Modulating risky decision-making in Parkinson's disease by transcranial direct current stimulation

Decision-making under ambiguity and risk and executive functions in Parkinson's disease patients: A scoping review of the studies investigating the Iowa Gambling Task and the Game of Dice

Evidence shows that patients affected by Parkinson's disease (PD) display the tendency toward making risky choices. This is due, at least in part, to the pathophysiological characteristics of the disease that affects neural areas underlying decision making (DM), in which a pivotal role is played by nonmotor corticostriatal circuits and dopamine. Executive functions (EFs), which can be impaired by PD as well, may sustain optimal choices in DM processes. However, few studies have investigated whether EFs can support PD patients to make good decisions. Adopting the scoping review approach, the present article is designed to deepen the cognitive mechanisms of DM under conditions of ambiguity and risk (that are conditions common to everyday life decisions) in PD patients without impulse control disorders. We focused our attention on the Iowa Gambling Task and the Game of Dice Task, because they are the most commonly used and reliable tasks to assess DM under ambiguity and under risk, respectively, and analyzed the performances in such tasks and their relationships with EFs tests in PD patients. The analysis supported the relationships between EFs and DM performance, especially when a higher cognitive load is required to make optimal decisions, as it happens under conditions of risk. Possible knowledge gaps and further research directions are suggested to better understand DM mechanisms in PD sustaining patients' cognitive functioning and preventing negative consequences in everyday life derived from suboptimal decisions.

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.

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.

Non-invasive brain stimulation targets and approaches to modulate gambling-related decisions: A systematic review

INTRODUCTION

Despite intense neuroscience research on the neurobiological underpinnings of Gambling Disorder (GD) and gambling-related decision-making, effective treatments targeting these dysfunctions are still lacking. Non Invasive Brain Stimulation (NIBS) techniques, such as transcranial Direct Current Stimulation (tDCS) and Transcranial Magnetic Stimulation (TMS), selectively modulate activity of brain circuits and have the potential to reverse alterations sustaining GD symptoms. Therefore, the aim of this systematic review was to determine the impact of different NIBS interventions on gambling-related decision processes.

METHODS

We conducted a comprehensive and translational search in three online databases (MEDLINE via PubMed, Scopus, Web of Science), in accordance with the PRISMA guidelines. We included studies applying neuromodulation (TMS, tDCS) techniques in GD patients or assessing gambling-related decision-making in healthy subjects. In addition, we explored the potential impact of NIBS in drug-induced GD (e.g., Parkinson's Disease).

RESULTS

Twenty-seven studies have been included. We summarized results to detect the impact of different targets and stimulation/inhibition protocols in terms of gambling-related decision-making. The majority of both tDCS and TMS studies targeted the dorsolateral prefrontal cortex. Although heterogeneous in protocols and parameters, results from tDCS and TMS studies converge in indicating that the stimulation (instead of inhibition) of prefrontal regions could be beneficial to contrast dysfunctional gambling-related decision processes.

CONCLUSION

NIBS interventions show promise to be further tested in controlled clinical settings for the treatment of behavioral addictions. Further studies are also necessary to investigate connectivity changes and laterality issues (unilateral versus bilateral; left versus right) of NIBS application in GD.

Frontotemporal Regulation of Subjective Value to Suppress Impulsivity in Intertemporal Choices

Impulsive decisions arise from preferring smaller but sooner rewards compared with larger but later rewards. How neural activity and attention to choice alternatives contribute to reward decisions during temporal discounting is not clear. Here we probed (1) attention to and (2) neural representation of delay and reward information in humans (both sexes) engaged in choices. We studied behavioral and frequency-specific dynamics supporting impulsive decisions on a fine-grained temporal scale using eye tracking and MEG recordings. In one condition, participants had to decide for themselves but pretended to decide for their best friend in a second prosocial condition, which required perspective taking. Hence, conditions varied in the value for themselves versus that pretending to choose for another person. Stronger impulsivity was reliably found across three independent groups for prosocial decisions. Eye tracking revealed a systematic shift of attention from the delay to the reward information and differences in eye tracking between conditions predicted differences in discounting. High-frequency activity (175-250 Hz) distributed over right frontotemporal sensors correlated with delay and reward information in consecutive temporal intervals for high value decisions for oneself but not the friend. Collectively, the results imply that the high-frequency activity recorded over frontotemporal MEG sensors plays a critical role in choice option integration.SIGNIFICANCE STATEMENT Humans face decisions between sooner smaller rewards and larger later rewards daily. An objective benefit of losing weight over a longer time might be devalued in face of ice cream because they prefer currently available options because of insufficiently considering long-term alternatives. The degree of contribution of neural representation and attention to choice alternatives is not clear. We investigated correlates of such decisions in participants deciding for themselves or pretending to choose for a friend. Behaviorally participants discounted less in self-choices compared with the prosocial condition. Eye movement and MEG recordings revealed how participants represent choice options most evident for options with high subjective value. These results advance our understanding of neural mechanisms underlying decision-making in humans.

Non-invasive brain stimulation for Parkinson's disease: Clinical evidence, latest concepts and future goals: A systematic review

Parkinson's disease (PD) is becoming a major public-health issue in an aging population. Available approaches to treat advanced PD still have limitations; new therapies are needed. The non-invasive brain stimulation (NIBS) may offer a complementary approach to treat advanced PD by personalized stimulation. Although NIBS is not as effective as the gold-standard levodopa, recent randomized controlled trials show promising outcomes in the treatment of PD symptoms. Nevertheless, only a few NIBS-stimulation paradigms have shown to improve PD's symptoms. Current clinical recommendations based on the level of evidence are reported in Table 1 through Table 3. Furthermore, novel technological advances hold promise and may soon enable the non-invasive stimulation of deeper brain structures for longer periods.

Non-invasive Transcranial Electrical Stimulation in Movement Disorders

Dysfunction within large-scale brain networks as the basis for movement disorders is an accepted hypothesis. The treatment options for restoring network function are limited. Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation are now being studied to modify the network. Transcranial electrical stimulation (tES) is also a portable, cost-effective, and non-invasive way of network modulation. Transcranial direct current stimulation and transcranial alternating current stimulation have been studied in Parkinson’s disease, dystonia, tremor, and ataxia. Transcranial pulsed current stimulation and transcranial random noise stimulation are not yet studied enough. The literature in the use of these techniques is intriguing, yet many unanswered questions remain. In this review, we highlight the studies using these four potential tES techniques and their electrophysiological basis and consider the therapeutic implication in the field of movement disorders. The objectives are to consolidate the current literature, demonstrate that these methods are feasible, and encourage the application of such techniques in the near future.

Effect of transcranial direct current stimulation on decision making and cognitive flexibility in gambling disorder

Decision making and cognitive flexibility are two components of cognitive control that play a critical role in the emergence, persistence, and relapse of gambling disorder. Transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) has been reported to enhance decision making and cognitive flexibility in healthy volunteers and individuals with addictive disorders. In this triple-blind randomized sham-controlled parallel study, we aimed to determine whether tDCS over DLPFC would modulate decision making and cognitive flexibility in individuals with gambling disorder. Twenty participants with gambling disorder were administered Iowa Gambling Task (IGT) and Wisconsin Card Sorting Test (WCST). Subsequently, participants were administered three every other day sessions of active right anodal /left cathodal tDCS (20 min, 2 mA) or sham stimulation over bilateral DLPFC. WCST and IGT were readministered following the last session. Baseline clinical severity, depression, impulsivity levels, and cognitive performance were similar between groups. TDCS over the DLPFC resulted in more advantageous decision making (F_1,16 = 8.128, p = 0.01, ɳp² =0.33) and better cognitive flexibility (F_1,16 =8.782, p = 0.009, ɳp² = 0.35), representing large effect sizes. The results suggest for the first time that tDCS enhanced decision making and cognitive flexibility in gambling disorder. Therefore, tDCS may be a promising neuromodulation-based therapeutic approach in gambling disorder.Trial registration: Clinicaltrials.gov NCT03477799.

Anodal transcranial direct current stimulation prevents methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity by modulating autophagy in an in vivo mouse model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the accumulation of protein inclusions and the loss of dopaminergic neurons. Transcranial direct current stimulation (tDCS) is a non-invasive brain-stimulating technique that has demonstrated promising results in clinical studies of PD. Despite accumulating evidence indicating that tDCS exerts a protective effect, the mechanism underlying its activity remains unknown. In the present study, we first investigated the neuroprotective effect of tDCS in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model and then evaluated the effect of tDCS on the autophagy pathway. tDCS improved behavioral alterations, increased tyrosine hydroxylase protein levels and suppressed α-synuclein protein levels in MPTP-treated mice. MPTP-treated mice subjected to tDCS also had lower levels of autophagy-related proteins, such as microtubule-associated protein 1 light chain 3 and AMP-activated protein kinase, and higher levels of mechanistic target of rapamycin and p62. In addition, the protein levels of phosphoinositide 3-kinase and brain-derived neurotrophic factor were higher, and the levels of unc-51-like kinase 1 were lower in MPTP-treated mice subjected to tDCS. Our findings suggest that tDCS protected against MPTP-induced PD in a mouse model by modulating autophagy.

Impaired decision-making and functional neuronal network activity in systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is associated with cognitive deficit but the exact neural mechanisms remain unclear.

Purpose

To explore sequential brain activities using functional magnetic resonance imaging (fMRI) during the performance of a decision‐making task, and to determine whether serum or clinical markers can reflect the involvement of the brain in SLE.

Subjects

Sixteen female SLE patients without overt clinical neuropsychiatric symptoms and 16 healthy controls were included.

Field Strength/Sequence

1.5T, T₁‐weighted anatomic images, gradient‐echo echo‐planar imaging sequence, and 3D images.

Assessment

The computer‐based Iowa Gambling Task (IGT) for assessing decision‐making was performed by SLE patients and 16 matched controls; brain activity was recorded via blood oxygen level‐dependent (BOLD) fMRI. The amplitudes of the average BOLD responses were calculated for each individual subject, and activation data from fMRI experiments were compared between the two groups.

Statistical Tests

Two‐sample t‐test; repeated‐measures analysis of variance (ANOVA); linear regression analyses.

Results

Imaging revealed activity in a distributed network of brain regions in both groups, including the ventromedial prefrontal cortex (vmPFC), the orbitofrontal cortex (OFC), the dorsolateral prefrontal cortex (dlPFC), the anterior cingulate cortex (ACC), the posterior cingulate cortex (PCC), and the striatum, as well as the insular, parietal, and occipital cortices. Compared to controls, SLE patients showed lower activation in a convergence zone and the limbic system, namely, the OFC, vmPFC, ACC, and PCC, but greater activation in memory, emotion, and behavior systems involving the dlPFC, the insular cortex and the striatum. Furthermore, brain activation in the vmPFC was positively correlated with IGT scores (r = 0.63, P < 0.001), but inversely related to disease activity (r = −0.57, P < 0.01).

Data Conclusion

The dynamics among the aforementioned neural systems (some hyperfunctioning, others hypofunctioning) may shed some light on the pathologic mechanisms underlying SLE without overt clinical neuropsychiatric symptoms. In addition, disease activity may potentially be used as an effective biomarker reflecting cerebral involvement in SLE.

Level of Evidence: 1

Technical Efficacy: Stage 3

J. Magn. Reson. Imaging 2018;48:1508–1517