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

Neuromodulation of dorsal and ventral prefrontal cortex during gambling task performance in low and high impulsive individuals

INTRODUCTION

Impulsivity has been widely associated to risky decision-making and addictive behaviours. Recent research is investigating transcranial direct current stimulation (tDCS) as a potential tool to improve gambling disorder symptomatology; however, few studies have considered the influence of impulsivity on tDCS effects targeting different brain areas to modulate gambling-related behaviours.

METHODS

Two experiments were performed with two-session crossover designs using the same methodology and different samples of low and high impulsive participants (N=64). Multielectrode tDCS montages were designed to target right dorsolateral prefrontal cortex (rDLPFC) and ventromedial prefrontal cortex (vmPFC) during Cambridge gambling task (GCT) performance.

RESULTS

Results showed tDCS effects on CGT in both low and high impulsive individuals, revealing specific findings associated to rDLPFC and vmPFC targets respectively. A potential influence of impulsivity on tDCS effects was suggested by the differences in delay aversion between LI and HI, shown only in real stimulation but not in sham. Low and high impulsive participants showed differences in task performance, especially in the lowest and highest risk conditions.

CONCLUSION

Future neuromodulation research may benefit from taking into consideration factors including personality traits, such as impulsivity and participants individual differences that may impact the responsiveness to tDCS, as well as from employing neuroimaging techniques to identify the underlaying tDCS effects on specific brain circuits.

Sex-specific Alterations in the mRNA Expression of Histone Deacetylases (HDACs) in the Rat Brain Following Prolonged Abstinence from Methamphetamine Self-administration

Methamphetamine (METH) use disorder (MUD) is a psychiatric disease that imposes substantial health burdens throughout the world. Significant sex-specific differences in misuse and relapse rates exist among human METH users and in preclinical models of MUD. We have been using a METH self-administration (SA) model to identify molecular substrates of sex-related behavioral manifestations. Rats were trained to self-administer METH (0.1 mg/kg/injection, i.v.) over 20 days. Hippocampus (HIP), prefrontal cortex (PFC), nucleus accumbens (NAc), and dorsal striatum (dSTR) were dissected and used to measure mRNA expression of HDACs because of their potential involvement in MUD. Compared to females, males self-administered more METH. Quantitative PCR revealed that control male rats had higher basal Hdac4 mRNA levels in their HIP and Hdac10 in the PFC in comparison to female controls. In contrast, female controls had higher basal levels of Hdac1, Hdac2, Hdac5, Hdac6, Hdac7, Hdac8, Sirt1, and Sirt2 mRNAs in the PFC. In addition, female METH takers showed decreased mRNA levels of Hdac1, Hdac2, Hdac3, Hdac4, Hdac5, Hdac6, Hdac7, Hdac8 and Hdac11 in their PFC when compared to female controls. Male METH rats had increased Hdac1, Hdac2, Hdac6, Sirt1, and Sirt2 mRNA levels in their PFC, but decreased Hdac4, Sirt4 and Sirt5 mRNA levels in HIP when compared to male controls. These results provide further evidence for sexual dimorphic responses to METH after a long withdrawal interval. These observations support the notion that sex-specific therapeutic approaches using epigenetic agents may be necessary against METH use disorder.

The effect of transcranial Direct Current Stimulation on the Iowa Gambling Task: a scoping review

Introduction

Among the tasks employed to investigate decisional processes, the Iowa Gambling Task (IGT) appears to be the most effective since it allows for deepening the progressive learning process based on feedback on previous choices. Recently, the study of decision making through the IGT has been combined with the application of transcranial direct current stimulation (tDCS) to understand the cognitive mechanisms and the neural structures involved. However, to date no review regarding the effects of tDCS on decisional processes assessed through the IGT is available. This scoping review aims to provide a comprehensive exploration of the potential effects of tDCS in enhancing decisional processes, assessed with the IGT, through the evaluation of the complete range of target cases.

Methods

The existing literature was analyzed through the PRISMA approach.

Results

Results reported that tDCS can enhance performance in the IGT and highlighted a pivotal role of the dorsolateral prefrontal cortex and the orbitofrontal cortex in risky and ambiguous decisions.

Discussion

Thus, tDCS over the brain regions identified improves the decisional processes in healthy subjects and patients, confirming its potential to enhance decision making in everyday contexts and deepen the neural correlates. Suggestions for further studies are provided to delve into decisional mechanisms and how to better support them.

Effects of chronic stress on cognitive function - From neurobiology to intervention

Exposure to chronic stress contributes considerably to the development of cognitive impairments in psychiatric disorders such as depression, generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and addictive behavior. Unfortunately, unlike mood-related symptoms, cognitive impairments are not effectively treated by available therapies, a situation in part resulting from a still incomplete knowledge of the neurobiological substrates that underly cognitive domains and the difficulty in generating interventions that are both efficacious and safe. In this review, we will present an overview of the cognitive domains affected by stress with a specific focus on cognitive flexibility, behavioral inhibition, and working memory. We will then consider the effects of stress on neuronal correlates of cognitive function and the factors which may modulate the interaction of stress and cognition. Finally, we will discuss intervention strategies for treatment of stress-related disorders and gaps in knowledge with emerging new treatments under development. Understanding how cognitive impairment occurs during exposure to chronic stress is crucial to make progress towards the development of new and effective therapeutic approaches.

High-Definition Transcranial Direct Current Stimulation Improves Decision-Making Ability: A Study Based on EEG

High-definition transcranial direct current stimulation (HD-tDCS) has been shown to modulate decision-making; however, the neurophysiological mechanisms underlying this effect remain unclear. To further explore the neurophysiological processes of decision-making modulated by HD-tDCS, health participants underwent ten anodal (n = 16)/sham (n = 17) HD-tDCS sessions targeting the left DLPFC. Iowa gambling task was performed simultaneously with electroencephalography (EEG) before and after HD-tDCS. Iowa gambling task performance, the P300 amplitude, and the power of theta oscillation as an index of decision-making were compared. Behavioral changes were found that showed anodal HD-tDCS could improve the decision-making function, in which participants could make more advantageous choices. The electrophysiological results showed that the P300 amplitude significantly increased in CZ, CPZ electrode placement site and theta oscillation power significantly activated in FCZ, CZ electrode placement site after anodal HD-tDCS. Significant positive correlations were observed between the changes in the percent use of negative feedback and the changes in theta oscillation power before and after anodal HD-tDCS. This study showed that HD-tDCS is a promising technology in improving decision-making and theta oscillation induced by may be a predictor of improved decision-making.

Effects of transcranial static magnetic field stimulation over the left dorsolateral prefrontal cortex on random number generation

OBJECTIVE

Focal application of transcranial static magnetic field stimulation (tSMS) is a neuromodulation technique, with predominantly inhibitory effects when applied to the motor, somatosensory or visual cortex. Whether this approach can also transiently interact with dorsolateral prefrontal cortex (DLPFC) function remains unclear. The suppression of habitual or competitive responses is one of the core executive functions linked to DLPFC function. This study aimed to assess the impact of tSMS on the prefrontal contributions to inhibitory control and response selection by means of a RNG task.

METHODS

We applied 20 min of tSMS over the left DLPFC of healthy subjects, using a real/sham cross-over design, during performance of a RNG task. We used an index of randomness calculated with the measures of entropy and correlation to assess the impact of stimulation on DLPFC function.

RESULTS

The randomness index of the sequences generated during the tSMS intervention was significantly higher compared to those produced in the sham condition.

CONCLUSIONS

Our results indicate that application of tSMS transiently modulates specific functional brain networks in DLPFC, which indicate a potential use of tSMS for treatment of neuropsychiatric disorders.

SIGNIFICANCE

This study provides evidence for the capacity of tSMS for modulating DLPFC function.

Decision-making biases in suicide attempters with major depressive disorder: A computational modeling study using the balloon analog risk task (BART)

BACKGROUND

In the last decade, suicidality has been increasingly theorized as a distinct phenomenon from major depressive disorder (MDD), with unique psychological and neural mechanisms, rather than being mostly a severe symptom of MDD. Although decision-making biases have been widely reported in suicide attempters with MDD, little is known regarding what components of these biases can be distinguished from depressiveness itself.

METHODS

Ninety-three patients with current MDD (40 with suicide attempts [SA group] and 53 without suicide attempts [NS group]) and 65 healthy controls (HCs) completed psychometric assessments and the balloon analog risk task (BART). To analyze and compare decision-making components among the three groups, we applied a five-parameter Bayesian computational modeling.

RESULTS

Psychological assessments showed that the SA group had greater suicidal ideation and psychological pain avoidance than the NS group. Computational modeling showed that both MDD groups had higher risk preference and lower ability to learn and adapt from within-task observations than HCs, without differences between the SA and NS patient groups. The SA group also had higher loss aversion than the NS and HC groups, which had similar loss aversion.

CONCLUSIONS

Our BART and computational modeling findings suggest that psychological pain avoidance and loss aversion may be important suicide risk factor that are distinguishable from depression illness itself.

Efficacy of Noninvasive Brain Stimulation on Borderline Personality Disorder Core Symptoms: A Systematic Review

Although psychotherapy is the first-line treatment of borderline personality disorder (BPD), psychopharmacological agents have not been approved yet. Modulating brain functions with noninvasive brain stimulation (NIBS) interventions, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), may have a role in the treatment of BPD. In light of the limited knowledge available and the emerging interest in the possible role of NIBS as a therapeutic tool, the authors' main aim is to systematically review the literature on the effect of both rTMS and tDCS on BPD symptoms, specifically affective dysregulation, impulsive-behavioral dyscontrol, and cognitive-perceptual difficulties. The review process was conducted in accordance with PRISMA guidelines. The research methods were registered on PROSPERO (id code CRD42020209491). Eleven studies were included in the review. Despite the limited number of studies retrieved, preliminary data showed an improvement in all domains. Further studies are needed to understand potential long-term advantages of NIBS.

Transcranial-Direct-Current-Stimulation Accelerates Motor Recovery After Cortical Infarction in Mice: The Interplay of Structural Cellular Responses and Functional Recovery

BACKGROUND

Transcranial direct current stimulation (tDCS) promotes recovery after stroke in humans. The underlying mechanisms, however, remain to be elucidated. Animal models suggest tDCS effects on neuroinflammation, stem cell proliferation, neurogenesis, and neural plasticity.

OBJECTIVE

In a longitudinal study, we employed tDCS in the subacute and chronic phase after experimental focal cerebral ischemia in mice to explore the relationship between functional recovery and cellular processes.

METHODS

Mice received photothrombosis in the right motor cortex, verified by Magnetic Resonance Imaging. A composite neuroscore quantified subsequent functional deficits. Mice received tDCS daily: either 5 sessions from day 5 to 9, or 10 sessions with days 12 to 16 in addition. TDCS with anodal or cathodal polarity was compared to sham stimulation. Further imaging to assess proliferation and neuroinflammation was performed by immunohistochemistry at different time points and Positron Emission Tomography at the end of the observation time of 3 weeks.

RESULTS

Cathodal tDCS at 198 kC/m² (220 A/m²) between days 5 and 9 accelerated functional recovery, increased neurogenesis, decreased microglial activation, and mitigated CD16/32-expression associated with M1-phenotype. Anodal tDCS exerted similar effects on neurogenesis and microglial polarization but not on recovery of function or microglial activation. TDCS on days 12 to 16 after stroke did not induce any further effects, suggesting that the therapeutic time window was closed by then.

CONCLUSION

Overall, data suggest that non-invasive neuromodulation by tDCS impacts neurogenesis and microglial activation as critical cellular processes influencing functional recovery during the early phase of regeneration from focal cerebral ischemia.

Non-invasive transcranial electrical brain stimulation guided by functional near-infrared spectroscopy for targeted neuromodulation: A review

One of the primary goals in cognitive neuroscience is to understand the neural mechanisms on which cognition is based. Researchers are trying to find how cognitive mechanisms are related to oscillations generated due to brain activity. The research focused on this topic has been considerably aided by developing non-invasive brain stimulation techniques. The dynamics of brain networks and the resultant behavior can be affected by non-invasive brain stimulation techniques, which make their use a focus of interest in many experiments and clinical fields. One essential non-invasive brain stimulation technique is transcranial electrical stimulation (tES), subdivided into transcranial direct and alternating current stimulation. tES has recently become more well-known because of the effective results achieved in treating chronic conditions. In addition, there has been exceptional progress in the interpretation and feasibility of tES techniques. Summarizing the beneficial effects of tES, this article provides an updated depiction of what has been accomplished to date, brief history, and the open questions that need to be addressed in the future. An essential issue in the field of tES is stimulation duration. This review briefly covers the stimulation durations that have been utilized in the field while monitoring the brain using functional-near infrared spectroscopy-based brain imaging.

The Counterproductive Effect of Right Anodal/Left Cathodal Transcranial Direct Current Stimulation Over the Dorsolateral Prefrontal Cortex on Impulsivity in Methamphetamine Addicts

The current study aimed to evaluate the effect of transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) on behavioral impulsivity in methamphetamine addicts. Forty-five methamphetamine addicts were recruited and randomly divided into active tDCS and sham tDCS groups to receive a daily tDCS intervention for 5 days, with the intensity set to 2 mA for the active group and 0 mA for the sham group. Anodal and cathodal electrodes were, respectively, placed over the right and left DLPFC. Behavioral impulsivity in methamphetamine addicts was examined by the 2-choice oddball task at 3-time points: before tDCS intervention (baseline), after the first intervention (day 1), and after 5 repeated interventions (day 5). Besides, twenty-four healthy male participants were recruited as the healthy controls who completed a 2-choice oddball task. Analysis of accuracy for the 2-choice oddball task showed that behavioral impulsivity was counterproductively increased in the active group, which was shown by the decreased accuracy for the deviant stimulus. The results suggested that the present protocol may not be optimal and other protocols should be considered for the intervention of methamphetamine addicts in the future.