Effects of non-invasive neurostimulation on craving: a meta-analysis

Pilot study with randomised control of dual site theta burst transcranial magnetic stimulation (TMS) for methamphetamine use disorder: a protocol for the TARTAN study

BACKGROUND

Transcranial magnetic stimulation (TMS) (including the theta burst stimulation (TBS) form of TMS used in this study) is a non-invasive means to stimulate nerve cells in superficial areas of the brain. In recent years, there has been a growth in the application of TMS to investigate the modulation of neural networks involved in substance use disorders. This study examines the feasibility of novel TMS protocols for the treatment of methamphetamine (MA) use disorder in an ambulatory drug and alcohol treatment setting.

METHODS

Thirty participants meeting the criteria for moderate to severe MA use disorder will be recruited in community drug and alcohol treatment settings and randomised to receive active TMS or sham (control) intervention. The treatment is intermittent TBS (iTBS) applied to the left dorsolateral prefrontal cortex (DLPFC), then continuous TBS (cTBS) to the left orbitofrontal cortex (OFC). Twelve sessions are administered over 4 weeks with opt-in weekly standardized cognitive behaviour therapy (CBT) counselling and a neuroimaging sub-study offered to participants. Primary outcomes are feasibility measures including recruitment, retention and acceptability of the intervention. Secondary outcomes include monitoring of safety and preliminary efficacy data including changes in substance use, cravings (cue reactivity) and cognition (response inhibition).

DISCUSSION

This study examines shorter TBS protocols of TMS for MA use disorder in real-world drug and alcohol outpatient settings where withdrawal and abstinence from MA, or other substances, are not eligibility requirements. TMS is a relatively affordable treatment and staff of ambulatory health settings can be trained to administer TMS. It is a potentially scalable and translatable treatment for existing drug and alcohol clinical settings. TMS has the potential to provide a much-needed adjuvant treatment to existing psychosocial interventions for MA use disorder. A limitation of this protocol is that the feasibility of follow-up is only examined at the end of treatment (4 weeks).

TRIAL REGISTRATION

Australia New Zealand Clinical Trial Registry ACTRN12622000762752. Registered on May 27, 2022, and retrospectively registered (first participant enrolled) on May 23, 2022, with protocol version 7 on February 24, 2023.

Non-invasive suppression of the human nucleus accumbens (NAc) with transcranial focused ultrasound (tFUS) modulates the reward network: a pilot study

Background

The nucleus accumbens (NAc) is a key node of the brain reward circuit driving reward-related behavior. Dysregulation of NAc has been demonstrated to contribute to pathological markers of addiction in substance use disorder (SUD) making it a potential therapeutic target for brain stimulation. Transcranial focused ultrasound (tFUS) is an emerging non-invasive brain stimulation approach that can modulate deep brain regions with a high spatial resolution. However, there is currently no evidence showing how the brain activity of NAc and brain functional connectivity within the reward network neuromodulated by tFUS on the NAc.

Methods

In this pilot study, we carried out a single-blind, sham-controlled clinical trial using functional magnetic resonance imaging (fMRI) to investigate the underlying mechanism of tFUS neuromodulating the reward network through NAc in ten healthy adults. Specifically, the experiment consists of a 20-min concurrent tFUS/fMRI scan and two 24-min resting-state fMRI before and after the tFUS session.

Results

Firstly, our results demonstrated the feasibility and safety of 20-min tFUS on NAc. Additionally, our findings demonstrated that bilateral NAc was inhibited during tFUS on the left NAc compared to sham. Lastly, increased functional connectivity between the NAc and medial prefrontal cortex (mPFC) was observed after tFUS on the left NAc, but no changes for the sham group.

Conclusion

Delivering tFUS to the NAc can modulate brain activations and functional connectivity within the reward network. These preliminary findings suggest that tFUS could be potentially a promising neuromodulation tool for the direct and non-invasive management of the NAc and shed new light on the treatment for SUD and other brain diseases that involve reward processing.

Case Reports of Binge Eating Patterns in the Recovery Phase of Anorexia Nervosa Patients With and Without Food Addiction

Food addiction refers to a condition in which individuals exhibit addictive-like behaviors toward food, like those observed in substance abuse. Although still debated, evidence supporting the validity and usefulness of the concept of food addiction is growing. Food addiction is particularly associated with obesity and eating disorders involving binge eating. This study discusses the cases of two adolescent patients who presented with anorexia nervosa. During the recovery phase of anorexia nervosa, binge eating was observed, and the patterns of binge eating significantly differed between patients, with and without food addiction. Therefore, healthcare professionals treating eating disorders should be aware of food addiction and modify their treatment strategies accordingly.

Targeting cravings in substance addiction with transcranial direct current stimulation: insights from a meta-analysis of sham-controlled trials

Addiction is a substantial health concern; craving-the core symptom of addiction-is strongly associated with relapse. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that reduces cravings by altering cortical excitability and connectivity in brain regions. This systematic review and meta-analysis was conducted (following the PRISMA guidelines) to evaluate the efficacy of tDCS in reducing cravings for substances. Our analysis included 43 randomized, sham-controlled trials involving 1,095 and 913 participants receiving tDCS and sham stimulation, respectively. We analyzed the changes in craving scores and found that tDCS led to a moderate reduction in cravings compared with the sham effects. This effect was particularly pronounced when bilateral stimulation was used, the anodal electrode was placed on the right dorsolateral prefrontal cortex, current intensities ranged from 1.5 to 2 mA, stimulation sessions lasted 20 minutes, and the electrodes size was ≥35 cm². Notably, tDCS effectively reduced cravings for opioids, methamphetamine, cocaine, and tobacco but not for alcohol or cannabis. Our findings indicate tDCS as a promising, noninvasive, and low-risk intervention for reducing cravings for opioids, methamphetamine, cocaine, and tobacco. Additional studies are warranted to refine stimulation parameters and evaluate the long-term efficacy of tDCS in managing substance cravings.

Brain and cortisol responses to smoking cues are linked in tobacco-smoking individuals

Cues associated with smoking can induce relapse, which is likely driven by cue-induced neurobiological and physiological mechanisms. For instance, greater relapse vulnerability is associated with increases in cue-induced insula activation and heightened cortisol concentrations. Determining if there is a link between such cue-induced responses is critical given the need for biomarkers that can be easily measured in clinical settings and used to drive targeted treatment. Further, comprehensively characterising biological reactions to cues promises to aid in the development of therapies that address this specific relapse risk factor. To determine whether brain and cortisol responses to smoking cues are linked, this study recruited 27 nicotine-dependent tobacco-smoking individuals and acquired whole-brain functional activation during a cue reactivity task; salivary cortisol was measured before and after scanning. The results showed that increases in blood-oxygen-level-dependent activation in the right anterior insula and right dorsolateral prefrontal cortex (DLPFC) when viewing smoking versus neutral cues were positively correlated with a post-scan rise in salivary cortisol concentrations. These brain regions have been previously implicated in substance use disorders for their role in salience, interoception and executive processes. These findings show that those who have a rise in cortisol following smoking cue exposure also have a related rise in cue-induced brain reactivity, in brain regions previously linked with heightened relapse vulnerability. This is clinically relevant as measuring cue-induced cortisol responses is a more accessible proxy for assessing the engagement of cue-induced neurobiological processes associated with the maintenance of nicotine dependence.

Approach-Bias Retraining and Other Training Interventions as Add-On in the Treatment of AUD Patients

In the past two decades, a variety of cognitive training interventions have been developed to help people overcome their addictive behaviors. Conceptually, it is important to distinguish between programs in which reactions to addiction-relevant cues are trained (varieties of cognitive bias modification, CBM) and programs in which general abilities are trained such as working memory or mindfulness. CBM was first developed to study the hypothesized causal role in mental disorders: by directly manipulating the bias, it was investigated to what extent this influenced disorder-relevant behavior. In these proof-of-principle studies, the bias was temporarily modified in volunteers, either temporarily increased or decreased, with corresponding effects on behavior (e.g., beer consumption), in case the bias was successfully manipulated. In subsequent clinical randomized controlled trials (RCTs), training (away from the substance vs. sham training) was added to clinical treatment. These studies have demonstrated that CBM, as added to treatment, reduces relapse with a small effect of about 10% (similar effect size as for medication, with the strongest evidence for approach-bias modification). This has not been found for general ability training (e.g., working memory training), although effects on other psychological functions have been found (e.g., impulsivity). Mindfulness also has been found to help people overcome addictions, and different from CBM, also as stand-alone intervention. Research on (neuro-)cognitive mechanisms underlying approach-bias modification has pointed to a new perspective in which automatic inferences rather than associations are influenced by training, which has led to the development of a new variety of training: ABC training.

Anodal stimulation of inhibitory control and craving in satiated restrained eaters

OBJECTIVES

Eating and weight disorders are severe and complex clinical conditions which, among other behaviors, include (attempts at) restrained eating, food avoidance, following dietary rules, and overeating. Comparable to women with obesity, restrained eaters (RE) without formal eating disorder diagnosis are worse at inhibiting their motor responses than unrestrained eaters (URE). According to neuroimaging studies, the right inferior frontal gyrus (rIFG) is involved in inhibitory control which, in turn, could be improved by neuromodulation such as anodal transcranial direct current stimulation (tDCS) across rIFG.

METHODS

This double-blind sham-controlled cross-over study was conducted after a standardized breakfast. Normal-weight female RE und URE performed a stop-signal task (SST) with food and non-food stimuli during sham or anodal tDCS. Food craving, hunger, and satiety were self-reported before and after tDCS. We employed a mixed between-subjects (group: RE vs. URE) and within-subjects factorial design (tDCS: anodal tDCS vs. sham; stimuli: food vs. control pictures).

RESULTS

Breakfast consumption was comparable for RE and URE, as well as craving, hunger, and thirst. Regarding inhibitory control, a significant two-way interaction between group and tDCS ermerged: RE had longer stop-signal reaction times (SSRTs) during sham tDCS, but they improved to the level of URE by application of anodal tDCS.

DISCUSSION

Results replicated an inhibitory control deficit in RE with longer SSRTs compared to URE without stimulation. During anodal tDCS to the rIFG, reduced SSRTs in RE indicated an improvement in inhibitory control. The findings suggest a specificity of rIFG stimulation in at-risk groups with regards to inhibitory control irrespective of craving.

Betting on Non-Invasive Brain Stimulation to Treat Gambling Disorder: A Systematic Review and Meta-Analysis

Gambling disorder (GD) is a behavioral addiction that severely impacts individuals' functioning, leading to high socioeconomic costs. Non-invasive brain stimulation (NiBS) has received attention for treating psychiatric and neurological conditions in recent decades, but there is no recommendation for its use for GD. Therefore, this study aimed to systematically review and analyze the available literature to determine the effectiveness of NiBS in treating GD. Following the PRISMA guidelines, we screened four electronic databases up to July 2022 and selected relevant English-written original articles. We included ten papers in the systematic review and seven in the meta-analysis. As only two studies employed a sham-controlled design, the pre-post standardized mean change (SMCC) was computed as effect size only for real stimulation. The results showed a significant effect of NiBS in reducing craving scores (SMCC = -0.69; 95% CI = [-1.2, -0.2], p = 0.010). Moreover, considering the GD's frequent comorbidity with mood disorders, we ran an exploratory analysis of the effects of NiBS on depressive symptoms, which showed significant decreases in post-treatment scores (SMCC = -0.71; 95% CI = [-1.1, -0.3], p < 0.001). These results provide initial evidence for developing NiBS as a feasible therapy for GD symptoms but further comprehensive research is needed to validate these findings. The limitations of the available literature are critically discussed.

Mid-Luteal Progesterone Is Inversely Associated with Premenstrual Food Cravings

It is not clear whether progesterone and estradiol associate with premenstrual food cravings, which significantly contribute to cardiometabolic adverse effects associated with obesity. We sought to investigate this question in the present study based on the prior literature showing a protective effect of progesterone on drug craving and extensive neurobiological overlaps between food and drug cravings. We enrolled 37 non-illicit drug- or medication-using women in the study to provide daily ratings of premenstrual food cravings and other symptoms across two-three menstrual cycles, based on which we classified them as premenstrual dysphoric disorder (PMDD) or control participants. In addition, the participants provided blood samples at eight clinic visits across the menstrual cycle. We aligned their mid-luteal progesterone and estradiol using a validated method which relies upon the peak serum luteinizing hormone and analyzed estradiol and progesterone using ultraperformance liquid chromatography tandem mass spectrometry. Hierarchical modeling, adjusted for BMI, showed a significant inverse effect of progesterone (p = 0.038) but no effect of estradiol on premenstrual food cravings. The association was not unique to PMDD or control participants. Results of research to date in humans and rodents showing that progesterone has dampening effects on the salience of the reinforcer translate to premenstrual food cravings.

Effects of prefrontal theta burst stimulation on neuronal activity and subsequent eating behavior: an interleaved rTMS and fNIRS study

The dorsolateral prefrontal cortex (dlPFC) and dorsomedial prefrontal cortex (dmPFC) are both important nodes for self-control and decision-making but through separable processes (cognitive control vs evaluative processing). This study aimed to examine the effects of excitatory brain stimulation [intermittent theta burst stimulation (iTBS)] targeting the dlPFC and dmPFC on eating behavior. iTBS was hypothesized to decrease consumption of appetitive snack foods, via enhanced interference control for dlPFC stimulation and reduced delay discounting (DD) for dmPFC stimulation. Using a single-blinded, between-subjects design, participants (N = 43) were randomly assigned to one of three conditions: (i) iTBS targeting the left dlPFC, (ii) iTBS targeting bilateral dmPFC or (iii) sham. Participants then completed two cognitive tasks (DD and Flanker), followed by a bogus taste test. Functional near-infrared spectroscopy imaging revealed that increases in the medial prefrontal cortex activity were evident in the dmPFC stimulation group during the DD task; likewise, a neural efficiency effect was observed in the dlPFC stimulation group during the Flanker. Gender significantly moderated during the taste test, with females in the dmPFC showing paradoxical increases in food consumption compared to sham. Findings suggest that amplification of evaluative processing may facilitate eating indulgence when preponderant social cues are permissive and food is appetitive.

Transcranial direct current stimulation (tDCS) to dorsolateral prefrontal cortex influences perceived pleasantness of food

The ability to regulate the intake of unhealthy foods is critical in modern, calorie dense food environments. Frontal areas of the brain, such as the dorsolateral prefrontal cortex (DLPFC), are thought to play a central role in cognitive control and emotional regulation. Therefore, increasing activity in the DLPFC may enhance these functions which could improve the ability to reappraise and resist consuming highly palatable but unhealthy foods. One technique for modifying brain activity is transcranial direct current stimulation (tDCS), a non-invasive technique for modulating neuronal excitability that can influence performance on a range of cognitive tasks. We tested whether anodal tDCS targeting the right DLPFC would influence how people perceived highly palatable foods. In the present study, 98 participants were randomly assigned to receive a single session of active tDCS (2.0 mA) or sham stimulation. While receiving active or sham stimulation, participants viewed images of highly palatable foods and reported how pleasant it would be to eat each food (liking) and how strong their urge was to eat each food (wanting). We found that participants who received active versus sham tDCS stimulation perceived food as less pleasant, but there was no difference in how strong their urge was to eat the foods. Our findings suggest that modulating excitability in the DLPFC influences "liking" but not "wanting" of highly palatable foods. Non-invasive brain stimulation might be a useful technique for influencing the hedonic experience of eating but more work is needed to understand when and how it influences food cravings.

Effects of 10 add-on HF-rTMS treatment sessions on alcohol use and craving among detoxified inpatients with alcohol use disorder: a randomized sham-controlled clinical trial

BACKGROUND AND AIMS

Alcohol use disorder (AUD) is a chronic disorder with high relapse rates. There are currently few clinical trials of high frequency repetitive transcranial magnetic stimulation (HF-rTMS) to reduce alcohol use among AUD patients, and results are mixed. The current study tested the effect of 10 add-on sessions of HF-rTMS over the right dorsolateral pre-frontal cortex (DLPFC) on alcohol use and craving.

DESIGN

Single-center, single blind sham-controlled parallel-group RCT (n = 80), with 3 and 6 months follow-up.

SETTING

Clinical treatment center in Amsterdam, the Netherlands.

PARTICIPANTS

Eighty detoxified and abstinent AUD inpatients in clinical treatment (20 females, average age = 44.35 years).

INTERVENTION

Ten sessions of active or sham HF-rTMS (60 10 Hz trains of 5 sec at 110% motor threshold) over the right DLPFC on 10 consecutive work-days.

MEASUREMENTS

The primary outcome measure is the number of abstinent days over 6-month follow-up (FU). Secondary outcome measures are craving over 6-month FU (alcohol urge questionnaire and obsessive-compulsive drinking scale), time to first relapse over 6-month FU and grams of alcohol consumed over 6-month FU. Additional outcome measures: full abstinence over 6-month FU and treatment success over 12-month FU.

FINDINGS

HF-rTMS did not affect the number of abstinent days over 6 months FU [sham = 124 ± 65.9 days, active = 115 ± 69.8 days, difference: 9 days, 95% confidence interval (CI) = Poisson model: 0.578-3.547]. Moreover, HF-rTMS did not affect craving (AUQ/OCDS) (sham = 15.38/5.28, active = 17.48/4.75, differences = 2.1/-0.53, 95% CI mixed-effects model = -9.14 to 2.07/-1.44 to 2.40).

CONCLUSIONS

There was no clear evidence that high-frequency repetitive transcranial magnetic stimulation over the right dorsolateral pre-frontal cortex treatment has a long-term positive effect on alcohol use or craving as add-on treatment for alcohol use disorder. High treatment response at 6-month follow-up could have limited the possibility to find an effect.

Psychological Effects of Repetitive Transcranial Magnetic Stimulation on Individuals With Methamphetamine Use Disorder: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the effects of rTMS on drug craving, depression, anxiety, sleep, and cognitive function in methamphetamine (MA) dependent individuals.

DATA SOURCES AND METHODS

Randomized controlled trials (RCTs) of rTMS interventions for MA-dependent patients were searched through PubMed, Embase, Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure (CNKI), Wanfang database, Chongqing Vipers (VIP) and China Biomedical Literature Database (CBLD). The included literature was statistically processed using Revman 5.4, and STATA 16.0 for sensitivity and bias analysis.

RESULTS

A total of 13 papers were included, and the results of the meta-analysis showed that rTMS was effective in reducing craving scores (SMD = -1.53, 95%CI:-2.08 ∼ -0.98, p < 0.00001), improving depression (SMD = -0.32, 95%CI:-0.58 ∼ -0.07, p = 0.01) and sleep scores (WMD = -1.26, 95%CI:-2.26 ∼ -0.27, p = 0.01), but had no effect on anxiety scores (SMD = -0.42, 95%CI:-0.88 ∼ 0.03, p = 0.07); in terms of cognitive function, there were improvements in the international shopping list task (ISL), Groton maze learning task (GML) and continuous paired association learning task (CPAL), except for no effect on the social emotional cognition task (SEC) and two back task (TWOB). Subgroup analysis showed significant differences in the effects of different intervention period on craving in MA-dependent individuals.

CONCLUSION

rTMS was effective in reducing MA dependent individuals' cravings, alleviating depressive symptoms, improving sleep quality and language learning, collaborative learning and executive skills. Due to the small sample size of this study, a large number of RCTs are needed to validate this.

Non-invasive brain stimulation for smoking cessation: a systematic review and meta-analysis

BACKGROUND AND AIMS

Non-invasive brain stimulation (NIBS) methods have showed promising results for the treatment of tobacco use disorder, but little is known about the efficacy of NIBS on sustained tobacco abstinence. We aimed to assess its effectiveness for long-term smoking cessation.

METHODS

Systematic review and meta-analysis of randomized controlled trials (RCT). PubMed, Cochrane library, Embase, PsycINFO and clinical trials registries were systematically searched for relevant studies up to May 2021. Relevant studies included adult smokers seeking smoking cessation, included in an RCT using NIBS [specifically repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)], and with follow-up of more than 4 weeks. There were no restrictions on location. Abstinence rates in the active NIBS groups were compared with abstinence rates in sham NIBS or in usual treatment groups, from 4 weeks to 12 months following the quit attempt. Smoking abstinence was measured on an intention-to-treat basis and we used risk ratios (RRs) as measures of effect size.

RESULTS

Seven studies were included (n = 699 patients). In all included studies, the control groups were receiving sham NIBS and only data from 3 to 6 months were analysable. By pooling the seven included studies, the RR of sustained abstinence of any form of NIBS relative to sham NIBS was 2.39 [95% confidence interval (CI) = 1.26-4.55; I²  = 40%]. Subgroup analyses found that the RR was even higher when excitatory rTMS was used on the left dorsolateral prefrontal cortex (RR = 4.34; 95% CI = 1.69-11.18; I²  = 0%) or when using deep rTMS targeting the lateral prefrontal cortex and insula bilaterally (RR = 4.64; 95% CI = 1.61-13.39; I²  = 0%). A high risk of bias was found in four included studies. We also determined, using grades of recommendation, assessment, development and evaluation, that overall there was a low level of confidence in the results.

CONCLUSION

Non-invasive brain stimulation (NIBS) may improve smoking abstinence rates from 3 to 6 months after quitting smoking, compared with sham NIBS or usual treatment.

Transcranial direct current stimulation to modulate fMRI drug cue reactivity in methamphetamine users: A randomized clinical trial

Transcranial direct current stimulation (tDCS) has been studied as a therapeutic option to alter maladaptive brain functions associated with chronic substance use. We present a randomized, triple-blind, sham-controlled, clinical trial to determine the neural substrates of tDCS effects on drug craving. Sixty participants with methamphetamine use disorder were assigned to two groups: active tDCS (5 x 7 cm² , 2 mA, 20 min, anode/cathode over the F4/Fp1) and sham stimulation. Neuroimaging data of a methamphetamine cue reactivity task were collected immediately before and after stimulation. There was a significant reduction in self-reported craving after stimulation without any significant effect of time-by-group interaction. Our whole-brain analysis demonstrated that there was a global decrease in brain reactivity to cues following sham but not active tDCS. There were significant time-by-group interactions in five main clusters in middle and inferior frontal gyri, anterior insula, inferior parietal lobule, and precuneus with higher activations after active stimulation. There was a significant effect of stimulation type in the relationship between electrical current at the individual level and changes in task-modulated activation. Brain regions with the highest electric current in the prefrontal cortex showed a significant time-by-group interaction in task-modulated connectivity in the frontoparietal network. In this trial, there was no significant effect of the one session of active-F4/Fp1 tDCS on drug craving self-report compared to sham stimulation. However, activation and connectivity differences induced by active compared to sham stimulation suggested some potential mechanisms of tDCS to modulate neural response to drug cues.

Dissecting ultra-processed foods and drinks: Do they have a potential to impact the brain?

Ultra-processed foods and drinks (UPF) are formulation of ingredients, mostly of exclusive industrial use, that result from a series of industrial processes. They usually have a low nutrient but high energy density, with a high content of saturated and trans fats, and added sugars. In addition, they have characteristic organoleptic properties, and usually contain sophisticated additives, including artificial sweeteners, to intensify their sensory qualities and imitate the appearance of minimally processed foods. In addition, recent research has warned about the presence of chemicals (e.g., bisphenol) and neo-formed contaminants in these products. UPF production and consumption growth have been spectacular in the last decades, being specially consumed in children and adolescents. UPF features have been associated with a range of adverse health effects such as overeating, the promotion of inflammatory and oxidative stress processes, gut dysbiosis, and metabolic dysfunction including problems in glucose regulation. The evidence that these UPF-related adverse health effects may have on the neural network implicated in eating behavior are discussed, including the potential impact on serotonergic and dopaminergic neurotransmission, brain integrity and function. We end this review by placing UPF in the context of current food environments, by suggesting that an increased exposure to these products through different channels, such as marketing, may contribute to the automatic recruitment of the brain regions associated with food consumption and choice, with a detrimental effect on inhibitory-related prefrontal cortices. While further research is essential, preliminary evidence point to UPF consumption as a potential detrimental factor for brain health and eating behavior.

Forgetting Alcohol: A Double-Blind, Randomized Controlled Trial Investigating Memory Inhibition Training in Young Binge Drinkers

Background

Binge Drinking (BD) has been associated with altered inhibitory control and augmented alcohol-cue reactivity. Memory inhibition (MI), the ability to voluntarily suppress unwanted thoughts/memories, may lead to forgetting of memories in several psychiatric conditions. However, despite its potential clinical implications, no study to date has explored the MI abilities in populations with substance misuse, such as binge drinkers (BDs).

Method

This study—registered in the NIH Clinical Trials Database (ClinicalTrials.gov identifier: NCT05237414)—aims firstly to examine the behavioral and electroencephalographic (EEG) correlates of MI among college BDs. For this purpose, 45 BDs and 45 age-matched non/low-drinkers (50% female) will be assessed by EEG while performing the Think/No-Think Alcohol task, a paradigm that evaluates alcohol-related MI. Additionally, this work aims to evaluate an alcohol-specific MI intervention protocol using cognitive training (CT) and transcranial direct current stimulation (tDCS) while its effects on behavioral and EEG outcomes are assessed. BDs will be randomly assigned to one MI training group: combined [CT and verum tDCS applied over the right dorsolateral prefrontal cortex (DLPFC)], cognitive (CT and sham tDCS), or control (sham CT and sham tDCS). Training will occur in three consecutive days, in three sessions. MI will be re-assessed in BDs through a post-training EEG assessment. Alcohol use and craving will be measured at the first EEG assessment, and both 10-days and 3-months post-training. In addition, behavioral and EEG data will be collected during the performance of an alcohol cue reactivity (ACR) task, which evaluates attentional bias toward alcoholic stimuli, before, and after the MI training sessions.

Discussion

This study protocol will provide the first behavioral and neurofunctional MI assessment in BDs. Along with poor MI abilities, BDs are expected to show alterations in event-related potentials and functional connectivity patterns associated with MI. Results should also demonstrate the effectiveness of the protocol, with BDs exhibiting an improved capacity to suppress alcohol-related memories after both combined and cognitive training, along with a reduction in alcohol use and craving in the short/medium-term. Collectively, these findings might have major implications for the understanding and treatment of alcohol misuse.

Clinical Trial Registration

[www.ClinicalTrials.gov], identifier [NCT05237414].

Deep Brain Stimulation for Addictive Disorders-Where Are We Now?

In the face of a global epidemic of drug addiction, neglecting to develop new effective therapies will perpetuate the staggering human and economic costs of substance use. This review aims to summarize and evaluate the preclinical and clinical studies of deep brain stimulation (DBS) as a novel therapy for refractory addiction, in hopes to engage and inform future research in this promising novel treatment avenue. An electronic database search (MEDLINE, EMBASE, Cochrane library) was performed using keywords and predefined inclusion criteria between 1974 and 6/18/2021 (registered on Open Science Registry). Selected articles were reviewed in full text and key details were summarized and analyzed to understand DBS' therapeutic potential and possible mechanisms of action. The search yielded 25 animal and 22 human studies. Animal studies showed that DBS of targets such as nucleus accumbens (NAc), insula, and subthalamic nucleus reduces drug use and seeking. All human studies were case series/reports (level 4/5 evidence), mostly targeting the NAc with generally positive outcomes. From the limited evidence in the literature, DBS, particularly of the NAc, appears to be a reasonable last resort option for refractory addictive disorders. We propose that future research in objective electrophysiological (e.g., local field potentials) and neurochemical (e.g., extracellular dopamine levels) biomarkers would assist monitoring the progress of treatment and developing a closed-loop DBS system. Preclinical literature also highlighted the prefrontal cortex as a promising DBS target, which should be explored in human research.

Electrophysiological resting-state hyperconnectivity and poorer behavioural regulation as predisposing profiles of adolescent binge drinking

Adolescent Binge Drinking (BD) has become an increasing health and social concern, with detrimental consequences for brain development and functional integrity. However, research on neurophysiological and neuropsychological traits predisposing to BD are limited at this time. In this work, we conducted a 2‐year longitudinal magnetoencephalography (MEG) study over a cohort of initially alcohol‐naïve adolescents with the purpose of exploring anomalies in resting‐state electrophysiological networks, impulsivity, sensation‐seeking, and dysexecutive behaviour able to predict future BD patterns. In a sample of 67 alcohol‐naïve adolescents (age = 14.5 ± 0.9), we measured resting‐state activity using MEG. Additionally, we evaluated their neuropsychological traits using self‐report ecological scales (BIS‐11, SSS‐V, BDEFS, BRIEF‐SR and DEX). In a second evaluation, 2 years later, we measured participant's alcohol consumption, sub‐dividing the original sample in two groups: future binge drinkers (22 individuals, age 14.6 ± 0.8; eight females) and future light/no drinkers (17 individuals, age 14.5 ± 0.8; eight females). Then, we searched for differences predating alcohol BD intake. We found abnormalities in MEG resting state, in a form of gamma band hyperconnectivity, in those adolescents who transitioned into BD years later. Furthermore, they showed higher impulsivity, dysexecutive behaviours and sensation seeking, positively correlated with functional connectivity (FC). Sensation seeking and impulsivity mainly predicted BD severity in the future, while the relationship between dysexecutive trait and FC with future BD was mediated by sensation seeking. These findings shed light to electrophysiological and neuropsychological traits of vulnerability towards alcohol consumption. We hypothesise that these differences may rely on divergent neurobiological development of inhibitory neurotransmission pathways and executive prefrontal circuits.

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.

Boosting the hypnotic experience. Inhibition of the dorsolateral prefrontal cortex alters hypnotizability and sense of agency. A randomized, double-blind and sham-controlled tDCS study

Hypnotizability refers to the individual responsiveness to hypnosis, and literature shows that the greater the hypnotizability, the more effective the hypnotic suggestions. So far, few studies attempted to enhance hypnotizability, and only two adopted brain stimulation with magnetic pulses. In the present study, we aimed to boost hypnotizability through transcranial direct current stimulation (tDCS). To this aim, bilateral tDCS was applied over the dorsolateral prefrontal cortex (DLPFC) with the target electrode providing negative current (cathodal stimulation) over the left hemisphere. Twenty-nine subjects participated in the study and they were randomly assigned to the sham or the active group in a double-blind design. The hypnotic experience was assessed before and after the stimulation through a phenomenological measure of consciousness (the PCI-HAP). The main findings revealed that a single tDCS session enhanced the hypnotic depth by 11% and reduced the volitional control by 30%, while no differences emerged in the sham group. This is the first study adopting the electrical neurostimulation to produce an alteration of hypnotizability and sense of agency, and confirmed the key-role of the DLPFC and executive control in the hypnotic phenomena. If confirmed, these findings could have relevant implications as enhanced hypnotizability could be translated into better outcomes for many hypnotic interventions.

Ameliorating cognitive control in patients with binge eating disorder by electrical brain stimulation: study protocol of the randomized controlled ACCElect pilot trial

BACKGROUND

The current first-line treatment for binge eating disorder (BED), which is psychotherapy, is moderately effective in terms of abstinence from binge-eating. Neurobiological evidence suggests that people affected by BED show difficulties along the spectrum of impulsivity, including inhibitory control impairments and highlights the potential of novel treatment approaches directly targeting inhibitory control, including cognitive training approaches and non-invasive brain stimulation.

METHODS

ACCElect is a prospective, randomized controlled pilot trial investigating a novel, food-related inhibitory control training combined with transcranial direct current stimulation (tDCS). 40 patients with BED will be randomly assigned to receive the training either combined with verum or with sham stimulation (control condition). The inhibitory control training is based on principles of the antisaccade paradigm and comprises six training sessions over two weeks. Core aims are the investigation of feasibility and clinically relevant effects of a tDCS-enhanced inhibitory control training in BED patients and the establishment of a data basis for a larger efficacy trial. The primary clinical endpoint is binge-eating (BE) frequency in terms of changes in BE episodes four weeks after treatment termination as compared to baseline. Key secondary outcomes comprise ED pathology and general psychopathology, inhibitory control capacities, quality of life as well as acceptability and satisfaction with the intervention.

DISCUSSION

The results of the present trial will contribute to the development of novel neurobiologically informed treatment approaches for patients suffering from BED. Trial registration The ACCElect trial was prospectively registered on October 1, 2020, under the registration number NCT04572087 at ClinicalTrials.gov ( https://clinicaltrials.gov/ct2/show/NCT04572087 ).

rTMS Reduces Craving and Alcohol Use in Patients with Alcohol Use Disorder: Results of a Randomized, Sham-Controlled Clinical Trial

(1) Background: Current evidence-based treatments for alcohol use disorder (AUD) are moderately effective. Studies testing repetitive transcranial magnetic stimulation (rTMS) in AUD commonly apply a limited number of rTMS sessions with different rTMS settings, showing inconsistent effects on craving for alcohol. This study tested the efficacy of a robust rTMS protocol on craving and alcohol use. (2) Methods: In a single-blind randomized controlled trial in recently detoxified patients with AUD, ten days of high-frequency rTMS over the right dorsolateral prefrontal cortex on top of treatment as usual (n = 14) was compared with sham rTMS (n = 16). Outcome measures were alcohol craving and use over a follow-up period of one year. Analysis was performed by means of repeated measures multivariate analysis of variance. (3) Results: The results showed a main group-by-time interaction effect on craving (Wilks’ Λ = 0.348, F (12, 17) = 2.654, p = 0.032) and an effect of group on alcohol use (Wilk’s Λ = 0.44, F (6, 23) = 4.9, p = 0.002), with lower alcohol craving and use in the group with active rTMS compared to the control group. Differences in craving between groups were most prominent three months after treatment. At 12 months follow-up, there was no effect of rTMS on craving or abstinence. (4) Conclusions: This small-scale randomized controlled trial showed the efficacy of high-frequency rTMS over the right dlPFC diminished alcohol craving and use in recently detoxified patients with AUD during the first months after detoxification. These findings suggest that rTMS might be an effective add-on in treating patients with AUD and warrant replication in future large-scale studies.

Craving among individuals with stimulant use disorder in residential social model-based treatment - Can exercise help?

BACKGROUND

In a randomized controlled 8-week trial, we examined the efficacy of aerobic and resistance exercise in reducing craving for methamphetamine (MA) among individuals with MA-use disorder during residential treatment.

METHODS

Individuals with MA use disorder (138) who were newly enrolled in residential treatment volunteered for random assignment to either an 8-week exercise intervention (EX) or health education control (HE), with both conditions meeting 3 times weekly; 3 dropped out of the trial, bringing the analysis sample to 135. The majority of participants were male (80%), and 48% were Latino/Hispanic. The mean age of the sample was 31.7 (SD = 6.9) years. Using multivariate mixed models, differences between conditions were examined in: (1) craving for MA, measured by self-reported ratings on a Visual Analog Scale over the 8-week trial and, (2) MA use, measured by self-report and urine drug screens at baseline and 30 and 60 days after discharge from the 8-week study.

RESULTS

Results revealed significantly lower craving scores among the participants in the EX group than those in the HE group over the 8-week trial (median daily craving score for EX = 13.5, for HE = 21.8; p = .009). In addition, participants with less craving during treatment had significantly lower rates of MA use after discharge than participants with high craving measured at 30-days (p = .004) and 60-days post-discharge (p < .001).

CONCLUSIONS

Results support the utility of incorporating a structured exercise program for individuals with MA-use disorder to reduce craving and improve MA-use outcomes.

Repetitive Transcranial Magnetic Stimulation (rTMS) as a Promising Treatment for Craving in Stimulant Drugs and Behavioral Addiction: A Meta-Analysis

Addiction is a mental disorder with limited available treatment options. The therapeutic potential of repetitive transcranial magnetic stimulation (rTMS) on it, by targeting craving in particular, has been explored with heterogenous results. This meta-analysis uses updated evidence to assess overall rTMS efficacy on craving, differential effects between addiction types clustered into three groups (depressant (alcohol, cannabis, opiate), stimulant (nicotine, cocaine, methamphetamine), and behavioral addiction (gambling, eating disorder)), and stimulation settings. Studies on substance use, gambling, and eating disorders are included, with unrestricted stimulation settings, by searching the PubMed, Embase, PsycINFO, and Cochrane databases up to 30 April 2020. A total of 34 eligible studies (42 units of analysis) were identified. Because of highly significant heterogeneity in primary results, a sensitivity analysis was performed on a remaining sample of 26 studies (30 units of analysis). Analyses performed using random effects model revealed a small effect size favoring active rTMS over shamTMS stimulation in the reduction in craving. We found a significant difference between addiction types, with a persistent small effect only for stimulant and behavioral groups. In these groups we found no difference between the different combinations of target and frequency of stimulation, but a significant correlation between number of sessions and craving reduction. In conclusion, efficacy of rTMS on craving in stimulant and behavioral addiction was highlighted, but recommendations on optimal stimulation settings and its clinical application await further research.

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.

Improvement of Impulsivity and Decision Making by Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex in a Patient with Gambling Disorder

Gambling disorder (GD) is a form of behavioral addiction. In recent years, it has been suggested that the application of transcranial Direct Current Stimulation (tDCS) to the dorsolateral prefrontal cortex (DLPFC), which plays a key role in top-down inhibitory control and impulsivity, may represent a new therapeutic approach for treating addictions. Here we investigated the effectiveness of a novel low dose tDCS protocol (i.e. six sessions of right anodal/left cathodal tDCS for 20 min, with a current intensity of 1 mA) applied to DLPFC in a patient with GD. To evaluate the effect of the proposed intervention, cognitive, psychological and behavioural evaluations were performed at different time points, pre and post intervention. The results showed improvement of impulsivity, decision making, and cognitive functioning after tDCS intervention. Findings of the present study suggest that low doses of right anodal/left cathodal tDCS to DLPFC may effectively improve gambling behaviour. They also suggest to carefully evaluate the effects of this tDCS polarity on the patient's emotional state. The current protocol warrants further investigation in large groups of patients, as it may provide relevant insights into the design of effective, low dose treatments of gambling disorder.

The prevalence of substance use disorders and substance use in anorexia nervosa: a systematic review and meta-analysis

AIM

Individuals with anorexia nervosa (AN) often present with substance use and substance use disorders (SUDs). However, the prevalence of substance use and SUDs in AN has not been studied in-depth, especially the differences in the prevalence of SUDs between AN types [e.g., AN-R (restrictive type) and AN-BP (binge-eating/purge type]. Therefore, this systematic review and meta-analysis aimed to assess the prevalence of SUDs and substance use in AN samples.

METHOD

Systematic database searches of the peer-reviewed literature were conducted in the following online databases: MEDLINE, PsycINFO, Embase, and CINAHL from inception to January 2021. We restricted review eligibility to peer-reviewed research studies reporting the prevalence for either SUDs or substance use in individuals with AN. Random-effects meta-analyses using Freeman-Tukey double arcsine transformations were performed on eligible studies to estimate pooled proportions and 95% confidence intervals (CIs).

RESULTS

Fifty-two studies met the inclusion criteria, including 14,695 individuals identified as having AN (mean age: 22.82 years). Random pooled estimates showed that substance use disorders had a 16% prevalence in those with AN (AN-BP = 18% vs. AN-R = 7%). Drug abuse/dependence disorders had a prevalence of 7% in AN (AN-BP = 9% vs. AN-R = 5%). In studies that looked at specific abuse/dependence disorders, there was a 10% prevalence of alcohol abuse/dependence in AN (AN-BP = 15% vs. AN-R = 3%) and a 6% prevalence of cannabis abuse/dependence (AN-BP = 4% vs. AN-R = 0%). In addition, in terms of substance use, there was a 37% prevalence for caffeine use, 29% prevalence for alcohol use, 25% for tobacco use, and 14% for cannabis use in individuals with AN.

CONCLUSION

This is the most comprehensive meta-analysis on the comorbid prevalence of SUDs and substance use in persons with AN, with an overall pooled prevalence of 16%. Comorbid SUDs, including drugs, alcohol, and cannabis, were all more common in AN-BP compared to AN-R throughout. Therefore, clinicians should be aware of the high prevalence of SUD comorbidity and substance use in individuals with AN. Finally, clinicians should consider screening for SUDs and integrating treatments that target SUDs in individuals with AN. Individuals with anorexia nervosa (AN) may also present with substance use or have a substance use disorder (SUDs). Thus, we conducted a systematic review and meta-analysis to determine the prevalence of substance use and substance use disorders in individuals with AN. We examined published studies that reported the prevalence of either substance use or SUDs in individuals with AN. We found that substance use disorders had a 16% prevalence and that drug abuse/dependence disorders had a prevalence of 7% in those with AN. These rates were much higher in individuals with binge-eating/purging type compared to the restrictive AN. However, many specific substance use disorders and substance use types were low in individuals with AN. Nonetheless, clinicians should be aware of the high prevalence of SUD comorbidity and substance use in individuals with AN.

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 combined with alcohol cue inhibitory control training reduces the risk of early alcohol relapse: A randomized placebo-controlled clinical trial

BACKGROUND

Approximately half of all people with alcohol use disorder (AUD) relapse into alcohol reuse in the next few weeks after a withdrawal treatment. Brain stimulation and cognitive training represent recent forms of complementary interventions in the context of AUD.

OBJECTIVE

To evaluate the clinical efficacy of five sessions of 2 mA bilateral transcranial direct current stimulation (tDCS) for 20 min over the dorsolateral prefrontal cortex (DLPFC) (left cathodal/right anodal) combined with alcohol cue inhibitory control training (ICT) as part of rehabilitation. The secondary outcomes were executive functioning (e.g. response inhibition) and craving intensity, two mechanisms strongly related to abstinence.

METHODS

A randomized clinical trial with patients (n = 125) with severe AUD at a withdrawal treatment unit. Each patient was randomly assigned to one of four conditions, in a 2 [verum vs. sham tDCS] x 2 [alcohol cue vs. neutral ICT] factorial design. The main outcome of treatment was the abstinence rate after two weeks or more (up to one year).

RESULTS

Verum tDCS improved the abstinence rate at the 2-week follow-up compared to the sham condition, independently of the training condition (79.7% [95% CI = 69.8-89.6] vs. 60.7% [95% CI = 48.3-73.1]; p = .02). A priori contrasts analyses revealed higher abstinence rates for the verum tDCS associated with alcohol cue ICT (86.1% [31/36; 95% CI = 74.6-97.6]) than for the other three conditions (64% [57/89; 95% CI = 54-74]). These positive clinical effects on abstinence did not persist beyond two weeks after the intervention. Neither the reduction of craving nor the improvement in executive control resulted specifically from prefrontal-tDCS and ICT.

CONCLUSIONS

AUD patients who received tDCS applied to DLPFC showed a significantly higher abstinence rate during the weeks following rehabilitation. When combined with alcohol specific ICT, brain stimulation may provide better clinical outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT03447054 https://clinicaltrials.gov/ct2/show/NCT03447054.

Treating cocaine and opioid use disorder with transcranial magnetic stimulation: A path forward

Developing new, effective treatments for substance use disorders (SUDs), especially cocaine and opioid use disorders (CUD and OUD), are of immense importance. These are chronic, relapsing brain diseases characterized by dysregulated circuits manifesting from neuroplastic change brought on by repeated exposure to substances of abuse. A potential treatment is therapeutically inducing neuroplastic change in targeted dysregulated circuits. One such intervention, repetitive transcranial magnetic stimulation (rTMS) has gained traction over the past two decades as a method of noninvasively stimulating cortical structures in order to induce subcortical neuroplastic change. By doing so, rTMS ameliorates symptoms that are consequent of dysregulations in disease-related circuits, such as craving, and reduces drug use. Although rTMS has been successfully applied as a treatment for other clinical disorders, progress toward treatment applications for SUDs has been stymied by what we dub "known unknowns". These are fundamental lines of research within the rTMS-SUD field that have yet to be systematically understood which could help to optimize TMS as an intervention for SUDs. Because progress in treatment for CUD and OUD is imperative given the widespread severity of OUD and the lack of treatment for CUD, it is necessary to critically reflect on the ways in which rTMS research for these disorders can most effectively move forward to help patients. We articulate six "known unknowns" and outline a direction of research to address each. Briefly, the "known unknowns" in the field are: 1) Cortical target selection, 2) subcortical circuit engagement, 3) optimizing rTMS sequences, 4) rTMS as an adjuvant to existing interventions, 5) manipulating brain state, and 6) selecting outcome measures. We also outline research design approaches to address these "known unknowns" in the rTMS-SUDs field. Unification of efforts across research laboratories is necessary to develop empirically validated treatments that will benefit patients in a timely fashion.

Alteration of regional heterogeneity and functional connectivity for obese undergraduates: evidence from resting-state fMRI

Obesity was found to be related with the changes of brain functions in human beings. There were several brain areas that were verified to be correlated with the obesity, including the parietal cortex, frontal cortex and so on. However, the cortical regions found from different studies were discrepant due to the different ages, gender distribution and satiation degree of participants. We found that the regional homogeneity of right angular gyrus were smaller in obese undergraduates than that in normal-weight undergraduates. Moreover, functional connectivity of the left middle temporal cortex and the right angular gyrus were found to be smaller in obese group than that in normal-weight group by setting the right angular gyrus as seed region. In addition, multiple regression analysis suggested that the right superior frontal gyrus and left middle temporal gyrus were significantly correlated with their body mass index for normal-weight undergraduates, but no significant correlation was found for obese group. In summary, these findings indicated the functional changes of the cortex in obese undergraduates, which might be significant for providing imaging-based biomarkers for intervention and therapy of obesity.

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.

Non-invasive and invasive brain stimulation in alcohol use disorders: A critical review of selected human evidence and methodological considerations to guide future research

INTRODUCTION

Alcohol use disorder (AUD) ranks among the leading causes of decrements in disability-adjusted life-years. Long-term exposure to alcohol leads to an imbalance of activity between frontal cortical systems and the striatum, thereby enhancing impulsive behaviours and weakening inhibitory control. Alternative therapeutic approaches such as non-invasive and invasive brain stimulation have gained some momentum in the field of addictology by capitalizing on their ability to target specific anatomical structures and correct abnormalities in dysfunctional brain circuits.

MATERIALS AND METHODS

The current review, covers original peer-reviewed published research on the use of brain stimulation methods for the rehabilitation of AUD. A broad and systematic search was carried out on four electronic databases: NCBI PubMed, Web of Science, Handbooks and the Cochrane Library. Any original article in English or French language, without restrictions of patient age or gender, article type and publication outlet, were included in the final pool of selected studies.

RESULTS

The outcomes of this systematic review suggest that the dorsolateral prefrontral cortex (DLPFC) is a promising target for treating AUD with high frequency repetitive transcranial magnetic stimulation. Such effect would reduce feelings of craving by enhancing cognitive control and modulating striatal function. Existing literature also supports the notion that changes of DLPFC activity driven by transcranial direct current stimulation, could decrease alcohol craving and consumption. However, to date, no major differences have been found between the efficacy of these two non-invasive brain-stimulation approaches, which require further confirmation. In contrast, beneficial stronger evidence supports an impact of deep brain stimulation reducing craving and improving quality of life in AUD, effects that would be mediated by an impact on the nucleus accumbens, a central structure of the brain's reward circuitry. Overall, neurostimulation shows promise contributing to the treatment of AUD. Nonetheless, progress has been limited by a number of factors such as the low number of controlled randomized trials, small sample sizes, variety of stimulation parameters precluding comparability and incomplete or questionable sham-conditions. Additionally, a lack of data concerning clinical impact on the severity of AUD or craving and the short follow up periods precluding and accurate estimation of effect duration after discontinuing the treatment, has also limited the clinical relevance of final outcomes.

CONCLUSION

Brain stimulation remains a promising approach to contribute to AUD therapy, co-adjuvant of more conventional procedures. However, a stronger therapeutic rational based on solid physio-pathological evidence and accurate estimates of efficacy, are still required to achieve further therapeutic success and expand clinical use.

Concurrent Transcranial Direct Current Stimulation and Resting-State Functional Magnetic Resonance Imaging in Patients with Gambling Disorder

Background/Introduction: Transcranial direct current stimulation (tDCS) delivered over the dorsolateral prefrontal cortex (DLPFC) while patients are at rest can decrease craving in patients with substance-related and addictive disorders. Yet, the effects of tDCS on resting-state brain activity remain unknown in this population. This study examined the effects of tDCS on resting-state functional connectivity (rsFC) with concurrent stimulation and functional magnetic resonance imaging in patients with gambling disorder. Methods: This was a randomized, sham-controlled, double-blind, crossover study. The anodal and cathodal electrodes were applied over the right and left DLPFC, respectively. Patients received 30 min of active and sham stimulation on separate days. rsFC was assessed before and during stimulation with seed-based analyses. Results: There was a significant increase of rsFC between the right DLPFC seed and the right superior parietal lobule during active stimulation as compared to during sham stimulation (p = 0.0059, corrected for multiple comparisons). There was also a positive correlation between rsFC change of this frontoparietal network and brain volume of the right DLPFC (p = 0.0042, corrected for multiple comparisons). Discussion: A single session of tDCS targeting the DLPFC strengthened functional connectivity in a frontoparietal circuit, known to be implicated in cognitive control, especially in patients with a greater volume of the region under the anode electrode. Impact statement Transcranial direct current stimulation increased the functional connectivity of a frontoparietal circuit in patients with gambling disorder. These changes were larger in patients with greater volume of the dorsolateral prefrontal cortex. Transcranial direct current stimulation strengthened the connectivity of a brain network known to be associated with cognitive control.

Repetitive transcranial magnetic stimulation as a potential treatment approach for cannabis use disorder

The expanding legalization of cannabis across the United States is associated with increases in cannabis use, and accordingly, an increase in the number and severity of individuals with cannabis use disorder (CUD). The lack of FDA-approved pharmacotherapies and modest efficacy of psychotherapeutic interventions means that many of those who seek treatment for CUD relapse within the first few months. Consequently, there is a pressing need for innovative, evidence-based treatment development for CUD. Preliminary evidence suggests that repetitive transcranial magnetic stimulation (rTMS) may be a novel, non-invasive therapeutic neuromodulation tool for the treatment of a variety of substance use disorders (SUDs), including recently receiving FDA clearance (August 2020) for use as a smoking cessation aid in tobacco cigarette smokers. However, the potential of rTMS for CUD has not yet been reviewed. This paper provides a primer on therapeutic neuromodulation techniques for SUDs, with a particular focus on reviewing the current status of rTMS research in people who use cannabis. Lastly, future directions are proposed for rTMS treatment development in CUD, with suggestions for study design parameters and clinical endpoints based on current gold-standard practices for therapeutic neuromodulation research.

Examining the relationships among adolescent health behaviours, prefrontal function, and academic achievement using fNIRS

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Prior studies document effects of lifestyle behaviors on the brain and academics.

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Among adolescents we found that activity and eating both predict task performance.

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Activity also predicts functional activation in the right lateral dlPFC, but not grades.

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Substance use predicted worse grades but not brain-related mediators.

Several adolescent health behaviours have been hypothesized to improve academic performance via their beneficial impact on cognitive control and functional aspects of the prefrontal cortex (PFC). The primary objective of this study is to examine the association between lifestyle behaviours and academic performance in a sample of adolescents, and to examine the extent to which activity within the PFC and behavioural indices of inhibition may mediate this relationship. Sixty-seven adolescents underwent two study sessions five days apart. Sleep and physical activity were measured using wrist-mounted accelerometry; eating habits, substance use and academic achievement were measured by self-report. Prefrontal function was quantified by Multi-Source Interference Task (MSIT) performance, and task-related activity via functional near-infrared spectroscopy (fNIRS). Higher levels of physical activity predicted higher MSIT accuracy scores (β = .321, ρ = 0.019) as well as greater activation within the right dlPFC (b = .008, SE = .004, ρ = .0322). Frequency of fast-food consumption and substance use were negatively associated with MSIT accuracy scores (β = −0.307, ρ = .023) and Math grades (b = −3.702, SE = 1.563, ρ = .022), respectively. Overall, the results of this study highlight the importance of lifestyle behaviours as predictors of prefrontal function and academic achievement in youth.

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.

Transcranial Direct Current Stimulation Targeting the Ventromedial Prefrontal Cortex Reduces Reactive Aggression and Modulates Electrophysiological Responses in a Forensic Population

BACKGROUND

Studies have shown that impairments in the ventromedial prefrontal cortex play a crucial role in violent behavior in forensic patients who also abuse cocaine and alcohol. Moreover, interventions that aimed to reduce violence risk in those patients are found not to be optimal. A promising intervention might be to modulate the ventromedial prefrontal cortex by high-definition (HD) transcranial direct current stimulation (tDCS). The current study aimed to examine HD-tDCS as an intervention to increase empathic abilities and reduce violent behavior in forensic substance dependent offenders. In addition, using electroencephalography, we examined the effects on the P3 and the late positive potential of the event-related potentials in reaction to situations that depict victims of aggression.

METHODS

Fifty male forensic patients with a substance dependence were tested in a double-blind, placebo-controlled randomized study. The patients received HD-tDCS 2 times a day for 20 minutes for 5 consecutive days. Before and after the intervention, the patients completed self-reports and performed the Point Subtraction Aggression Paradigm, and electroencephalography was recorded while patients performed an empathy task.

RESULTS

Results showed a decrease in aggressive responses on the Point Subtraction Aggression Paradigm and in self-reported reactive aggression in the active tDCS group. Additionally, we found a general increase in late positive potential amplitude after active tDCS. No effects on trait empathy and the P3 were found.

CONCLUSIONS

Current findings are the first to find positive effects of HD-tDCS in reducing aggression and modulating electrophysiological responses in forensic patients, showing the potential of using tDCS as an intervention to reduce aggression in forensic mental health care.

Add-on repetitive transcranial magnetic stimulation in patients with opioid use disorder undergoing methadone maintenance therapy

Background: Repetitive transcranial magnetic stimulation (rTMS) shows potential therapeutic effects for individuals with addiction, but few studies have examined individuals with opioid use disorder (OUD).Objectives: We conducted an add-on double-blinded, sham-controlled rTMS feasibility pilot trial to examine OUD participants undergoing methadone maintenance therapy (MMT). The current report focused on the effects of rTMS on (1) craving and heroin use behavior and (2) depression, impulsivity, and attention.Methods: Active or sham rTMS treatment was applied to the left dorsolateral prefrontal cortex (DLPFC) over a total of 11 sessions in 4 weeks (15-Hz frequency, 4 seconds per train, intertrain interval of 26 seconds, 40 trains per session) in OUD participants (ClinicalTrials.gov registration number: NCT03229642). Craving, heroin use severity, urine morphine tests, the Hamilton Depression Rating Scale (HDRS), the Barratt Impulsiveness Scale-11 (BIS-11), and the Continuous Performance Tests (CPTs) were measured.Results: Twenty-two OUD participants were enrolled, of which eleven (8 males) were undergoing active rTMS and nine (8 males) were in the sham rTMS group. After 12 weeks of follow-up, the active rTMS group did not show significantly greater improvements than the sham group with respect to craving, heroin use, or urine morphine test results. However, HDRS scores, BIS-11 attentional subscales, and CPTs commission T-scores (C-TS) were significantly lower in the active rTMS group (P = .003, 0.04, and 0.02, respectively) than in the sham group.Conclusion: Add-on rTMS did not appear to improve heroin use behavior but may have benefitted depressive symptoms, impulse control and attention in OUD participants undergoing MMT.

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.

Anodal tDCS over the dorsolateral prefrontal cortex reduces Stroop errors. A comparison of different tasks and designs

In the present work, we evaluated the possibility to induce changes in the inhibitory control through non-invasive excitatory stimulation of the prefrontal cortex (PFC). To this aim, different montages of the transcranial direct current stimulation (tDCS) were adopted in three separate experiments, wherein different cognitive tasks were performed before and after the stimulation. In the first experiment, participants performed a visual Go/no-go task, and a bilateral anodic or sham stimulation was provided over the scalp area corresponding to the inferior frontal gyrus (IFG). In the second experiment, the IFG was stimulated unilaterally over the right hemisphere, and participants performed a Stroop task combined with a concurrent n-back task, which was aimed at overloading PFC activity. Since no behavioral effects of tDCS were observed in both experiments, we conducted a third experiment with different montage and paradigm. Stimulation was provided bilaterally over the dorsolateral PFC (DLPFC) in the context of a classic Stroop task: results indicated that anodal stimulation favored a reduction of errors. Present findings suggest that the bihemispheric stimulation of the DLPFC might be effective to increase inhibition in healthy subjects, and that this effect might be mediated by the implementation of sustained attention, as predicted by the attentional account of the inhibitory control.

Are Malaysian Youths Overdependent on the Internet?: A Narrative Review

Overdependence on the internet is a grave concern that has enveloped Malaysian youths which could lead to a variety of sequelae. This narrative review aims to determine the definition of internet overdependence and its associated factors, as well as the potential preventive and treatment strategies for internet overdependence. From the literature, internet overdependence is regarded as a 3-factor model encompassing salience, self-control failure, and serious consequences. Sociodemographic factors such as age, gender, and ethnicity, as well as psychosocial factors such as depression, anxiety, stress, and loneliness, were found to be associated with internet overdependence among Malaysian youths. A multimodal treatment approach is recommended by the implementation of various types of treatments, integrating disciplines such as pharmacology, psychotherapy, and family counseling. Despite various terminologies being used and unclear conceptualization of its nomenclature, overdependence on the internet is prevalent among youths in Malaysia. Future research should go toward establishing a clear definition of its terminology and attaining more robust evidence on treatment strategies.

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.

Consequences Of Prefrontal TDCS On Inhibitory Control And Reactive Aggression

Increased aggression and impulsivity represent a key component of several psychiatric disorders, including substance use disorder, which is often associated with deficient prefrontal brain activation. Thus, innovative tools to increase cognitive control are highly warranted. The current study investigates the potential of transcranial direct current stimulation (tDCS), a tool to modulate cortical activation and to increase cognitive control in individuals with a high potential for impulsive and aggressive behavior. In a double-blind, sham-controlled study, we applied anodal tDCS over the right dorsolateral prefrontal cortex in an all-male sample of alcohol-dependent patients (AD), tobacco users (TU) and healthy controls (HC), who completed the Taylor Aggression Paradigm and Stop Signal Reaction Time Task twice. While there were no observable effects of tDCS in controls, the results revealed altered aggressive behavior in AD following active stimulation. Specifically, these individuals did not show the standard increase in aggression over time seen in the other groups. Furthermore, improved response inhibition was found in AD and TU following active but not sham stimulation. Our study demonstrates that prefrontal tDCS improves our laboratory measure of impulse control in at-risk groups, illustrating the importance of sample characteristics such as nicotine intake and personality traits for understanding the effects of brain stimulation.

The Effects of Acute Transcranial Direct Current Stimulation on Attentional Bias in Pedophilic Disorder: A Preregistered Pilot Study

OBJECTIVES

Individuals with pedophilic disorder (PD) experience personal and interpersonal difficulties and are at risk of sexually offending against children. As such, innovative and empirically validated treatments are needed. Recent studies have indicated that men who have sexually offended against children (SOC) with PD display an automatic attention bias for child-related stimuli as well as reduced activity in the dorsolateral prefrontal cortex (dlPFC), a brain area involved in cognitive control, including control over sexual arousal. In this preregistered pilot study, we are the first to investigate whether acutely increasing prefrontal activity could reduce the putative pedophilic attention bias.

MATERIALS AND METHODS

We delivered a single 20-min session of active anodal versus sham transcranial direct current stimulation (tDCS) over the left dlPFC to 16 SOC with PD and 16 matched healthy controls, while they performed a task requiring controlled attention to computer-generated images of clothed and nude children and adults. We collected responses unobtrusively by recording eye movements.

RESULTS

Our results did not support the presence of the expected automatic attention bias across outcome measures. Nonetheless, we found a response facilitation with child targets in patients and, unexpectedly, in controls, likely due to unwanted salience effects. Active versus sham tDCS reduced this bias across groups, as indicated by a significant group*condition interaction (p = 0.04). However, no attentional bias and no tDCS effects on attentional responses to child and adult images emerged following tDCS.

CONCLUSIONS

These results suggest enhanced cognitive control in response to salient stimuli during active tDCS. Thus, to assist future studies on neuromodulation in PD, we provide suggestions for design improvement.