A universal role of the ventral striatum in reward-based learning: evidence from human studies

Let me in: The neural correlates of inclusion motivation in loneliness

BACKGROUND

While it is well-established that humans possess an innate need for social belonging, the neural mechanisms underlying motivation for connection are still largely unknown. We propose that inclusion motivation - measured through the effort that individuals are willing to invest to be included in social interactions - may serve as one of the basic building blocks of social behavior and may change in lonely individuals.

METHODS

Following the screening of 303 participants, we scanned 30 low- and 28 high-loneliness individuals with functional magnetic resonance imaging while they performed the Active Inclusion Task (AIT). The AIT assesses the participants' levels of effort invested in influencing their inclusion during classic Cyberball conditions of fair play and exclusion.

RESULTS

High- compared to low-loneliness individuals showed higher urgency for inclusion, specifically during fair play, which correlated with higher activity in the right thalamus. Furthermore, in high-loneliness individuals, we found increased functional connectivity between the thalamus and the temporoparietal junction, putamen, and insula.

LIMITATIONS

Participants interacted with computerized avatars, reducing ecological validity. Additionally, although increasing inclusion in the task required action, the physical demand was not high. Additional limitations are discussed.

CONCLUSIONS

Inclusion motivation in loneliness is heightened during fair but not exclusionary interactions, and is linked to activity in brain regions implicated in appetitive behavior and social cognition. The findings indicate that lonely individuals may view threat in inclusionary interactions, prompting them to take action to regain connection. This suggests that inclusion motivation may help explain social difficulties in loneliness.

OPTIMAL theory's claims about motivation lack evidence in the motor learning literature

Motivation is commonly recognized by researchers and practitioners as a key factor for motor learning. The OPTIMAL theory of motor learning (Wulf & Lewthwaite, 2016) claims that practice conditions that enhance learners' expectancies for future successful outcomes or that are autonomy supportive are motivating, thus leading to better learning. To examine the current evidence of the association between motivation and motor learning, we searched the literature for studies that manipulated expectancies and/or autonomy support. Specifically, our goals were to assess whether these manipulations resulted in group differences in motivation and, if so, whether increased motivation was associated with learning advantages. Results showed that out of 166 experiments, only 21% (n = 35) included at least one measure of motivation, even though this is the main factor proposed by OPTIMAL theory to explain the learning benefits of these manipulations. Among those, only 23% (n = 8) found group-level effects on motivation, suggesting that these manipulations might not be as motivating as expected. Of the eight experiments that found a group-level effect on motivation, five also observed learning benefits, offering limited evidence that when practice conditions increase motivation, learning is more likely to occur. Overall, the small number of studies assessing motivation precludes any reliable conclusions on the association between motivation and motor learning from being drawn. Together, our results question whether manipulations implemented in the research lines supporting OPTIMAL theory are indeed motivating and highlight the lack of sufficient evidence in these literatures to support that increased motivation benefits motor learning.

Neural response to monetary and social rewards in adolescent girls and their parents

Functional magnetic resonance imaging (fMRI) studies have indicated that the mesocorticolimbic dopamine system is heavily involved in all stages of reward processing. However, the majority of research has been conducted using monetary rewards and it is unclear to what extent other types of rewards, such as social rewards, evoke similar or different neural activation. There have also been few investigations into potential differences or similarities between reward processing in parents and offspring. The present study examined fMRI neural activation in response to monetary and social reward in a sample of 14-22-year-old adolescent girls (N = 145) and a biological parent (N = 124) and compared activation across adolescent-parent dyads (N = 82). Across all participants, both monetary and social reward elicited bilateral striatal activation, which did not differ between reward types or between adolescents and their parents. Neural activation in response to the different reward types were positively correlated in the striatum among adolescents and in the mPFC and OFC among parents. Overall, the present study suggests that both monetary and social reward elicit striatal activation regardless of age and provides evidence that neural mechanisms underlying reward processing may converge differentially among youth and adults.

The neuroscience of active learning and direct instruction

Throughout the educational system, students experiencing active learning pedagogy perform better and fail less than those taught through direct instruction. Can this be ascribed to differences in learning from a neuroscientific perspective? This review examines mechanistic, neuroscientific evidence that might explain differences in cognitive engagement contributing to learning outcomes between these instructional approaches. In classrooms, direct instruction comprehensively describes academic content, while active learning provides structured opportunities for learners to explore, apply, and manipulate content. Synaptic plasticity and its modulation by arousal or novelty are central to all learning and both approaches. As a form of social learning, direct instruction relies upon working memory. The reinforcement learning circuit, associated agency, curiosity, and peer-to-peer social interactions combine to enhance motivation, improve retention, and build higher-order-thinking skills in active learning environments. When working memory becomes overwhelmed, additionally engaging the reinforcement learning circuit improves retention, providing an explanation for the benefits of active learning. This analysis provides a mechanistic examination of how emerging neuroscience principles might inform pedagogical choices at all educational levels.

Unveiling the therapeutic prospects of EGFR inhibition in rotenone-mediated parkinsonism in rats: Modulation of dopamine D3 receptor

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The dopamine D3 receptor (D3R) plays a significant role in the pathogenesis and treatment of PD. Activation of receptor tyrosine kinases (RTKs) inhibits signaling mediated by G protein-coupled receptor (GPCR). Epidermal growth factor receptors (EGFRs) and dopamine D3 receptors in the brain are directly associated with PD, both in terms of its development and potential treatment. Therefore, we investigated the impact of modulating the EGFR, a member of the RTKs family, and the dopamine D3R, a member of the GPCR family. In the present study, 100 mg/kg of lapatinib (LAP) was administered to rotenone-intoxicated rats for three weeks. Our findings indicate that LAP effectively alleviated motor impairment, improved histopathological abnormalities, and restored dopaminergic neurons in the substantia nigra. This restoration was achieved through the upregulation of dopamine D3R and increase of tyrosine hydroxylase (TH) expression, as well as boosting dopamine levels. Furthermore, LAP inhibited the activity of p-EGFR, GRK2, and SCR. Additionally, LAP exhibited antioxidant properties by inhibiting the 4-hydroxynonenal (4-HNE) and PLCγ/PKCβII pathway, while enhancing the antioxidant defense mechanism by increasing GSH-GPX4 pathway. The current study offers insights into the potential repositioning of LAP as a disease-modifying drug for PD. This could be achieved by modulating the dopaminergic system and curbing oxidative stress.

Distinct dopaminergic spike-timing-dependent plasticity rules are suited to different functional roles

Various mathematical models have been formulated to describe the changes in synaptic strengths resulting from spike-timing-dependent plasticity (STDP). A subset of these models include a third factor, dopamine, which interacts with the timing of pre- and postsynaptic spiking to contribute to plasticity at specific synapses, notably those from cortex to striatum at the input layer of the basal ganglia. Theoretical work to analyze these plasticity models has largely focused on abstract issues, such as the conditions under which they may promote synchronization and the weight distributions induced by inputs with simple correlation structures, rather than on scenarios associated with specific tasks, and has generally not considered dopamine-dependent forms of STDP. In this paper, we analyze, mathematically and with simulations, three forms of dopamine-modulated STDP in three scenarios that are relevant to corticostriatal synapses. Two of the models considered comprise previously proposed STDP rules with modifications to incorporate dopamine, while the third is a corticostriatal dopamine-dependent STDP rule adapted from a similar one already in the literature. We test the ability of each of the three models to maintain its weights in the face of noise and to complete simple reward prediction and action selection tasks, studying the learned weight distributions and corresponding task performance in each setting. Interestingly, we find that each of the three plasticity rules is well suited to a subset of the scenarios studied but falls short in others. These results show that different tasks may require different forms of synaptic plasticity, yielding the prediction that the precise form of the STDP mechanism may vary across regions of the striatum, and other brain areas impacted by dopamine, that are involved in distinct computational functions.

Brain gray matter volume of reward-related structures in Inuit adolescents pre- and postnatally exposed to lead, mercury and polychlorinated biphenyls

This study aimed to assess associations between prenatal and postnatal exposure to lead (Pb), mercury (Hg) and polychlorinated biphenyls (PCBs) and gray matter volume of key regions of the brain reward circuit, namely the caudate nucleus, putamen, nucleus accumbens (nAcc), the amygdala, the orbitofrontal cortex (OFC) and the anterior cingulate cortex (ACC). Structural magnetic resonance imaging (MRI) was conducted in 77 Inuit adolescents (mean age = 18.39) from Nunavik, Canada, who also completed the Brief Sensation Seeking Scale (BSSS-4) and Sensation Seeking - 2 (SS-2), two self-report questionnaires evaluating the tendency toward sensation seeking, which is a proxy of reward-related behaviors. Exposures to Pb, Hg and PCBs were measured in cord blood at birth, in blood samples at 11 years old and at time of testing (18 years old). Multivariate linear regressions were corrected for multiple comparisons and adjusted for potential confounders, such as participants' sociodemographic characteristics and nutrient fish intake. Results showed that higher cord blood Pb levels predicted smaller gray matter volume in the bilateral nAcc, caudate nucleus, amygdala and OFC as well as in left ACC. A moderating effect of sex was identified, indicating that the Pb-related reduction in volume in the nAcc and caudate nucleus was more pronounced in female. Higher blood Hg levels at age 11 predicted smaller right amygdala independently of sex. No significant associations were found between blood PCBs levels at all three times of exposure. This study provides scientific support for the detrimental effects of prenatal Pb and childhood Hg blood concentrations on gray matter volume in key reward-related brain structures.

Examining neural responses to anticipating or receiving monetary rewards and the development of binge eating in youth. A registered report using data from the Adolescent Brain Cognitive Development (ABCD) study

Binge eating is characterized as eating a large amount of food and feeling a loss of control while eating. However, the neurobiological mechanisms associated with the onset and maintenance of binge eating are largely unknown. Recent neuroimaging work has suggested that increased responsivity within reward regions of the brain to the anticipation or receipt of rewards is related to binge eating; however, limited longitudinal data has precluded understanding of the role of reward responsivity in the development of binge eating. The current study used data from the Adolescent Brain and Cognitive Development® (ABCD) longitudinal study dataset to assess whether heightened neural responses to different phases of reward processing (reward anticipation and receipt) (1) differentiated individuals with binge eating from matched controls, and (2) predicted the onset of binge eating in an "at risk" sample. Consistent with hypotheses, heightened neural responsivity in the right caudate and bilateral VS during reward anticipation differentiated youth with and without binge eating. Moreover, greater VS response to reward anticipation predicted binge eating two years later. Neural responses to reward receipt also were consistent with hypotheses, such that heightened VS and OFC responses differentiated youth with and without binge eating and predicted the presence of binge eating two years later. Findings from the current study suggest that hypersensitivity to rewards may contribute to the development of binge eating during early adolescence.

Neural response to monetary and social rewards and familial risk for psychopathology in adolescent females

BACKGROUND

Adolescence is a key developmental period for the emergence of psychopathology. Reward-related brain activity increases across adolescence and has been identified as a potential neurobiological mechanism of risk for different forms of psychopathology. The reward positivity (RewP) is an event-related potential component that indexes reward system activation and has been associated with both concurrent and family history of psychopathology. However, it is unclear whether the RewP is also associated with higher-order psychopathology subfactors and whether this relationship is present across different types of reward.

METHODS

In a sample of 193 adolescent females and a biological parent, the present study examined the association between adolescent and parental psychopathology subfactors and adolescent RewP to monetary and social reward.

RESULTS

Results indicated that the adolescent and parental distress subfactors were negatively associated with the adolescent domain-general RewP. The adolescent and parental positive mood subfactors were negatively associated with the adolescent domain-general and domain-specific monetary RewP, respectively. Conversely, the adolescent and parental fear/obsessions subfactors were positively associated with the adolescent domain-general RewP. The associations between parental and adolescent psychopathology subfactors and the adolescent RewP were independent of each other.

CONCLUSIONS

The RewP in adolescent females is associated with both concurrent and parental psychopathology symptoms, suggesting that it indexes both severity and risk for higher-order subfactors.

Neural Reward Anticipation Moderates Longitudinal Relation between Parents' Familism Values and Latinx American Youth's School Disengagement

Parents' familism values predict a variety of Latinx American youth's academic adjustment. However, it is unclear how cultural values such as familism interact with youth's brain development, which is sensitive to sociocultural input, to shape their academic adjustment. Using a sample of 1916 Latinx American youth (mean age = 9.90 years, SD = .63 years; 50% girls) and their primary caregivers (mean age = 38.43 years, SD = 6.81 years; 90% mothers) from the Adolescent Brain Cognitive Development Study, this study examined the longitudinal relation between parents' familism values and youth's school disengagement, as well as the moderating role of youth's neural sensitivity to personal reward. Parents' familism values predicted youth's decreased school disengagement 1 year later, adjusting for their baseline school disengagement and demographic covariates. Notably, this association was more salient among youth who showed lower (vs. higher) neural activation in the ventral striatum and the lateral OFC during the anticipation of a personal reward. These findings underscore the protective role of familism for Latinx American youth, highlighting the necessity of developing culturally informed interventions that take into consideration a youth's brain development.

Increased ventral anterior insular connectivity to sports betting availability indexes problem gambling

With the advent of digital technologies, online sports betting is spurring a fast-growing expansion. In this study, we examined how sports betting availability modulates the brain connectivity of frequent sports bettors with [problem bettors (PB)] or without [non-problem bettors (NPB)] problematic sports betting. We conducted functional connectivity analyses centred on the ventral anterior insular cortex (vAI), a brain region playing a key role in the dynamic interplay between reward-based processes. We re-analysed a dataset on sports betting availability undertaken in PB (n = 30) and NPB (n = 35). Across all participants, we observed that sports betting availability elicited positive vAI coupling with extended clusters of brain activation (encompassing the putamen, cerebellum, occipital, temporal, precentral and central operculum regions) and negative vAI coupling with the orbitofrontal cortex. Between-group analyses showed increased positive vAI coupling in the PB group, as compared with the NPB group, in the left lateral occipital cortex, extending to the left inferior frontal gyrus, the anterior cingulate gyrus and the right frontal pole. Taken together, these results are in line with the central assumptions of triadic models of addictions, which posit that the insular cortex plays a pivotal role in promoting the drive and motivation to get a reward by 'hijacking' goal-oriented processes toward addiction-related cues. Taken together, these findings showed that vAI functional connectivity is sensitive not only to gambling availability but also to the status of problematic sport betting.

The place of Free Will: the freedom of the prisoner

Debates about the concept of Free Will date back to ancient times. About 40 years ago, Benjamin Libet designed an experiment showing that the conscious intention to move is preceded by a specific pattern of brain activation. His finding suggested that unconscious processes determine our decisions. Libet-style experiments have continued to dominate the debate about Free Will, pushing some authors to argue that the existence of Free Will is a mere illusion. We believe that this dispute is because we often measure Free Will using arbitrary human decisions rather than deliberate actions. After reviewing the definition of Free Will and the related literature, we conclude that the scientific evidence does not disprove the existence of Free Will. However, our will encounters several constraints and limitations that should be considered when evaluating our deeds' personal responsibility.

Dopaminergic reinforcement in the motor system: Implications for Parkinson's disease and deep brain stimulation

Millions of people suffer from dopamine-related disorders spanning disturbances in movement, cognition and emotion. These changes are often attributed to changes in striatal dopamine function. Thus, understanding how dopamine signalling in the striatum and basal ganglia shapes human behaviour is fundamental to advancing the treatment of affected patients. Dopaminergic neurons innervate large-scale brain networks, and accordingly, many different roles for dopamine signals have been proposed, such as invigoration of movement and tracking of reward contingencies. The canonical circuit architecture of cortico-striatal loops sparks the question, of whether dopamine signals in the basal ganglia serve an overarching computational principle. Such a holistic understanding of dopamine functioning could provide new insights into symptom generation in psychiatry to neurology. Here, we review the perspective that dopamine could bidirectionally control neural population dynamics, increasing or decreasing their strength and likelihood to reoccur in the future, a process previously termed neural reinforcement. We outline how the basal ganglia pathways could drive strengthening and weakening of circuit dynamics and discuss the implication of this hypothesis on the understanding of motor signs of Parkinson's disease (PD), the most frequent dopaminergic disorder. We propose that loss of dopamine in PD may lead to a pathological brain state where repetition of neural activity leads to weakening and instability, possibly explanatory for the fact that movement in PD deteriorates with repetition. Finally, we speculate on how therapeutic interventions such as deep brain stimulation may be able to reinstate reinforcement signals and thereby improve treatment strategies for PD in the future.

The road not taken: Common and distinct neural correlates of regret and relief

Humans anticipate and evaluate both obtained and counterfactual outcomes - outcomes that could have been had an alternate decision been taken - and experience associated emotions of regret and relief. Although many functional magnetic resonance imaging (fMRI) studies have examined the neural correlates of these emotions, there is substantial heterogeneity in their results. We conducted coordinate-based ALE and network-based ANM meta-analysis of fMRI studies of experienced regret and relief to examine commonalities and differences in their neural correlates. Regionally, we observed that the experience of both regret and relief was associated with greater activation in the right ventral striatum (VS), which is implicated in tracking reward prediction error. At the network level, regret and relief shared the reward-sensitive mesocorticolimbic network with preferential activation of the medial orbitofrontal cortex (mOFC) for regret processing and medial cingulate cortex (MCC) for relief processing. Our research identified shared and separable brain systems subserving regret and relief experience, which may inform the treatment of regret-related mood disorders.

Resolving the Delusion Paradox

BACKGROUND AND HYPOTHESIS

The neurocomputational framework of predictive processing (PP) provides a promising approach to explaining delusions, a key symptom of psychotic disorders. According to PP, the brain makes inferences about the world by weighing prior beliefs against the available sensory data. Mismatches between prior beliefs and sensory data result in prediction errors that may update the brain's model of the world. Psychosis has been associated with reduced weighting of priors relative to the sensory data. However, delusional beliefs are highly resistant to change, suggesting increased rather than decreased weighting of priors. We propose that this "delusion paradox" can be resolved within a hierarchical PP model: Reduced weighting of prior beliefs at low hierarchical levels may be compensated by an increased influence of higher-order beliefs represented at high hierarchical levels, including delusional beliefs. This may sculpt perceptual processing into conformity with delusions and foster their resistance to contradictory evidence.

STUDY DESIGN

We review several lines of experimental evidence on low- and high-level processes, and their neurocognitive underpinnings in delusion-related phenotypes and link them to predicted processing.

STUDY RESULTS

The reviewed evidence supports the notion of decreased weighting of low-level priors and increased weighting of high-level priors, in both delusional and delusion-prone individuals. Moreover, we highlight the role of prefrontal cortex as a neural basis for the increased weighting of high-level prior beliefs and discuss possible clinical implications of the proposed hierarchical predictive-processing model.

CONCLUSIONS

Our review suggests the delusion paradox can be resolved within a hierarchical PP model.

Neural processing of observed performance-based errors and rewards in the context of friends and unfamiliar peers across adolescence

Adolescence is characterized by changes in performance monitoring, whereby action outcomes are monitored to subsequently adapt behavior and optimize performance. Observation of performance-based outcomes (i.e., errors and rewards) received by others forms the basis of observational learning. Adolescence is also a period of increasing importance of peers, especially friends, and observing peers forms a crucial aspect of learning in the social context of the classroom. However, to our knowledge, no developmental fMRI studies have examined the neural mechanisms underlying observed performance monitoring of errors and rewards in the context of peers. The current fMRI study investigated the neural correlates of observing performance-based errors and rewards of peers in adolescents aged 9-16 years (N = 80). In the scanner, participants observed either their best friend or an unfamiliar peer play a shooting game resulting in performance-dependent rewards (based on hits) or losses (based on misses, i. e, errors), where outcomes affected both the player and the observing participant. Findings showed higher activation in the bilateral striatum and bilateral anterior insula when adolescents observed peers (i.e., best friend and unfamiliar peer) receive performance-based rewards compared to losses. This might reflect the heightened salience of observed reward processing in the peer context in adolescence. Our results further revealed lower activation in the left temporoparietal junction (TPJ) while adolescents observed the performance-based outcomes (rewards and losses) for their best friend than for an unfamiliar peer. Considering that observation of others' performance-based errors and rewards forms the basis of observational learning, this study provides a crucial first step in understanding and potentially improving adolescent observational learning in the peer context.

Sex differences in the relationship between cannabis use motives and cannabis craving in daily life in emerging adults

OBJECTIVE

Cannabis use motives and craving are associated with increased risk for cannabis-related problems and are ideal targets for prevention and early intervention. Patterns of motives and craving reactivity to cannabis cues differ by sex; however, few studies closely examine the relationship between motives and craving and how it may differ by valence (±) across men and women.

METHOD

The present study used Cue Reactivity Ecological Momentary Assessment to assess reward (+) and relief (-) craving four semirandom times per day for 2 weeks in a sample of 63 emerging adults (age 18-21; 54% cisgender women; 85.7% White) who frequently use cannabis (≥ 3 times per week). We assessed craving before and after exposure to brief neutral or cannabis image cues and examined within- and between-participant effects of cue type, motives, sex/gender, and their interactions, on postcue cannabis craving.

RESULTS

Regardless of cue type, women with high coping motives (-) reported less postcue relief (-) craving, and men with high enhancement motives (+) reported more postcue reward (+) craving. High enhancement motives (+), regardless of sex/gender, were associated with elevated relief (-) craving reactivity to cannabis cues, and women with high coping motives (-) reported elevated reward (+) craving reactivity to cannabis cues.

CONCLUSIONS

Sex/gender differences in the relationships between cannabis motives and craving reactivity indicate the value of a more targeted examination of valence (±) of craving experiences in addition to motives for use. Higher levels of precision may better inform interventions for emerging adults at risk for experiencing cannabis-related problems. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Preserved Metacognition for Undetected Visuomotor Deviations

Humans can successfully correct deviations of movements without conscious detection of such deviations, suggesting limited awareness of movement details. We ask whether such limited awareness impairs confidence (metacognition). We recorded functional magnetic resonance imaging data while 31 human female and male participants detected cursor deviations during a visuomotor reaching task and rated their confidence retrospectively. We show that participants monitor a summary statistic of the unfolding visual feedback (the peak cursor error) to detect visuomotor deviations and adjust their confidence ratings, even when they report being unaware of a deviation. Crucially, confidence ratings were as metacognitively efficient for aware and unaware deviations. At the neural level, activity in the ventral striatum tracks high confidence, whereas a broad network encodes cursor error but not confidence. These findings challenge the notion of limited conscious action monitoring and uncover how humans monitor their movements as they unfold, even when unaware of ongoing deviations.SIGNIFICANCE STATEMENT We are unaware of the small corrections we apply to our movements as long as our goals are achieved. Here, although we replicate the finding that participants deny perceiving small deviations they correct, we show that their confidence reliably reflects the presence or absence of a deviation. This observation shows they can metacognitively monitor the presence of a deviation, even when they deny perceiving it. We also describe the hemodynamic correlates of confidence ratings. Our study questions the extent to which humans are unaware of the details of their movements; describes a plausible mechanism for metacognition in a visuomotor task, along with its neural correlates; and has important implications for the construction of the sense of self.

UBE3A expression during early postnatal brain development is required for proper dorsomedial striatal maturation

Angelman syndrome (AS) is a severe neurodevelopmental disorder (NDD) caused by loss of functional ubiquitin protein ligase E3A (UBE3A). Previous studies showed that UBE3A plays an important role in the first postnatal weeks of mouse brain development, but its precise role is unknown. Since impaired striatal maturation has been implicated in several mouse models for NDDs, we studied the importance of UBE3A in striatal maturation. We used inducible Ube3a mouse models to investigate the maturation of medium spiny neurons (MSNs) from dorsomedial striatum. MSNs of mutant mice matured properly till postnatal day 15 (P15) but remained hyperexcitable with fewer excitatory synaptic events at later ages, indicative of stalled striatal maturation in Ube3a mice. Reinstatement of UBE3A expression at P21 fully restored MSN excitability but only partially restored synaptic transmission and the operant conditioning behavioral phenotype. Gene reinstatement at P70 failed to rescue both electrophysiological and behavioral phenotypes. In contrast, deletion of Ube3a after normal brain development did not result in these electrophysiological and behavioral phenotypes. This study emphasizes the role of UBE3A in striatal maturation and the importance of early postnatal reinstatement of UBE3A expression to obtain a full rescue of behavioral phenotypes associated with striatal function in AS.

Serotonin transporter availability in physically aggressive personality disordered patients: associations with trait and state aggression, and response to fluoxetine

RATIONALE

Characterizing the neuroanatomical basis of serotonergic abnormalities in severe, chronic, impulsive aggression will allow for rational treatment selection, development of novel therapeutics, and biomarkers to identify at-risk individuals.

OBJECTIVES

The aim of this study is to identify associations between regional serotonin transporter (5-HTT) availability and trait and state aggression, as well as response to the anti-aggressive effects of fluoxetine.

METHODS

We examined 5-HTT availability using positron emission tomography (PET) imaging with [¹¹C]DASB in personality disordered patients with current physical intermittent explosive disorder (IED; n = 18), and healthy comparison participants (HC; n = 11), in the anterior cingulate cortex (ACC), amygdala (AMY), ventral striatum (VST), and midbrain (MID). After PET imaging, IED patients were treated with fluoxetine 20 mg daily (n = 9) or placebo (n = 6) for 12 weeks. Trait and state aggression, trait callousness, and childhood trauma were assessed.

RESULTS

In IED patients, trait aggression was positively associated with [¹¹C]DASB binding in the ACC and VST; covarying for trait callousness and childhood trauma enhanced these correlations. Baseline state aggression was positively correlated with ACC [¹¹C]DASB in IED patients. Greater baseline VST [¹¹C]DASB binding predicted greater decreases in state aggression with fluoxetine treatment.

CONCLUSIONS

Consistent with prior reports, ACC 5-HTT is related to trait aggression, and adjusting for factors related to proactive (callousness) and reactive (childhood trauma) aggression subtypes further resolves this relationship. Novel findings of the study include a better understanding of the association between regional 5-HTT availability and state aggression, and the involvement of VST 5-HTT with trait aggression, and with the anti-aggressive effects of fluoxetine.

Hazardous or harmful alcohol use and reward processing in people with HIV

The intersecting epidemics of HIV and hazardous or harmful alcohol use (HAU) can have significant detrimental consequences. Both HIV and HAU have independent negative influences on executive function. Dysfunction in reward processing may play a role in these co-occurring epidemics. In this cross-sectional case-control study, we investigated the association of HAU with reward processing amongst people with HIV (PWH). We investigated the function of the ventral-striatal reward system using a functional MRI (fMRI) monetary incentive delay (MID) task in a sample of 60 South African adults (mean age 32.7 years): 42 living with HIV and on ART (21 with harmful alcohol use [HIV + HAU], 21 without [HIV-HAU]) and 18 healthy controls, matched for age, gender, and resident community. Education significantly influenced task performance, with those with a secondary level of education demonstrating a greater increase in reaction time (p = 0.048) and accuracy (p = 0.002) than those without. There were no significant differences in reward anticipation in the ventral striatum (VS) between HIV + HAU, HIV-HAU, and healthy controls when controlling for level of education. There were also no significant differences in reward outcome in the orbitofrontal cortex (OFC) between HIV + HAU, HIV-HAU, and healthy controls when controlling for level of education. In a sample of South African adults, we did not demonstrate significant differences in reward anticipation in the VS and reward outcome in the OFC in PWH, with and without HAU, and controls. Factors, such as task performance, education, and depression may have influenced our results. Further studies are needed to better delineate the potential links between HIV, HAU, and depression and reward system function.

Neuroimaging-Derived Biomarkers of the Antidepressant Effects of Ketamine

Major depressive disorder is a highly prevalent psychiatric disorder. Despite an extensive range of treatment options, about a third of patients still struggle to respond to available therapies. In the last 20 years, ketamine has gained considerable attention in the psychiatric field as a promising treatment of depression, particularly in patients who are treatment resistant or at high risk for suicide. At a subanesthetic dose, ketamine produces a rapid and pronounced reduction in depressive symptoms and suicidal ideation, and serial treatment appears to produce a greater and more sustained therapeutic response. However, the mechanism driving ketamine's antidepressant effects is not yet well understood. Biomarker discovery may advance knowledge of ketamine's antidepressant action, which could in turn translate to more personalized and effective treatment strategies. At the brain systems level, neuroimaging can be used to identify functional pathways and networks contributing to ketamine's therapeutic effects by studying how it alters brain structure, function, connectivity, and metabolism. In this review, we summarize and appraise recent work in this area, including 51 articles that use resting-state and task-based functional magnetic resonance imaging, arterial spin labeling, positron emission tomography, structural magnetic resonance imaging, diffusion magnetic resonance imaging, or magnetic resonance spectroscopy to study brain and clinical changes 24 hours or longer after ketamine treatment in populations with unipolar or bipolar depression. Though individual studies have included relatively small samples, used different methodological approaches, and reported disparate regional findings, converging evidence supports that ketamine leads to neuroplasticity in structural and functional brain networks that contribute to or are relevant to its antidepressant effects.

Altered reward processing underpins emotional apathy in dementia

Introduction

While apathy is broadly defined as a loss of motivation, it is increasingly recognised as a multidimensional syndrome spanning executive, emotional, and initiation domains. Emotional apathy is purportedly driven by deficits in using socioemotional rewards to guide behaviour, yet the link between these symptoms and reward processing, and their common neural correlates, has not been directly examined.

Methods

Sixty-four patients (33 behavioural-variant frontotemporal dementia, 14 Alzheimer’s disease, 8 semantic dementia, 6 progressive nonfluent aphasia, 3 logopenic progressive aphasia) were classified into high (HEA; n = 36) and low (LEA; n = 28) emotional apathy groups based on emotional apathy subscale scores on the Dimensional Apathy Scale. Patients and age-matched healthy controls (n = 27) performed an instrumental reward learning task where they learned to associate cues with either social or monetary outcomes.

Results

HEA patients showed impaired learning on both the social and monetary reward conditions, relative to LEA patients (p = 0.016) and controls (p = 0.005). Conversely, the LEA group did not differ from controls (p = 0.925). Importantly, multiple regression analyses indicated that social reward learning significantly predicted emotional apathy. Voxel-based morphometry analyses revealed that emotional apathy and social reward learning were both associated with orbitofrontal cortex, ventral striatum, and insula atrophy.

Discussion

Our results demonstrate a unique link between impaired social reward learning and emotional apathy in dementia and reveal a shared neurobiological basis. Greater understanding of these neurocognitive mechanisms of reward processing will help improve the identification of emotional apathy in dementia and inform the development of novel interventions to address these symptoms.

Ultrastructural evidence for glutamatergic dysregulation in schizophrenia

The aim of this paper is to summarize ultrastructural evidence for glutamatergic dysregulation in several linked regions in postmortem schizophrenia brain. Following a brief summary of glutamate circuitry and how synapses are identified at the electron microscopic (EM) level, we will review EM pathology in the cortex and basal ganglia. We will include the effects of antipsychotic drugs and the relation of treatment response. We will discuss how these findings support or confirm other postmortem findings as well as imaging results. Briefly, synaptic and mitochondrial density in anterior cingulate cortex was decreased in schizophrenia, versus normal controls (NCs), in a selective layer specific pattern. In dorsal striatum, increases in excitatory synaptic density were detected in caudate matrix, a compartment associated with cognitive and motor function, and in the putamen patches, a region associated with limbic function and in the core of the nucleus accumbens. Patients who were treatment resistant or untreated had significantly elevated numbers of excitatory synapses in limbic striatal areas in comparison to NCs and responders. Protein levels of vGLUT2, found in subcortical glutamatergic neurons, were increased in the nucleus accumbens in schizophrenia. At the EM level, schizophrenia subjects had an increase in density of excitatory synapses in several areas of the basal ganglia. In the substantia nigra, the protein levels of vGLUT2 were elevated in untreated patients compared to NCs. The density of inhibitory synapses was decreased in schizophrenia versus NCs. In schizophrenia, glutamatergic synapses are differentially affected depending on the brain region, treatment status, and treatment response.

Internally Triggered Experiences of Hedonic Valence in Nonhuman Animals: Cognitive and Welfare Considerations

Do any nonhuman animals have hedonically valenced experiences not directly caused by stimuli in their current environment? Do they, like us humans, experience anticipated or previously experienced pains and pleasures as respectively painful and pleasurable? We review evidence from comparative neuroscience about hippocampus-dependent simulation in relation to this question. Hippocampal sharp-wave ripples and theta oscillations have been found to instantiate previous and anticipated experiences. These hippocampal activations coordinate with neural reward and fear centers as well as sensory and cortical areas in ways that are associated with conscious episodic mental imagery in humans. Moreover, such hippocampal “re- and preplay” has been found to contribute to instrumental decision making, the learning of value representations, and the delay of rewards in rats. The functional and structural features of hippocampal simulation are highly conserved across mammals. This evidence makes it reasonable to assume that internally triggered experiences of hedonic valence (IHVs) are pervasive across (at least) all mammals. This conclusion has important welfare implications. Most prominently, IHVs act as a kind of “welfare multiplier” through which the welfare impacts of any given experience of pain or pleasure are increased through each future retrieval. However, IHVs also have practical implications for welfare assessment and cause prioritization.

Visual consequent stimulus complexity affects performance in audiovisual associative learning

In associative learning (AL), cues and/or outcome events are coupled together. AL is typically tested in visual learning paradigms. Recently, our group developed various AL tests based on the Rutgers Acquired Equivalence Test (RAET), both visual and audiovisual, keeping the structure and logic of RAET but with different stimuli. In this study, 55 volunteers were tested in two of our audiovisual tests, SoundFace (SF) and SoundPolygon (SP). The antecedent stimuli in both tests are sounds, and the consequent stimuli are images. The consequents in SF are cartoon faces, while in SP, they are simple geometric shapes. The aim was to test how the complexity of the applied consequent stimuli influences performance regarding the various aspects of learning the tests assess (stimulus pair learning, retrieval, and generalization of the previously learned associations to new but predictable stimulus pairs). In SP, behavioral performance was significantly poorer than in SF, and the reaction times were significantly longer, for all phases of the test. The results suggest that audiovisual associative learning is significantly influenced by the complexity of the consequent stimuli.

The value of confidence: Confidence prediction errors drive value-based learning in the absence of external feedback

Reinforcement learning algorithms have a long-standing success story in explaining the dynamics of instrumental conditioning in humans and other species. While normative reinforcement learning models are critically dependent on external feedback, recent findings in the field of perceptual learning point to a crucial role of internally generated reinforcement signals based on subjective confidence, when external feedback is not available. Here, we investigated the existence of such confidence-based learning signals in a key domain of reinforcement-based learning: instrumental conditioning. We conducted a value-based decision making experiment which included phases with and without external feedback and in which participants reported their confidence in addition to choices. Behaviorally, we found signatures of self-reinforcement in phases without feedback, reflected in an increase of subjective confidence and choice consistency. To clarify the mechanistic role of confidence in value-based learning, we compared a family of confidence-based learning models with more standard models predicting either no change in value estimates or a devaluation over time when no external reward is provided. We found that confidence-based models indeed outperformed these reference models, whereby the learning signal of the winning model was based on the prediction error between current confidence and a stimulus-unspecific average of previous confidence levels. Interestingly, individuals with more volatile reward-based value updates in the presence of feedback also showed more volatile confidence-based value updates when feedback was not available. Together, our results provide evidence that confidence-based learning signals affect instrumentally learned subjective values in the absence of external feedback.

Reinforcement learning models successfully simulate value-based learning processes (e.g., “How worthwhile is it to choose the same option again?”) when external reward feedback is provided (e.g., drops of sweet liquids or money). But does learning stagnate if such feedback is no longer provided? Recently, a number of studies have shown that subjective confidence can likewise act as an internal reward signal, when external feedback is not available. These results are in line with the intuitive experience that being confident about choices and actions comes with a satisfying feeling of accomplishment. To better understand the role of confidence in value-based learning, we designed a study in which participants had to learn the value of choice options in phases with and without external feedback. Behaviorally, we found signatures of self-reinforcement, such as increased confidence and choice consistency, in phases without feedback. To examine the underlying mechanisms, we compared computational models, in which learning was guided by confidence signals, with more standard reinforcement learning models. A statistical comparison of these models showed that a confidence-based model in which generic confidence prediction errors (e.g., “Am I as confident as expected?”) guide learning indeed outperformed the standard models.

Neural correlates associated with processing food stimuli in anorexia nervosa and bulimia nervosa: an activation likelihood estimation meta-analysis of fMRI studies

PURPOSE

Various neurobiological models have utilised symptom categories to explore the underlying neural correlates in both anorexia nervosa (AN) and bulimia nervosa (BN). The aim of this research was to investigate the brain activity patterns associated with viewing food stimuli in anorexia nervosa and bulimia nervosa.

METHODS

Electronic databases including PsycInfo and PubMed were systematically searched from data base inception until 1st of December 2020, identifying 14 suitable functional magnetic resonance imaging studies (fMRI), involving 470 participants. ALE meta-analysis was used to statistically analyse the overlap of activation foci from different fMRI studies in response to visual food stimuli.

RESULTS

Comparing patients with AN with healthy control (HC), we detected hypoactivation in brain areas related to reward processing (i.e., amygdala and lentiform nucleus), and interoceptive processing (i.e., insula). In addition, patients with AN showed hyperactivations in cognitive control areas (i.e., prefrontal and anterior cingulate cortex). In contrast, patients with BN exhibited hyperactivations in brain areas related to reward processing (i.e., lentiform nucleus), and interoceptive processing (i.e., insula). Furthermore, patients with BN showed hypoactivations in brain regions associated with cognitive control (i.e., prefrontal and anterior cingulate cortex).

CONCLUSIONS

Our study shows differing neural endotypes of the two types of eating disorders, that underpin their behavioural phenotypes. While exploratory in nature, these findings might be relevant for guiding new emerging therapies, including invasive and non-invasive neuromodulation techniques in treatment of eating disorders.

LEVEL OF EVIDENCE

Level I, meta-analysis.

Gray-Matter Morphometry of Internalizing-Symptom Dimensions During Adolescence

Understanding the neuroanatomical correlates of internalizing psychopathology during adolescence may shed light on to neurodevelopmental processes that make this a critical period for the trajectory of mental illness. However, few studies have simultaneously examined co-occurring and dissociable features of internalizing psychopathology during this formative developmental stage. In the current study we identify the neuroanatomical correlates of four dimensions of internalizing psychopathology symptoms in adolescents: a common internalizing dimension capturing covariance in symptoms across internalizing disorders, as well as low positive affect-, anxious arousal-, and anxious apprehension-specific residuals. Our results suggest that these dimensions are associated with neuroanatomy across much of the brain, including prefrontal and limbic regions implicated in case-control studies, but also regions supporting visual processing. Importantly, results differed between males and females in regions that are sexually dimorphic in adulthood and the direction of the effects were largely opposite to what has been observed in adults and children.

Altered brain activation during reward anticipation in bipolar disorder

Although altered reward sensitivity has been observed in individuals with bipolar disorder (BD), the brain function findings related to reward processing remain unexplored and inconsistent. This meta-analysis aimed to identify brain activation alterations underlying reward anticipation in BD. A systematic literature research was conducted to identify fMRI studies of reward-relevant tasks performed by BD individuals. Using Anisotropic Effect Size Signed Differential Mapping, whole-brain and ROI of the ventral striatum (VS) coordinate-based meta-analyses were performed to explore brain regions showing anomalous activation in individuals with BD compared to healthy controls (HC), respectively. A total of 21 studies were identified in the meta-analysis, 15 of which were included in the whole-brain meta-analysis and 17 in the ROI meta-analysis. The whole-brain meta-analysis revealed hypoactivation in the bilateral angular gyrus and right inferior frontal gyrus during reward anticipation in individuals with BD compared to HC. No significant activation differences were observed in bilateral VS between two groups by whole-brain or ROI-based meta-analysis. Individuals with BD type I and individuals with euthymic BD showed altered activation in prefrontal, angular, fusiform, middle occipital gyrus, and striatum. Hypoactivation in the right angular gyrus was positively correlated with the illness duration of BD. The present study reveals the potential neural mechanism underlying impairment in reward anticipation in BD. Some clinical features such as clinical subtype, mood state, and duration of illness confound the underlying neurobiological abnormality reward anticipation in BD. These findings may have implications for identifying clinically relevant biomarkers to guide intervention strategies for BD.

A corticostriatal pathway mediating self-efficacy enhancement

Forming positive beliefs about one's ability to perform challenging tasks, often termed self-efficacy, is fundamental to motivation and emotional well-being. Self-efficacy crucially depends on positive social feedback, yet people differ in the degree to which they integrate such feedback into self-beliefs (i.e., positive bias). While diminished positive bias of this sort is linked to mood and anxiety, the neural processes by which positive feedback on public performance enhances self-efficacy remain unclear. To address this, we conducted a behavioral and fMRI study wherein participants delivered a public speech and received fictitious positive and neutral feedback on their performance in the MRI scanner. Before and after receiving feedback, participants evaluated their actual and expected performance. We found that reduced positive bias in updating self-efficacy based on positive social feedback associated with a psychopathological dimension reflecting symptoms of anxiety, depression, and low self-esteem. Analysis of brain encoding of social feedback showed that a positive self-efficacy update bias associated with a stronger reward-related response in the ventral striatum (VS) and stronger coupling of the VS with a temporoparietal region involved in self-processing. Together, our findings demarcate a corticostriatal circuit that promotes positive bias in self-efficacy updating based on social feedback, and highlight the centrality of such bias to emotional well-being.

Dopamine D2 receptor signaling in the brain modulates circadian liver metabolomic profiles

SignificanceWe analyzed the liver metabolome of mice deficient in the expression of the dopamine D2 receptor (D2R) in striatal medium spiny neurons (iMSN-D2RKO) and found profound changes in the liver circadian metabolome compared to control mice. Additionally, we show activation of dopaminergic circuits by acute cocaine administration in iMSN-D2RKO mice reprograms the circadian liver metabolome in response to cocaine. D2R signaling in MSNs is key for striatal output and essential for regulating the first response to the cellular and rewarding effects of cocaine. Our results suggest changes in dopamine signaling in specific striatal neurons evoke major changes in liver physiology. Dysregulation of liver metabolism could contribute to an altered allostatic state and therefore be involved in continued use of drugs.

Reward and plasticity: Implications for neurorehabilitation

Neuroplasticity follows nervous system injury in the presence or absence of rehabilitative treatments. Rehabilitative interventions can be used to modulate adaptive neuroplasticity, reducing motor impairment and improving activities of daily living in patients with brain lesions. Learning principles guide some rehabilitative interventions. While basic science research has shown that reward combined with training enhances learning, this principle has been only recently explored in the context of neurorehabilitation. Commonly used reinforcers may be more or less rewarding depending on the individual or the context in which the task is performed. Studies in healthy humans showed that both reward and punishment can enhance within-session motor performance; but reward, and not punishment, improves consolidation and retention of motor skills. On the other hand, neurorehabilitative training after brain lesions involves complex tasks (e.g., walking and activities of daily living). The contribution of reward to neurorehabilitation is incompletely understood. Here, we discuss recent research on the role of reward in neurorehabilitation and the needed directions of future research.

Task-induced subjective fatigue and resting-state striatal connectivity following traumatic brain injury

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Fatigue is a very frequent and disabling symptom in traumatic brain injury (TBI).

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Effects of task-induced fatigue on resting-state functional connectivity (rsFC).

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Striatal rsFC relates differently to subjective fatigue in TBI compared to controls.

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Default mode network rsFC relates similar to subjective fatigue in TBI and controls.

Background

People with traumatic brain injury (TBI) often experience fatigue, but an understanding of the neural underpinnings of fatigue following TBI is still lacking. This study used resting-state functional magnetic resonance imaging (rs-fMRI) to examine associations between functional connectivity (FC) changes and task-induced changes in subjective fatigue in people with moderate-severe TBI.

Methods

Sixteen people with moderate-severe TBI and 17 matched healthy controls (HC) performed an adaptive N-back task (working memory task) to induce cognitive fatigue. Before and after the task they rated their state fatigue level and underwent rs-fMRI. Seed-to-voxel analyses with seeds in areas involved in cognitive fatigue, namely the striatum and default mode network (DMN) including, medial prefrontal cortex and posterior cingulate cortex, were performed.

Results

The adaptive N-back task was effective in inducing fatigue in both groups. Subjective task-induced fatigue was positively associated with FC between striatum and precuneus in people with TBI, while there was a negative association in HC. In contrast, subjective task-induced fatigue was negatively associated with FC between striatum and cerebellum in the TBI group, while there was no association in HC. Similar associations between task-induced subjective fatigue and DMN FC were found across the groups.

Conclusions

Our results suggest that the subjective experience of fatigue was linked to DMN connectivity in both groups and was differently associated with striatal connectivity in people with moderate-severe TBI compared to HC. Defining fatigue-induced neuronal network changes is pertinent to the development of treatments that target abnormal neuronal activity after TBI.

Neurosurgery and neuromodulation for anorexia nervosa in the 21st century: a systematic review of treatment outcomes

As current psychosocial and pharmacological interventions show limited efficacy in the treatment of anorexia nervosa (AN), interest in the potential value of neurosurgical intervention and neuromodulation in managing severe and enduring illness has grown. We conducted a systematic review of 20 trials of neurosurgical and neuromodulatory treatments for AN, including neurosurgical ablation, deep brain stimulation (DBS), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS). Overall, there is evidence to support the role of stereotactic ablation and DBS in the treatment of AN. In contrast, results for rTMS and tDCS have been modest and generally more mixed. Neurosurgical treatment may offer important new avenues for the treatment of AN. Additional randomized clinical trials with comparable patient populations will be needed, in which change in affective, cognitive, and perceptual symptom phenomena, and interrogation of targeted circuits, pre- and post-intervention, are carefully documented.

Effects of social and emotional context on neural activation and synchrony during movie viewing

Sharing emotional experiences impacts how we perceive and interact with the world, but the neural mechanisms that support this sharing are not well characterized. In this study, participants (N = 52) watched videos in an MRI scanner in the presence of an unfamiliar peer. Videos varied in valence and social context (i.e., participants believed their partner was viewing the same (joint condition) or a different (solo condition) video). Reported togetherness increased during positive videos regardless of social condition, indicating that positive contexts may lessen the experience of being alone. Two analysis approaches were used to examine both sustained neural activity averaged over time and dynamic synchrony throughout the videos. Both approaches revealed clusters in the medial prefrontal cortex that were more responsive to the joint condition. We observed a time‐averaged social‐emotion interaction in the ventromedial prefrontal cortex, although this region did not demonstrate synchrony effects. Alternatively, social‐emotion interactions in the amygdala and superior temporal sulcus showed greater neural synchrony in the joint compared to solo conditions during positive videos, but the opposite pattern for negative videos. These findings suggest that positive stimuli may be more salient when experienced together, suggesting a mechanism for forming social bonds.

Executive Function Assigns Value to Novel Goal-Congruent Outcomes

People often learn from the outcomes of their actions, even when these outcomes do not involve material rewards or punishments. How does our brain provide this flexibility? We combined behavior, computational modeling, and functional neuroimaging to probe whether learning from abstract novel outcomes harnesses the same circuitry that supports learning from familiar secondary reinforcers. Behavior and neuroimaging revealed that novel images can act as a substitute for rewards during instrumental learning, producing reliable reward-like signals in dopaminergic circuits. Moreover, we found evidence that prefrontal correlates of executive control may play a role in shaping flexible responses in reward circuits. These results suggest that learning from novel outcomes is supported by an interplay between high-level representations in prefrontal cortex and low-level responses in subcortical reward circuits. This interaction may allow for human reinforcement learning over arbitrarily abstract reward functions.

The Brain's Reward System in Health and Disease

Rhythmic gene expression is found throughout the central nervous system. This harmonized regulation can be dependent on- and independent of- the master regulator of biological clocks, the suprachiasmatic nucleus (SCN). Substantial oscillatory activity in the brain's reward system is regulated by dopamine. While light serves as a primary time-giver (zeitgeber) of physiological clocks and synchronizes biological rhythms in 24-h cycles, nonphotic stimuli have a profound influence over circadian biology. Indeed, reward-related activities (e.g., feeding, exercise, sex, substance use, and social interactions), which lead to an elevated level of dopamine, alters rhythms in the SCN and the brain's reward system. In this chapter, we will discuss the influence of the dopaminergic reward pathways on circadian system and the implication of this interplay on human health.

Aberrant Striatal Value Representation in Huntington's Disease Gene Carriers 25 Years Before Onset

BACKGROUND

In this study, we asked whether differences in striatal activity during a reinforcement learning (RL) task with gain and loss domains could be one of the earliest functional imaging features associated with carrying the Huntington's disease (HD) gene. Based on previous work, we hypothesized that HD gene carriers would show either neural or behavioral asymmetry between gain and loss learning.

METHODS

We recruited 35 HD gene carriers, expected to demonstrate onset of motor symptoms in an average of 26 years, and 35 well-matched gene-negative control subjects. Participants were placed in a functional magnetic resonance imaging scanner, where they completed an RL task in which they were required to learn to choose between abstract stimuli with the aim of gaining rewards and avoiding losses. Task behavior was modeled using an RL model, and variables from this model were used to probe functional magnetic resonance imaging data.

RESULTS

In comparison with well-matched control subjects, gene carriers more than 25 years from motor onset showed exaggerated striatal responses to gain-predicting stimuli compared with loss-predicting stimuli (p = .002) in our RL task. Using computational analysis, we also found group differences in striatal representation of stimulus value (p = .0004). We found no group differences in behavior, cognitive scores, or caudate volumes.

CONCLUSIONS

Behaviorally, gene carriers 9 years from predicted onset have been shown to learn better from gains than from losses. Our data suggest that a window exists in which HD-related functional neural changes are detectable long before associated behavioral change and 25 years before predicted motor onset. These represent the earliest functional imaging differences between HD gene carriers and control subjects.

Reduced neural differentiation of rewards and punishment during passive avoidance learning in adolescents with generalized anxiety disorder

BACKGROUND

It has been proposed that individuals with generalized anxiety disorder (GAD) show dysfunctional computations related to approach-avoidance decision-making. However, few studies have examined the neural basis of this impairment, particularly in adolescents with GAD. The goal of the current study was to address this gap in the literature.

METHOD

The study involved 51 adolescents with GAD and 51 typically developing (TD) comparison individuals matched on age (16.10 and 15.75 respective means), gender (30 F/21 M and 24 F/27 M), and IQ (103.20 and 103.18 respective means). Participants underwent functional magnetic resonance imaging during a passive avoidance task.

RESULTS

We found a significant Group-by-Reinforcement interaction within reward-related brain regions including the caudate, putamen, mid cingulate/paracentral lobule, and superior and middle frontal gyrus. TD adolescents showed a greater differential response to reward versus punishment feedback within these regions relative to adolescents with GAD. In particular, this reflected reduced responses to rewards in the adolescents with GAD. There were no group differences in neural responses when making approach/avoidance responses.

CONCLUSION

The results of this study suggest reduced differential responsiveness to reinforcement as a component of the pathophysiology seen in adolescents with GAD. This dysfunction likely underpins decision-making impairments that may exacerbate the participants' worry.

Social neural sensitivity as a susceptibility marker to family context in predicting adolescent externalizing behavior

Adolescence represents a period of risk for developing patterns of risk-taking and conduct problems, and the quality of the family environment is one robust predictor of such externalizing behavior. However, family factors may not affect all youth uniformly, and individual differences in neurobiological susceptibility to the family context may moderate its influence. The current study investigated brain-based individual differences in social motivational processing as a susceptibility marker to family conflict in predicting externalizing behavior in early adolescent youth. 163 adolescents (M_age = 12.87 years) completed an fMRI scan during which they anticipated social rewards and social punishments. For adolescents with heightened ventral striatum and amygdala blood oxygen-level dependent (BOLD) response during the anticipation of social rewards and heightened ventral striatum BOLD response during the anticipation of social punishments, higher levels of family conflict were associated with greater externalizing behavior. BOLD response when anticipating both social rewards and punishments suggested increased susceptibility to maladaptive family contexts, highlighting the importance of considering adolescent social motivation in positive and negatively valenced contexts.

Increased brain reactivity to gambling unavailability as a marker of problem gambling

The unprecedented development and ubiquity of sports betting constitute an emerging public health concern. It is crucial to provide markers that could help to better identify people experiencing sports betting-related harms. The current study investigated whether problem gambling status, sports betting passion, and trait-self-control modulate brain reactivity to sports betting cues. Sixty-five frequent sports bettors (35 "nonproblem bettors" and 30 "problem bettors") were exposed to cues representing real upcoming sport events (with varying levels of winning confidence) that were made available or blocked for betting, during functional magnetic resonance imaging (fMRI) recording. Sports betting passion and trait-self-control were assessed using self-report scales. Sport events nonavailable for betting elicited higher insular and striatal activation in problem bettors, as compared with nonproblem bettors. Within a large cluster encompassing the ventral striatum, hippocampus, and amygdala, lower trait-self-control was associated with increased brain reactivity to sport events with high levels of winning confidence that were nonavailable for betting. No significant effect of sports betting passion was observed. These findings suggest that sports bettors' brain reactivity to gambling unavailability might be a relevant marker of sports betting-related harms, as well as of blunted trait-self-control.

Reduced feelings of regret and enhanced fronto-striatal connectivity in elders with long-term Tai Chi experience

The current study investigates how long-term Tai Chi experience affects the neural and emotional response to regret in elders. Participants perform the sequential risk-taking task while undergoing functional magnetic resonance imaging (fMRI) scanning. In the task, participants opened a series of boxes consecutively and decided when to stop. Each box contained a reward, except for one which contained a devil. If the devil was revealed, then this served to zero the participant’s gain in that trial. Once stopped, participant’s gains and missed chances were revealed. Behaviorally, the Tai Chi group showed less regret, reduced risk taking, higher levels of nonjudgment of inner experience and less emotional sensitivity to outcome. fMRI results showed that the Tai Chi group demonstrated stronger fronto-striatal functional connectivity in trials with numerous missed chances. The nonjudgment of inner experience mediated the impact of fronto-striatal functional connectivity on Tai Chi practitioners’ emotional sensitivity to outcome. These results highlight that long-term Tai Chi exercise may be effective in alleviating feelings of regret in elders by promoting reduced judgment of inner experience and enhanced emotion regulation through the strengthening of fronto-striatal functional connectivity.

The basal ganglia and the cerebellum in human emotion

The basal ganglia (BG) and the cerebellum historically have been relegated to a functional role in producing or modulating motor output. Recent research, however, has emphasized the importance of these subcortical structures in multiple functional domains, including affective processes such as emotion recognition, subjective feeling elicitation and reward valuation. The pathways through the thalamus that connect the BG and cerebellum directly to each other and with extensive regions of the cortex provide a structural basis for their combined influence on limbic function. By regulating cortical oscillations to guide learning and strengthening rewarded behaviors or thought patterns to achieve a desired goal state, these regions can shape the way an individual processes emotional stimuli. This review will discuss the basic structure and function of the BG and cerebellum and propose an updated view of their functional role in human affective processing.

Neural Response to Monetary and Social Feedback Demonstrate Differential Associations with Depression and Social Anxiety

An aberrant neural response to rewards has been linked to both depression and social anxiety. Most studies have focused on the neural response to monetary rewards, and few have tested different modalities of reward (e.g. social) that are more salient to particular forms of psychopathology. In addition, most studies contain critical confounds, including contrasting positive and negative feedback and failing to disentangle being correct from obtaining positive feedback. In the present study, 204 participants underwent electroencephalography during monetary and social feedback tasks that were matched in trial structure, timing and feedback stimuli. The reward positivity (RewP) was measured in response to correctly identifying stimuli that resulted in monetary win, monetary loss, social like or social dislike feedback. All monetary and social tasks elicited a RewP, which were positively correlated. Across all tasks, the RewP was negatively associated with depression and positively associated with social anxiety. The RewP to social dislike feedback, independent of monetary and social like feedback, was also associated with social anxiety. The present study suggests that a domain-general neural response to correct feedback demonstrates a differential association with depression and social anxiety, but a domain-specific neural response to social dislike feedback is uniquely associated with social anxiety.

Neural correlates of recursive thinking during interpersonal strategic interactions

To navigate the complex social world, individuals need to represent others' mental states to think strategically and predict their next move. Strategic mentalizing can be classified into different levels of theory of mind according to its order of mental state attribution of other people's beliefs, desires, intentions, and so forth. For example, reasoning people's beliefs about simple world facts is the first-order attribution while going further to reason people's beliefs about the minds of others is the second-order attribution. The neural substrates that support such high-order recursive reasoning in strategic interpersonal interactions are still unclear. Here, using a sequential-move interactional game together with functional magnetic resonance imaging (fMRI), we showed that recursive reasoning engaged the frontal-subcortical regions. At the stimulus stage, the ventral striatum was more activated in high-order reasoning as compared with low-order reasoning. At the decision stage, high-order reasoning activated the medial prefrontal cortex (mPFC) and other mentalizing regions. Moreover, functional connectivity between the dorsomedial prefrontal cortex (dmPFC) and the insula/hippocampus was positively correlated with individual differences in high-order social reasoning. This work delineates the neural correlates of high-order recursive thinking in strategic games and highlights the key role of the interplay between mPFC and subcortical regions in advanced social decision-making.

Healing the next generation: an adaptive agent model for the effects of parental narcissism

Parents play an important role in the mental development of a child. In our previous work, we addressed how a narcissistic parent influences a child (online/offline) when (s)he is happy and admires the child. Now, we address the influence of a parent who is not so much pleased, and may curse the child for being the reason for his or her unhappiness. An abusive relationship with a parent can also cause trauma and poor mental health of the child. We also address how certain coping behaviors can help the child cope with such a situation. Therefore, the aim of the study is threefold. We present an adaptive agent model of a child, while incorporating the concept of mirroring through social contagion, the avoidance behaviors from a child, and the effects of regulation strategies to cope with stressful situations.

The neural underpinnings of allocentric thinking in a novel signaling task

The ability to adopt the perspectives of others is fundamental to effective communication in social interactions. However, the neural correlates of allocentric thinking in communicative signaling remain unclear. We adapted a novel signaling task in which the signaler was given the target word and must choose a one-word signal to help the receiver guess the target. Behavioral results suggest that speakers can use allocentric thinking to choose signals that are salient from the perspective of the receiver rather than their own point of view. At the neural level, functional magnetic resonance imaging (fMRI) data reveal that the medial prefrontal cortex (mPFC), ventral striatum, and temporal-parietal junction are more activated when signalers engage in allocentric than egocentric thinking. Moreover, functional connectivity between the mPFC and ventral striatum predicted individuals' perspective-taking ability during successful communication. These findings reveal that neural representations in the mPFC-striatum network support perspective-taking in complex social decision making, providing a new perspective on how the brain arbitrates between allocentric thinking and egocentric thinking in communication and social coordination.