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

Cross-species translational paradigms for assessing positive valence system as defined by the RDoC matrix

Functions associated with processing reward-related information are fundamental drivers of motivation, learning, and goal-directed behavior. Such functions have been classified as the positive valence system under the Research Domain and Criteria (RDoC) criteria and are negatively impacted across a range of psychiatric disorders and mental illnesses. The positive valence system is composed of three comprehensive categories containing related but dissociable functions that are organized into either Reward Responsiveness, Reward Learning, or Reward Valuation. The presence of overlapping behavioral dysfunction across diagnostic mental disorders is in-part what motivated the RDoC initiative, which emphasized that the study of mental illness focus on investigating relevant behavior and cognitive functions and their underlying mechanisms, rather than separating efforts on diagnostic categories (i.e., transdiagnostic). Moreover, the RDoC approach is well-suited for preclinical neuroscience research, as the rise in genetic toolboxes and associated neurotechnologies enables researchers to probe specific cellular targets with high specificity. Thus, there is an opportunity to dissect whether behaviors and cognitive functions are supported by shared or distinct neural mechanisms. For preclinical research to effectively inform our understandings of human behavior however, the cognitive and behavioral paradigms should have predictive, neurobiological, and pharmacological predictive validity to the human test. Touchscreen-based testing systems provide a further advantage for this endeavor enabling tasks to be presented to animals using the same media and task design as in humans. Here, we outline the primary categories of the positive valence system and review the work that has been done cross-species to investigate the neurobiology and neurochemistry underlying reward-related functioning. Additionally, we provide clinical tasks outlined by RDoC, along with validity and/or need for further validation for analogous rodent paradigms with a focus on implementing the touchscreen-based cognitive testing systems.

A Causal Role of Right Temporoparietal Junction in Prosocial Learning: A Transcranial Direct Current Stimulation Study

Prosocial behavior is a common and important aspect of everyday social life. To behave prosocially, we need to learn the consequences of our actions for other people, known as prosocial learning. Previous studies have identified the right temporoparietal junction (rTPJ) as the critical neurological substrate for prosocial behavior. However, little is known about the causal role of the rTPJ in prosocial learning. To clarify the role of the rTPJ in prosocial learning, we used a reinforcement learning paradigm and transcranial direct current stimulation (tDCS). A total of 75 participants were recruited and randomly assigned to the anodal or sham tDCS group. While receiving tDCS stimulation over the rTPJ, participants were instructed to choose between different stimuli that were probabilistically associated with rewards for themselves in the self-learning condition or for another person in the prosocial-learning condition. Participants were able to learn to obtain rewards for themselves or others, and learning performance in the self-learning condition was better than that in the prosocial-learning condition. However, anodal tDCS over the rTPJ significantly improved learning performance in the prosocial-learning condition. These results indicate that the rTPJ plays a causal role in prosocial learning.

Lateralization of self-control over the dorsolateral prefrontal cortex in decision-making: a systematic review and meta-analytic evidence from noninvasive brain stimulation

The dorsolateral prefrontal cortex (DLPFC) has been widely recognized as a crucial brain "control area." Recently, its causal role in promoting deliberate decision-making through self-control and the asymmetric performance of the left and right DLPFC in control functions have attracted the interest of many researchers. This study was designed to investigate the role of DLPFC in decision-making behaviors and lateralization of its control function by systematically examining the effects of noninvasive brain stimulation (NIBS) over the DLPFC on intertemporal choice, risk decision-making, and social fairness-related decision-making tasks. Literature searches were implemented at PubMed, Embase, Cochrane, Web of Science, Wanfang Data, China Science and Technology Journal Database, and China National Knowledge Infrastructure until May 10, 2022. Meta-analytic results for included studies were estimated by random-effect models. A total of 33 eligible studies were identified, yielding 130 effect sizes. Our results indicated that compared to sham group, excitatory NIBS over the left DLPFC reduced delay discounting rate (standardized mean differences, SMD = -0.51; 95% confidence interval, 95% CI: [-0.81, -0.21]) and risk-taking performance (SMD = -0.39, 95% CI [-0.68, -0.10]), and inhibitory NIBS over the right DLPFC increased self-interested choice of unfair offers (SMD = 0.50, 95% CI [0.04, 0.97]). Finding of current work indicated that neural excitement of the DLPFC activation improve individuals' self-control during decision-makings, whereas neural inhibition results in impaired control. In addition, our analyses furnish causal evidence for the presence of functional lateralization in the left and right DLPFC in monetary impulsive decision-making and social decision-making, respectively.

Neural mechanisms of intertemporal and risky decision-making in individuals with internet use disorder: A perspective from directed functional connectivity

Background and aims

The intertemporal and risk decision-making impairments are vital cognitive mechanisms in internet use disorder (IUD). However, the underlying neural mechanisms for these two decision-making dysfunctions in individuals with IUD remain unclear.

Methods

This study employed Functional Near-Infrared Spectroscopy (fNIRS) to record changes in blood oxygen concentration in the prefrontal cortex of individuals with IUD during intertemporal and risk decision-making tasks.

Results

The findings revealed that the intertemporal decision-making deficits in IUD group were primarily associated with reduced activation in the left dorsolateral prefrontal cortex (dlPFC) and orbitofrontal cortex (OFC) and FC from the left dlPFC to the right dlPFC. On the other hand, risk decision-making impairments were linked to decreased OFC activation and weakened functional connectivity from the left dlPFC to the right dlPFC and OFC.

Discussions and Conslusions

These results suggested that while there were common neural mechanisms underlying intertemporal and risk decision-making impairments in individuals with IUD, specific neural foundations existed for each type of dysfunction.

Transcranial direct current stimulation (tDCS) over the orbitofrontal cortex reduces delay discounting

Delay discounting (DD) is a quantifiable psychological phenomenon that regulates decision-making. Nevertheless, the neural substrates of DD and its relationship with other cognitive domains are not well understood. The orbitofrontal cortex (OFC) is a potential candidate for supporting the expression of DD, but due to its wide involvement in several psychological functions and neural networks, its central role remains elusive. In this study, healthy subjects underwent transcranial direct current stimulation (tDCS) while performing an intertemporal choice task for the quantification of DD and a working memory task. To selectively engage the OFC, two electrode configurations have been tested, namely, anodal Fp1-cathodal Fp2 and cathodal Fp1-anodal Fp2. Our results show that stimulation of the OFC reduces DD, independently from electrode configuration. In addition, no relationship was found between DD measures and either working memory performance or baseline impulsivity assessed through established tests. Our work will direct future investigations aimed at unveiling the specific neural mechanisms underlying the involvement of the OFC in DD, and at testing the efficacy of OFC tDCS in reducing DD in psychological conditions where this phenomenon has been strongly implicated, such as addiction and eating disorders.

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

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

Neural Correlates of Delay Discounting in the Light of Brain Imaging and Non-Invasive Brain Stimulation: What We Know and What Is Missed

In decision making, the subjective value of a reward declines with the delay to its receipt, describing a hyperbolic function. Although this phenomenon, referred to as delay discounting (DD), has been extensively characterized and reported in many animal species, still, little is known about the neuronal processes that support it. Here, after drawing a comprehensive portrait, we consider the latest neuroimaging and lesion studies, the outcomes of which often appear contradictory among comparable experimental settings. In the second part of the manuscript, we focus on a more recent and effective route of investigation: non-invasive brain stimulation (NIBS). We provide a comprehensive review of the available studies that applied transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to affect subjects’ performance in DD tasks. The aim of our survey is not only to highlight the superiority of NIBS in investigating DD, but also to suggest targets for future experimental studies, since the regions considered in these studies represent only a fraction of the possible ones. In particular, we argue that, based on the available neurophysiological evidence from lesion and brain imaging studies, a very promising and underrepresented region for future neuromodulation studies investigating DD is the orbitofrontal cortex.

The brain stimulation of DLPFC regulates choice preference in intertemporal choice self-other differences

Intertemporal choice requires to make decision by evaluating the value of two options consisting of different times and benefits. The dorsolateral prefrontal cortex (DLPFC) is a key brain region for modulating intertemporal choice. The aim of this study is to investigate the effect of non-invasive brain stimulation over DLPFC on intertemporal choice behavior for self and others. We used transcranial direct current stimulation (tDCS) and continuous theta burst stimulation (cTBS) to stimulate bilateral DLPFC in two experiments respectively. After stimulation, subjects made a choice between a Smaller-Sooner (SS) reward and a Larger-Later (LL) reward in intertemporal choice task. The results showed that cTBS stimulation on the left DLPFC reduced the choice preference for SS reward when individuals made choices for themselves. The cTBS stimulation caused preference difference between choosing for self and parents. But tDCS stimulation had no effect on regulating choice preference. In addition, subjects preferred SS reward for self than strangers. Time-types and monetary difference of rewards affected the choice preference. The presence of immediate time increased the choice preference of SS reward. As the monetary difference increased, the choice proportion of SS reward decreased. Our study demonstrates that brain stimulation on the left DLPFC can regulate choice preference behavior in intertemporal choice.

Distinct role of the right temporoparietal junction in advantageous and disadvantageous inequity: A tDCS study

Fairness is a hallmark of humans' ability to maintain cooperative relationships with large numbers of unrelated others. It influences many aspects of daily life, from how people share their resources with partners to how policymakers shape income distribution policy. The right temporoparietal junction (rTPJ) is a hub of the mentalizing network and it has been proposed to play a key role in guiding human reciprocal behavior; however, its precise functional contribution to fair behavior in situations of advantageous and disadvantageous inequity remains unclear. The purpose of this study was to clarify the role of the rTPJ in relation to fair behavior in situations of advantageous and disadvantageous inequity by modulating the activation of the rTPJ through transcranial direct current stimulation (tDCS). Anodal tDCS at 1.5 mA over the primary visual cortex (VC) or rTPJ was performed and participants subsequently played a binary-choice version of the Dictator Game. We found that anodal tDCS over the rTPJ increased the participants' equity choices in the disadvantageous inequity situation but not in the advantageous inequity situation. The tDCS effect is moderated by sex and, in particular, the tDCS effect increases female equity choices. The results suggest that the rTPJ plays a distinct role in inequity aversion in these two types of inequity situations.

Decision neuroscience and neuroeconomics: Recent progress and ongoing challenges

In the past decade, decision neuroscience and neuroeconomics have developed many new insights in the study of decision making. This review provides an overarching update on how the field has advanced in this time period. Although our initial review a decade ago outlined several theoretical, conceptual, methodological, empirical, and practical challenges, there has only been limited progress in resolving these challenges. We summarize significant trends in decision neuroscience through the lens of the challenges outlined for the field and review examples where the field has had significant, direct, and applicable impacts across economics and psychology. First, we review progress on topics including reward learning, explore-exploit decisions, risk and ambiguity, intertemporal choice, and valuation. Next, we assess the impacts of emotion, social rewards, and social context on decision making. Then, we follow up with how individual differences impact choices and new exciting developments in the prediction and neuroforecasting of future decisions. Finally, we consider how trends in decision-neuroscience research reflect progress toward resolving past challenges, discuss new and exciting applications of recent research, and identify new challenges for the field. This article is categorized under: Psychology > Reasoning and Decision Making Psychology > Emotion and Motivation.

Distinguishing the Roles of the Dorsomedial Prefrontal Cortex and Right Temporoparietal Junction in Altruism in Situations of Inequality: A Transcranial Direct Current Stimulation Study

The right temporoparietal junction (rTPJ) and dorsomedial prefrontal cortex (dmPFC), which are involved in social cognition, have been proposed to play key roles in guiding human altruistic behavior. However, no study has provided empirical evidence that the rTPJ and dmPFC play distinct roles in altruism under situations of inequality. A total of 107 healthy young adults were randomly assigned to receive anodal or sham transcranial direct current stimulation (tDCS) to either the dmPFC or rTPJ, and they participated in a modified dictator game. The stimulation of the dmPFC increased the level of altruistic behavior, while the stimulation of the rTPJ did not. Furthermore, we determined that the increase in altruism induced by tDCS of the dmPFC could be modulated by perspective taking. These results demonstrate that the dmPFC and rTPJ play distinct roles in the enhancement of altruism in situations of inequality; this finding is consistent with theories proposing that the dmPFC has evolved mechanisms dedicated to perspective taking.

Transcranial Direct Current Stimulation (tDCS) over the Frontopolar Cortex (FPC) Alters the Demand for Precommitment

Caving into temptation leads to deviation from the planned path, which reduces our performance, adds trouble to our daily life, and can even bring about psychiatric disorders. Precommitment is an effective way to remedy the failure of willpower by removing the tempting short-term option. This paper aims to test the neural mechanisms of precommitment through a monetary task that excluded the interference of heterogeneous individual preferences and complements present researches. We examined whether transcranial direct current stimulation (tDCS) over the frontopolar cortex (FPC) could affect the demand for precommitment. The participants were required to make a decision regarding whether they were willing to precommit to binding later-lar ger rewards and remove the sooner-smaller rewards. Three conditions, including no precommitment, loose precommitment and strict precommitment, were established to perform a comprehensive investigation. We found that tDCS over the FPC altered the demand for precommitment in the condition involving loose precommitment with the control of delay discounting, specifically, anodal stimulation led to more precommitment, whereas cathodal stimulation reduced the demand for precommitment. Our findings established a causal correlation between the FPC and willingness to precommit and suggested a feasible method to enhance self-control in addition to exercising willpower.

Causal Role of the Right Dorsolateral Prefrontal Cortex in Organizational Fairness Perception: Evidence From a Transcranial Direct Current Stimulation Study

The right dorsolateral prefrontal cortex (rDLPFC) plays an essential role in social decision-making. Although several neural imaging studies have provided evidence that the rDLPFC is correlated with fairness perception, little research has investigated the causal effect of this encephalic region on individuals’ consciousness, particularly perceptions of organizational fairness. The present study explores the causal relationship between the rDLPFC and organizational fairness perception by using brain modulation techniques. Healthy participants received transcranial direct current stimulation (tDCS) and fulfilled the modified ultimatum game (UG) in the sham-controlled experiment. Our results showed that only cathodal stimulation of the rDLPFC resulted in increasing rejection offers compared with the sham stimulation in conditions of disadvantageous inequity. No differences were found between the anodal and sham stimulation in any inequity condition. This study strengthens the main functional effects of the rDLPFC in negative emotional control in relation to organizational fairness perceptions.

Anodal and cathodal tDCS modulate neural activity and selectively affect GABA and glutamate syntheses in the visual cortex of cats

KEY POINTS

The present study showed that anodal and cathodal transcranial direct current stimulation (tDCS) can respectively increase and decrease the amplitude of visually evoked field potentials in the stimulated visual cortex of cats, with the effect lasting for ∼60-70 min. We directly measured tDCS-induced changes in the concentration of inhibitory and excitatory neurotransmitters in the visual cortex using the enzyme-linked immunosorbent assay method and showed that anodal and cathodal tDCS can selectively decrease the concentration of GABA and glutamate in the stimulated cortical area. Anodal and cathodal tDCS can selectively inhibit the synthesis of GABA and glutamate by suppressing the expression of GABA- and glutamate-synthesizing enzymes, respectively.

ABSTRACT

Transcranial direct current stimulation (tDCS) evokes long-lasting neuronal excitability in the target brain region. The underlying neural mechanisms remain poorly understood. The present study examined tDCS-induced alterations in neuronal activities, as well as the concentration and synthesis of GABA and glutamate (GLU), in area 21a (A21a) of cat visual cortex. Our analysis showed that anodal and cathodal tDCS respectively enhanced and suppressed neuronal activities in A21a, as indicated by a significantly increased and decreased amplitude of visually evoked field potentials (VEPs). The tDCS-induced effect lasted for ∼60-70 min. By contrast, sham tDCS had no significant impact on the VEPs in A21a. On the other hand, the concentration of GABA, but not that of GLU, in A21a significantly decreased after anodal tDCS relative to sham tDCS, whereas the concentration of GLU, but not that of GABA, in A21a significantly decreased after cathodal tDCS relative to sham tDCS. Furthermore, the expression of GABA-synthesizing enzymes GAD65 and GAD67 in A21a significantly decreased in terms of both mRNA and protein concentrations after anodal tDCS relative to sham tDCS, whereas that of GLU-synthesizing enzyme glutaminase (GLS) did not change significantly after anodal tDCS. By contrast, both mRNA and protein concentrations of GLS in A21a significantly decreased after cathodal tDCS relative to sham tDCS, whereas those of GAD65/GAD67 showed no significant change after cathodal tDCS. Taken together, these results indicate that anodal and cathodal tDCS may selectively reduce GABA and GLU syntheses and thus respectively enhance and suppress neuronal excitability in the stimulated brain area.