left DLPFC, participants showed a more conservative strategy to avoid the risk of no rewards. The additional experiment confirmed that tDCS did not affect the ability of timing control regarding the time intervals at which they aimed to respond. These results suggest a potential role for the DLPFC in modulating action selection in motor decision-making under risk.