Reward anticipation revisited- evidence from an fMRI study in euthymic bipolar I patients and healthy first-degree relatives

How to study psychological mechanisms of mania? A systematic review on the methodology of experimental studies on manic mood dysregulation of leading theories on bipolar disorder

INTRODUCTION

Although there are several psychological theories on bipolar disorders (BD), the empirical evidence on these theories through experimental studies is still limited. The current study systematically reviews experimental methods used in studies on the main theories of BD: Reward Hypersensitivity Theory (RST) or Behavioral Activation System (BAS), Integrative Cognitive Model (ICM), Positive Emotion Persistence (PEP), Manic Defense theory (MD), and Mental Imagery (MI). The primary aim is to provide an overview of the used methods and to identify limitations and suggest areas of improvement.

METHODS

A systematic search of six databases until October 2023 was conducted. Study selection involved two independent reviewers extracting data on experimental study design and methodology.

RESULTS

A total of 84 experimental studies were reviewed. BAS and RST were the most frequently studied theories. The majority of these experimental studies focus on mechanisms of reward sensitivity. Other important elements of the reviewed theories, such as goal setting and-attainment, situation selection (avoidance or approach), activation, affective/emotional reactivity, and regulatory strategies, are understudied. Self-report and neuropsychological tasks are most often used, while mood induction and physiological measures are rarely used.

CONCLUSION

There is a need for more consensus on the operationalization of psychological theories of mania. Standardization of test batteries could improve comparability among studies and foster a more systematic approach to experimental research. Research on affective (activated) states is still underrepresented in comparison with studies on trait vulnerabilities.

Reward anticipation-related neural activation following cued reinforcement in adults with psychotic psychopathology and biological relatives

BACKGROUND

Schizophrenia is associated with hypoactivation of reward sensitive brain areas during reward anticipation. However, it is unclear whether these neural functions are similarly impaired in other disorders with psychotic symptomatology or individuals with genetic liability for psychosis. If abnormalities in reward sensitive brain areas are shared across individuals with psychotic psychopathology and people with heightened genetic liability for psychosis, there may be a common neural basis for symptoms of diminished pleasure and motivation.

METHODS

We compared performance and neural activity in 123 people with a history of psychosis (PwP), 81 of their first-degree biological relatives, and 49 controls during a modified Monetary Incentive Delay task during fMRI.

RESULTS

PwP exhibited hypoactivation of the striatum and anterior insula (AI) during cueing of potential future rewards with each diagnostic group showing hypoactivations during reward anticipation compared to controls. Despite normative task performance, relatives demonstrated caudate activation intermediate between controls and PwP, nucleus accumbens activation more similar to PwP than controls, but putamen activation on par with controls. Across diagnostic groups of PwP there was less functional connectivity between bilateral caudate and several regions of the salience network (medial frontal gyrus, anterior cingulate, AI) during reward anticipation.

CONCLUSIONS

Findings implicate less activation and connectivity in reward processing brain regions across a spectrum of disorders involving psychotic psychopathology. Specifically, aberrations in striatal and insular activity during reward anticipation seen in schizophrenia are partially shared with other forms of psychotic psychopathology and associated with genetic liability for psychosis.

Neural markers of mania that distinguish inpatient adolescents with bipolar disorder from those with other psychopathology

Pediatric bipolar disorder (BD) is difficult to distinguish from other psychiatric disorders, a challenge which can result in delayed or incorrect interventions. Using neuroimaging we aimed to identify neural measures differentiating a rarified sample of inpatient adolescents with BD from other inpatient psychopathology (OP) and healthy adolescents (HC) during a reward task. We hypothesized reduced subcortical and elevated cortical activation in BD relative to other groups, and that these markers will be related to self-reported mania scores. We examined inpatient adolescents with diagnosis of BD-I/II (n = 29), OP (n = 43), and HC (n = 20) from the Inpatient Child and Adolescent Bipolar Spectrum Imaging study. Inpatient adolescents with BD showed reduced activity in right thalamus, left thalamus, and left amygdala, relative to inpatient adolescents with OP and HC. This reduced neural function explained 21% of the variance in past month and 23% of the variance in lifetime mania scores. Lower activity in regions associated with the reward network, during reward processing, differentiates BD from OP in inpatient adolescents and explains >20% of the variance in mania scores. These findings highlight potential targets to aid earlier identification of, and guide new treatment developments for, pediatric BD.

Trajectory of reward-related abnormalities in unaffected relatives of patients with bipolar disorder - A longitudinal fMRI study

First-degree relatives of patients with bipolar disorder are at heightened risk of mood episodes, which may be attributed to the existence of endophenotypes i.e., heritable (neuro)biological changes present in patients and their unaffected relatives (UR). In this longitudinal MRI study, we aim to investigate the trajectories of aberrant reward-related functional changes identified in UR vs healthy controls (HC). Sixty-eight UR and 65 HC of similar age and gender distribution underwent MRI at baseline while performing a card guessing task. Of these, 29 UR and 36 HC were investigated with the same protocol following a 16-month period in average. We first identified brain regions showing group differences in the neural response to expected value (EV) and reward prediction error (PE) at baseline and analyzed how the reward-related response in these regions changed over time in UR vs HC. Relative to HC at baseline, UR showed lower EV signal in the right ventrolateral prefrontal cortex (vlPFC) and paracingulate gyrus and lower PE signal in the left vlPFC and dorsomedial PFC. The trajectories of these abnormalities in UR showed a normalization of the prefrontal EV signals, whereas the PE signals which correlated with depressive symptoms remained stable over time. While the UR showed both blunted EV and PE signals, none of these abnormalities increased over time, which is consistent with the observed stable mood symptoms.

The human cerebellum in reward anticipation and reward outcome processing: An activation likelihood estimation meta-analysis

The cerebellum generates internal prediction models and actively compares anticipated and actual outcomes in order to reach a desired end state. In this process, reward can serve as a reinforcer that shapes internal prediction models, enabling context-appropriate behavior. While the involvement of the cerebellum in reward processing has been established in animals, there is no detailed account of which cerebellar regions are involved in reward anticipation and reward outcome processing in humans. To this end, an activation likelihood estimation meta-analysis of functional neuroimaging studies was performed to investigate cerebellar functional activity patterns associated with reward anticipation and reward outcome processing in healthy adults. Results showed that reward anticipation (k=31) was associated with regional activity in the bilateral anterior lobe, bilateral lobule VI, left Crus I and the posterior vermis, while reward outcome (k=16) was associated with regional activity in the declive and left lobule VI. The findings of this meta-analysis show distinct involvement of the cerebellum in reward anticipation and reward outcome processing as part of a predictive coding routine.

Emotion regulation in bipolar disorder type-I: multivariate analysis of fMRI data

BACKGROUND

Bipolar disorder type-I (BD-I) patients are known to show emotion regulation abnormalities. In a previous fMRI study using an explicit emotion regulation paradigm, we compared responses from 19 BD-I patients and 17 matched healthy controls (HC). A standard general linear model-based univariate analysis revealed that BD patients showed increased activations in inferior frontal gyrus when instructed to decrease their emotional response as elicited by neutral images. We implemented multivariate pattern recognition analyses on the same data to examine if we could classify conditions within-group as well as HC versus BD.

METHODS

We reanalyzed explicit emotion regulation data using a multivariate pattern recognition approach, as implemented in PRONTO software. The original experimental paradigm consisted of a full 2 × 2 factorial design, with valence (Negative/Neutral) and instruction (Look/Decrease) as within subject factors.

RESULTS

The multivariate models were able to accurately classify different task conditions when HC and BD were analyzed separately (63.24%-75.00%, p = 0.001-0.012). In addition, the models were able to correctly classify HC versus BD with significant accuracy in conditions where subjects were instructed to downregulate their felt emotion (59.60%-60.84%, p = 0.014-0.018). The results for HC versus BD classification demonstrated contributions from the salience network, several occipital and frontal regions, inferior parietal lobes, as well as other cortical regions, to achieve above-chance classifications.

CONCLUSIONS

Our multivariate analysis successfully reproduced some of the main results obtained in the previous univariate analysis, confirming that these findings are not dependent on the analysis approach. In particular, both types of analyses suggest that there is a significant difference of neural patterns between conditions within each subject group. The multivariate approach also revealed that reappraisal conditions provide the most informative activity for differentiating HC versus BD, irrespective of emotional valence (negative or neutral). The current results illustrate the importance of investigating the cognitive control of emotion in BD. We also propose a set of candidate regions for further study of emotional control in BD.

Trajectory of aberrant reward processing in patients with bipolar disorder - A longitudinal fMRI study

BACKGROUND

Bipolar disorder (BD), and especially the mania phenotype, is characterized by heightened reward responsivity and aberrant reward processing. In this longitudinal fMRI study, we investigated neuronal response during reward anticipation as the computed expected value (EV) and outcome evaluation as reward prediction error (RPE) in recently diagnosed patients with BD.

METHODS

Eighty remitted patients with BD and 60 healthy controls (HC) underwent fMRI during which they performed a card guessing task. Of these, 41 patients and 36 HC were re-scanned after 16 months. We compared reward-related neural activity between groups at baseline and longitudinally and assessed the impact of mood relapse.

RESULTS

Patients showed lower RPE signal in areas of the ventrolateral prefrontal cortex (vlPFC) than HC. In these regions, the HC showed decrease in RPE signal over time, which was absent in patients. Patients further exhibited decreased EV signal in the occipital cortex across baseline and follow-up. Patients who remained in remission showed normalization of the EV signal at follow-up. Baseline activity in the identified regions was not associated with subsequent relapse.

LIMITATIONS

Follow-up scans were only available in a relatively small sample. Medication status, follow-up time and BD illness duration prior to diagnosis varied.

CONCLUSIONS

Lower RPE signal in the vlPFC in patients with BD at baseline and its lack of normative reduction over time may represent a trait marker of dysfunctional reward-based learning or habituation. The increase in EV signal in the occipital cortex over time in patients who remained in remission may indicate normalization of reward anticipation activity.

Subjects with bipolar disorder showed different reward system activation than subjects with major depressive disorder in the monetary incentive delay task

BACKGROUND

Differentiating between bipolar disorder (BD) and major depressive disorder (MDD) during the depressive episode is an important clinical challenge. Reward system abnormalities have received much attention as one of the biological underpinnings of BD and MDD, but few studies have directly compared these abnormalities in remitted and depressed states.

METHODS

This was a functional MRI study using the Monetary Incentive Delay task in 65 patients (BD [n = 33], MDD [n = 32]) and 33 healthy controls (HC). Regions of interest (ROI) analysis with 21 ROIs related to reward anticipation and 17 ROIs related to gain outcome were implemented, as well as whole-brain analysis. The difference in the dimensional effect of depression on brain activation was also examined.

RESULTS

Relative to the HC group, BD patients showed significantly decreased activation during reward anticipation in the anterior cingulate cortex, anterior insula (AI), and putamen, and MDD patients showed significantly decreased activation in the AI and brainstem. The dimensional effect of depression severity showed a trend-level difference between BD and MDD in the right brainstem and left AI.

CONCLUSIONS

The current study showed a possible differential effect of depression on the reward system between MDD and BD. Further studies on reward systems might offer reliable markers to distinguish between MDD and BD patients in the depressive phase.

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.

Multi-band FMRI compromises detection of mesolimbic reward responses

Recent innovations in Functional Magnetic Resonance Imaging (FMRI) have sped data collection by enabling simultaneous scans of neural activity in multiple brain locations, but have these innovations come at a cost? In a meta-analysis and preregistered direct comparison of original data, we examined whether acquiring FMRI data with multi-band versus single-band scanning protocols might compromise detection of mesolimbic activity during reward processing. Meta-analytic results (n = 44 studies; cumulative n = 5005 subjects) indicated that relative to single-band scans, multi-band scans showed significantly decreased effect sizes for reward anticipation in the Nucleus Accumbens (NAcc) by more than half. Direct within-subject comparison of single-band versus multi-band scanning data (multi-band factors = 4 and 8; n = 12 subjects) acquired during repeated administration of the Monetary Incentive Delay task indicated that reductions in temporal signal-to-noise ratio could account for compromised detection of task-related responses in mesolimbic regions (i.e., the NAcc). Together, these findings imply that researchers should opt for single-band over multi-band scanning protocols when probing mesolimbic responses with FMRI. The findings also have implications for inferring mesolimbic activity during related tasks and rest, for summarizing historical results, and for using neuroimaging data to track individual differences in reward-related brain activity.

Functional imaging in youth at risk for transdiagnostic serious mental illness: Initial results from the PROCAN study

BACKGROUND

In their early stages, serious mental illnesses (SMIs) are often indistinguishable from one another, suggesting that studying alterations in brain activity in a transdiagnostic fashion could help to understand the neurophysiological origins of different SMI. The purpose of this study was to examine brain activity in youth at varying stages of risk for SMI using functional magnetic resonance imaging tasks (fMRI) that engage brain systems believed to be affected.

METHODS

Two hundred and forty three participants at different stages of risk for SMI were recruited to the Canadian Psychiatric Risk and Outcome (PROCAN) study, however only 179 were scanned. Stages included asymptomatic participants at no elevated risk, asymptomatic participants at elevated risk due to family history, participants with undifferentiated general symptoms of mental illness, and those experiencing attenuated versions of diagnosable psychiatric illnesses. The fMRI tasks included: (1) a monetary incentive delay task; (2) an emotional Go-NoGo and (3) an n-back working memory task.

RESULTS

Strong main effects with each of the tasks were found in brain regions previously described in the literature. However, there were no significant differences in brain activity between any of the stages of risk for SMI for any of the task contrasts, after accounting for site, sex and age. Furthermore, results indicated no significant differences even when participants were dichotomized as asymptomatic or symptomatic.

CONCLUSIONS

These results suggest that univariate BOLD responses during typical fMRI tasks are not sensitive markers of SMI risk and that further study, particularly longitudinal designs, will be necessary to understand brain changes underlying the early stages of SMI.

Reward mechanism of depressive episodes in bipolar disorder: Enhanced theta power in feedback-related negativity

INTRODUCTION

This study aimed to explore the reward-related neural mechanism in patients with depressive mood in bipolar disorder (BD) using event-related potentials. It remains unknown whether or not different neurobiological markers underlying depression symptoms in BD depression and major depression disorder (MDD).

METHODS

24 patients with BD depression and 20 healthy controls were included. Participants underwent evaluation with the Temporal Experience of Pleasure Scale (TEPS), followed by the classical gambling paradigm, while undergoing 64-channel electroencephalography. The waveform of feedback-related negativity (FRN) was extracted from the 250-350 ms time-window after participants received feedback regarding loss or gain. Event-related potential datasets were obtained using time-frequency analysis.

RESULTS

(1) The TEPS scores of the patients were significantly lower than those of the controls [t₍₄₂₎ = 5.16, p < 0.01]. (2) The event of loss elicited a deeper FRN in patients than that in controls [t₍₄₂₎ = 2.19, p < 0.05], while no difference was observed in the event of gains (t₍₄₂₎ = 1.12, p > 0.05). (3) Theta power rooted in FRN in patients was significantly higher in loss than in gain [F_(1,42) = 30.32, p < 0.01]. (4) Analysis of Variance (ANOVA) illustrated the interaction effect of theta power in gain/loss between two groups [F_(1,42) = 3.59, p = 0.06].

LIMITATION

Our study did not analyze the effect of different drugs which might affect our results.

CONCLUSION

The enhanced reflection of negative feedback was consistent with the negative bias, impulse control impairment, and emotional dysregulation observed in the bipolar disorder spectrum. We suggested that the extreme theta power generated from the anterior cingulate gyrus (ACC) might be the main component of abnormal FRN.

Altered spatiotemporal consistency of corticolimbic circuitry in euthymic pediatric bipolar disorder

Bipolar disorder (BD) is a life-threatening illness which clinically defined by an alternating pattern of depressive and manic episodes with a separated period of euthymia. It remains unknown about the consistency of temporal-spatial spontaneous brain activity in euthymic patients, especially in pediatric BD (PBD) patients.Resting-state fMRI signals of sixteen euthymic PBD patients and 16 healthy controls were processed and FOur-dimensional (spatiotemporal) Consistency of local neural Activities (FOCA) and functional connectivity were calculated in the present study. Voxel-wised correlation between clinical and cognitive indices and FOCA in PBD was calculated.Compared with healthy subjects, euthymic PBD patients showed worse performance in tests of Stroop Color-Word Test, Digit Span Test and Trail Making Test. Euthymic PBD patients demonstrated increased FOCA in left inferior frontal gyrus, left anterior cingulate cortex and left superior frontal gyrus and decreased FOCA in right orbital frontal gyrus, bilateral precuneus, right superior occipital gyrus and bilateral superior parietal gyrus. Decreased functional connectivities were found between right orbital frontal gyrus and left amygdala, between left superior frontal gyrus and left putamen, and between left superior frontal gyrus and left insula. And increased functional connectivity was found between right superior occipital gyrus and right hippocampus. FOCA of parahippocampal gyrus was negatively correlated with the SCWT-B score in PBD patients.Abnormal spatiotemporal consistency of brain regions of corticolimbic circuitry is possible to contribute to an imbalance between emotional processing and cognitive control in euthymic PBD. The measurement of FOCA measure may provide important clues of understanding PBD.

Mapping working memory-specific dysfunction using a transdiagnostic approach

Background

Working memory (WM) is an executive ability that allows one to hold and manipulate information for a short period of time. Schizophrenia and mood disorders are severe psychiatric conditions with overlapping genetic and clinical symptoms. Whilst WM has been suggested as meeting the criteria for being an endophenotype for schizophrenia and mood disorders, it still unclear whether they share overlapping neural circuitry.

Objective

The n-back task has been widely used to measure WM capacity, such as maintenance, flexible updating, and interference control. Here we compiled studies that included psychiatric populations, i.e., schizophrenia, bipolar disorder and major depressive disorder.

Methods

We performed a coordinate-based meta-analysis that combined 34 BOLD-fMRI studies comparing activity associated with n-back working memory between psychiatric patients and healthy controls. We specifically focused our search using the n-back task to diminish study heterogeneity.

Results

All patient groups showed blunted activity in the striatum, anterior insula and frontal lobe. The same brain networks related to WM were compromised in schizophrenia, major depressive disorder and bipolar disorder.

Conclusion

Our findings support the suggestion of commonal functional abnormalities across schizophrenia and mood disorders related to WM.

Neural reward circuit dysfunction as a risk factor for bipolar spectrum disorders and substance use disorders: A review and integration

Bipolar spectrum disorders (BSDs) and substance use disorders (SUDs) are associated with neural reward dysfunction. However, it is unclear what pattern of neural reward function underlies pre-existing vulnerability to BSDs and SUDs, or whether neural reward function explains their high co-occurrence. The current paper provides an overview of the separate literatures on neural reward sensitivity in BSDs and SUDs. We provide a systematic review of 35 studies relevant to identifying neural reward function vulnerability to BSDs and SUDs. These studies include those examining neural reward processing on a monetary reward task with prospective designs predicting initial onset of SUDs, familial risk studies that examine unaffected offspring or first-degree relatives of family members with BSDs or SUDs, and studies that examine individuals with BSDs or SUDs who are not currently in an episode of the disorder. Findings from the review highlight that aberrant responding and connectivity across neural regions associated with reward and cognitive control confers risk for the development of BSDs and SUDs. Discussion focuses on limitations of the extant literature. We conclude with an integration and theoretical model for understanding how aberrant neural reward responding may constitute a vulnerability to the development of both BSDs and SUDs.

Abnormal prefrontal cortex processing of reward prediction errors in recently diagnosed patients with bipolar disorder and their unaffected relatives

OBJECTIVE

Bipolar disorder (BD) has been associated with abnormal reward functioning including pleasure-seeking and impulsivity. Here we sought to clarify whether these changes can be attributed to abnormalities in the neural processing of reward valuation or error prediction. Moreover, we tested whether abnormalities in these processes are associated with familial vulnerability to BD.

METHODS

We obtained functional magnetic resonance imaging data from patients with recently diagnosed BD (n = 85), their unaffected first-degree relatives (n = 44), and healthy control participants (n = 66) while they were performing a monetary card game. We used a region-of-interest approach to test for group differences in the activation of the midbrain, the ventral striatum, and the prefrontal cortex during reward valuation and error prediction.

RESULTS

Patients with BD showed decreased prediction error signal in ventrolateral prefrontal cortex and the unaffected relatives showed decreased prediction error signal in the supplementary motor area in comparison to healthy controls. There were no significant group differences in the activation of the ventral striatum during the task. In healthy controls, prediction error signal in dorsal anterior cingulate cortex correlated with an out-of-scanner measure of motor inhibition but this association was absent in patients and relatives.

CONCLUSIONS

The findings indicate that abnormal reward processing in BD is primarily related to deficits in the engagement of prefrontal regions involved in inhibitory control during error prediction. In contrast, deficient activation in supplementary motor cortex involved in planning of movement emerged as a familial vulnerability to BD.

Anticipatory feelings: Neural correlates and linguistic markers

This review introduces anticipatory feelings (AF) as a new construct related to the process of anticipation and prediction of future events. AF, defined as the state of awareness of physiological and neurocognitive changes that occur within an oganism in the form of a process of adapting to future events, are an important component of anticipation and expectancy. They encompass bodily-related interoceptive and affective components and are influenced by intrapersonal and dispositional factors, such as optimism, hope, pessimism, or worry. In the present review, we consider evidence from animal and human research, including neuroimaging studies, to characterize the brain structures and brain networks involved in AF. The majority of studies reviewed revealed three brain regions involved in future oriented feelings: 1) the insula; 2) the ventromedial prefrontal cortex (vmPFC); and 3) the amygdala. Moreover, these brain regions were confirmed by a meta-analysis, using a platform for large-scale, automated synthesis of fMRI data. Finally, by adopting a neurolinguistic and a big data approach, we illustrate how AF are expressed in language.

Longitudinal changes in brain activation during anticipation of monetary loss in bipolar disorder

BACKGROUND

Individuals with bipolar disorder (BD) show aberrant brain activation patterns during reward and loss anticipation. We examined for the first time longitudinal changes in brain activation during win and loss anticipation to identify trait markers of aberrant anticipatory processing in BD.

METHODS

Thirty-four euthymic and depressed individuals with BD-I and 17 healthy controls (HC) were scanned using functional magnetic resonance imaging twice 6 months apart during a reward task.

RESULTS

HC, but not individuals with BD, showed longitudinal reductions in the right lateral occipital cortex (RLOC) activation during processing of cues predicting possible money loss (p-corrected <0.05). This result was not affected by psychotropic medication, mood state or the changes in depression/mania severity between the two scans in BD. Elevated symptoms of subthreshold hypo/mania at baseline predicted more aberrant longitudinal patterns of RLOC activation explaining 12.5% of variance in individuals with BD.

CONCLUSIONS

Increased activation in occipital cortex during negative outcome anticipation may be related to elevated negative emotional arousal during anticipatory cue processing. One interpretation is that, unlike HC, individuals with BD were not able to learn at baseline that monetary losses were smaller than monetary gains and were not able to reduce emotional arousal for negative cues 6 months later. Future research in BD should examine how modulating occipital cortical activation affects learning from experience in individuals with BD.

Neural responses to monetary incentives in bipolar disorder

Although behavioral sensitivity to reward predicts the onset and course of mania in bipolar disorder, the evidence for neural abnormalities in reward processing in bipolar disorder is mixed. To probe neural responsiveness to anticipated and received rewards in the context of bipolar disorder, we scanned individuals with remitted bipolar I disorder (n = 24) and well-matched controls (n = 24; matched for age and gender) using Functional Magnetic Resonance Imaging (FMRI) during a Monetary Incentive Delay (MID) task. Relative to controls, the bipolar group showed reduced NAcc activity during anticipation of gains. Across groups, this blunting correlated with individual differences in impulsive responses to positive emotions (Positive Urgency), which statistically accounted for the association of blunted NAcc activity with bipolar diagnosis. These results suggest that blunted NAcc responses during gain anticipation in the context of bipolar disorder may reflect individual differences in Positive Urgency. These findings may help resolve discrepancies in the literature on neural responses to reward in bipolar disorder, and clarify the relationship between brain activity and the propensity to experience manic episodes.

Love is analogous to money in human brain: Coordinate-based and functional connectivity meta-analyses of social and monetary reward anticipation

Both social and material rewards play a crucial role in daily life and function as strong incentives for various goal-directed behaviors. However, it remains unclear whether the incentive effects of social and material reward are supported by common or distinct neural circuits. Here, we have addressed this issue by quantitatively synthesizing and comparing neural signatures underlying social (21 contrasts, 207 foci, 696 subjects) and monetary (94 contrasts, 1083 foci, 2060 subjects) reward anticipation. We demonstrated that social and monetary reward anticipation engaged a common neural circuit consisting of the ventral tegmental area, ventral striatum, anterior insula, and supplementary motor area, which are intensively connected during both task and resting states. Functional decoding findings indicate that this generic neural pathway mediates positive value, motivational relevance, and action preparation during reward anticipation, which together motivate individuals to prepare well for the response to the upcoming target. Our findings support the common neural currency hypothesis by providing the first meta-analytic evidence to quantitatively show the common involvement of brain regions in both social and material reward anticipation.

Presentation and Neurobiology of Anhedonia in Mood Disorders: Commonalities and Distinctions

PURPOSE OF REVIEW

To focus on the clinical and behavioral presentation of anhedonia in mood disorders, as well as the differences and commonalities in the underlying neurocircuitry.

RECENT FINDINGS

Evidence suggests that depression is characterized by hypofunction of the reward system, while bipolar disorder manifests dysregulation of the behavioral activation system that increases goal-directed reward behavior. Importantly, strong evidence does not exist to suggest significant differences in anhedonia severity between depressed unipolar and bipolar patients, suggesting that there are more nuanced fluctuations in reward processing deficits in bipolar patients depending on their state. Both euthymic unipolar and bipolar patients frequently report residual reward dysfunction, which highlights the potential of reward processing deficits that give rise to the clinical symptom of anhedonia to be trait factors of mood disorders; however, the possibility that therapies are not adequately treating anhedonia could also explain the presence of residual symptoms. Reward processing represents a potential diagnostic and treatment marker for mood disorders. Further research should systematically explore the facets of reward processing in at-risk, affected, and remitted patients.