Reward processing dysfunction in major depression, bipolar disorder and schizophrenia

Smoking as a Common Modulator of Sensory Gating and Reward Learning in Individuals with Psychotic Disorders

Motivational and perceptual disturbances co-occur in psychosis and have been linked to aberrations in reward learning and sensory gating, respectively. Although traditionally studied independently, when viewed through a predictive coding framework, these processes can both be linked to dysfunction in striatal dopaminergic prediction error signaling. This study examined whether reward learning and sensory gating are correlated in individuals with psychotic disorders, and whether nicotine—a psychostimulant that amplifies phasic striatal dopamine firing—is a common modulator of these two processes. We recruited 183 patients with psychotic disorders (79 schizophrenia, 104 psychotic bipolar disorder) and 129 controls and assessed reward learning (behavioral probabilistic reward task), sensory gating (P50 event-related potential), and smoking history. Reward learning and sensory gating were correlated across the sample. Smoking influenced reward learning and sensory gating in both patient groups; however, the effects were in opposite directions. Specifically, smoking was associated with improved performance in individuals with schizophrenia but impaired performance in individuals with psychotic bipolar disorder. These findings suggest that reward learning and sensory gating are linked and modulated by smoking. However, disorder-specific associations with smoking suggest that nicotine may expose pathophysiological differences in the architecture and function of prediction error circuitry in these overlapping yet distinct psychotic disorders.

Systematic Input-Output Mapping Reveals Structural Plasticity of VTA Dopamine Neurons-Zona Incerta Loop Underlying the Social Buffering Effects in Learned Helplessness

A common phenomenon called social buffering (SB), communication within conspecific animals is a benefit for a stressed individual to better recover from aversive events, is crucial to all mammals. Although the dopamine reward system has been implicated in SB, it is not clear which neuronal populations are relevant and how they contribute. Here, we adopted a learned helplessness (LH) animal model of depression and found that LH subjects housed with a conspecific partner show better performance in the shuttle box test, showing that SB improves the stress-coping abilities to deal with stress. Bidirectional manipulation of ventral tegmental area (VTA) dopamine neurons by chemogenetic tools can mimic or block the SB effect in LH mice. To screen for SB-induced structure plasticity of VTA dopamine neurons, we employed viral genetic tools for mapping input and output architecture and found LH- and SB-triggered circuit-level changes in neuronal ensembles. Zona incerta (ZI), an overlapping brain region, was significantly changed in both anterograde and retrograde tracing during LH and SB. These results reveal a neural loop with structural plasticity between VTA dopamine neurons and ZI underlies the SB effects in LH and lays a foundation for studying how VTA dopamine neurons regulate SB-related neural circuits.

Peripheral immune cell reactivity and neural response to reward in patients with depression and anhedonia

Increased levels of peripheral cytokines have been previously associated with depression in preclinical and clinical research. Although the precise nature of peripheral immune dysfunction in depression remains unclear, evidence from animal studies points towards a dysregulated response of peripheral leukocytes as a risk factor for stress susceptibility. This study examined dynamic release of inflammatory blood factors from peripheral blood mononuclear cells (PBMC) in depressed patients and associations with neural and behavioral measures of reward processing. Thirty unmedicated patients meeting criteria for unipolar depressive disorder and 21 healthy control volunteers were enrolled. PBMCs were isolated from whole blood and stimulated ex vivo with lipopolysaccharide (LPS). Olink multiplex assay was used to analyze a large panel of inflammatory proteins. Participants completed functional magnetic resonance imaging with an incentive flanker task to probe neural responses to reward anticipation, as well as clinical measures of anhedonia and pleasure including the Temporal Experience of Pleasure Scale (TEPS) and the Snaith-Hamilton Pleasure Scale (SHAPS). LPS stimulation revealed larger increases in immune factors in depressed compared to healthy subjects using an aggregate immune score (t₄₉= 2.83, p = 0.007). Higher peripheral immune score was associated with reduced neural responses to reward anticipation within the ventral striatum (VS) (r = -0.39, p = 0.01), and with reduced anticipation of pleasure as measured with the TEPS anticipatory sub-score (r = -0.318, p = 0.023). Our study provides new evidence suggesting that dynamic hyper-reactivity of peripheral leukocytes in depressed patients is associated with blunted activation of the brain reward system and lower subjective anticipation of pleasure.

An Oppositional Tolerance Account for Potential Cognitive Deficits Caused by the Discontinuation of Antidepressant Drugs

Depression is the leading cause of disability worldwide, making antidepressant drugs the most used psychiatric drugs in the USA. Withdrawal effects and rebound symptoms frequently occur after the reduction and/or discontinuation of these drugs. Although these phenomena have been investigated with respect to the clinical symptomatology, no studies have systematically investigated the effects of withdrawal/rebound on general cognition. We present a novel framework based on the idea of allostatic adaptation, which allows to predict how different antidepressants likely impair different cognitive processes as a result of withdrawal and rebound effects. This framework relies on the assumptions that the type of cognitive impairments evoked by an antidepressant is determined by the targeted neurotransmitter systems, while the severity of deficits depends on its half-life. Our model predicts that the severity of detrimental cognitive withdrawal and rebound effects increases with a shorter half-life of the discontinued antidepressant drug. It further proposes drug-specific effects: antidepressants mainly targeting serotonin should primarily impair aversive and emotional processing, those targeting norepinephrine should impair the processing of alerting signals, those targeting dopamine should impair motivational processes and reward processing, and those targeting acetylcholine should impair spatial learning and memory. We hope that this framework will motivate further research to better understand and explain cognitive changes as a consequence of antidepressant discontinuation.

Sex differences in anxiety and depression: circuits and mechanisms

Epidemiological sex differences in anxiety disorders and major depression are well characterized. Yet the circuits and mechanisms that contribute to these differences are understudied, because preclinical studies have historically excluded female rodents. This oversight is beginning to be addressed, and recent studies that include male and female rodents are identifying sex differences in neurobiological processes that underlie features of these disorders, including conflict anxiety, fear processing, arousal, social avoidance, learned helplessness and anhedonia. These findings allow us to conceptualize various types of sex differences in the brain, which in turn have broader implications for considering sex as a biological variable. Importantly, comparing the sexes could aid in the discovery of novel therapeutics.

Doors P300 moderates the relationship between reward positivity and current depression status in adults

BACKGROUND

Previous research has found deficits in both the reward positivity (RewP) and P300 components of the event-related potential (ERP) in relation to depression. The current study examined whether the P300, elicited from imperative stimuli in a gambling task, relates to depression - and can be utilized in tandem with the RewP to better account for individual differences in depression.

METHODS

In the current study, 80 adults with current depression (M_age = 39.65, 79% female) and 43 healthy controls (M_age = 37.02, 81% female) completed clinical interviews, self-report questionnaires, and the doors gambling task while EEG was recorded.

RESULTS

Results indicated a reduced P300 to doors stimuli (i.e., doors P300) in depression, especially among depressed individuals reporting heightened anhedonia. Gain and loss feedback P300s did not differ between groups. Moreover, the doors P300 moderated the association between RewP and depression status: individuals with relatively intact reward processing (i.e., larger RewP) were more likely to be currently depressed if they exhibited a reduced P300.

LIMITATIONS

The majority of the sample identified as Caucasian which reduces generalizability of current results. Additionally, the current study is cross sectional design which limits insight into how these ERPs coincide with changes in the disorder.

CONCLUSIONS

The current study demonstrates that a novel P300 component to the doors stimulus appears to be blunted in currently depressed individuals, and that using the doors P300 in combination with the RewP accounts for significantly more variance in depression.

Acute stress reduces reward-related neural activity: Evidence from the reward positivity

Stress and blunted reward processing are risk factors for Major Depressive Disorder (MDD). The experience of acute stress reduces fMRI correlates of reward-related neural activity; however, few studies have examined how acute stress impacts measures of reward derived from event-related potentials (ERPs). The current study examined the impact of an acute stressor on the Reward Positivity (RewP), an ERP that indexes reward sensitivity, in twenty-six college students. Participants completed a monetary reward task while they placed their left hand in cold water set at 13 °C (i.e. acute stress condition) and again while their hand was placed in room temperature water (i.e. control condition). These conditions were separated by one week and performed in a counter-balanced order across participants. The results revealed that the RewP amplitude was blunted in the acute stress condition compared to the control condition. Moreover, there was a trend toward this effect interacting with self-reported depressive symptoms: the RewP was reduced only among individuals who reported low depressive symptoms. The current study suggests that an acute stressor reduces the RewP, and that this effect might be moderated by current depressive symptoms. Future studies might examine the temporal association between reward processing and stress, and how they interact to predict depressive symptoms.LAY SUMMARYThe current study examined the impact of acute stress on the brain's reward system. The results indicated that acute stress reduced activity within the brain's reward system, particularly among individuals with low depressive symptoms.

Anhedonia difference between major depressive disorder and bipolar disorder II

OBJECTIVE

This study aims to explore the difference in anhedonia between Major Depressive Disorder (MDD) and Bipolar Disorder II (BD-II), and attempt to distinguish the two diseases through Snaith-Hamilton Pleasure Scale (SHAPS).

METHODS

A total of 164 drug-free depressive patients (98 MDD patients, 66 BD-II patients) completed the investigation. 17-item Hamilton Depression Scale (HAMD-17) and Hamilton Anxiety Scale (HAMA) and SHAPS were assessed in all participants.

RESULTS

Our results showed that BD-II patients had higher SHAPS scores than MDD patients. The stepwise logistic regression analysis further revealed that SHAPS score, drinking habit, and extroversion as influencing factors for the identification of BD-II. The ROC curve analysis indicated that SHAPS could differentiate BD-II from MDD patients (AUC = 0.655, P = 0.001, 95% CI = 0.568 to 0.742), with the best screening cutoff at 26, and the corresponding sensitivity and specificity was 0.788 and 0.520, respectively.

CONCLUSION

Our results suggest that BD-II patients had more severe anhedonia compared to MDD patients, and the difference in anhedonia may help clinicians preliminary identify BD patients from MDD patients. The preliminary findings are worthly of further exploration.

Emotion prediction errors guide socially adaptive behaviour

People make decisions based on deviations from expected outcomes, known as prediction errors. Past work has focused on reward prediction errors, largely ignoring violations of expected emotional experiences—emotion prediction errors. We leverage a method to measure real-time fluctuations in emotion as people decide to punish or forgive others. Across four studies (N=1,016), we reveal that emotion and reward prediction errors have distinguishable contributions to choice, such that emotion prediction errors exert the strongest impact during decision-making. We additionally find that a choice to punish or forgive can be decoded in less than a second from an evolving emotional response, suggesting emotions swiftly influence choice. Finally, individuals reporting significant levels of depression exhibit selective impairments in using emotion—but not reward—prediction errors. Evidence for emotion prediction errors potently guiding social behaviors challenge standard decision-making models that have focused solely on reward.

Maternal suicidality interacts with blunted reward processing to prospectively predict increases in depressive symptoms in 8-to-14-year-old girls

Both a hypoactive reward system and maternal depression are associated with the onset of Major Depressive Disorder (MDD) in youth. Recent research indicates that blunted reward processing and maternal history of depression may interact to predict increases in depressive symptoms, however, the role of specific maternal depressive symptoms has not been examined. The current study investigated whether maternal depressive symptoms, history of MDD, and suicidal thoughts and/or behaviors (STBs) might lead to prospective increases in depressive symptoms one year later in the context of hypoactive reward processing. In a sample (N = 212) of 8 to 14-year-old girls, we assessed depressive symptoms in youth at baseline and follow up, while reward processing was measured using the Reward Positivity (RewP) event-related brain potential. Maternal STBs, current depressive symptoms, and history of maternal MDD were assessed at baseline. The results indicated that only girls with a blunted RewP and maternal STBs exhibited increased depressive symptoms one year later. These results were not evident when maternal depressive symptoms or maternal history of MDD was examined as the moderator. Overall, the current study provides evidence that maternal STBs uniquely impact youth with blunted reward processing.

Cannabis use and resting state functional connectivity in adolescent bipolar disorder

BACKGROUND

Adolescents with bipolar disorder have high rates of cannabis use, and cannabis use is associated with increased symptom severity and treatment resistance in bipolar disorder. Studies have identified anomalous resting-state functional connectivity among reward networks in bipolar disorder and cannabis use independently, but have yet to examine their convergence.

METHODS

Participants included 134 adolescents, aged 13 to 20 years: 40 with bipolar disorder and lifetime cannabis use, 31 with bipolar disorder and no history of cannabis use, and 63 healthy controls without lifetime cannabis use. We used a seed-to-voxel analysis to assess the restingstate functional connectivity of the amygdala, the nucleus accumbens and the orbitofrontal cortex, regions implicated in bipolar disorder and cannabis use. We used a generalized linear model to explore bivariate correlations for each seed, controlling for age and sex.

RESULTS

We found 3 significant clusters. Resting-state functional connectivity between the left nucleus accumbens seed and the left superior parietal lobe was negative in adolescents with bipolar disorder and no history of cannabis use, and positive in healthy controls. Resting-state functional connectivity between the right orbitofrontal cortex seed and the right lateral occipital cortex was positive in adolescents with bipolar disorder and lifetime cannabis use, and negative in healthy controls and adolescents with bipolar disorder and no history of cannabis use. Resting-state functional connectivity between the right orbitofrontal cortex seed and right occipital pole was positive in adolescents with bipolar disorder and lifetime cannabis use, and negative in adolescents with bipolar disorder and no history of cannabis use.

LIMITATIONS

The study did not include a cannabis-using control group.

CONCLUSION

This study provides preliminary evidence of cannabis-related differences in functional reward circuits in adolescents with bipolar disorder. Further studies are necessary to evaluate whether the present findings reflect consequences of or predisposition to cannabis use.

Examining the effects of psychoactive drugs on complex behavioral processes in laboratory animals

Behavioral pharmacology has been aided significantly by the development of innovative cognitive tasks designed to examine complex behavioral processes in laboratory animals. Performance outcomes under these conditions have provided key metrics of drug action which serve to supplement traditional in vivo assays of physiologic and behavioral effects of psychoactive drugs. This chapter provides a primer of cognitive tasks designed to assay different aspects of complex behavior, including learning, cognitive flexibility, memory, attention, motivation, and impulsivity. Both capstone studies and recent publications are highlighted throughout to illustrate task value for two distinct but often interconnected translational strategies. First, task performance in laboratory animals can be utilized to elucidate how drugs of abuse affect complex behavioral processes. Here, the expectation is that adverse effects on such processes will have predictive relevance to consequences that will be experienced by humans. Second, these same task outcomes can be used to evaluate candidate therapeutics. In this case, the extent to which drug doses with medicinal value perturb task performance can contribute critical information for a more complete safety profile appraisal and advance the process of medications development. Methodological and theoretical considerations are discussed and include an emphasis on determining selectivity in drug action on complex behavioral processes.

Neural Response to Rewards in Youths with Insomnia

STUDY OBJECTIVES

Insomnia and depression are common comorbid conditions in youths. Emerging evidence suggests that disrupted reward processing may be implicated in the association between insomnia and the increased risk for depression. Reduced reward positivity (RewP) as measured by event-related potential (ERP) has been linked to depression, but has not been tested in youths with insomnia.

METHODS

Twenty-eight participants with insomnia disorder and without any comorbid psychiatric disorders and 29 healthy sleepers aged between 15-24 completed a monetary reward task, the Cued Door task, whilst electroencephalographic activity was recorded. RewP (reward minus non-reward difference waves) was calculated as the mean amplitudes within 200ms to 300ms time window at FCz. Two analyses of covariance (ANCOVAs) were conducted with age as a covariate on RewP amplitude and latency, respectively.

RESULTS

Participants with insomnia had a significantly lower RewP amplitude regardless of cue types (Gain, Control, and Loss) than healthy sleepers, F (1, 51) = 4.95, p = .031, indicating blunted reward processing. On the behavioural level, healthy sleepers were more prudential (slower reaction time) in decision making towards Loss/Gain cues than their insomnia counterparts. Trial-by-trial behavioural adjustment analyses showed that, compared with healthy sleepers, participants with insomnia were less likely to dynamically change their choices in response to Loss cues.

CONCLUSIONS

Dysfunctional reward processing, coupled with inflexibility of behavioural adjustment in decision-making, is associated with insomnia disorder among youth, independent of mood disorders. Future studies with long-term follow-up are needed to further delineate the developmental trajectory of insomnia-related reward dysfunctions in youth.

Interactions and implications of Fuzzy-Trace theory for risk taking behaviors in bipolar disorder

BACKGROUND

According to Fuzzy-Trace Theory (FTT), qualitative, bottom-line, "gist" reasoning leads to less risk taking and more mature decision-making, less easily swayed by emotions than quantitative, detail-oriented, "verbatim" reasoning. In Bipolar disorder deleterious risky behaviors are common. Prior research confirmed the relationships posited between FTT and risk taking. We aim to understand whether FTT acts upon risk taking in the manner proposed in the FTT framework, namely, that (a) gist "values" mediate the role of "categorical gist". Furthermore, the roles of mania and impulsivity, cited as factors for risk-taking, remain to be clarified. In this study, we investigate if (b) manic symptoms and impulsivity moderate these relationships.

METHODS

Participants (N = 105) completed an online survey including demographics, clinical variables, symptomatology, FTT, risk taking and risk perception.

RESULTS

Mediational models indicated that (a) Gist Values mediated Categorical Gist's effect on risk taking, as expected by the FTT framework. (b) Impulsivity moderates risk taking, but manic-type symptomatology does not.

LIMITATIONS

Voluntary, self-report surveys may have low participant motivation and limit the diagnostic validity and the inpatient generalizability of the results.

CONCLUSIONS

The results move beyond a focus on mood-related aspects of Bipolar disorder and confirm the importance of understanding reasoning processes like FTT in combination with impulsivity, as potential behavioral factors of risk taking in Bipolar disorder. The clarifications on FTT's functioning as a mechanism prescribe possible openings for more efficacious reduction of risky behaviors through behavioral interventions focusing on value creation.

Manipulating feedback on schizophrenia: Evidence from a Posner task

Individuals with schizophrenia show difficulties in achieving vital objectives. Abnormal behavioral and emotional responses to environmental feedback may be some of the psychological mechanisms underlying this lack of goal attainment in schizophrenia. The present study aims to assess how different types of feedback may affect performance in a computerized affective Posner task (non-monetary vs. monetary rewards; contingent vs. non-contingent feedback). The sample was composed of 32 patients with schizophrenia and 35 controls. Reaction times and error rates were the behavioral measurements. The emotional experience was assessed through self-reported affective scales. The results indicated that: ii) the performance with monetary rewards was better than with non-monetary ones in all participants, especially in patients with schizophrenia when higher attentional resources are required (invalid trials). Second, all participants demonstrated faster reaction times, but higher error rates, with non-contingent feedback (frustration condition). Significantly, the schizophrenia group only equaled the controls performance in the non-contingent condition with monetary rewards. Additionally, the higher the negative symptoms were in patients, the worse performance they had under frustration. Third, discrepancies between performance and self-report affect were found in patients. Specifically, after the induction of frustration, the patients reported feeling better and having no arousal changes. Therefore, the findings suggest that, in schizophrenia: i) non-monetary rewards are relatively less important; ii) monetary rewards lessen the negative effects of frustration, iii) discrepancies in self-reported affective scales suggest an unrealistic self-evaluation made under frustration. These findings shed light on the underlying mechanisms of the lack of goal attainment in schizophrenia.

Radically open dialectical behaviour therapy adapted for adolescents: a case series

BACKGROUND

Overcontrol is a transdiagnostic cluster of traits associated with excessive psychological, behavioural and social inhibitory control. It is associated with psychiatric diagnoses of depression, restrictive eating disorders and/or obsessive-compulsive personality disorder. Radically Open Dialectical Behaviour Therapy is a transdiagnostic treatment for maladaptive overcontrol. This case series evaluates an adolescent adaption (RO-A) for a transdiagnostic group of adolescents identified as overcontrolled.

METHODS

Twenty-eight adolescents were consecutively referred for RO-A from two different National and Specialist Child and Adolescent Mental Health Services between June 2017 and February 2020. Baseline self-report measures assessed overcontrol characteristics, relationship and attachment quality and mental health symptoms of depression and eating disorders, which were repeated at discharge.

RESULTS

Adolescents in this case series reported high rates of depression (78.6%), self-harm (64.3%) and eating disorders (78.6%). Most (85.7%) had two or more mental health diagnoses and all had previous mental health treatments before starting RO-A. The mean number of RO-A sessions attended was 18 group-based skills classes and 21 individual sessions over a mean period of 34 weeks. Significant improvements with medium and large effect sizes were reported in cognitive flexibility (d = 1.63), risk aversion (d = 1.17), increased reward processing (d = .79) and reduced suppression of emotional expression (d = .72). Adolescents also reported feeling less socially withdrawn (d = .97), more connected to others (d = 1.03), as well as more confident (d = 1.10) and comfortable (d = .85) in attachment relationships. Symptoms of depression (d = .71), eating disorders (d = 1.06) and rates of self-harm (V = .39) also significantly improved. Exploratory correlation analyses suggest improvements in overcontrol are moderately to strongly correlated with improvements in symptoms of depression and eating disorders.

CONCLUSIONS

This case series provides preliminary data that RO-A may be an effective new treatment for adolescents with overcontrol and moderate to severe mental health disorders like depression and eating disorders. RO-A led to improved management of overcontrol, improved relationship quality and reduced mental health symptoms. Further evaluation is indicated by this case series, particularly for underweight young people with eating disorders. More rigorous testing of the model is required as conclusions are only tentative due to the small sample size and methodological limitations.

Antistress Action of Melanocortin Derivatives Associated with Correction of Gene Expression Patterns in the Hippocampus of Male Rats Following Acute Stress

Natural melanocortins (MCs) have been used in the successful development of drugs with neuroprotective properties. Here, we studied the behavioral effects and molecular genetic mechanisms of two synthetic MC derivatives-ACTH(4-7)PGP (Semax) and ACTH(6-9)PGP under normal and acute restraint stress (ARS) conditions. Administration of Semax or ACTH(6-9)PGP (100 μg/kg) to rats 30 min before ARS attenuated ARS-induced behavioral alterations. Using high-throughput RNA sequencing (RNA-Seq), we identified 1359 differentially expressed genes (DEGs) in the hippocampus of vehicle-treated rats subjected to ARS, using a cutoff of >1.5 fold change and adjusted p-value (Padj) < 0.05, in samples collected 4.5 h after the ARS. Semax administration produced > 1500 DEGs, whereas ACTH(6-9)PGP administration led to <400 DEGs at 4.5 h after ARS. Nevertheless, ~250 overlapping DEGs were identified, and expression of these DEGs was changed unidirectionally by both peptides under ARS conditions. Modulation of the expression of genes associated with biogenesis, translation of RNA, DNA replication, and immune and nervous system function was produced by both peptides. Furthermore, both peptides upregulated the expression levels of many genes that displayed decreased expression after ARS, and vice versa, the MC peptides downregulated the expression levels of genes that were upregulated by ARS. Consequently, the antistress action of MC peptides may be associated with a correction of gene expression patterns that are disrupted during ARS.

The putative role of the relaxin-3/RXFP3 system in clinical depression and anxiety: A systematic literature review

The relaxin-3/RXFP3 system is one of several neuropeptidergic systems putatively implicated in regulating the behavioural alterations that characterise clinical depression and anxiety, making it a potential target for clinical translation. Accordingly, this systematic review identified published reports on the role of relaxin-3/RXFP3 signalling in these neuropsychiatric disorders and their behavioural endophenotypes, evaluating evidence from animal and human studies to ascertain any relationship. We searched PubMed, EMBASE, PsycINFO and Google Scholar databases up to February 2021, finding 609 relevant records. After stringent screening, 51 of these studies were included in the final synthesis. There was considerable heterogeneity in study designs and some inconsistency across study outcomes. However, experimental evidence is consistent with an ability of relaxin-3/RXFP3 signalling to promote arousal and suppress depressive- and anxiety-like behaviour. Moreover, meta-analyses of six to eight articles investigating food intake revealed that acute RXFP3 activation had strong orexigenic effects in rats. This appraisal also identified the lack of high-quality clinical studies pertinent to the relaxin-3/RXFP3 system, a gap that future research should attempt to bridge.

Reward learning and working memory: Effects of massed versus spaced training and post-learning delay period

Neuroscience research has illuminated the mechanisms supporting learning from reward feedback, demonstrating a critical role for the striatum and midbrain dopamine system. However, in humans, short-term working memory that is dependent on frontal and parietal cortices can also play an important role, particularly in commonly used paradigms in which learning is relatively condensed in time. Given the growing use of reward-based learning tasks in translational studies in computational psychiatry, it is important to understand the extent of the influence of working memory and also how core gradual learning mechanisms can be better isolated. In our experiments, we manipulated the spacing between repetitions along with a post-learning delay preceding a test phase. We found that learning was slower for stimuli repeated after a long delay (spaced-trained) compared to those repeated immediately (massed-trained), likely reflecting the remaining contribution of feedback learning mechanisms when working memory is not available. For massed learning, brief interruptions led to drops in subsequent performance, and individual differences in working memory capacity positively correlated with overall performance. Interestingly, when tested after a delay period but not immediately, relative preferences decayed in the massed condition and increased in the spaced condition. Our results provide additional support for a large role of working memory in reward-based learning in temporally condensed designs. We suggest that spacing training within or between sessions is a promising approach to better isolate and understand mechanisms supporting gradual reward-based learning, with particular importance for understanding potential learning dysfunctions in addiction and psychiatric disorders.

Characterizing anhedonia: A systematic review of neuroimaging across the subtypes of reward processing deficits in depression

Anhedonia is a key symptom of major depressive disorder (MDD) and comprises behavioural deficits in three reward processing subtypes: reward liking, reward wanting, and reward learning. However, neuroimaging findings regarding the neural abnormalities underpinning these deficits are complex. We have conducted a systematic review to update, reframe and summarize neuroimaging findings across the three subtypes of anhedonia in MDD. Using PubMed, The Cochrane Library, PsycINFO, and Web of Science databases, we identified 59 fMRI studies comparing participants with current or remitted MDD with controls, using reward processing tasks. For reward liking and wanting, striatal hypoactivation was observed, alongside hypoactivation and hyperactivation across frontal regions. For reward learning, blunted frontostriatal sensitivity to positive feedback was observed. These findings highlight the importance of studying anhedonia not only as a clinical manifestation but also as a neurobiological mechanism underlying depressive disorder and other broader psychiatric conditions.

A Conceptual Framework for Multi-Dimensional Measurements of Food Related Pleasure-The Food Pleasure Scale

In modern times, the majority of food intake is believed to be driven by hedonic processes, rather than homeostatic ones. Various factors have been found to influence the hedonic eating experience and thereby influence eating behaviour, and each factor can be regarded a piece that contributes to parts of the total picture of the hedonic response to food. As a result, the literature on the hedonic response to food-related experiences is comprehensive, but at the same time rather fragmented; and importantly, it is not clear how individuals/segments differ in key drivers of their hedonic experience and the extent to which food pleasure is perceived. In this paper, we present a conceptual framework for the development of a scale (self-report questionnaire) to measure the qualitative and quantitative aspects of food-related pleasure, the Food Pleasure Scale. We introduce the concept of (an)hedonia and scales developed in the past for its measurement, identify the spectrum of characteristics influencing food-related pleasure and explain the relevance of developing such a scale. Based on this theoretical framework, a strategy for the development of the Food Pleasure Scale is proposed.

Anhedonia as a central factor in depression: Neural mechanisms revealed from preclinical to clinical evidence

Anhedonia is one of the core symptoms of major depressive disorder (MDD), which is often inadequately treated by traditional antidepressants. The modern framework of anhedonia extends the definition from impaired consummatory pleasure or interest in rewards to a broad spectrum of deficits that impact functions such as reward anticipation, approach motivation, effort expenditure, reward valuation, expectation, and reward-cue association learning. Substantial preclinical and clinical research has explored the neural basis of reward deficits in the context of depression, and has implicated mesocorticolimbic reward circuitry comprising the nucleus accumbens, ventral pallidum, ventral tegmental area, amygdala, hippocampus, anterior cingulate, insula, orbitofrontal cortex, and other prefrontal cortex regions. Dopamine modulates several reward facets including anticipation, motivation, effort, and learning. As well, serotonin, norepinephrine, opioids, glutamate, Gamma aminobutyric acid (GABA), and acetylcholine are also involved in anhedonia, and medications targeting these systems may also potentially normalize reward processing in depression. Unfortunately, whereas reward anticipation and reward outcome are extensively explored by both preclinical and clinical studies, translational gaps remain in reward motivation, effort, valuation, and learning, where clinical neuroimaging studies are in the early stages. This review aims to synthesize the neurobiological mechanisms underlying anhedonia in MDD uncovered by preclinical and clinical research. The translational difficulties in studying the neural basis of reward are also discussed.

Alterations in the default mode-salience network circuit provide a potential mechanism supporting negativity bias in depression

Aberrant effective connectivity between default mode (DMN) and salience (SAL) networks may support the tendency of depressed individuals to find it difficult to disengage from self-focused, negatively-biased thinking and may contribute to the onset and maintenance of depression. Assessment of effective connectivity, which can statistically characterize the direction of influence between regions within neural circuits, may provide new insights into the nature of DMN-SAL connectivity disruptions in depression. Functional magnetic resonance imaging (fMRI) was collected from 38 individuals with a history of major depression and 50 healthy comparison participants during completion of an emotion-word Stroop task. Activation within DMN and SAL networks and effective connectivity between DMN and SAL, assessed via Granger causality, were examined. Individuals with a history of depression exhibited greater overall network activation, greater directed connectivity from DMN to SAL, and less directed connectivity from SAL to DMN than healthy comparison participants during negative-word trials. Among individuals with a history of depression, greater DMN-to-SAL connectivity was associated with lower overall network activation and worse task performance during positive-word trials; this pattern was not observed among healthy participants. Present findings indicate that greater network activation and, specifically, influence of DMN on SAL, support negativity bias among previously depressed individuals.

Ventral striatal activation during reward differs between major depression with and without impaired mood reactivity

BACKGROUND

Recent efforts to classify subtypes of major depressive disorder marked by different psychophysiological indicators have identified blunted reward-related brain activation in gambling tasks as a characteristic linked specifically to depressed participants with impaired mood reactivity.

METHODS

The current study compared individuals diagnosed with current depressive disorder (n = 26) with healthy controls (n = 24) regarding brain responses to gain and loss trials in an fMRI version of the "Doors" choice-feedback task. Study aims were to examine reward-related brain activation in relation to depression, depressive subtypes, and course of depression.

RESULTS

Across the sample, participants showed a significant response to gain versus loss in left and right ventral striatum as well as medial and left lateral prefrontal cortex. Relative to controls, participants with current depression were characterized by blunted reactivity in left ventral striatum. Furthermore, activation in the left ventral striatum differentiated subgroups of depression with and without impaired mood reactivity. Finally, left striatal hypoactivation to reward predicted remission when controlling for current depressive symptomatology, albeit at a trend level.

CONCLUSIONS

Blunted reward-related activation in the left ventral striatum might be useful as a marker for depression subtype and may have the potential to predict future course of depression.

Honeycomb: a template for reproducible psychophysiological tasks for clinic, laboratory, and home use

Objective:

To improve the ability of psychiatry researchers to build, deploy, maintain, reproduce, and share their own psychophysiological tasks. Psychophysiological tasks are a useful tool for studying human behavior driven by mental processes such as cognitive control, reward evaluation, and learning. Neural mechanisms during behavioral tasks are often studied via simultaneous electrophysiological recordings. Popular online platforms such as Amazon Mechanical Turk (MTurk) and Prolific enable deployment of tasks to numerous participants simultaneously. However, there is currently no task-creation framework available for flexibly deploying tasks both online and during simultaneous electrophysiology.

Methods:

We developed a task creation template, termed Honeycomb, that standardizes best practices for building jsPsych-based tasks. Honeycomb offers continuous deployment configurations for seamless transition between use in research settings and at home. Further, we have curated a public library, termed BeeHive, of ready-to-use tasks.

Results:

We demonstrate the benefits of using Honeycomb tasks with a participant in an ongoing study of deep brain stimulation for obsessive compulsive disorder, who completed repeated tasks both in the clinic and at home.

Conclusion:

Honeycomb enables researchers to deploy tasks online, in clinic, and at home in more ecologically valid environments and during concurrent electrophysiology.

Cohort profile for the STratifying Resilience and Depression Longitudinally (STRADL) study: A depression-focused investigation of Generation Scotland, using detailed clinical, cognitive, and neuroimaging assessments

STratifying Resilience and Depression Longitudinally (STRADL) is a population-based study built on the Generation Scotland: Scottish Family Health Study (GS:SFHS) resource. The aim of STRADL is to subtype major depressive disorder (MDD) on the basis of its aetiology, using detailed clinical, cognitive, and brain imaging assessments. The GS:SFHS provides an important opportunity to study complex gene-environment interactions, incorporating linkage to existing datasets and inclusion of early-life variables for two longitudinal birth cohorts. Specifically, data collection in STRADL included: socio-economic and lifestyle variables; physical measures; questionnaire data that assesses resilience, early-life adversity, personality, psychological health, and lifetime history of mood disorder; laboratory samples; cognitive tests; and brain magnetic resonance imaging. Some of the questionnaire and cognitive data were first assessed at the GS:SFHS baseline assessment between 2006-2011, thus providing longitudinal measures relevant to the study of depression, psychological resilience, and cognition. In addition, routinely collected historic NHS data and early-life variables are linked to STRADL data, further providing opportunities for longitudinal analysis. Recruitment has been completed and we consented and tested 1,188 participants.

Ketamine Modulates the Neural Correlates of Reward Processing in Unmedicated Patients in Remission from Depression

BACKGROUND

Ketamine as an antidepressant improves anhedonia as early as 2h post-infusion. These drug effects are thought to be exerted via actions on reward-related brain areas-yet, these actions remain largely unknown. Our study investigates ketamine's effects during the anticipation and receipt of an expected reward, after the psychotomimetic effects of ketamine have passed, when early antidepressant effects are reported.

METHODS

We examined ketamine's effects during the anticipation and receipt of expected rewards on pre-defined brain areas, namely the dorsal and ventral striatum, the ventral tegmental area, the amygdala and the insula. We have recruited 37 male and female participants who remitted from depression and were free from symptoms and antidepressant treatments at the time of the scan. Participants were scanned, 2h after drug administration, in a double-blind cross over design (ketamine:0.5mg/kg and placebo) while performing a monetary reward task.

RESULTS

A significant main effect of ketamine, across all ROIs, was observed during the anticipation and feedback phases of win and no-win trials. The drug effects were particularly prominent in the nucleus accumbens and putamen, which showed increased activation upon the receipt of smaller rewards compared to neutral. The levels of (2R,6R)-HNK, 2h post-infusion, significantly correlated with the activation observed in the ventral tegmental area for that contrast.

CONCLUSIONS

These findings demonstrate that ketamine can produce detectable changes in reward-related brain areas, 2h after infusion, which occur without symptom changes and support the idea that ketamine might improve reward-related symptoms via modulation of response to feedback.

Functional connectivity of the right inferior frontal gyrus and orbitofrontal cortex in depression

The orbitofrontal cortex extends into the laterally adjacent inferior frontal gyrus. We analyzed how voxel-level functional connectivity of the inferior frontal gyrus and orbitofrontal cortex is related to depression in 282 people with major depressive disorder (125 were unmedicated) and 254 controls, using FDR correction P < 0.05 for pairs of voxels. In the unmedicated group, higher functional connectivity was found of the right inferior frontal gyrus with voxels in the lateral and medial orbitofrontal cortex, cingulate cortex, temporal lobe, angular gyrus, precuneus, hippocampus and frontal gyri. In medicated patients, these functional connectivities were lower and toward those in controls. Functional connectivities between the lateral orbitofrontal cortex and the precuneus, posterior cingulate cortex, inferior frontal gyrus, ventromedial prefrontal cortex and the angular and middle frontal gyri were higher in unmedicated patients, and closer to controls in medicated patients. Medial orbitofrontal cortex voxels had lower functional connectivity with temporal cortex areas, the parahippocampal gyrus and fusiform gyrus, and medication did not result in these being closer to controls. These findings are consistent with the hypothesis that the orbitofrontal cortex is involved in depression, and can influence mood and behavior via the right inferior frontal gyrus, which projects to premotor cortical areas.

Neonatal resource scarcity alters maternal care and impacts offspring core temperature and growth in rats

Stressful experiences during childhood, including poverty and inconsistent parental care, can enhance vulnerability for worsened physical and mental health outcomes in adulthood. Using Sprague Dawley rats, the present study explored the impact of limited resource availability on maternal behavior and physiological and emotional behavior outcomes in the offspring. Early life adversity was induced by incorporating aspects of the limited bedding and nesting and scarcity models, wherein limited resource availability has previously been shown to provoke unpredictable or adverse maternal care respectively. In our hands, neonatal limited bedding (NLB) stress during postnatal days (P)2-9 altered maternal care, augmenting pup-directed behaviors and reducing self-directed behaviors, and modestly increased the frequency of transitions between discrete behaviors across consecutive timed observations. NLB-exposed pups had lower core body temperatures immediately following the stressful manipulation and exhibited decreased body weight gain across development. However, NLB exposure did not impact adult offspring's social or emotional behavior outcomes in the three-chamber social interaction, novelty-suppressed feeding, splash, or forced swim tests. These findings add to the literature demonstrating that early life adversity impacts maternal care in rodents and can disrupt certain metabolic and thermoregulatory outcomes in the offspring.

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.

Early-Stage Repetitive Transcranial Magnetic Stimulation Altered Posterior-Anterior Cerebrum Effective Connectivity in Methylazoxymethanol Acetate Rats

The aim of the current resting-state functional magnetic resonance imaging (fMRI) study was to investigate the potential mechanism of schizophrenia through the posterior-anterior cerebrum imbalance in methylazoxymethanol acetate (MAM) rats and to evaluate the effectiveness of repetitive transcranial magnetic stimulation (rTMS) as an early-stage intervention. The rats were divided into four groups: the MAM-sham group, vehicle-sham group, MAM-rTMS group, and vehicle-rTMS group. The rTMS treatment was targeted in the visual cortex (VC) in adolescent rats. Granger Causality Analysis (GCA) was used to evaluate the effective connectivity between regions of interest. Results demonstrated a critical right VC-nucleus accumbens (Acb)-orbitofrontal cortex (OFC) pathway in MAM rats; significant differences of effective connectivity (EC) were found between MAM-sham and vehicle-sham groups (from Acb shell to OFC: t = -2.553, p = 0.021), MAM-rTMS and MAM-sham groups (from VC to Acb core: t = -2.206, p = 0.043; from Acb core to OFC: t = 4.861, p < 0.001; from Acb shell to OFC: t = 4.025, p = 0.001), and MAM-rTMS and vehicle-rTMS groups (from VC to Acb core: t = -2.482, p = 0.025; from VC to Acb shell: t = -2.872, p = 0.012; from Acb core to OFC: t = 4.066, p = 0.001; from Acb shell to OFC: t = 3.458, p = 0.004) in the right hemisphere. Results of the early-stage rTMS intervention revealed that right nucleus accumbens played the role as a central hub, and VC was a potentially novel rTMS target region during adolescent schizophrenia. Moreover, the EC of right nucleus accumbens shell and orbitofrontal cortex was demonstrated to be a potential biomarker. To our knowledge, this was the first resting-state fMRI study using GCA to assess the deficits of a visual-reward neural pathway and the effectiveness of rTMS treatment in MAM rats. More randomized controlled trials in both animal models and schizophrenia patients are needed to further elucidate the disease characteristics.

The Paraventricular Thalamus: A Potential Sensor and Integrator of Emotionally Salient Early-Life Experiences

Early-life experiences influence a broad spectrum of behaviors throughout the lifespan that contribute to resilience or vulnerability to mental health disorders. Yet, how emotionally salient experiences early in life are encoded, stored, and processed and the mechanisms by which they influence future behaviors remain poorly understood. The paraventricular nucleus of the thalamus (PVT) is a key structure in modulating positive and negative experiences and behaviors in adults. However, little is known of the PVT's role in encoding and integrating emotionally salient experiences that occur during neonatal, infancy, and childhood periods. In this review, we (1) describe the functions and connections of the PVT and its regulation of behavior, (2) introduce novel technical approaches to elucidating the role of the PVT in mediating enduring changes in adult behaviors resulting from early-life experiences, and (3) conclude that PVT neurons of neonatal rodents are engaged by both positive and negative emotionally salient experiences, and their activation may enduringly govern future behavior-modulating PVT activity during emotionally salient contexts.

Reward-related neural correlates of early life stress in school-aged children

OBJECTIVES

Early life stress likely contributes to dysfunction in neural reward processing systems. However, studies to date have focused almost exclusively on adolescents and adults, measured early life stress retrospectively, and have often failed to control for concurrent levels of stress. The current study examined the contribution of prospectively measured cumulative life stress in preschool-age children on reward-related neural activation and connectivity in school-age children.

METHODS

Children (N = 46) and caregivers reported children's exposure to early life stress between birth and preschool age (mean = 4.8 years, SD = 0.80). At follow-up (mean age = 7.52 years, SD = .78), participants performed a child-friendly monetary incentive delay task during functional magnetic resonance imaging.

RESULTS

Children with higher levels of cumulative early life stress, controlling for concurrent stressful life events, exhibited aberrant patterns of neural activation and connectivity in reward- and emotion-related regions (e.g., prefrontal cortex, temporal pole, culmen), depending on the presence of a potential reward and whether or not the target was hit or missed.

CONCLUSIONS

Findings suggest that stress exposure during early childhood may impact neural reward processing systems earlier in development than has previously been demonstrated. Understanding how early life stress relates to alterations in reward processing could guide earlier, more mechanistic interventions.

Reward processing as a common diathesis for chronic pain and depression

Pain disorders and psychiatric illness are strongly comorbid, particularly in the context of Major Depressive Disorder (MDD). While these disorders account for a significant amount of global disability, the mechanisms of their overlap remain unclear. Understanding these mechanisms is of vital importance to developing prevention strategies and interventions that target both disorders. Of note, brain reward processing may be relevant to explaining how the comorbidity arises, given pain disorders and MDD can result in maladaptive reward responsivity that limits reward learning, appetitive approach behaviours and consummatory response. In this review, we discuss this research and explore the possibility of reward processing deficits as a common diathesis to explain the manifestation of pain disorders and MDD. Specifically, we hypothesize that contextual physical or psychological events (e.g. surgery, divorce) in the presence of a reward impairment diathesis worsens symptoms and results in a negative feedback loop that increases the chronicity and probability of developing the other disorder. We also highlight the implications for treatment and provide a framework for future research.

Schizophrenia and bipolar disorder are associated with opposite brain reward anticipation-associated response

Blunted and exaggerated neuronal response to rewards are hypothesized to be core features of schizophrenia spectrum disorders (SZ) and bipolar disorder (BD), respectively. Nonetheless, direct tests of this hypothesis, in which response between SZ and BD is compared in the same study, are lacking. Here we examined the functional correlates of reward processing during the Incentivized Control Engagement Task (ICE-T) using 3T fMRI. Reward-associated activation was examined in 49 healthy controls (HCs), 52 recent-onset individuals with SZ, and 22 recent-onset individuals with Type I BD using anterior cingulate (ACC), anterior insula, and ventral striatal regions of interest. Significant group X reward condition (neutral vs. reward) interactions were observed during reward anticipation in the dorsal ACC (F(2,120) = 4.21, P = 0.017) and right insula (F(2,120) = 4.77, P = 0.010). The ACC interaction was driven by relatively higher activation in the BD group vs. HCs (P = 0.007) and vs. individuals with SZ (P = 0.010). The insula interaction was driven by reduced activation in the SZ group relative to HCs (P = 0.018) and vs. people with BD (P = 0.008). A composite of reward anticipation-associated response across all associated ROIs also differed significantly by diagnosis (F(1,120) = 5.59, P = 0.02), BD > HC > SZ. No effects of group or group X reward interactions were observed during reward feedback. These results suggest that people with SZ and BD have opposite patterns of activation associated with reward anticipation but not reward receipt. Implications of these findings in regard to Research Domain Criteria-based classification of illness and the neurobiology of reward in psychosis are discussed.

A preliminary study on functional activation and connectivity during frustration in youths with bipolar disorder

OBJECTIVES

Frustration is associated with impaired attention, heightened arousal, and greater unhappiness in youths with bipolar disorder (BD) vs healthy volunteers (HV). Little is known about functional activation and connectivity in the brain of BD youths in response to frustration. This exploratory study compared BD youths and HV on attentional abilities, self-reported affect, and functional activation and connectivity during a frustrating attention task.

METHODS

Twenty BD (Mage  = 15.86) and 20 HV (Mage  = 15.55) youths completed an fMRI paradigm that differentiated neural responses during processing of frustrating feedback from neural responses during attention orienting following frustrating feedback. We examined group differences in (a) functional connectivity using amygdala, inferior frontal gyrus (IFG), and striatum as seeds and (b) whole-brain and regions of interest (amygdala, IFG, striatum) activation. We explored task performance (accuracy, reaction time), self-reported frustration and unhappiness, and correlations between these variables and irritability, depressive, and manic symptoms.

RESULTS

Bipolar disorder youths, relative to HV, exhibited positive IFG-ventromedial prefrontal cortex (vmPFC) connectivity yet failed to show negative striatum-insula connectivity during feedback processing. Irritability symptoms were positively associated with striatum-insula connectivity during feedback processing. Moreover, BD vs HV youths showed positive IFG-parahippocampal gyrus (PHG)/periaqueductal gray (PAG) connectivity and negative amygdala-cerebellum connectivity during attention orienting following frustration. BD was not associated with atypical activation patterns.

CONCLUSIONS

Positive IFG-vmPFC connectivity and striatum-insula decoupling in BD during feedback processing may mediate heightened sensitivity to reward-relevant stimuli. Elevated IFG-PAG/PHG connectivity in BD following frustration may suggest greater recruitment of attention network to regulate arousal and maintain goal-directed behavior.

Understanding urbanicity: how interdisciplinary methods help to unravel the effects of the city on mental health

Twenty-first century urbanization poses increasing challenges for mental health. Epidemiological studies have shown that mental health problems often accumulate in urban areas, compared to rural areas, and suggested possible underlying causes associated with the social and physical urban environments. Emerging work indicates complex urban effects that depend on many individual and contextual factors at the neighbourhood and country level and novel experimental work is starting to dissect potential underlying mechanisms. This review summarizes findings from epidemiology and population-based studies, neuroscience, experimental and experience-based research and illustrates how a combined approach can move the field towards an increased understanding of the urbanicity-mental health nexus.

Anxiety increases sensitivity to errors and negative feedback over time

Anxiety is characterized by sensitivity to negative external and internal information, apparent both in symptoms (e.g., hypervigilance and worry) and neural performance monitoring measures (i.e., feedback- and error-related negativity (FRN and ERN)). Here we examine whether anxiety is associated with persistent neural sensitivity to negative performance markers reflected in both the FRN and ERN (n = 273). Higher anxiety was associated with larger responses to both negative feedback and errors as the task progressed compared to those with lower anxiety particularly in women, suggesting that anxiety makes reactions to negative cues more persistent. Similar hypotheses were investigated for depression, which is associated with similar negative cognitive biases and deficits in reward-related processing, but results were mixed. Together, the findings identify variation over time-in-task as an overlooked dimension by which FRN and ERN may serve as a biomarker of anxiety but suggest that depression is not consistently related to performance monitoring.

Uncovering the prevalence and neural substrates of anhedonia in frontotemporal dementia

Much of human behaviour is motivated by the drive to experience pleasure. The capacity to envisage pleasurable outcomes and to engage in goal-directed behaviour to secure these outcomes depends upon the integrity of frontostriatal circuits in the brain. Anhedonia refers to the diminished ability to experience, and to pursue, pleasurable outcomes, and represents a prominent motivational disturbance in neuropsychiatric disorders. Despite increasing evidence of motivational disturbances in frontotemporal dementia (FTD), no study to date has explored the hedonic experience in these syndromes. Here, we present the first study to document the prevalence and neural correlates of anhedonia in FTD in comparison with Alzheimer's disease, and its potential overlap with related motivational symptoms including apathy and depression. A total of 172 participants were recruited, including 87 FTD, 34 Alzheimer's disease, and 51 healthy older control participants. Within the FTD group, 55 cases were diagnosed with clinically probable behavioural variant FTD, 24 presented with semantic dementia, and eight cases had progressive non-fluent aphasia (PNFA). Premorbid and current anhedonia was measured using the Snaith-Hamilton Pleasure Scale, while apathy was assessed using the Dimensional Apathy Scale, and depression was indexed via the Depression, Anxiety and Stress Scale. Whole-brain voxel-based morphometry analysis was used to examine associations between grey matter atrophy and levels of anhedonia, apathy, and depression in patients. Relative to controls, behavioural variant FTD and semantic dementia, but not PNFA or Alzheimer's disease, patients showed clinically significant anhedonia, representing a clear departure from pre-morbid levels. Voxel-based morphometry analyses revealed that anhedonia was associated with atrophy in an extended frontostriatal network including orbitofrontal and medial prefrontal, paracingulate and insular cortices, as well as the putamen. Although correlated on the behavioural level, the neural correlates of anhedonia were largely dissociable from that of apathy, with only a small region of overlap detected in the right orbitofrontal cortices whilst no overlapping regions were found between anhedonia and depression. This is the first study, to our knowledge, to demonstrate profound anhedonia in FTD syndromes, reflecting atrophy of predominantly frontostriatal brain regions specialized for hedonic tone. Our findings point to the importance of considering anhedonia as a primary presenting feature of behavioural variant FTD and semantic dementia, with distinct neural drivers to that of apathy or depression. Future studies will be essential to address the impact of anhedonia on everyday activities, and to inform the development of targeted interventions to improve quality of life in patients and their families.

Reward learning in unmedicated women with bulimia nervosa: A pilot investigation

Bulimia nervosa (BN) is characterized by recurrent engagement in eating disorder behaviors despite negative consequences, potentially reflecting aberrant stimulus-response or reward-learning processes. Indeed, frontostriatal circuitry involved in reward learning is altered in persons with BN and preliminary research suggests reward learning is impaired in persons with BN. Additional research on reward learning in BN and its association with eating disorder symptom expression is warranted to further the field's understanding of potential pathophysiological mechanisms of BN. To this end, the probabilistic reward learning task (PRLT) was administered to unmedicated women with BN (n = 15) and demographically matched psychiatrically healthy women (n = 18). Contrary to our hypotheses, results demonstrated that women with BN showed greater reward learning during the PRLT relative to healthy comparison women when covarying for symptoms of depression, social anxiety, and mania. Exploratory analyses showed that binge-eating frequency was inversely associated with reward learning in women with BN; however, results should be interpreted with caution due to the small sample size. Together, results suggest that women with BN do not have deficits in implicit reward learning. Given the preliminary nature of this investigation, larger-scale studies are needed to further examine reward learning in current BN and could compare reward learning using general (e.g., monetary) and disorder-specific (e.g., food) reinforcers. Further work is needed to confirm the inverse association between reward learning and binge eating.

Anhedonia and Increased Evoked Immune Response

There is a growing body of evidence supporting the association between immune processes and psychopathology, including major depressive disorder (MDD). However, lack of diagnostic specificity has given rise to a search for specific symptom types, as opposed to more heterogeneous categorical diagnoses, linked to increased inflammation. One such symptom could be anhedonia, which is not only a key feature of MDD, but also a pervasive and persistent transdiagnostic symptom. To evaluate the specific role of anhedonia as well as categorical MDD diagnoses, we examined endotoxin-evoked immune responses in vitro in relation to current levels of anhedonia and history of recurrent MDD (rMDD) in a sample of adults recruited from the community. A total of 39 participants either had a history of rMDD (n ​= ​20) or no lifetime history of any MDD episodes (n ​= ​19). The average age of participants was 36.81 years and the majority were women (87.2%) and Caucasian (76.3%). We found that higher levels of current anhedonia, but not history of rMDD, were associated with increased lipopolysaccharide-stimulated levels of inflammatory markers even after we statistically adjusted for the potential influence of participants’ demographic (age, sex, ethnicity, income) and physiological (body temperature, BMI) characteristics, current symptoms of depression and anxiety, and the time of day of the sample collection. These findings highlight the relation of anhedonia specifically, rather than rMDD more generally, with inflammatory processes and identify endotoxin-stimulated cytokine production as a plausible biological marker of current anhedonia.

Motivational differences in unipolar and bipolar depression, manic bipolar, acute and stable phase schizophrenia

BACKGROUND

Motivational anhedonia has been observed in patients with a wide range of mental disorders. However, the similarity and uniqueness of this deficit across diagnostic groups has not been thoroughly investigated.

METHOD

The study compared motivational deficits in 37 patients with major depressive disorder (MDD), 32 with bipolar depression, 33 with manic bipolar disorder (BD), 30 with acute phase and 33 with stable phase schizophrenia, as well as 47 healthy controls. Participants were administered the Effort-Expenditure for Reward Task which measures allocation of effort between a high-effort and a low-effort task for monetary rewards at varying magnitudes and probabilities.

RESULTS

Compared with healthy controls, BD manic, acute and stable phase schizophrenia patients were significantly less likely to choose the high-effort task in the high reward magnitude condition. BD manic and acute phase schizophrenia patients were significantly less likely to choose the high-effort task in the high probability condition. Acute and stable phase schizophrenia patients made less effort in the high estimated value condition. Bipolar manic patients made excessive effort in low estimated value but less effort in high estimated value. Contrary to expectations, both the unipolar and bipolar depression patients did not differ significantly from healthy controls in reward magnitude, probability, and estimated value conditions. Anhedonia and negative symptoms were associated with fewer high-effort task choices in schizophrenia patients.

CONCLUSION

Motivation anhedonia showed distinct patterns across psychiatric patients: acute phase schizophrenia was the most severely affected, bipolar mania was similar to schizophrenia, but bipolar depression was similar to unipolar depression.

Dopamine and the phosphorylated dopamine transporter are increased in the diacylglycerol kinase η-knockout mouse brain

The molecular mechanisms generating the mania-like abnormal behaviors caused by diacylglycerol (DG) kinase (DGK) η deficiency remain unclear. Here, we found that DGKη knockout markedly increased dopamine (DA) levels in the midbrain (DA-producing region, 2.8-fold) and cerebral cortex (DA projection region, 1.2-fold). Moreover, DGKη deficiency significantly augmented phosphorylated DA transporter (DAT) levels (1.4-fold increase), which induce DA efflux to the synaptic cleft, in the cerebral cortex. Moreover, phosphorylation levels of protein kinase C-β, which is activated by DG and involved in DAT phosphorylation, were also increased. DAT expressed in Neuro-2a cells recruited DGKη to the plasma membrane and colocalized with it. These results strongly suggest that dopaminergic hyperfunction caused by DGKη deficiency in the brain leads to mania-like behaviors.

Systemic inflammation and grey matter volume in schizophrenia and bipolar disorder: Moderation by childhood trauma severity

BACKGROUND

Elevated levels of systemic inflammation are consistently reported in both schizophrenia (SZ) and bipolar-I disorder (BD), and are associated with childhood trauma exposure. We tested whether childhood trauma exposure moderates associations between systemic inflammation and brain morphology in people with these diagnoses.

METHODS

Participants were 55 SZ cases, 52 BD cases and 59 healthy controls (HC) who underwent magnetic resonance imaging. Systemic inflammation was measured using a composite z-score derived from serum concentrations of interleukin 6, tumor necrosis factor alpha and C-reactive protein. Indices of grey matter volume covariation (GMC) were derived from independent component analysis. Childhood trauma was measured using the Childhood Trauma Questionnaire (CTQ Total score).

RESULTS

A series of moderated moderation analyses indicated that increased systemic inflammation were associated with increased GMC in the striatum and cerebellum among all participants. Severity of childhood trauma exposure moderated the relationship between systemic inflammation and GMC in one component, differently among the groups. Specifically, decreased GMC in the PCC/precuneus, parietal lobule and postcentral gyrus, and increased GMC in the left middle temporal gyrus was associated with increased systemic inflammation in HC individuals exposed to high (but not low or average) levels of trauma and in SZ cases exposed to low (but not average or high) levels of trauma, but not in BD cases.

CONCLUSIONS

Increased systemic inflammation is associated with grey matter changes in people with psychosis, and these relationships may be partially and differentially moderated by childhood trauma exposure according to diagnosis.

Intrinsic reward circuit connectivity profiles underlying symptom and quality of life outcomes following antidepressant medication: a report from the iSPOT-D trial

There is a critical need to better understand the neural basis of antidepressant medication (ADM) response with respect to both symptom alleviation and quality of life (QoL) in major depressive disorder (MDD). Reward neurocircuitry has been implicated in QoL, the neural basis of MDD, and the mechanisms of ADM response. Yet, we do not know whether change in reward neurocircuitry as a function of ADM is associated with change in symptoms and QoL. To address this gap in knowledge, we analyzed data from 128 patients with MDD who participated in the iSPOT-D trial and were assessed with functional neuroimaging pre- and post-ADM treatment (randomized to sertraline, venlafaxine-XR, or escitalopram). 58 matched healthy controls were scanned at the same time points. We quantified functional connectivity (FC) of reward neurocircuitry using nucleus accumbens (NAc) seed regions of interest, and then characterized how changes in FC relate to symptom response (primary outcome) and QoL response (secondary outcome). Symptom responders showed an increase in NAc-dorsal anterior cingulate cortex (ACC) FC relative to non-responders (p < 0.001) which was associated with improvement in physical QoL (p < 0.0003), and a decrease in NAc-inferior parietal lobule FC relative to controls (p < 0.001). QoL response was characterized by increases in FC between NAc-ventral ACC for environmental, NAc-thalamus for physical, and NAc-paracingulate gyrus for social domains (p < 0.001). Symptom responders to sertraline were distinguished by a decrease in NAc-insula FC (p < 0.001) and to venlafaxine-XR by an increase in NAc-inferior temporal gyrus FC (p < 0.005). Findings suggest that change in reward neurocircuitry may underlie differential ADM response profiles with respect to symptoms and QoL in depression.

Sex differences in neural responses to reward and the influences of individual reward and punishment sensitivity

BACKGROUND

Men and women show differences in sensitivity to reward and punishment, which may impact behavior in health and disease. However, the neural bases of these sex differences remain under-investigated. Here, by combining functional magnetic resonance imaging (fMRI) and a variant of the Monetary Incentive Delay Task (MIDT), we examined sex differences in the neural responses to wins and losses and how individual reward and punishment sensitivity modulates these regional activities.

METHODS

Thirty-sex men and 27 women participated in the fMRI study. We assessed sensitivity to punishment (SP) and sensitivity to reward (SR) with the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ). In the MIDT, participants pressed a button to collect reward ($1, 1¢, or nil), with the reaction time window titrated across trials so participants achieved a success rate of approximately 67%. We processed the Imaging data with published routines and evaluated the results with a corrected threshold.

RESULTS

Women showed higher SP score than men and men showed higher SR score than women. Men relative to women showed higher response to the receipt of dollar or cent reward in bilateral orbitofrontal and visual cortex. Men as compared to women also showed higher response to dollar loss in bilateral orbitofrontal cortex. Further, in whole-brain regressions, women relative to men demonstrated more significant modulation by SP in the neural responses to wins and larger wins, and the sex differences were confirmed by slope tests.

CONCLUSIONS

Together, men showed higher SR and neural sensitivity to both wins, large or small, and losses than women. Individual differences in SP were associated with diminished neural responses to wins and larger wins in women only. These findings highlight how men and women may differ in reward-related brain activations in the MIDT and add to the imaging literature of sex differences in cognitive and affective functions.

Associations between insomnia and reward learning in clinical depression

BACKGROUND

Depression and insomnia commonly co-occur. Yet, little is known about the mechanisms through which insomnia influences depression. Recent research and theory highlight reward system dysfunction as a potential mediator of the relationship between insomnia and depression. This study is the first to examine the impact of insomnia on reward learning, a key component of reward system functioning, in clinical depression.

METHODS

The sample consisted of 72 veterans with unipolar depression who endorsed sleep disturbance symptoms. Participants completed the Structured Clinical Interview for DSM-IV, self-report measures of insomnia, depression, and reward processing, and a previously validated signal detection task (Pizzagalli et al., 2005, Biological Psychiatry, 57(4), 319-327). Trial-by-trial response bias (RB) estimates calculated for each of the 200 task trials were examined using linear mixed-model analyses to investigate change in reward learning.

RESULTS

Findings demonstrated diminished rate and magnitude of reward learning in the Insomnia group relative to the Hypersomnia/Mixed Symptom group across the task. Within the Insomnia group, participants with more severe insomnia evidenced the lowest rates of reward learning, with increased RB across the task with decreasing insomnia severity.

CONCLUSIONS

Among individuals with depression, insomnia is associated with decreased ability to learn associations between neutral stimuli and rewarding outcomes and/or modify behavior in response to differential receipt of reward. This attenuated reward learning may contribute to clinically meaningful decreases in motivation and increased withdrawal in this comorbid group. Results extend existing theory by highlighting impairments in reward learning specifically as a potential mediator of the association between insomnia and depression.

Diacylglycerol Kinase η Activity in Cells Using Protein Myristoylation and Cellular Phosphatidic Acid Sensor

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol to produce phosphatidic acid (PtdOH) and regulates the balance between two lipid second messengers: diacylglycerol and PtdOH. Several lines of evidence suggest that the η isozyme of DGK is involved in the pathogenesis of bipolar disorder. However, the detailed molecular mechanisms regulating the pathophysiological functions remain unclear. One reason is that it is difficult to detect the cellular activity of DGKη. To overcome this difficulty, we utilized protein myristoylation and a cellular PtdOH sensor, the N-terminal region of α-synuclein (α-Syn-N). Although DGKη expressed in COS-7 cells was broadly distributed in the cytoplasm, myristoylated (Myr)-AcGFP-DGKη and Myr-AcGFP-DGKη-KD (inactive (kinase-dead) mutant) were substantially localized in the plasma membrane. Moreover, DsRed monomer-α-Syn-N significantly colocalized with Myr-AcGFP-DGKη but not Myr-AcGFP-DGKη-KD at the plasma membrane. When COS-7 cells were osmotically shocked, all DGKη constructs were exclusively translocated to osmotic shock-responsive granules (OSRG). DsRed monomer-α-Syn-N markedly colocalized with only Myr-AcGFP-DGKη at OSRG and exhibited a higher signal/background ratio (3.4) than Myr-AcGFP-DGKη at the plasma membrane in unstimulated COS-7 cells (2.5), indicating that α-Syn-N more effectively detects Myr-AcGFP-DGKη activity in OSRG. Therefore, these results demonstrated that the combination of myristoylation and the PtdOH sensor effectively detects DGKη activity in cells and that this method is convenient to examine the molecular functions of DGKη. Moreover, this method will be useful for the development of drugs targeting DGKη. Furthermore, the combination of myristoylation (intensive accumulation in membranes) and α-Syn-N can be applicable to assays for various cytosolic PtdOH-generating enzymes.