Focused transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex modulates specific domains of self-regulation

Efficacy of transcranial magnetic stimulation treatment in reducing neuropsychiatric symptomatology after traumatic brain injury

Background

Neuropsychiatric disorders are highly disabling in traumatic brain injury (TBI) patients, and psychopharmacological treatments often fail to adequately mitigate their detrimental effects. Repetitive transcranial magnetic stimulation (rTMS) is an emerging treatment in neurology and psychiatry, showing potential in treating psychiatric disorders.

Objective

This study investigates the efficacy of a novel, dual-site sequential rTMS protocol designed to treat neuropsychiatric symptoms in a TBI patient who was refractory to conventional treatments.

Methods

A 34-year-old woman with severe head trauma and complex psychopathology underwent 20 daily sessions of focal-coil rTMS, combining inhibitory stimulation (1 Hz) on the right dorsolateral prefrontal cortex (DLPFC) and excitatory (10 Hz) on the left DLPFC, guided by a neuronavigation system. Psychiatric and neurocognitive assessments were conducted at baseline and at 2, 4, and 8 weeks following the beginning of rTMS treatment.

Results

After 2 weeks of treatment, the patient showed decreased impulsivity and obsessive-compulsive symptoms, along with improvements in attention and processing speed. After 4 weeks, impulsivity further declined, though no other significant changes were noted. At 8 weeks, a persistent positive effect was observed, including enhanced positive emotions.

Discussion

These findings suggest that guided, alternating neurostimulation of the DLPFC may modulate activity within cortico-striato-thalamo-cortical circuits, providing a promising alternative for managing neuropsychiatric symptoms in TBI patients who are resistant to traditional treatments.

Preventing prefrontal dysfunction by tDCS modulates stress-induced creativity impairment in women: an fNIRS study

Stress is a major external factor threatening creative activity. The study explored whether left-lateralized activation in the dorsolateral prefrontal cortex manipulated through transcranial direct current stimulation could alleviate stress-induced impairment in creativity. Functional near-infrared spectroscopy was used to explore the underlying neural mechanisms. Ninety female participants were randomly assigned to three groups that received stress induction with sham stimulation, stress induction with true stimulation (anode over the left and cathode over the right dorsolateral prefrontal cortex), and control manipulation with sham stimulation, respectively. Participants underwent the stress or control task after the transcranial direct current stimulation manipulation, and then completed the Alternative Uses Task to measure creativity. Behavioral results showed that transcranial direct current stimulation reduced stress responses in heart rate and anxiety. The functional near-infrared spectroscopy results revealed that transcranial direct current stimulation alleviated dysfunction of the prefrontal cortex under stress, as evidenced by higher activation of the dorsolateral prefrontal cortex and frontopolar cortex, as well as stronger inter-hemispheric and intra-hemispheric functional connectivity within the prefrontal cortex. Further analysis demonstrated that the cortical regulatory effect prevented creativity impairment induced by stress. The findings validated the hemispheric asymmetry hypothesis regarding stress and highlighted the potential for brain stimulation to alleviate stress-related mental disorders and enhance creativity.

A Randomized Clinical Trial to Assess the Effect of Medication Therapy Plus tDCS on Problem-solving and Emotion Regulation of Patients with Bipolar Disorder Type I

Objective

This study aims to evaluate the effectiveness of medication therapy combined with transcranial Direct Current Stimulation (tDCS) in improving problem-solving and emotion regulation abilities of patients with bipolar disorder (BD) type I.

Methods

This is a randomized clinical trial conducted on 30 patients with BD I, randomly assigned into two groups of Medication (n = 15, receiving mood stabilizers including 2-5 tablets of lithium 300 mg, sodium valproate 200 mg, and carbamazepine 200 mg) and Medication + tDCS (n = 15, receiving mood stabilizers plus tDCS with 2 mA intensity over the right dorsolateral prefrontal cortex for 10 days, two sessions per day each for 20 minutes). The Tower of London (TOL) test and Emotion Regulation Questionnaire (ERQ) were used for assessments before, immediately, and 3 months after interventions.

Results

There was a significant difference between groups in total ERQ (p = 0.001) and its cognitive reappraisal domain (p = 0.000) which were increased, but the difference was not significant in its expressive suppression domain (p > 0.05). After 3 months, their level decreased. In examining problem-solving variable, the combined therapy could significantly reduce only the total number of errors under TOL test (p = 0.00), but it remained unchanged after 3 months.

Conclusion

Medication therapy plus tDCS is effective in improving problem-solving and emotional regulation (cognitive reappraisal) skills of patients with BD I.

Efficacy and tolerability of Brain Stimulation interventions in Borderline Personality Disorder: state of the art and future perspectives - A systematic review

Treating Borderline Personality Disorder (BPD) is a major challenge for psychiatrists. As Brain Stimulation represents an alternative approach to treat psychiatric disorders, our systematic review is the first to focus on both invasive and Non-Invasive Brain Stimulation (NIBS) interventions in people living with BPD, examining clinical effects over core features and comorbid conditions. Following PRISMA guidelines, out of 422 original records, 24 papers were included regarding Deep Brain Stimulation (n = 1), Electroconvulsive therapy (n = 5), Transcranial Magnetic Stimulation (n = 13) and transcranial Direct Current Stimulation (n = 5). According to impulsivity and emotional dysregulated domain improvements, NIBS in BPD appears to restore frontolimbic network deficiencies. NIBS seems also to modulate depressive features. Safety and tolerability profiles for each technique are discussed. Despite encouraging results, definitive recommendations on Brain Stimulation in BPD are mitigated by protocols heterogeneity, lack of randomized controlled trials and poor quality of included studies, including high risk of methodological biases. To serve as guide for future systematic investigations, protocols optimization proposals are provided, focusing on alternative stimulation sites and suggesting a NIBS symptom-based approach.

Dissociating the role of dACC and dlPFC for emotion appraisal and mood regulation using cathodal tDCS

Several neuroimaging studies have shown that a distributed network of brain regions is involved in our ability to appraise the emotions we experience in daily life. In particular, scholars suggested that the dorsal anterior cingulate cortex (dACC) may play a role in the appraisal of emotional stimuli together with subcortical regions, especially when stimuli are negatively valenced, and the dorsolateral prefrontal cortex (dlPFC) may play a role in regulating emotions. However, proofs of the causal role of these regions are lacking. In the present study, we aim at testing this model by stimulating both the dACC and the left dlPFC via cathodal tDCS. Twenty-four participants were asked to attend and rate the arousal and valence of negative and neutral emotional stimuli (pictures and words) in three different experimental sessions: cathodal stimulation of dACC, left dlPFC, or sham. In addition to the experimental task, the baseline affective state was measured before and after the stimulation to further assess the effect of stimulation over the baseline affective state after the experimental session. Results showed that cathodal stimulation of dACC, but not the left dlPFC, was associated with reduced arousal ratings of emotional stimuli, both compared with the sham condition. Moreover, cathodal stimulation of left dlPFC decreased participant's positive affective state after the session. These findings suggest for the first time, a dissociation between the dACC and dlPFC, with the former more involved in emotion appraisal, and the latter more involved in mood modulation.

Transcranial direct current stimulation of bilateral dorsolateral prefrontal cortex eliminates creativity impairment induced by acute stress

The creativity impairment under acute stress may be closely related to the down-regulation of the prefrontal cortex function caused by stress-related neurotransmitters and hormones. In the current study, we explored whether transcranial direct current stimulation (tDCS) over bilateral dorsolateral prefrontal cortex (DLPFC) eliminated stress-induced creativity impairment and the potential mechanism from the perspective of stress response recovery. Seventy participants were randomly allocated to a group undergoing the activation of right DLPFC and the deactivation of left DLPFC (R+L-; N = 35), and a group of sham stimulation (sham; N = 35). Participants received tDCS after the stress induction, and then completed the Alternative Uses Task (AUT) and the Remote Association Task (RAT) during the stimulation. The stress response was indicated using heart rate, cortisol, and emotion changes. Results showed that R+L- stimulation facilitated the recovery of anxious state compared to sham stimulation. We also found that the decreased value of AUT scores after stress in the R+L- group was significantly lower than that in the sham group. Moreover, further analysis revealed state anxiety mediated the effect of tDCS on the flexibility component of the AUT. We concluded that bilateral tDCS over the DLPFC is efficient in alleviating stress-induced creativity impairment, which may correlate with greater recovery of state anxiety. Our findings provide causal evidence for the neurophysiological mechanisms by which stress affects creativity, as well as clinical suggestions for stress-related psychiatric disorders prevention and intervention.

Enhancing reappraisal of negative emotional memories with transcranial direct current stimulation

Reappraisal of negative memories and experiences is central for mental health and well-being. Deficiency of reappraisal lies at the core of many psychiatric disorders and is a key target for treatment. Here we apply transcranial direct current stimulation (tDCS) to enhance reappraisal of negative emotional memories. In a randomised, sham-controlled, 2 × 2 between-subject and double-blinded study, we applied single sessions of anodal and sham tDCS over the right dorsolateral prefrontal cortex (dlPFC) of 101 healthy participants while reappraising a personal negative memory or engaging in a control task. We hypothesised that (i) reappraisal decreases negative valence, arousal and evaluations of the memory and leads to improved decision making, and (ii) tDCS leads to additional changes in these reappraisal outcomes. In line with these hypotheses, participants’ personal memories were rated as less negative and less arousing following reappraisal. Anodal tDCS during reappraisal was associated with significant short-term reductions in negative valence compared to sham stimulation. Our results indicate that tDCS may enhance some of the effects of reappraisal. If replicated, our findings suggest potential benefits elicited by tDCS stimulation that may help optimise current treatment approaches for psychiatric disorders.

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.

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.

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.

Transcranial electrical and magnetic stimulation (tES and TMS) for addiction medicine: A consensus paper on the present state of the science and the road ahead

There is growing interest in non-invasive brain stimulation (NIBS) as a novel treatment option for substance-use disorders (SUDs). Recent momentum stems from a foundation of preclinical neuroscience demonstrating links between neural circuits and drug consuming behavior, as well as recent FDA-approval of NIBS treatments for mental health disorders that share overlapping pathology with SUDs. As with any emerging field, enthusiasm must be tempered by reason; lessons learned from the past should be prudently applied to future therapies. Here, an international ensemble of experts provides an overview of the state of transcranial-electrical (tES) and transcranial-magnetic (TMS) stimulation applied in SUDs. This consensus paper provides a systematic literature review on published data - emphasizing the heterogeneity of methods and outcome measures while suggesting strategies to help bridge knowledge gaps. The goal of this effort is to provide the community with guidelines for best practices in tES/TMS SUD research. We hope this will accelerate the speed at which the community translates basic neuroscience into advanced neuromodulation tools for clinical practice in addiction medicine.

Affect and prefrontal hemodynamics during exercise under immersive audiovisual stimulation: Improving the experience of exercise for overweight adults

OBJECTIVE

Research on methods of improving the affective experience of exercise remains limited, especially for low-active overweight adults. We investigated the effectiveness of a virtual-reality headset and headphones in improving affective responses over conventionally delivered audiovisual stimulation.

METHODS

Low-active, overweight adults (16 women, 5 men; age: 34.67 ± 9.62 years; body mass index: 28.56 ± 4.95 kg/m²; peak oxygen uptake for men: 29.14 ± 6.56 mL/kg/min, for women: 22.67 ± 4.52 mL/kg/min, mean ± SD) completed 15-min sessions of recumbent cycling at the ventilatory threshold: (a) high immersion (HI, virtual reality headset and headphones), (b) low immersion (LI, television screen and speakers), and (c) Control. During-exercise pleasure and post-exercise enjoyment were self-reported. Oxygenation of the right dorsolateral prefrontal cortex (dlPFC) was assessed with near infrared spectroscopy.

RESULTS

Higher pleasure was reported during HI than during LI and Control (Condition × Time interaction; p < 0.001, η _p ² = 0.43). Participants who reported a preference for low exercise intensity showed higher dlPFC oxygenation during Control, but this difference diminished during LI and HI (Condition × Time × Preference interaction; p = 0.036, η_p ² = 0.10).

CONCLUSION

Compared with conventionally delivered audiovisual stimulation, using a virtual-reality headset strengthens the dissociative effect, further improving affective responses to exercise at the ventilatory threshold among overweight, low-active adults. Presumably by competing with interoceptive afferents at the level of sensory input, audiovisual stimulation may lessen reliance on cognitive efforts to attenuate declining affect, as indicated by lower right dlPFC activity, particularly among participants disinclined toward high exercise intensity.

Modulating Activity in the Prefrontal Cortex Changes Intertemporal Choice for Loss: A Transcranial Direct Current Stimulation Study

Intertemporal choice refers to decisions involving tradeoffs between costs and benefits occurring at different times. Studies have found that weighting the time and benefits during decision-making involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). However, in contrast to literature regarding intertemporal choice for gains, studies have not provided causal evidence that the DLPFC is involved in intertemporal choice for losses. We examined whether bifrontal transcranial direct current stimulation (tDCS) applied over the right and left prefrontal cortex can alter the balance of intertemporal preference in the loss condition. A total of 60 participants performed delay discounting tasks for losses while receiving either right anodal/left cathodal, left anodal/right cathodal, or sham stimulation. The results showed that participants tended to choose larger delayed losses after receiving left anodal/right cathodal tDCS. Left anodal/right cathodal tDCS significantly decreased the discounting rate compared with the sham stimulation. These findings confirm that DLPFC activity is critical during intertemporal decision-making for losses.

Stimulating Self-Regulation: A Review of Non-invasive Brain Stimulation Studies of Goal-Directed Behavior

Self-regulation enables individuals to guide their thoughts, feelings, and behaviors in a purposeful manner. Self-regulation is thus crucial for goal-directed behavior and contributes to many consequential outcomes in life including physical health, psychological well-being, ethical decision making, and strong interpersonal relationships. Neuroscientific research has revealed that the prefrontal cortex plays a central role in self-regulation, specifically by exerting top-down control over subcortical regions involved in reward (e.g., striatum) and emotion (e.g., amygdala). To orient readers, we first offer a methodological overview of tDCS and then review experiments using non-invasive brain stimulation techniques (especially transcranial direct current stimulation) to target prefrontal brain regions implicated in self-regulation. We focus on brain stimulation studies of self-regulatory behavior across three broad domains of response: persistence, delay behavior, and impulse control. We suggest that stimulating the prefrontal cortex promotes successful self-regulation by altering the balance in activity between the prefrontal cortex and subcortical regions involved in emotion and reward processing.

Lack of effect of transcranial direct current stimulation (tDCS) on short-term smoking cessation: Results of a randomized, sham-controlled clinical trial

BACKGROUND

Transcranial direct current stimulation (tDCS) has been shown to improve measures of executive cognitive function and reduce cigarette consumption. Studies conducted to date have been small, and the results are mixed.

METHODS

This randomized, double-blind, parallel arm clinical trial tested the effects of active anodal tDCS targeted to the left dorsolateral prefrontal cortex (versus sham) on 7-day smoking cessation in 106 treatment-seeking smokers. Participants received three sessions of sham (n = 35), 1 mA (n = 35), or 2 mA (n = 36) tDCS in the context of a validated smoking lapse paradigm then received brief smoking cessation counseling and completed a monitored quit attempt. The primary outcome was total number of days of abstinence confirmed via exhaled carbon monoxide.

RESULTS

During the quit period, there were no effects of dose group on days of abstinence (sham, M (SD): 2.5 days (±2.5); 1 mA: 2.5 days (±2.5); 2 mA: 2.4 days (±2.3); β = -0.08; p = 0.76) or on change in daily smoking rate (sham, M (SD): 12.6 CPD (±4.8); 1 mA: -11.8 CPD (±4.4); 2 mA: -11.7 CPD (±5.3); β = 0.42, p = 0.49), nor were there effects of dose group on latency to smoke or number of cigarettes smoked during the smoking lapse paradigm. Side effects of tDCS were generally mild (<5 out of 10), and participants were not able to distinguish between active and sham treatment.

CONCLUSIONS

These results do not support the efficacy of tDCS targeted to the left dorsolateral prefrontal cortex (DLPFC) for smoking cessation.

Ventrolateral but not Dorsolateral Prefrontal Cortex tDCS effectively impact emotion reappraisal - effects on Emotional Experience and Interbeat Interval

Emotions can be understood as behavioral, physiological, and subjective individual’s alteration due to a given situation. Several times, an efficient regulation of these emotions can promote psychological and social survival. It has been demonstrated that the Prefrontal Cortex (PFC) presents a relevant role in cognitive control, especially during emotion regulation strategies. However, evidence for the role of the PFC and emotional regulation comes mostly from neuroimaging experiments lacking from causal information. Transcranial Direct Current Stimulation (tDCS) has been shown to be an efficient noninvasive neuromodulation technique capable to address causal hypothesis. The aim of this study was to investigate the role of two regions of the PFC (Dorsolateral and Ventrolateral region) on different strategies of emotional reappraisal during the observation of negative images. 180 undergraduate students (mean age 21,75 ± 3,38) participated in this study, divided in two experiments (Dorsolateral PFC - n = 90; Ventrolateral PFC - n = 90). As not expected, DLPFC tDCS did not modulate the responses on the emotional regulation task. However, VLPFC tDCS resulted in less negative valence of negative images as well as decreased cardiac interbeat interval on earlier moments of emotional processing. These findings supports the general view about the role of the PFC on emotional regulation and, at the same time, advances the field by providing evidence that evaluation of negative stimuli is much more based on the VLPFC than on the DLPCF.

Neuromodulation interventions for addictive disorders: challenges, promise, and roadmap for future research

Addictive disorders are a major public health concern, associated with high relapse rates, significant disability and substantial mortality. Unfortunately, current interventions are only modestly effective. Preclinical studies as well as human neuroimaging studies have provided strong evidence that the observable behaviours that characterize the addiction phenotype, such as compulsive drug consumption, impaired self-control, and behavioural inflexibility, reflect underlying dysregulation and malfunction in specific neural circuits. These developments have been accompanied by advances in neuromodulation interventions, both invasive as deep brain stimulation, and non-invasive such as repetitive transcranial magnetic stimulation and transcranial direct current stimulation. These interventions appear particularly promising as they may not only allow us to probe affected brain circuits in addictive disorders, but also seem to have unique therapeutic applications to directly target and remodel impaired circuits. However, the available literature is still relatively small and sparse, and the long-term safety and efficacy of these interventions need to be confirmed. Here we review the literature on the use of neuromodulation in addictive disorders to highlight progress limitations with the aim to suggest future directions for this field.

Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS)

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.

Prefrontal transcranial direct current stimulation facilitates affective flexibility

Performance on paradigms involving switching between emotional and non-emotional task-sets (affective flexibility) predicts emotion regulation abilities and is impaired in patients with different emotional disorders. A better understanding of how neurostimulation techniques such as transcranial direct current stimulation (tDCS) influence affective switching may provide support for the improvement of rehabilitation programs. In the current study healthy volunteers received anodal tDCS over the right dorsolateral prefrontal cortex (DLPFC), the left DLPFC or sham stimulation while performing an affective-switching task. Participants had to repeat or switch between facial judgments of emotional expressions (emotional task-set) or gender (non-emotional task-set). Right tDCS resulted in faster responses in the gender task only when it followed a judgment of emotion. These effects were not observed following left tDCS. Further, switching away from emotion was easier for the right compared to left tDCS group (reduced switch costs for gender), while switching away from gender toward emotion was easier for the left compared to the right group (reduced switch-costs for emotion). In sum, tDCS over the DLPFC may modulate affective flexibility and right stimulation may be particularly helpful to facilitate disengagement from emotional task-sets. The usefulness of tDCS-trained affective switching may be further investigated on larger therapeutic protocols targeting emotional disorders.

A Randomized Placebo-Controlled Trial of Targeted Prefrontal Cortex Modulation with Bilateral tDCS in Patients with Crack-Cocaine Dependence

BACKGROUND

Transcranial direct current stimulation over the dorsolateral prefrontal cortex has been shown to be clinically useful in the treatment of drug addiction.

METHODS

We conducted a double-blind randomized clinical trial aiming to assess the effects of bilateral dorsolateral prefrontal cortex transcranial direct current stimulation (left cathodal/right anodal) on crack-cocaine addiction. We defined craving as the primary outcome, and other clinical measurements, including depressive and anxiety symptoms, and quality of life, as secondary outcomes. Seventeen male crack-cocaine users (mean age 30.4 ± 9.8 SD) were randomized to receive 5 sessions of active transcranial direct current stimulation (2 mA, 35 cm(2), for 20 minutes), every other day, and 19 males (mean age 30.3 ± 8.4 SD) to receive sham-transcranial direct current stimulation (placebo) as control group.

RESULTS

Craving scores were significantly reduced in the transcranial direct current stimulation group after treatment when compared with sham-transcranial direct current stimulation (P = .028) and baseline values (P = .003), and decreased linearly over 4 weeks (before, during, and after treatment) in the transcranial direct current stimulation group only (P = .047). Changes of anxiety scores towards increase in the sham-transcranial direct current stimulation and decrease in the transcranial direct current stimulation group (P = .03), and of the overall perception of quality of life (P = .031) and of health (P = .048) towards decrease in the sham-transcranial direct current stimulation group and increase in the transcranial direct current stimulation group differed significantly between groups.

CONCLUSIONS

Repetitive bilateral transcranial direct current stimulation over the dorsolateral prefrontal cortex reduced craving for crack-cocaine use, decreased anxiety, and improved quality of life. We hypothesize that transcranial direct current stimulation effects may be associated with increased prefrontal processing and regulation of craving behavior.