Ventral striatal and medial prefrontal BOLD activation is correlated with reward-related electrocortical activity: A combined ERP and fMRI study

A systematic review of event-related potentials as outcome measures of attention bias modification

Attention bias modification (ABM) was initially developed with the goal of reducing attentional bias to threat-and subsequently anxious symptoms-in individuals with heightened anxiety. Although controversial, ABM appears to be generally effective in achieving this goal. Yet, the primary outcome measure of ABM (i.e., the reaction time-based differences score) has poor reliability and temporal resolution, which limits the inferences that can be drawn. In contrast, event-related potentials (ERPs) have superior reliability as well as temporal resolution and may therefore be better outcome measures of ABM. In this review, I systematically assess the research using ERPs as outcome measures in ABM protocols. I focus on the extent to which the ERPs modified by ABM represent earlier or later stages of information processing. In addition, I explore the extent to which ABM produces near and/or far transfer of learning effects on ERP measures. The reviewed literature suggests that ERPs are promising outcome measures of ABM. ABM modulates the effects of affective stimuli on posterior visually evoked ERPs (i.e., P1) as well as ERPs at anterior electrodes (i.e., P2, N2, and ERN). Based on the state of the field, several directions for future research are identified.

Altered reward responsiveness and depressive symptoms: An examination of social and monetary reward domains and interactions with rejection sensitivity

BACKGROUND

Alterations in positive valence systems and social processes, including low reward responsiveness and high rejection sensitivity, have been observed in depression. Most reward research focuses on the monetary domain, but social reward responsiveness may be particularly relevant to understanding the etiology of depression, especially in combination with other social processes. Pathways to depression are complex, and research testing interactions between multiple factors is needed. The present study examined the interactive effects of reward responsiveness and rejection sensitivity on depressive symptoms using both social and monetary reward electroencephalogram (EEG) tasks.

METHODS

Emerging adults (N = 120) completed peer interaction and monetary incentive delay tasks while EEG data were recorded, as well as self-report measures of rejection sensitivity and depressive symptoms.

RESULTS

The interaction between social reward responsiveness and self-reported rejection sensitivity was significantly associated with depressive symptoms, such that rejection sensitivity was associated with greater depressive symptoms for those with a relatively reduced response to social reward. The interaction between monetary reward responsiveness and rejection sensitivity was not significant.

LIMITATIONS

The study was cross-sectional and used a non-clinical sample.

CONCLUSIONS

Results suggest a possible pathway for depressive symptoms characterized by the combination of high rejection sensitivity and low social reward responsiveness. Findings highlight the need for consideration of multiple domains of reward responsiveness in clinical neuroscience research. With extension to longitudinal studies and clinical samples, the present findings may inform understanding of targets for intervention.

Electrophysiological investigation of reward anticipation and outcome evaluation during slot machine play

Slot machines are a popular form of gambling, offering a tractable way to experimentally model reward processes. This study used a 3-reel slot paradigm to assess psychologically distinct phases of reward processing, reflecting anticipation, and early- and late-stage outcome processing. EEG measures of winning, nearly missing (a losing outcome revealed at the final, third reel), and "totally" missing (a losing outcome revealed earlier, at the second reel) were collected from healthy adults (n=54). Condition effects were evaluated in: i) event-related potential (ERP) components reflecting anticipatory attention (stimulus preceding negativity, SPN) and outcome processing (reward positivity, RewP and late-positive potential, LPP) and ii) total power and phase synchrony of theta and delta band oscillations. Behaviorally, trial initiation was fastest after a near miss outcome and slowest after a winning outcome. As expected, a significant SPN was observed for possible wins (AA) vs. total misses (AB), consistent with reward anticipation. Larger win (AAA) vs. near miss (AAB) amplitudes were observed for the RewP; LPP amplitudes were largest for wins (AAA), intermediate for near misses (AAB), and smallest for total misses (ABC), reflecting significant early (RewP) and late-stage (LPP) outcome processing effects. There was an effect of reel position on the RewP, with larger amplitude in the final reel (AAA-AAB) relative to the 2^nd-reel locked difference waves (AA-AB). Across all outcomes, near misses elicited the largest and most phase-synchronized theta responses, while wins elicited larger and more phase-synchronized delta responses than total misses, with delta band measures not distinguishing between near misses and wins. . Phase locking measures contrasting win vs. near miss delta and theta synchronization, within time windows corresponding to ERP measurements, covaried with RewP, but not SPN or LPP, amplitude. Lastly, EEG measures showed differential relationships with age and self-reported consummatory pleasure. In the context of slot machine play, where reward anticipation and attainment place minimal demands on effort and skill, ERP and time-frequency methods capture distinct neurophysiological signatures of reward anticipation and outcome processing.

Self-awareness buffers the consequences of negative feedback: Evidence from an ERP study

Previous studies have found that self-awareness can help people to recruit more cognitive resources, while people with more cognitive resources can better buffer the detrimental effects of negative events. However, it is not clear whether self-awareness can directly buffer the consequences of negative feedback (i.e., reducing neural sensitivity to negative feedback). To explore this issue, we used a scrambled sentence task (SST) to manipulate participants' self-awareness (self vs. other) and investigated whether outcome evaluations in a gambling task are modulated by the self-awareness priming. Event-related brain potentials (ERPs) were recorded while 27 normal adults performed a gambling task. The ERP analysis focused on the feedback-related negativity (FRN), reward positivity (RewP) and P300 component. We found that the self-awareness priming resulted in a smaller FRN response to the losses compared with the other-awareness priming. There was no significant difference in the RewP response to wins between the self-awareness condition and the other-awareness condition. We also found that the self-awareness condition evoked larger P300 amplitude than the other-awareness condition. The present findings suggest that self-awareness can help people to cope with negative feedback in the early semiautomatic outcome evaluation stage (i.e., reducing neural sensitivity to negative feedback) and enhance top-down evaluation to both positive and negative feedback in the late and deliberate stage, providing direct evidence of the adaptive function of self-awareness on outcome experience.

Cannabis users demonstrate enhanced neural reactivity to reward: An event-related potential and time-frequency EEG study

INTRODUCTION

Disruptions in neural measures of reward responsiveness are implicated in risk for and the development of Substance Use Disorders (SUDs) in general, but it is not clear if this is also true for Cannabis Use Disorder (CUD). To date, no studies have examined neural reward responsiveness in cannabis users using EEG.

METHODS

Cannabis users (CU; n = 67) and non-users (n = 60) were drawn from larger studies of individuals with and without internalizing and externalizing psychopathology. Groups were matched on current and lifetime psychopathology. Participants completed a validated monetary reward task during electroencephalogram (EEG). One-way between subject analysis of covariance (ANCOVA) models examined group differences in four EEG indicators of reward responsiveness - the reward positivity (RewP) and feedback negativity (FN) event-related potentials and two time-frequency measures (reward-related delta and loss-related theta).

RESULTS

CU demonstrated an enhanced RewP to the attainment of monetary reward compared to non-users (p = .004), even after controlling for relevant covariates. Secondary analyses found that occasional CU, but not current CUD or remitted CUD, showed enhanced RewP compared to non-users. There were no significant differences in FN, reward-related delta, or loss-related theta time-frequency measures between groups.

CONCLUSIONS

To our knowledge, this is the first study to show preliminary evidence that CU have an enhanced RewP to reward and the extent of disruption may be related to CUD status. Our findings suggest that greater neural reward responsiveness may only be seen among occasional CU, not necessarily among CU with current or remitted CUD.

Emotion context insensitivity in depression: Toward an integrated and contextualized approach

Major depressive disorder (MDD) is characterized by pervasive mood disturbance as well as deficits in emotional processing, reactivity, and regulation. There is accumulating evidence that MDD is characterized by emotional patterns consistent with environmental disengagement, as reflected in attenuated positive and negative emotional reactivity, consistent with Emotion Context Insensitivity (ECI) theory. However, MDD individuals vary considerably in the extent to which they exhibit specific alterations in patterns of emotional responding. Emotions are complex, multicomponent processes that invoke responses across multiple functional domains and levels of analysis, including subjective experience, behavior, autonomic regulation, cognition, and neural processing. In this article, I review the current state of the literature on emotional responding and MDD from the lens of ECI. I focus on the importance of assessing emotional indices from multiple levels of analysis across development and contexts. I also discuss methodological and measurement issues that may contribute to inconsistent findings. In particular, I emphasize how psychophysiological measures can help elucidate emotional processes that underlie the pathophysiology of MDD as part of an integrated and contextualized approach.

Striatal activation to monetary reward is associated with alcohol reward sensitivity

One well-known phenotypic risk factor for the development of alcohol use disorder is sensitivity to the rewarding effects of alcohol. In the present study, we examined whether individuals who are sensitive to alcohol reward are also sensitive to nondrug rewards, thereby reflecting a broader individual difference risk factor. Specifically, we tested the hypothesis that subjective response to acute rewarding effects of alcohol would be related to neural activation during monetary reward receipt relative to loss (in the absence of alcohol). Community-recruited healthy young social drinkers (N = 58) completed four laboratory sessions in which they received alcohol (0.8 g/kg) and placebo in alternating order under double-blind conditions, providing self-report measures of subjective response to alcohol at regular intervals. At a separate visit 1-3 weeks later, they completed a reward-guessing game, the 'Doors' task, during fMRI in a drug-free state. Participants who reported greater motivation (i.e., wanting) to consume more alcohol after a single moderate dose of alcohol also exhibited greater neural activation in the bilateral ventral caudate and the nucleus accumbens during reward receipt relative to loss. Striatal activation was not related to other subjective ratings including alcohol-induced sedation, stimulation, or pleasure (i.e., feeling, liking). Our study is the first to show that measures of alcohol reward are related to neural indices of monetary reward in humans. These results support growing evidence that individual differences in responses to drug and nondrug reward are linked and together form a risk profile for drug use or abuse, particularly in young adults.

Neural responses to social acceptance predict behavioral adjustments following peer feedback in the context of a real-time social interaction task

Strong social connections are important predictors of both mental and physical health. The ability to effectively process social feedback from other people and adjust behavior accordingly is a critical part of skillfully navigating the social landscape. However, relatively few studies have considered neural systems driving these behavioral adjustments. In this study, 254 participants engaged in a peer interaction game while electroencephalogram (EEG) was recorded. In this game, participants repeatedly "interact" with a small set of virtual peers over a series of rounds, in which they provide feedback to their peers, and receive feedback from them in turn. A reward-sensitive event-related potential called the Reward Positivity (RewP) was extracted from the EEG following positive feedback from peers, and multilevel modeling was used to examine whether the RewP moderated associations between the feedback participants received during the task and their subsequent behavior. Participants were more likely to accept coplayers who had previously voted to accept them, and to like coplayers who had voted to accept them on the same round. A larger RewP was associated with a stronger tendency to modify behavior following feedback from peers, both in terms of voting behavior and expressions of liking. These data suggest that initial neural responsiveness to reward within 300 ms of positive social feedback may guide social behaviors. Thus, this line of research represents an important step toward a more complete understanding of the ways in which neural responses to feedback are involved in human social behaviors.

Revenge is sweet: Investigation of the effects of Approach-Motivated anger on the RewP in the motivated anger delay (MAD) paradigm

Past research has found that neural activity associated with feedback processing is enhanced by positive approach-motivated states. However, no past work has examined how reward processing changes in the context of revenge. Using a novel aggression paradigm, we sought to explore the influence of approach-motivated anger on neural responses to feedback indicating the opportunity to seek revenge against an offending opponent by examining the reward positivity (RewP), an event-related potential indexing performance feedback. In Experiment 1, after receiving insulting feedback from an opponent, participants played a reaction time game with three trial types: revenge trials, aggravation trials, and no-consequence trials. Results revealed that RewP amplitudes were larger to revenge trial win feedback than no-consequence trial win feedback or revenge trial loss feedback. RewP amplitudes were larger to both aggravation trial win and loss feedback than on no-consequence trials. Experiment 2 examined the influence of approach-motivated anger during the acquisition of rewards on the RewP without the possibility of retribution from the offending individual. Participants played a reaction time game similar to Experiment 1, except instead of giving or receiving noise blasts, participants could win money from the insulter (revenge trials) or a neutral-party (e.g., bank). Results indicated that revenge wins elicited larger RewP amplitudes than bank wins. These results suggest that anger enhances revenge-related RewP amplitudes to obtaining revenge opportunities and further aggravation wins or losses. Anger appears to enhance the pleasurable feelings of revenge.

Neural Indicators of Anhedonia: Predictors and Mechanisms of Treatment Change in a Randomized Clinical Trial in Early Childhood Depression

BACKGROUND

Early childhood depression is associated with anhedonia and reduced event-related potential (ERP) responses to rewarding or pleasant stimuli. Whether these neural measures are indicators of target engagement or treatment outcome is not yet known.

METHODS

We measured ERP responses to win and loss feedback in a guessing task and to pleasant versus neutral pictures in young (4.0-6.9 years of age) depressed children before and after randomization to either 18 weeks of Parent-Child Interaction Therapy-Emotion Development (PCIT-ED) or waitlist.

RESULTS

Analyses included reward positivity (RewP) data from 118 children randomly assigned to PCIT-ED (n = 60) or waitlist (n = 58) at baseline and late positive potential (LPP) data from 99 children (44 assigned to PCIT-ED vs. 55 assigned to waitlist) at baseline. Children undergoing PCIT-ED showed a greater reduction in anhedonia (F_1,103 = 10.32, p = .002, partial η² = .09). RewP reward responses increased more (F_1,86 = 5.98, p = .02, partial η² = .07) for PCIT-ED, but a greater change in RewP was not significantly associated with a greater reduction in major depressive disorder symptoms (r = -.12, p > .4). Baseline RewP did not predict treatment change. LPPs to positive pictures did not change across treatment, but greater baseline LPPs to positive pictures predicted a higher likelihood of remission from major depressive disorder in children undergoing PCIT-ED (B = 0.14; SE = 0.07; odds ratio = 1.15; p = .03).

CONCLUSIONS

The ERP reward response improved in young children with depression during a treatment designed to enhance emotion development, providing evidence of target engagement of the neural systems associated with reward. Further, greater baseline LPP responses to positive pictures was associated with a greater likelihood of depression remission, suggesting that this ERP measure can predict which children are most likely to respond to treatment.

A Systematic Review of the Positive Valence System in Autism Spectrum Disorder

This review synthesized current literature of behavioral and cognitive studies targeting reward processing in autism spectrum disorder (ASD). The National Institute of Mental Health's Research Domain Criteria (RDoC) Positive Valence System (PVS) domain was used as an overarching framework. The objectives were to determine which component operations of reward processing may be atypical in ASD and consequently postulate a heuristic model of reward processing in ASD that could be evaluated with future research. 34 studies were identified from the Embase, PubMed, PsycINFO, and Web of Science databases and included in the review using guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (also known as PRISMA guidelines). The extant literature suggested potential relationships between social symptoms of ASD and PVS sub-constructs of reward anticipation, probabilistic and reinforcement learning, reward prediction error, reward (probability), delay, and effort as well as between restricted and repetitive behaviors and interests (RRBIs) and PVS-sub constructs of initial response to reward, reward anticipation, reward (probability), delay, and effort. However, these findings are limited by a sparse and mixed literature for some sub-constructs. We put forward a developmentally informed heuristic model that posits how these component reward processes may be implicated in early ASD behaviors as well as later emerging and more intransigent symptoms. Future research is needed to comprehensively evaluate the proposed model.

Blunted neural effects of perceived control on reward feedback in major depressive disorder

BACKGROUND

Blunted reward processing has emerged as an endophenotype of major depressive disorder (MDD), but mechanistic understanding for this deficit remains elusive. The current event-related potential study examined whether this aberration is driven by the blunted effect of perceived control on reward processing.

METHODS

We adapted a well-validated gambling task in which perceived control was exercised by choice in 29 individuals with current MDD and 31 healthy controls. We examined the reward positivity in response to personally chosen versus passively received rewards.

RESULTS

We found that MDD patients relative to healthy controls exhibited a blunted reward positivity when rewards were delivered following voluntary choices but not when they were delivered following passive choices. This pattern was not observed during the relatively late stage, as indexed by the P300, of feedback processing.

LIMITATION

The current findings may be confounded with medication and anxiety.

CONCLUSIONS

These findings suggest that deficient reward processing in MDD is attributable to the deficiency in boosting reward responsivity by perceived control exercised by choice.

Social Feedback Valence Differentially Modulates the Reward Positivity, P300, and Late Positive Potential

Abnormal social or reward processing is associated with several mental disorders. Although most studies examining reward processing have focused on monetary rewards, recent research also has tested neural reactivity to social rewards (e.g., positive social feedback). However, the majority of these studies only include two feedback valences (e.g., acceptance, rejection). Yet, social evaluation is rarely binary (positive vs. negative) and people often give 'on the fence' or neutral evaluations of others. Processing of this type of social feedback may be ambiguous and impacted by factors such as psychopathology, self-esteem, and prior experiences of rejection. Thus, the present study probed the reward positivity (RewP), P300, and late positive potential (LPP) following acceptance, rejection, and "one the fence" [between acceptance and rejection] feedback in undergraduate students (n = 45). Results indicated that the RewP showed more positive amplitudes following acceptance compared to both rejection and "on the fence" feedback, and the RewP was larger (i.e., more positive) following rejection relative to "on the fence" feedback. In contrast, the P300 did not differ between rejection and "on the fence" feedback, and both were reduced compared to acceptance. The LPP was blunted in response to rejection relative to acceptance and "on the fence" feedback (which did not differ from each other). Exploratory analyses demonstrated that greater self-reported rejection sensitivity was associated with a reduced LPP to acceptance. Taken together, these findings suggest that the neural systems underlying the RewP, P300, and LPP may evaluate "on the fence" social feedback differently, and that individuals high on rejection sensitivity may exhibit reduced attention toward and elaborative processing of social acceptance.

Neural response to rewards predicts risk-taking in late but not early adolescent females

Risk-taking peaks in adolescence and reflects, in part, hyperactivity of the brain's reward system. However, it has not been established whether the association between reward-related brain activity and risk-taking varies across adolescence. The present study investigated how neural reward sensitivity is associated with laboratory risk-taking in a sample of female adolescents as a function of age. Sixty-three female adolescents ages 10-19 completed the Balloon Analogue Risk Task, a laboratory measure of risk-taking behavior, as well as a forced choice monetary gambling task while an electroencephalogram (EEG) was recorded. This gambling task elicits the reward positivity (RewP), a frontocentral event-related potential component that is sensitive to feedback signaling reward. We observed a negative quadratic association between age and risk-taking, such that those in early and late adolescence had lower relative risk-taking compared to mid-adolescence, with risk-taking peaking at around 15 years of age. In predicting risk-taking, we observed an interaction between age and RewP, such that reward-related brain activity was not associated with risk-taking in early adolescence but was associated with a greater propensity for risk in later adolescence. These findings suggest that for females, neural response to rewards is an important factor in predicting risk-taking only in later adolescence.

Differentiating clinically depressed adolescents with and without active suicidality: An examination of neurophysiological and self-report measures of reward responsiveness

BACKGROUND

Suicidality in youth is a major public health problem and objective methods for identifying those at greatest risk are critically needed. Suicidality has been associated with alterations in reward-related decision-making, but the extent to which measures of reward responsiveness (RR) can differentiate youth with and without suicidality in clinical samples remains unclear.

METHODS

We examined reliable and accessible neurophysiological (i.e., reward positivity [RewP] event-related potential) and self-report (Behavioral Activation System subscales) measures of RR in relation to active suicidality in 58 clinically depressed adolescents (14- to 18-year-olds).

RESULTS

Logistic regression analysis indicated that active suicidality in depressed adolescents was associated with heightened RR at both the self-report and neurophysiological levels. A relatively more positive RewP to win and a more negative RewP to loss uniquely predicted active suicidality beyond demographic, clinical, and self-report measures.

CONCLUSIONS

Results support the utility of neurophysiological measures in differentiating clinically depressed adolescents with and without suicidality. Although depression is commonly characterized by reduced RR, depressed adolescents with active suicidality exhibited relatively enhanced neural responses to reward and loss feedback. Results highlight the need for consideration of heterogeneity in RR in depression and research on personalized depression treatment.

EEG correlates of physical effort and reward processing during reinforcement learning

Effort-based decision making is often modeled using subjective value, a function of reward discounted by effort. We asked whether EEG event-related potential (ERP) correlates of reward processing are also modulated by physical effort. Human participants performed a task in which they were required to accurately produce target levels of muscle activation to receive rewards. Quadriceps muscle activation was recorded with electromyography (EMG) during isometric knee extension. On a given trial, the target muscle activation required either low or high effort. The effort was determined probabilistically according to a binary choice, such that the responses were associated with 20% and 80% probability of high effort. This contingency could only be learned through experience, and it reversed periodically. Binary reinforcement feedback depended on accurately producing the target muscle activity. Participants adaptively avoided effort by switching responses more frequently after choices that resulted in hard effort. Feedback after participants' choices that revealed the resulting effort requirement did not elicit modulation of the feedback-related negativity/reward positivity (FRN/RP). However, the neural response to reinforcement outcome after effort production was increased by preceding physical effort. Source decomposition revealed separable early and late positive deflections contributing to the ERP. The main effect of reward outcome, characteristic of the FRN/RP, loaded onto the earlier component, whereas the reward × effort interaction was observed only in the later positivity, which resembled the P300. Thus, retrospective effort modulates reward processing. This may explain paradoxical behavioral findings whereby rewards requiring more effort to obtain can become more powerful reinforcers.NEW & NOTEWORTHY Choices probabilistically determined the physical effort requirements for a subsequent task, and reward depended on task performance. Feedback revealing whether choices resulted in easy or hard effort did not elicit reinforcement learning signals. However, the neural responses to reinforcement were modulated by preceding effort. Thus, effort itself was not treated as loss or punishment, but it affected the responses to subsequent reinforcement outcomes. This may explain how effort can enhance the motivational effect of reward.

Reward-Related Neural Predictors and Mechanisms of Symptom Change in Cognitive Behavioral Therapy for Depressed Adolescent Girls

BACKGROUND

Approximately half of depressed adolescents fail to respond to cognitive behavioral therapy (CBT). Given the variability in response, it is important to identify pretreatment characteristics that predict prognosis. Knowledge of which depressed adolescents are likely to exhibit a positive versus poor outcome to CBT may have important clinical implications (e.g., informing treatment recommendations). Emerging evidence suggests that neural reward responsiveness represents one promising predictor.

METHODS

Adolescents with major depressive disorder (n = 36) received CBT and completed a reward task at 3 time points (pretreatment, midtreatment and posttreatment) while 128-channel electroencephalographic data were acquired. Healthy control participants (n = 29) completed the same task at 3 corresponding time points. Analyses focused on event-related potentials linked to 2 stages of neural processing: initial response to rewards (reward positivity) and later, elaborative processing (late positive potential). Moreover, time-frequency analyses decomposed the reward positivity into 2 constituent components: reward-related delta and loss-related theta activity.

RESULTS

Multilevel modeling revealed that greater pretreatment reward responsiveness, as measured by the late positive potential to rewards, predicted greater depressive symptom change. In addition, a group × condition × time interaction emerged for theta activity to losses, reflecting normalization of theta power in the group with major depressive disorder from baseline to posttreatment.

CONCLUSIONS

An event-related potential measure of sustained (late positive potential)-but not initial (reward positivity)-reward responsiveness predicted symptom improvement, which may help inform which depressed adolescents are most likely to benefit from CBT. In addition to alleviating depression, successful CBT may attenuate underlying neural (theta) hypersensitivity to negative outcomes in depressed youths.

Shifts in attentional scope modulate event-related potentials evoked by reward

Emotions broaden or narrow the scope of attention in order to facilitate adaptive responses in threatening and rewarding contexts. In the current study, rather than asking how emotions influence attentional scope, we considered the possibility that the relationship between attentional breadth and emotion is bidirectional by asking whether shifts in attentional scope alter emotional processes using an event-related potential (ERP) paradigm. Participants (N = 30) completed a modified version of a Monetary Incentive Delay (MID) task, wherein their attention was either narrowed or broadened as they attempted to win rewards. Behaviorally, narrowing attention improved task performance in the form of reduced errors and increased monetary winnings. During cue processing, narrowing (compared to broadening) attention reduced the Cue-P3 (irrespective of cue type). During feedback processing, narrowing (compared to broadening) attention reduced the Feedback-P3 to monetary wins and increased the Feedback-P2 and the Feedback-P3 to monetary non-wins. Results highlight complexity and bidirectionality in the relationship between attentional scope and affective processes.

Stressful life events moderate the effect of neural reward responsiveness in childhood on depressive symptoms in adolescence

BACKGROUND

Reward processing deficits have been implicated in the etiology of depression. A blunted reward positivity (RewP), an event-related potential elicited by feedback to monetary gain relative to loss, predicts new onsets and increases in depression symptoms. Etiological models of depression also highlight stressful life events. However, no studies have examined whether stressful life events moderate the effect of the RewP on subsequent depression symptoms. We examined this question during the key developmental transition from childhood to adolescence.

METHODS

A community sample of 369 children (mean age of 9) completed a self-report measure of depression symptoms. The RewP to winning v. losing was elicited using a monetary reward task. Three years later, we assessed stressful life events occurring in the year prior to the follow-up. Youth depressive symptoms were rated by the children and their parents at baseline and follow-up.

RESULTS

Stressful life events moderated the effect of the RewP on depression symptoms at follow-up such that a blunted RewP predicted higher depression symptoms in individuals with higher levels of stressful life events. This effect was also evident when events that were independent of the youth's behavior were examined separately.

CONCLUSIONS

These results suggest that the RewP reflects a vulnerability for depression that is activated by stress.

Developmental trajectories to reduced activation of positive valence systems: A review of biological and environmental contributions

Reduced activation of positive valence systems (PVS), including blunted neural and physiological responses to pleasant stimuli and rewards, has been shown to prospectively predict the development of psychopathology. Yet, little is known about how reduced PVS activation emerges across development or what implications it has for prevention. We review genetic, temperament, parenting, and naturalistic and laboratory stress research on neural measures of PVS and outline developmentally-informed models of trajectories of PVS activation. PVS function is partly heritable and appears to reflect individual differences in early-emerging temperament traits. Although lab-induced stressors blunt PVS activation, effects of parenting and naturalistic stress on PVS are mixed and depend on the type of stressor, developmental timing, and interactions amongst risk factors. We propose that there may be multiple, dynamic developmental trajectories to reduced PVS activation in which combinations of genes, temperament, and exposure to severe, prolonged, or uncontrollable stress may exert direct and interactive effects on PVS function. Critically, these risk factors may alter PVS developmental trajectories and/or PVS sensitivity to proximal stressors. Distinct factors may converge such that PVS activation proceeds along a typical, accelerated, chronically low, or stress-reactive trajectory. Finally, we present directions for future research with translational implications.

The effect of perceived effort and perceived control on reward valuation: Using the reward positivity to test a dissonance theory prediction

Past psychological theory and research suggest two opposing relationships between effort and reward valuation. Cognitive dissonance theory and research suggest that increased effort is associated with increased reward valuation, whereas theory and research on effort discounting suggest that increased effort is associated with decreased reward valuation. The present study was designed to test these two opposing perspectives, by examining a potential moderator of the relationship between effort and reward valuation - the belief that the effort was necessary to obtain the reward. Results (n = 44) suggested that increased perceptions of effort following a task were associated with larger neural responses to rewards (as assessed by the event-related potential referred to as the reward positivity) when individuals believed that their effort led to the reward but not when they believed that their effort did not lead to the reward. Discussion considers the implications of these results.

The reward positivity: Comparing visual and auditory feedback

Past work has demonstrated that the reward positivity (RewP) indexes a feedback-monitoring system sensitive to positive outcomes. Research on the RewP has frequently used simple guessing tasks. In the doors task, participants receive either feedback denoting monetary gain or loss on each trial after choosing one of two doors to "open." Typically, these tasks present visual stimuli on a computer monitor. The current study developed and validated a version of the doors task utilizing auditory stimuli to indicate gains and losses. Thirty-eight young adults completed both a standard visual doors task and a novel auditory doors task. Results indicated that the audio RewP was more positive and peaked earlier than the visual RewP. Additionally, the audio RewP both moderately correlated with and demonstrated similar internal consistency as the visual RewP. These results suggest that the auditory doors task elicits the same feedback-monitoring processes as the visual doors task.

Functional heterogeneity of perceived control in feedback processing

Perceived control is a fundamental psychological function that can either boost positive affect or buffer negative affect. The current study addressed the electrophysiological correlates underlying perceived control, as exercised by choice, in the processing of feedback valence. Thirty-six participants performed an EEG choice task during which they received positive or negative feedback following choices made either by themselves or by a computer. Perceived control resulted in an enhanced reward positivity for positive feedback but increased theta power for negative feedback. Further, perceived control led to greater feedback P3 amplitude and delta power, regardless of feedback valence. These results suggest functional heterogeneity of perceived control in feedback processing as diverse as magnifying the reward signal, enhancing the need for control and increasing the motivational salience of outcome irrespective of valence.

The Effect of Perceived Effort on Reward Valuation: Taking the Reward Positivity (RewP) to Dissonance Theory

The present research was designed to test whether the subjective experience of more effort related to more reward valuation as measured by a neural response. This prediction was derived from the theory of cognitive dissonance and its effort justification paradigm. Young adult participants (n = 82) engaged in multiple trails of a low or high effort task that resulted in a loss or reward on each trial. Neural responses to the reward (loss) cue were measured using EEG so that the event-related potential known as the Reward Positivity (RewP) could be assessed. Results revealed no significant differences between low and high effort conditions on the RewP. However, within the high effort condition, a more subjective experience of effort was associated with a larger RewP. This research extends past research on the effort justification paradigm of cognitive dissonance theory by suggesting that effort justification is associated with an implicit measure of reward valuation. It, therefore, challenges recent perspectives on dissonance processes that posit that these evaluative changes should only occur on explicit but not implicit measures.

A randomized proof-of-mechanism trial applying the 'fast-fail' approach to evaluating κ-opioid antagonism as a treatment for anhedonia

The National Institute of Mental Health (NIMH) 'fast-fail' approach seeks to improve too-often-misleading early-phase drug development methods by incorporating biomarker-based proof-of-mechanism (POM) testing in phase 2a. This first comprehensive application of the fast-fail approach evaluated the potential of κ-opioid receptor (KOR) antagonism for treating anhedonia with a POM study determining whether robust target engagement favorably impacts the brain circuitry hypothesized to mediate clinical effects. Here we report the results from a multicenter, 8-week, double-blind, placebo-controlled, randomized trial in patients with anhedonia and a mood or anxiety disorder (selective KOR antagonist (JNJ-67953964, 10 mg; n = 45) and placebo (n = 44)). JNJ-67953964 significantly increased functional magnetic resonance imaging (fMRI) ventral striatum activation during reward anticipation (primary outcome) as compared to placebo (baseline-adjusted mean: JNJ-67953964, 0.72 (s.d. = 0.67); placebo, 0.33 (s.d. = 0.68); F(1,86) = 5.58, P < 0.01; effect size = 0.58 (95% confidence interval, 0.13-0.99)). JNJ-67953964, generally well tolerated, was not associated with any serious adverse events. This study supports proceeding with assessment of the clinical impact of target engagement and serves as a model for implementing the 'fast-fail' approach.

Reward Responsiveness in Suicide Attempters: An Electroencephalography/Event-Related Potential Study

BACKGROUND

The present study aimed to objectively examine the Research Domain Criteria (RDoC) subconstructs of reward anticipation and initial response to reward in adult suicide attempters, compared with nonattempters, using electroencephalography (EEG) and event-related potentials (ERPs) within the context of the RDoC-recommended experimental paradigms for these subconstructs.

METHODS

Participants had either a history of at least 1 suicide attempt (n = 30) or no history of attempting suicide (n = 30). They completed diagnostic interviews, self-report questionnaires, and 2 computer-based tasks-the monetary incentive delay task and the doors task-during which continuous EEG was recorded. Temporospatial principal component analysis was used to isolate each of the ERP components of interest from other temporally or spatially overlapping components. Exploratory time-frequency analyses were also conducted to supplement the ERP analyses.

RESULTS

Suicide attempters, compared with nonattempters, exhibited specific deficits in reward anticipation (i.e., blunted cue-P3 ERP during the monetary incentive delay task) and in initial response to reward (i.e., reduced feedback-related delta power in the gain condition of the doors task). These results were at least partially independent of current symptoms or diagnoses of depression and anxiety.

CONCLUSIONS

These findings constitute an important step in obtaining a more fine-grained understanding of the specific reward-related abnormalities that might contribute to suicide risk.

Neuropsychiatric symptoms in Parkinson's disease: aetiology, diagnosis and treatment

Historically, Parkinson's disease was viewed as a motor disorder and it is only in recent years that the spectrum of non-motor disorders associated with the condition has been fully recognised. There is a broad scope of neuropsychiatric manifestations, including depression, anxiety, apathy, psychosis and cognitive impairment. Patients are more predisposed to delirium, and Parkinson's disease treatments give rise to specific syndromes, including impulse control disorders, dopamine agonist withdrawal syndrome and dopamine dysregulation syndrome. This article gives a broad overview of the spectrum of these conditions, describes the association with severity of Parkinson's disease and the degree to which dopaminergic degeneration and/or treatment influence symptoms. We highlight useful assessment scales that inform diagnosis and current treatment strategies to ameliorate these troublesome symptoms, which frequently negatively affect quality of life.

Decomposing the effort paradox in reward processing: Time matters

Effort expenditure not only discounts reward value prospectively but also accrues reward value retrospectively. To decompose the effort paradox in reward processing, the current event-related potential study investigated the neural dynamics underlying effects of effort expenditure on subsequent reward processing. Participants exerted one of two levels of effort to obtain an opportunity of winning a high or low amount of monetary reward, and we focused on electrophysiological activity during the anticipatory and consummatory phases of reward processing. During the anticipatory phase, the stimulus-preceding negativity was enhanced when potential high rewards were anticipated, but this reward effect disappeared following high-effort expenditure. During the consummatory phase, feedback-related ERPs were increased for high relative to low rewards, and this reward effect was enlarged following effort expenditure during the early stage (200-300 ms) as indexed by the reward positivity but not the late stage (400-600 ms) as indexed by the P3. Our findings provide a strong support for the psychological contrast theory and indicate that time matters in decomposing the effort paradox for reward processing such that effort expenditure reduces reward sensitivity during the anticipatory phase but enhances reward sensitivity during the consummatory phase.

Repeated noninvasive stimulation of the ventromedial prefrontal cortex reveals cumulative amplification of pleasant compared to unpleasant scene processing: A single subject pilot study

The ventromedial prefrontal cortex (vmPFC) is a major hub of the reward system and has been shown to activate specifically in response to pleasant / rewarding stimuli. Previous studies demonstrate enhanced pleasant cue reactivity after single applications of transcranial direct current stimulation (tDCS) to the vmPFC. Here we present a pilot case study in which we assess the cumulative impact of multiple consecutive vmPFC-tDCS sessions on the processing of visual emotional stimuli in an event-related MEG recording design. The results point to stable modulation of increased positivity biases (pleasant > unpleasant stimulus signal strength) after excitatory vmPFC stimulation and a reversed pattern (pleasant < unpleasant) after inhibitory stimulation across five consecutive tDCS sessions. Moreover, cumulative effects of these emotional bias modulations were observable for several source-localized spatio-temporal clusters, suggesting an increase in modulatory efficiency by repeated tDCS sessions. This pilot study provides evidence for improvements in the effectiveness and utility of a novel tDCS paradigm in the context of emotional processing.

Optimizing Behavioral Paradigms to Facilitate Development of New Treatments for Anhedonia and Reward Processing Deficits in Schizophrenia and Major Depressive Disorder: Study Protocol

Background: Behavioral tasks focusing on different subdomains of reward processing may provide more objective and quantifiable measures of anhedonia and impaired motivation compared with clinical scales. Typically, single tasks are used in relatively small studies to compare cases and controls in one indication, but they are rarely included in larger multisite trials. This is due to limited systematic standardization as well as the challenges of deployment in international studies and stringent adherence to the high regulatory requirements for data integrity. The Reward Task Optimization Consortium (RTOC) was formed to facilitate operational implementation of reward processing tasks, making them suitable for use in future large-scale, international, multisite drug development studies across multiple indications. The RTOC clinical study aims to conduct initial optimization of a set of tasks in patients with major depressive disorder (MDD) or schizophrenia (SZ). Methods: We will conduct a multicenter study across four EU countries. Participants (MDD = 37, SZ = 37, with ≤80 age- and gender-matched healthy volunteers) will attend a study visit comprising screening, self-report and clinically rated assessments of anhedonia and symptom severity, and three reward processing tasks; specifically, the Grip Strength Effort task, the Doors task, and the Reinforcement Learning Working Memory task. The Grip Strength Effort and Doors tasks include simultaneous electroencephalography/event-related potential recordings. Outcomes will be compared using a two-way group design of MDD and SZ with matched controls, respectively. Further analyses will include anhedonia assessment scores as covariates. Planned analyses will assess whether our findings replicate previously published data, and multisite deployment will be evaluated through assessments of quality and conduct. A subset of participants will complete a second visit, to assess test-retest reliability of the task battery. Discussion: This study will evaluate the operational deployment of three reward processing tasks to the regulatory standards required for use in drug development trials. We will explore the potential of these tasks to differentiate patients from controls and to provide a quantitative marker of anhedonia and/or impaired motivation, establishing their usefulness as endpoints in multisite clinical trials. This study should demonstrate where multifaceted reward deficits are similar or divergent across patient populations. Registration: ClinicalTrials.gov (NCT04024371).

Ruminative Tendency Relates to Ventral Striatum Functionality: Evidence From Task and Resting-State fMRI

BACKGROUND

Ruminative responding involves repetitive and passive thinking about one's negative affect. This tendency interferes with initiation of goal-directed rewarding strategies, which could alleviate depressive states. Such reward-directed response selection has been shown to be mediated by ventral striatum/nucleus accumbens (VS/NAcc) function. However, to date, no study has examined whether trait rumination relates to VS/NAcc functionality. Here, we tested whether rumination moderates VS/NAcc function both in response to reward and during a ruminative state.

METHODS

Trait rumination was considered dimensionally using Rumination Response Scale (RRS) scores. Our sample (N = 80) consisted of individuals from a community sample and from patients diagnosed with major depressive disorder, providing a broad range of RRS scores. Participants underwent fMRI to assess two modes of VS/NAcc functionality: 1) in response to reward, and 2) during resting-state, as a proxy for ruminative state. We then tested for associations between RRS scores and VS/NAcc functional profiles, statistically controlling for overall depressive symptom severity.

RESULTS

RRS scores correlated positively with VS/NAcc response to reward. Furthermore, we noted that higher RRS scores were associated with increased ruminative-dependent resting-state functional connectivity of the VS/NAcc with the left orbitofrontal cortex.

CONCLUSIONS

These findings suggest that ruminative tendencies manifest in VS/NAcc reward- and rumination-related functions, providing support for a theoretical-clinical perspective of rumination as a habitual impairment in selection of rewarding, adaptive coping strategies.

Links between adolescent bullying and neural activation to viewing social exclusion

Neuroscientists who have studied bullying have primarily focused on the psychopathology of diagnosable offenders or the resulting symptomatology of victimization. Less attention has been given to theories that suggest that bullying may be an interpersonal strategy. In an exploratory study, we recruited a sample of adolescents (N = 24) who engaged in high rates of delinquent behavior and collected self-report ratings of bullying behaviors. During an fMRI scan, adolescents observed instances of social exclusion and social inclusion. The adolescents' self-reported bullying was associated with greater ventral striatum, amygdala, medial prefrontal cortex, and insula activation when viewing social exclusion > social inclusion. Activation in these regions is commonly associated with reward-learning, salience monitoring, and motivational processes, suggesting that bullies show altered processing of interpersonal cues and social dynamic experiences in their environment. Our findings highlight the need for developmental neuroscientists to further explore the role of social motivation in processing socio-affective information, with a particular focus on goal-directed antisocial behavior.

Electrophysiological correlates of feedback processing in subarachnoid hemorrhage patients

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Subarachnoid hemorrhage patients show a reduced sensitivity to negative feedback, depicted by diminished amplitude of the feedback-related negativity (FRN).

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A delayed increase of theta oscillatory activity (4–8 Hz) was found for the patient group in presence of monetary losses compared to the healthy control group.

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No significant differences between groups were found at positive feedback event-related (ERP) components, such as the feedback P300 (FB-P3), neither on the time-frequency domain (beta-gamma band −25–35).

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Damage to medial prefrontal cortex (mPFC) regions might be altering the performance monitoring mechanisms associated to feedback processing and belief updating, resulting in altered day-to-day decision-making functioning.

Patients with subarachnoid hemorrhage (SAH) secondary to anterior communicating artery (AComA) aneurysm rupture often experience deficits in executive functioning and decision-making. Effective decision-making is based on the subjects’ ability to adjust their performance based on feedback processing, ascribing either positive or negative value to the actions performed reinforcing the most adaptive behavior in an appropriate temporal framework. A crucial brain structure associated to feedback processing is the medial prefrontal cortex (mPFC), a brain region frequently damaged after AComA aneurysm rupture. In the present study, we recorded electrophysiological responses (event-related potentials (ERPs') and oscillatory activity (time frequency analysis) during a gambling task in a series of 15 SAH patients. Previous studies have identified a feedback related negativity (FRN) component associated with an increase on frontal medial theta power in response to negative feedback or monetary losses, which is thought to reflect the degree of negative prediction error. Our findings show a decreased FRN component in response to negative feedback and a delayed increase of theta oscillatory activity in the SAH patient group when compared to the healthy controls, indicating a reduced sensitivity to negative feedback processing and an effortful signaling of cognitive control and monitoring processes lengthened in time, respectively. These results provide us with novel neurophysiological markers regarding feedback processing and performance monitoring patterns in SAH patients, illustrating a dysfunctional reinforcement learning system probably contributing to the maladaptive day-to-day functioning in these patients.

Neurocognitive Processes Implicated in Adolescent Suicidal Thoughts and Behaviors: Applying an RDoC Framework for Conceptualizing Risk

Purpose of Review

Identifying risk factors for STBs during adolescence is essential for suicide prevention. In this review, we employ the Research Domain Criteria (RDoC) framework to synthesize studies on key neurocognitive processes-cognitive control, reward responsiveness/valuation, and negative urgency-relevant to adolescent STBs.

Recent Findings

Within subdomains of Cognitive Control, studies of inhibition/suppression and updating/maintenance were mixed, while response selection (i.e., decision-making) deficits were consistently associated with suicide attempts. Fewer studies, by comparison, have probed the Positive Valence Systems. Relative to healthy controls, adolescents with prior STBs may show a blunted neural response to rewards and value rewards less, but findings require replication. Finally, negative urgency, which may span subdomains within both Cognitive Control and the Positive Valence Systems, was associated with recent suicide attempts in the only study to directly test this association.

Summary

Few studies have examined neurocognitive functioning in relation to adolescent STBs, despite the relevance of this research to detecting suicide risk. We recommend that future studies incorporate developmental contexts relevant to both neurocognitive processes and STBs.Broadly, cognitive control is associated with activation of the prefrontal cortex (PFC) and its interaction with other brain areas (e.g., reward and motor regions) [32]. Functional magnetic resonance imaging (fMRI) studies using emotional stimuli have provided evidence of abnormalities in neural regions supporting cognitive control among youth with STBs. [33] computed neural activation corresponding to viewing angry faces (relative to a fixation cross) in a sample of depressed youth. They found that, relative to non-attempters, attempters had: (a) increased activation in the right anterior gyrus and dorsolateral PFC and (b) reduced functional connectivity between the anterior cingulate gyrus and bilateral insulae. Relatedly, youth with bipolar disorder and a history of suicide attempts showed reduced functional connectivity between the amygdala and the left ventral PFC while viewing emotional (happy, fearful) and neutral faces compared to patient non-attempters [34]. The findings indicate that attempters may have problems regulating and appropriately deploying attention, as well as planning and executing behavioral responses, in emotional contexts.

Neural and Attentional Correlates of Intrinsic Motivation Resulting from Social Performance Expectancy

Some models of motivation distinguish between intrinsic and extrinsic motivation. While past work has examined the neural and cognitive correlates of extrinsic motivation, research on intrinsic motivation has relied primarily on behavioral measures of performance and learning. In particular, no past work has examined the neural and cognitive correlates of social performance expectancy, which is linked to intrinsic motivation. The current study manipulated expectancy of difficult (vs. easy) trials on a cued flanker task and assessed attentional scope and performance. EEG was used to examine motor-action preparation as measured by suppression of beta band activity over the motor cortex and feedback processing as measured by the Reward Positivity (RewP). Results revealed expectancy of difficult (vs. easy) trials narrowed attentional scope, reduced beta activity over the motor cortex, and enhanced RewP amplitudes to win feedback. These findings suggest that enhancing intrinsic motivation through expectancies of positive social comparison engages similar neural and cognitive correlates as extrinsic motivators high in motivational intensity.

Blunted Reward Sensitivity and Trait Disinhibition Interact to Predict Substance Use Problems

Reward deficit models of addiction posit weaknesses in reward sensitivity to be promotive of substance dependence, while the externalizing spectrum model views substance problems as arising in large part from a general disinhibitory liability. The current study sought to integrate these perspectives by testing for separate and interactive associations of disinhibition and reward dysfunction with interview-assessed substance use disorders (SUDs). Community and college adults (N = 199) completed a scale measure of trait disinhibition and performed a gambling-feedback task yielding a neural index of reward sensitivity, the 'Reward Positivity' (RewP). Disinhibition and blunted RewP independently predicted SUDs, and also operated synergistically, such that participants - in particular, men - with high levels of disinhibition together with blunted RewP exhibited especially severe substance problems. Though limited by its cross-sectional design, this work provides new information about the interplay of disinhibition, reward processing, and gender in SUDs and suggests important directions for future research.

Money for me and money for friend: An ERP study of social reward processing in adolescents and adults

Peer relations during adolescence contribute significantly to the development of socio-cognitive skills and pro-sociality. The current study probed the characteristics of adolescent socio-cognitive processing through a card game where they earn money for self and friend. We investigated the choice preference and temporal dynamics of information processing by measuring ERP responses to wins or losses (valence) directed toward self and friend (recipient). Choice data showed that despite adults and adolescents earning equivalent amounts across recipients combined, adults won significantly more for self than a friend; no such difference was found in adolescents. The ERPs in response to choice outcomes showed that the valence information was processed earlier (at P2) in adults, while it was processed later (at P3) in adolescents. Furthermore, a strong effect of recipient was present in adults later in the time course (at P3), while such an effect was weak in adolescents; if any, adolescents showed sensitivity to recipient information earlier at P2. These ERP data suggest a relatively equal allocation of the P3-mediated attentional process to both self and friend's outcomes in adolescents, which parallels the choice behavior. Collectively our results characterize adolescent pro-sociality toward friends, reflecting the importance of peer relationship during this unique developmental period.

Electrophysiological measures reveal the role of anterior cingulate cortex in learning from unreliable feedback

Although a growing number of studies have investigated the neural mechanisms of reinforcement learning, it remains unclear how the brain responds to feedback that is unreliable. A recent theory proposes that the reward positivity (RewP) component of the event-related brain potential (ERP) and frontal midline theta (FMT) power reflect separate feedback-related processing functions of anterior cingulate cortex (ACC). In the present study, the electroencephalogram (EEG) was recorded from participants as they engaged in a time estimation task in which feedback reliability was manipulated across conditions. After each response, they received a cue that indicated that the following feedback stimulus was 100%, 75%, or 50% reliable. The results showed that participants' time estimates adjusted linearly according to the feedback reliability. Moreover, presentation of the cue indicating 100% reliability elicited a larger RewP-like ERP component than the other cues did, and feedback presentation elicited a RewP of approximately equal amplitude for all of the three reliability conditions. By contrast, FMT power elicited by negative feedback decreased linearly from the 100% condition to 75% and 50% condition, and only FMT power predicted behavioral adjustments on the following trials. In addition, an analysis of Beta power and cross-frequency coupling (CFC) of Beta power with FMT phase suggested that Beta-FMT communication modulated motor areas for the purpose of adjusting behavior. We interpreted these findings in terms of the hierarchical reinforcement learning account of ACC, in which the RewP and FMT are proposed to reflect reward processing and control functions of ACC, respectively.

Blunted Social Reward Responsiveness Moderates the Effect of Lifetime Social Stress Exposure on Depressive Symptoms

Exposure to social stress is a well-established risk factor for the development and recurrence of depression. Reduced neural responsiveness to monetary reward has been associated with greater symptoms following stress exposure. However, it remains unclear whether reduced reward responsiveness serves as a mediator or moderator of the effects of stress on internalizing symptoms or whether similar patterns emerge with responses to social reward. We addressed this issue by measuring lifetime stress exposure and event-related potentials (ERPs) to social reward in 231 emerging adults (M = 18.16, SD = 0.41 years old). Participants completed the Stress and Adversity Inventory (STRAIN) to assess severity of lifetime stressors and self-report measures of current internalizing symptoms. In addition, participants completed the Island Getaway task in which the reward positivity (RewP) ERP was recorded in response to social acceptance, adjusting for responses to rejection (RewP residual). In this task, participants vote to accept or reject peers and receive reward/acceptance and rejection feedback. Stressors were divided into social and non-social stress severity scores. Analyses were conducted to test social reward responsiveness as a mediator or moderator of the effects of social and non-social stress on internalizing symptoms. Both social and non-social stress exposure over the life course predicted symptoms of depression (ps < 0.001) and social anxiety (ps < 0.002). The effect of social stress on depression was moderated by the residual RewP to social reward, adjusting for responses to social rejection (p =0.024), such that greater lifetime social stress exposure and a relatively blunted RewP to social reward were associated with greater depressive symptoms. Social reward responsiveness did not mediate effects of stress on internalizing symptoms. Reduced processing of social reward may be a vulnerability for depression that increases risk for symptoms following exposure to social stress. Blunted social reward responsiveness appears to be a relatively unique vulnerability for depression, rather than social anxiety. Results support the utility of ERP measures in measuring individual differences in social reward processing that can be applied to better understand neural processes involved in the development of depression, and highlight the importance of considering specific dimensions of stressful life experiences.

A role for the CD38 rs3796863 polymorphism in alcohol and monetary reward: evidence from CD38 knockout mice and alcohol self-administration, [11C]-raclopride binding, and functional MRI in humans

Background: Cluster of differentiation 38 (CD38) is a transmembrane protein expressed in dopaminergic reward pathways in the brain, including the nucleus accumbens (NAc). The GG genotype of a common single nucleotide polymorphism (SNP) within CD38, rs3796863, is associated with increased social reward.Objective: Examine whether CD38 rs3796863 and Cd38 knockout (KO) are associated with reward-related neural and behavioral phenotypes.Methods: Data from four independent human studies were used to test whether rs3796863 genotype is associated with: (1) intravenous alcohol self-administration (n = 64, 30 females), (2) alcohol-stimulated dopamine (DA) release measured using ¹¹C-raclopride positron emission tomography (n = 22 men), (3) ventral striatum (VS) response to positive feedback measured using a card guessing functional magnetic resonance imaging (fMRI) paradigm (n = 531, 276 females), and (4) resting state functional connectivity (rsfc) of the VS (n = 51, 26 females). In a fifth study, we used a mouse model to examine whether cd38 knockout influences stimulated DA release in the NAc core and dorsal striatum using fast-scanning cyclic voltammetry.Results: Relative to T allele carriers, G homozygotes at rs3796863 within CD38 were characterized by greater alcohol self-administration, alcohol-stimulated dopamine release, VS response to positive feedback, and rsfc between the VS and anterior cingulate cortex. High-frequency stimulation reduced DA release among Cd38 KO mice had reduced dopamine release in the NAc.Conclusion: Converging evidence suggests that CD38 rs3796863 genotype may increase DA-related reward response and alcohol consumption.

Neural Response to Rewards, Stress and Sleep Interact to Prospectively Predict Depressive Symptoms in Adolescent Girls

Blunted reward processing both characterizes major depressive disorder and predicts increases in depressive symptoms. However, little is known about the interaction between blunted reward processing and other risk factors in relation to increases in depressive symptoms. Stressful life events and sleep problems are prominent risk factors that contribute to the etiopathogenesis of depression and have been linked to reward dysfunction; these factors may interact with reward dysfunction to predict increased depressive symptoms. In a large sample of 8- to 14-year-old adolescent girls, the current study examined how blunted reward processing, stressful life events, and sleep problems at baseline interacted to predict increases in depressive symptoms 1 year later. Reward processing was indexed by the reward positivity (RewP), an event-related potential elicited during a simple monetary reward paradigm (i.e., Doors task). Two-way interactions confirmed that a blunted RewP predicted increased depressive symptoms at (a) high levels of stress but not average or low levels of stress, and (b) high and average levels of sleep problems but not low levels of sleep problems. Finally, a 3-way interaction confirmed that a blunted RewP predicted increased depressive symptoms at high levels of stress and sleep problems but not average or low levels of stress and sleep problems. Thus, adolescents characterized by low reward response (i.e., blunted RewP) were at an increased risk of developing depressive symptoms if they experienced increased stressful life events or sleep problems; moreover, risk was greatest among adolescents characterized by all 3.