Effort-Based Reinforcement Processing and Functional Connectivity Underlying Amotivation in Medicated Patients with Depression and Schizophrenia

Improving Mental Health Outcomes in Patients with Major Depressive Disorder in the Gulf States: A Review of the Role of Electronic Enablers in Monitoring Residual Symptoms

Up to 75% of individuals with major depressive disorder (MDD) may have residual symptoms such as amotivation or anhedonia, which prevent full functional recovery and are associated with relapse. Globally and in the Gulf region, primary care physicians (PCPs) have an important role in alleviating stigma and in identifying and monitoring the residual symptoms of depression, as PCPs are the preliminary interface between patients and specialists in the collaborative care model. Therefore, mental healthcare upskilling programmes for PCPs are needed, as are basic instruments to evaluate residual symptoms swiftly and accurately in primary care. Currently, few if any electronic enablers have been designed to specifically monitor residual symptoms in patients with MDD. The objectives of this review are to highlight how accurate evaluation of residual symptoms with an easy-to-use electronic enabler in primary care may improve functional recovery and overall mental health outcomes, and how such an enabler may guide pharmacotherapy selection and positively impact the patient journey. Here, we show the potential advantages of electronic enablers in primary care, which include the possibility for a deeper "dive" into the patient journey and facilitation of treatment optimisation. At the policy and practice levels, electronic enablers endorsed by government agencies and local psychiatric associations may receive greater PCP attention and backing, improve patient involvement in shared clinical decision-making, and help to reduce the general stigma around mental health disorders. In the Gulf region, an easy-to-use electronic enabler in primary care, incorporating aspects of the Hamilton Depression Rating Scale to monitor amotivation, and aspects of the Montgomery-Åsberg Depression Rating Scale to monitor anhedonia, could markedly improve the patient journey from residual symptoms through to full functional recovery in individuals with MDD.

Roles of the medial and lateral orbitofrontal cortex in major depression and its treatment

We describe evidence for dissociable roles of the medial and lateral orbitofrontal cortex (OFC) in major depressive disorder (MDD) from structure, functional activation, functional connectivity, metabolism, and neurochemical systems. The reward-related medial orbitofrontal cortex has lower connectivity and less reward sensitivity in MDD associated with anhedonia symptoms; and the non-reward related lateral OFC has higher functional connectivity and more sensitivity to non-reward/aversive stimuli in MDD associated with negative bias symptoms. Importantly, we propose that conventional antidepressants act to normalize the hyperactive lateral (but not medial) OFC to reduce negative bias in MDD; while other treatments are needed to operate on the medial OFC to reduce anhedonia, with emerging evidence suggesting that ketamine may act in this way. The orbitofrontal cortex is the key cortical region in emotion and reward, and the current review presents much new evidence about the different ways that the medial and lateral OFC are involved in MDD.

Stress to inflammation and anhedonia: Mechanistic insights from preclinical and clinical models

Anhedonia, as evidenced by impaired pleasurable response to reward, reduced reward motivation, and/or deficits in reward-related learning, is a common feature of depression. Such deficits in reward processing are also an important clinical target as a risk factor for depression onset. Unfortunately, reward-related deficits remain difficult to treat. To address this gap and inform the development of effective prevention and treatment strategies, it is critical to understand the mechanisms that drive impairments in reward function. Stress-induced inflammation is a plausible mechanism of reward deficits. The purpose of this paper is to review evidence for two components of this psychobiological pathway: 1) the effects of stress on reward function; and 2) the effects of inflammation on reward function. Within these two areas, we draw upon preclinical and clinical models, distinguish between acute and chronic effects of stress and inflammation, and address specific domains of reward dysregulation. By addressing these contextual factors, the review reveals a nuanced literature which might be targeted for additional scientific inquiry to inform the development of precise interventions.

Decision-making and frontoparietal resting-state functional connectivity among impulsive-compulsive diagnoses. Insights from a Bayesian approach

The Iowa Gambling Task (IGT) is one of the most widely used paradigms for assessing decision-making. An impairment in this process may be linked to several psychopathological disorders, such as obsessive-compulsive disorder (OCD), substance abuse disorder (SUD) or attention-deficit/hyperactivity disorder (ADHD), which could make it a good candidate for being consider a transdiagnostic domain. Resting-state functional connectivity (rsFC) has been proposed as a promising biomarker of decision-making. In this study, we aimed to identify idiosyncratic decision-making profiles among healthy people and impulsive-compulsive spectrum patients during the IGT, and to investigate the role of frontoparietal network (FPN) rsFC as a possible biomarker of different decision-making patterns. Using functional near-infrared spectroscopy (fNIRS), rsFC of 114 adults (34 controls; 25 OCD; 41 SUD; 14 ADHD) was obtained. Then, they completed the IGT. Hybrid clustering methods based on individual deck choices yielded three decision-makers subgroups. Cluster 1 (n = 27) showed a long-term advantageous strategy. Cluster 2 (n = 25) presented a maladaptive decision-making strategy. Cluster 3 (n = 62) did not develop a preference for any deck during the task. Interestingly, the proportion of participants in each cluster was not different between diagnostic groups. A Bayesian general linear model showed no credible differences in the IGT performance between diagnostic groups nor credible evidence to support the role of FPN rsFC as a biomarker of decision-making under the IGT context. This study highlights the importance of exploring in depth the behavioral and neurophysiological variables that may drive decision-making in clinical and healthy populations.

Dopamine D1 receptor and effort-based decision making in rats: The moderating effect of sex

Dopamine is a modulating factor in effort-based decision-making, and emerging evidence from pharmacological research suggests that the dopamine D1 receptor is the primary regulator. Given the limited selectivity of pharmacological tools, we further explored this hypothesis using dopamine D1 mutant (DAD1^-/-) rats which have a specific genetic reduction in functional D1 receptors. Moreover, given the strong focus on males in neuroscience research in general and in the role of D1 receptors in effort-based learning, we compared both sexes in the present study. Adult male and female DAD1^-/- mutant rats and wild type controls were trained to press a lever for a reinforcer. Once trained, subjects completed multiple fixed ratio, progressive ratio, and operant effort-choice (concurrent progressive ratio/chow feeding task [PROG/chow]) experiments. We predicted that DAD1^-/- mutant rats would press the lever significantly less than controls across all experiments, have lower breakpoints, and consume more freely available food. As predicted, DAD1^-/- mutant rats (regardless of sex) pressed the lever significantly less than controls and had lower breakpoints. Interestingly, there was a sex * genotype interaction for acquisition rates of lever pressing and change in breakpoints with free food available. Only 31% of DAD1^-/- mutant males acquired lever pressing while 73% of DAD1^-/- mutant females acquired lever pressing. Additionally, DAD1^-/- mutant males had significantly larger decreases in breakpoints when free food was available. These findings extend the pharmacological research suggesting that the dopamine D1 receptor modulates decisions based on effort, which has implications for the development of treatment targeting amotivation in neuropsychiatric disorders. The sex * genotype interaction highlights the importance of including both sexes in future research, especially when there are sex differences in incidences and severity of neuropsychiatric disorders.

Decision value signals in the ventromedial prefrontal cortex and motivational and hedonic symptoms across mood and psychotic disorders

Deficits in motivation and pleasure are common across many psychiatric disorders, and manifest as symptoms of amotivation and anhedonia, which are prominent features of both mood and psychotic disorders. Here we provide evidence for an association between neural value signals and symptoms of amotivation and anhedonia across adults with major depression, bipolar disorder, schizophrenia, or no psychiatric diagnosis. We found that value signals in the ventromedial prefrontal cortex (vmPFC) during intertemporal decision-making were dampened in individuals with greater motivational and hedonic deficits, after accounting for primary diagnosis. This relationship remained significant while controlling for diagnosis-specific symptoms of mood and psychosis, such as depression as well as positive and negative symptoms. Our results demonstrate that dysfunction in the vmPFC during value-based decision-making is specifically linked to motivational and hedonic impairments. These findings provide a quantitative neural target for the potential development of novel treatments for amotivation and anhedonia.

Depression reduces neural correlates of reward salience with increasing effort over the course of the progressive ratio task

BACKGROUND

Depressive disorders have been associated with altered effort-cost decision making (ECDM) in behavioral investigations, such as a decreased willingness to expend effort for reward attainment. However, little is known about neural mechanisms implicated in altered ECDM.

METHODS

The study investigates neural correlates of reward attainment during a progressive ratio task in participants with a current depressive disorder (n = 65) and never-depressed healthy individuals (n = 44). On each trial, participants completed an increasing number of button presses to attain a fixed monetary reward, indicated by an auditory reward signal. Participants could decide to quit the task anytime (breakpoint). EEG was recorded during the task and P300 amplitudes were examined in response to the auditory signal of reward attainment.

RESULTS

There was no difference in breakpoint, as both groups completed comparable numbers of button presses. In contrast, results from mixed-effects models of trial-level ERP responses indicated depression-related effects on P300 amplitudes over the course of the task. Generally, the reward-locked P300 increased with ascending effort expenditure; however, compared to healthy participants, individuals with current depression were characterized by an attenuated trajectory of the reward-locked P300, pointing towards decreased reactivity to reward attainment with increasing effort.

LIMITATIONS

Sample size and reward magnitude were possibly not large enough to detect differences in breakpoint.

CONCLUSIONS

The results of the current study demonstrate that the investigation of reward-related P300 trajectory may represent an informative novel addition to the progressive ratio task, which could help shed light on depression-related alterations in motivation and ECDM.

Cognitive Effort Exertion Enhances Electrophysiological Responses to Rewarding Outcomes

Recent work has highlighted neural mechanisms underlying cognitive effort-related discounting of anticipated rewards. However, findings on whether effort exertion alters the subjective value of obtained rewards are inconsistent. Here, we provide a more nuanced account of how cognitive effort affects subsequent reward processing in a novel task designed to assess effort-induced modulations of the Reward Positivity, an event-related potential indexing reward-related neural activity. We found that neural responses to both gains and losses were significantly elevated in trials requiring more versus less cognitive effort. Moreover, time-frequency analysis revealed that these effects were mirrored in gain-related delta, but not in loss-related theta band activity, suggesting that people ascribed more value to high-effort outcomes. In addition, we also explored whether individual differences in behavioral effort discounting rates and reward sensitivity in the absence of effort may affect the relationship between effort exertion and subsequent reward processing. Together, our findings provide evidence that cognitive effort exertion can increase the subjective value of subsequent outcomes and that this effect may primarily rely on modulations of delta band activity.

Aberrant striatal coupling with default mode and central executive network relates to self-reported avolition and anhedonia in schizophrenia

BACKGROUND

Avolition and anhedonia are common symptoms in schizophrenia and are related to poor long-term prognosis. There is evidence for aberrant cortico-striatal function and connectivity as neural substrate of avolition and anhedonia. However, it remains unclear how both relate to shared or distinct striatal coupling with large-scale intrinsic networks. Using resting state functional magnetic resonance imaging (rs-fMRI) this study investigated the association of large-scale cortico-striatal functional connectivity with self-reported and clinician-rated avolition and anhedonia in subjects with schizophrenia.

METHODS

Seventeen subjects with schizophrenia (SZ) and 28 healthy controls (HC) underwent rs-fMRI. Using Independent Component Analysis (ICA), we assessed Independent Components (ICs) reflecting intrinsic connectivity networks (ICNs), intra intrinsic functional connectivity within the ICs (intra-iFC), and intrinsic functional connectivity between different ICs (inter-iFC). Avolition and anhedonia were assessed using the Self Evaluation Scale for Negative Symptoms and the Brief Negative Symptom Scale.

RESULTS

ICA revealed three striatal components and six cortical ICNs. Both self-rated avolition and anhedonia correlated with increased inter-iFC between the caudate and posterior Default Mode Network (pDMN) and between the caudate and Central Executive Network (CEN). In contrast, clinician-rated avolition and anhedonia were not correlated with cortico-striatal connectivity. Group comparison revealed trend-wise decreased inter-iFC between the caudate and Salience Network (SN) in schizophrenia patients compared to HC.

DISCUSSION

Self-rated, but not clinician-rated, avolition and anhedonia was associated with aberrant striatal coupling with the default mode and the central executive network. These findings suggest that self-reported and clinician-rated scores might capture different aspects of motivational and hedonic deficits in schizophrenia and therefore relate to different cortico-striatal functional abnormalities.

Altered motivation of effortful decision-making for self and others in subthreshold depression

BACKGROUND

Amotivation is a typical feature in major depressive disorders and refers to individuals exhibiting reduced willingness to exert effort for rewards. However, the motivation pattern when deciding whether to exert effort for self versus others in people with depression remains unclear.

METHODS

We conducted a functional magnetic resonance imaging study and employed an adapted Effort-Expenditure for Rewards Task in subthreshold depressive (SD) participants (n = 33) and healthy controls (HC) (n = 32). This required participants to choose between a fixed low-effort/low-reward and a variable high-effort/high-reward option, and then immediately exert effort to obtain corresponding rewards for themselves or for unfamiliar people.

RESULTS

Compared with the HC group, the SD group showed blunted activity in the left dorsal anterior cingulate cortex/dorsomedial prefrontal cortex, bilateral anterior insula (AI), and right putamen-left dorsolateral prefrontal cortex functional connectivity when choosing to exert effort for themselves. Additionally, the SD group exhibited increased willingness and greater activation in the bilateral AI when choosing to exert effort for others. Furthermore, these brain activations and functional connectivity were positively related to self-reported motivation.

CONCLUSIONS

These findings show altered motivation during effort-based decision-making in individuals with the mild depressive state, particularly with higher motivation for others. Thus, this suggests that motivational behaviors and prefrontal-striatal circuitry are altered in individuals with SD, which can be utilized to discover treatment targets and develop strategies to address mental illness caused by motivation disorders.

Resting-State Correlations of Fatigue Following Military Deployment

OBJECTIVE

Persistent fatigue is common among military servicemembers returning from deployment, especially those with a history of mild traumatic brain injury (mTBI). The purpose of this study was to characterize fatigue following deployment using the Multidimensional Fatigue Inventory (MFI), a multidimensional self-report instrument. The study was developed to test the hypothesis that if fatigue involves disrupted effort/reward processing, this should manifest as altered basal ganglia functional connectivity as observed in other amotivational states.

METHODS

Twenty-eight current and former servicemembers were recruited and completed the MFI. All 28 participants had a history of at least one mTBI during deployment. Twenty-six participants underwent resting-state functional MRI. To test the hypothesis that fatigue was associated with basal ganglia functional connectivity, the investigators measured correlations between MFI subscale scores and the functional connectivity of the left and right caudate, the putamen, and the globus pallidus with the rest of the brain, adjusting for the presence of depression.

RESULTS

The investigators found a significant correlation between functional connectivity of the left putamen and bilateral superior frontal gyri and mental fatigue scores. No correlations with the other MFI subscales survived multiple comparisons correction.

CONCLUSIONS

This exploratory study suggests that mental fatigue in military servicemembers with a history of deployment with at least one mTBI may be related to increased striatal-prefrontal functional connectivity, independent of depression. A finding of effort/reward mismatch may guide future treatment approaches.

The neural basis of effort valuation: A meta-analysis of functional magnetic resonance imaging studies

Choosing how much effort to expend is critical for everyday decisions. While several neuroimaging studies have examined effort-based decision-making, results have been highly heterogeneous, leaving unclear which brain regions process effort-related costs and integrate them with rewards. We conducted two meta-analyses of functional magnetic resonance imaging data to examine consistent neural correlates of effort demands (23 studies, 15 maps, 549 participants) and net value (15 studies, 11 maps, 428 participants). The pre-supplementary motor area (pre-SMA) scaled positively with pure effort demand, whereas the ventromedial prefrontal cortex (vmPFC) showed the opposite effect. Moreover, regions that have been previously implicated in value integration in other cost domains, such as the vmPFC and ventral striatum, were consistently involved in signaling net value. The opposite response patterns of the pre-SMA and vmPFC imply that they are differentially involved in the representation of effort costs and value integration. These findings provide conclusive evidence that the vmPFC is a central node for net value computation and reveal potential brain targets to treat motivation-related disorders.

Relationship of ventral striatum activation during effort discounting to clinical amotivation severity in schizophrenia

Motivational deficits play a central role in disability due to negative symptoms of schizophrenia (SZ), but limited pathophysiological understanding impedes critically needed therapeutic development. We applied an fMRI Effort Discounting Task (EDT) that quantifies motivation using a neuroeconomic decision-making approach, capturing the degree to which effort requirements produce reductions in the subjective value (SV) of monetary reward. An analyzed sample of 21 individuals with SZ and 23 group-matched controls performed the EDT during fMRI. We hypothesized that ventral striatum (VS) as well as extended brain motivation circuitry would encode SV, integrating reward and effort costs. We also hypothesized that VS hypoactivation during EDT decisions would demonstrate a dimensional relationship with clinical amotivation severity, reflecting greater suppression by effort costs. As hypothesized, VS as well as a broader cortico-limbic network were activated during the EDT and this activation correlated positively with SV. In SZ, activation to task decisions was reduced selectively in VS. Greater VS reductions correlated with more severe clinical amotivation in SZ and across all participants. However, these diagnosis and amotivation effects could not be explained by the response to parametric variation in reward, effort, or model-based SV. Our findings demonstrate that VS hypofunction in schizophrenia is manifested during effort-based decisions and reflects dimensional motivation impairment. Dysfunction of VS impacting effort-based decision-making can provide a target for biomarker development to guide novel efforts to assess and treat disabling amotivation.

Neural signatures of saliency-mapping in anhedonia: A narrative review

Anhedonia is the loss of pleasure or motivation to engage in previously enjoyable activities, and is a transdiagnostic symptom associated with significant clinical impairment. Anhedonia is implicated in several different psychiatric disorders, presenting a promising opportunity for transdiagnostic treatment. Thus, developing targeted treatments for anhedonia is of critical importance for population mental health. An important first step in doing so is establishing a thorough understanding of the neural correlates of anhedonia. The Triple Network Model of Psychopathology provides a frame for how brain activity may go awry in anhedonia, specifically in the context of Salience Network (SN) function (i.e., saliency-mapping). We present a narrative review examining saliency-mapping as it relates to anhedonia severity in depressed and transdiagnostic adult samples. Results revealed increased anhedonia to be associated with hyperactivity of the SN at rest and in the context of negative stimuli, as well as a global lack of SN engagement in the context of positive stimuli. Potential treatments for anhedonia are placed within this model, and future directions for research are discussed.

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.

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.

Depression and the willingness to expend cognitive and physical effort for rewards: A systematic review

Depression is associated with reduced motivation to engage in previously enjoyed activities. In particular, anhedonia has been linked to reduced motivation, though other depressive symptoms may also play a role. The purposes of this systematic review were to 1) examine the relationship between depression and motivation, as operationalized by a willingness to expend effort for rewards, 2) examine the relationship between anhedonia and motivation, and 3) examine potential methodological moderators of these relationships. Forty-three articles met our inclusion criteria for the review. Our review found that individuals with depression and anhedonia demonstrate reduced willingness to expend cognitive and physical effort for rewards, though the effect has been more robustly demonstrated for physical effort expenditure. Task design impacted the strength of these relationships, with stronger effects for tasks that used indices of decision-making and accuracy rather than response time. These findings have clinical implications for behavioral activation, which seeks to improve depressive symptoms by encouraging individuals to increase their activity level. Future research should examine the determinants of motivation in individuals with depression and anhedonia, to ultimately help these individuals become more active and hopefully improve their quality of life as a result.

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.

Microstructural Changes in the Left Mesocorticolimbic Pathway are Associated with the Comorbid Development of Fatigue and Depression in Multiple Sclerosis

BACKGROUND AND PURPOSE

Lower reward responsiveness has been associated with fatigue in multiple sclerosis (MS). However, association of MS-related fatigue with damage to the mesocorticolimbic reward pathway (superolateral medial forebrain bundle [slMFB]) has not been assessed. We investigated the association of fatigue and depression with slMFB damage in MS patients stratified based on longitudinal fatigue patterns.

METHODS

Patient stratification: 1. Sustained Fatigue (SF): latest two Modified Fatigue Impact Scale (MFIS) ≥ 38 (n = 26); 2. Reversible Fatigue (RF): latest MFIS < 38, and at least one previous MFIS ≥ 38 (n = 25); 3. Never Fatigued (NF): ≥ 5 consecutive MFIS < 38 (n = 42); 4. Healthy Controls (n = 6). Diffusion MRI-derived measures of fractional anisotropy (FA), axial (AD), mean (MD), and radial diffusivity (RD) of the slMFB were compared between the groups. Depression was assessed using the Center for Epidemiologic Studies-Depression Scale (CES-D).

RESULTS

Depressed (CES-D ≥ 16) SF patients showed significantly higher MD and RD than nondepressed SF and RF, and depressed RF patients, and significantly lower FA than nondepressed SF and depressed RF patients in their left slMFB. Depressed SF patients showed significantly higher left slMFB MD and AD than healthy controls.

CONCLUSION

Microstructural changes to the left slMFB may play a role in the comorbid development of fatigue and depression in MS.

The neuroscience of positive emotions and affect: Implications for cultivating happiness and wellbeing

This review paper provides an integrative account regarding neurophysiological correlates of positive emotions and affect that cumulatively contribute to the scaffolding for happiness and wellbeing in humans and other animals. This paper reviews the associations among neurotransmitters, hormones, brain networks, and cognitive functions in the context of positive emotions and affect. Consideration of lifespan developmental perspectives are incorporated, and we also examine the impact of healthy social relationships and environmental contexts on the modulation of positive emotions and affect. The neurophysiological processes that implement positive emotions are dynamic and modifiable, and meditative practices as well as flow states that change patterns of brain function and ultimately support wellbeing are also discussed. This review is part of "The Human Affectome Project" (http://neuroqualia.org/background.php), and in order to advance a primary aim of the Human Affectome Project, we also reviewed relevant linguistic dimensions and terminology that characterizes positive emotions and wellbeing. These linguistic dimensions are discussed within the context of the neuroscience literature with the overarching goal of generating novel recommendations for advancing neuroscience research on positive emotions and wellbeing.

The effort-doors task: Examining the temporal dynamics of effort-based reward processing using ERPs

Aberrant reward processing is a cardinal feature of various forms of psychopathology. However, recent research indicates that aberrant reward processing may manifest at temporally distinct substages and involve interdependent subcomponents of reward processing. To improve our understanding of both the temporal dynamics and distinct subcomponents of reward processing, we added an effort manipulation to the "doors" reward-task paradigm, to derive behavioral and event-related potential (ERP) measures of effort-based reward processing. Behavioral measures consisting of reaction time, response rate, and response rate change were used to index effort expenditure, and ERP measures were used to index attention allocated toward effort-completion cues, anticipation of reward, valuation of reward, and attention toward monetary feedback. Reduced response rate and slowing of response were evident during the high effort versus the low effort condition. ERP findings indicated increased attention to signals of high- compared to low-effort completion cues-as well as reduced anticipation of rewards, and reduced attention toward feedback information following high effort expenditure. Participants showing the most response-rate slowing evidenced the greatest reward devaluation following high versus low effort. Findings demonstrate that the addition of an effort expenditure manipulation to the doors reward paradigm produced reliable ERP and behavioral measures of effort-based reward processing, providing opportunities for future researchers to utilize the effort-doors task to parse the temporal dynamics of both anticipatory and consummatory reward processing components.

Role of the Medial Orbitofrontal Cortex and Ventral Tegmental Area in Effort-Related Responding

The posterior subdivision of the medial orbitofrontal cortex (mOFC-p) mediates the willingness to expend effort to reach a selected goal. However, the neural circuitry through which the mOFC-p modulates effort-related function is as yet unknown. The mOFC-p projects prominently to the posterior ventral tegmental area (pVTA). Therefore, we analyzed the role of the mOFC-p and interactions with the pVTA in effort-related responding using a combination of behavioral, pharmacological, and neural circuit analysis methods in rats. Pharmacological inhibition of the mOFC-p was found to increase lever pressing for food under a progressive ratio (PR) schedule of reinforcement. These findings provide further support for a modulation of effort-related function by the mOFC-p. Then, we investigated effects of disconnecting the mOFC-p and pVTA on PR responding using unilateral pharmacological inhibition of both areas. This asymmetric intervention was also found to increase PR responding suggesting that the mOFC-p controls effort-related function through interactions with the pVTA. Possibly, a reduced excitatory mOFC-p drive on pVTA gamma-aminobutyric acid (GABA)ergic relays disinhibits VTA dopamine neurons which are known to support PR responding. Collectively, our findings suggest that the mOFC-p and pVTA are key components of a neural circuit mediating the willingness to expend effort to reach a goal.

Differences in Functional Connectivity Networks Related to the Midbrain Dopaminergic System-Related Area in Various Psychiatric Disorders

OBJECTIVE

Disruptions in the dopamine system have been observed in psychiatric disorders. Since dopamine is mainly produced in the ventral tegmental area (VTA), elucidating the differences in the VTA neural network across psychiatric disorders would facilitate a greater understanding of the pathophysiological mechanisms underlying these disorders. However, no study has compared VTA-seed-based functional connectivity across psychiatric disorders. Therefore, we conducted a resting-state functional magnetic resonance imaging (rs-fMRI) study to perform a seed-based fMRI analysis, using the VTA as a seed.

METHODS

We included participants with major depressive disorder (MDD; n = 45), schizophrenia (n = 32), and bipolar disorder (BPD; n = 30), along with healthy control participants (n = 46) who were matched for age, gender, and handedness.

RESULTS

The results showed that patients with MDD and BPD had altered VTA-related connectivity in the superior frontal gyrus, frontal pole regions, hippocampus, cerebellum, and posterior cingulate cortex. Some of these differences in connectivity were also found between affective disorders and schizophrenia; however, there were no differences between the schizophrenia and control groups. Connectivity between the VTA and the hippocampus was correlated with positive symptoms in the schizophrenia group. The connectivity was not associated with medication dose, and the results remained significant after controlling for dose.

CONCLUSIONS

The results suggest that altered brain functional connectivity related to VTA networks could be associated with the distinctive pathophysiologies of psychiatric disorders, especially affective disorders.

Effort, avolition and motivational experience in schizophrenia: Analysis of behavioral and neuroimaging data with relationships to daily motivational experience

Recent research suggests that schizophrenia is associated with reduced effort allocation. We examined willingness to expend effort, neural correlates of effort allocation, and the relationship of effort to daily motivational experience in schizophrenia. We recruited 28 individuals with schizophrenia and 30 controls to perform an effort task during fMRI. Individuals with schizophrenia also completed an ecological momentary assessment (EMA) protocol. Individuals with schizophrenia with high negative symptoms were less willing to expend effort for rewards. Daily EMA assessments of motivation were positively associated with effort allocation at a trend-level. Individuals with schizophrenia and controls displayed similar increases in BOLD activation in frontal, cingulate, parietal, and insular regions during effort-based decision-making. However, negative symptoms were associated with reduced BOLD activation in bilateral ventral striatum. These results replicate previous reports of reduced effort allocation in schizophrenia patients with severe negative symptoms, and provide evidence for the role of ventral striatum in effort impairments.

A transnosographic approach of negative symptoms pathophysiology in schizophrenia and depressive disorders

BACKGROUND

Negative Symptoms (blunted affect, alogia, anhedonia, avolition and asociality) are observed in schizophrenia but also in depressive disorders.

OBJECTIVE

To gather cognitive, neuroanatomical, neurofunctional and neurobiological knowledge of negative symptoms in studies on schizophrenia, depressive disorder, and transnosographic studies.

RESULTS

Blunted affect in schizophrenia is characterized by amygdala hyperactivation and frontal hypoactivation, also found in depressive disorder. Mirror neurons, may be related to blunted affect in schizophrenia. Alogia may be related to cognitive dysfunction and basal ganglia area impairments in schizophrenia. Data surrounding alogia in depressive disorder is scarce; wider speech deficits are often studied instead. Consummatory Anhedonia may be less affected than Anticipatory Anhedonia in schizophrenia. Anhedonia is associated with reward impairments and altered striatal functions in both diagnostics. Amotivation is associated with Corticostriatal Hypoactivation in both disorders. Anhedonia and amotivation are transnosographically associated with dopamine dysregulation. Asociality may be related to oxytocin.

CONCLUSION

Pathophysiological hypotheses are specific to each dimension of negative symptoms and overlap across diagnostic boundaries, possibly underpinning the observed clinical continuum.

Grant Report on Social Reward Learning in Schizophrenia †

We report on the ongoing R21 project “Social Reward Learning in Schizophrenia”. Impairments in social cognition are a hallmark of schizophrenia. However, little work has been done on social reward learning deficits in schizophrenia. The overall goal of the project is to assess social reward learning in schizophrenia. A probabilistic reward learning (PRL) task is being used in the MRI scanner to evaluate reward learning to negative and positive social feedback. Monetary reward learning is used as a comparison to assess specificity. Behavioral outcomes and brain areas, included those involved in reward, are assessed in patients with schizophrenia or schizoaffective disorder and controls. It is also critical to determine whether decreased expected value (EV) of social stimuli and/or reward prediction error (RPE) learning underlie social reward learning deficits to inform potential treatment pathways. Our central hypothesis is that the pattern of social learning deficits is an extension of a more general reward learning impairment in schizophrenia and that social reward learning deficits critically contribute to deficits in social motivation and pleasure. We hypothesize that people with schizophrenia will show impaired behavioral social reward learning compared to controls, as well as decreased ventromedial prefrontal cortex (vmPFC) EV signaling at time of choice and decreased striatal RPE signaling at time of outcome, with potentially greater impairment to positive than negative feedback. The grant is in its second year. It is hoped that this innovative approach may lead to novel and more targeted treatment approaches for social cognitive impairments, using cognitive remediation and/or brain stimulation.

Dopamine D1 receptors in the medial orbitofrontal cortex support effort-related responding in rats

Rodent studies on effort-related responding provide a tool to analyze basal aspects of motivation and to model psychiatric motivational dysfunctions reflecting low exertion of effort or reduced behavioral activation. It turned out that dopamine (DA) signaling in brain areas such as nucleus accumbens are essential in regulating effort-related motivational function and could play a major role in motivational dysfunction in psychiatric disorders. Recent rodent studies revealed that the medial orbitofrontal cortex (mOFC) is another key component of the neural circuitry regulating effort-related motivational function. The mOFC receives prominent DA input, however, the behavioral role of mOFC DA signaling is unknown. Here, we investigated whether DA signaling in the mOFC supports effort-related responding in rats. Results demonstrate that an intra-mOFC D1 receptor blockade markedly reduced effort-related responding in a progressive ratio task. Notably, the magnitude of this effect was comparable to the one caused by a systemic DA depletion induced by the VMAT-2 inhibitor tetrabenazine or by a satiety-induced motivational downshift. Collectively, our data show for the first time that D1 receptor activity in the mOFC plays a critical role in high effort responding. These results support findings in humans pointing to a role of the mOFC in effort-related responding. It is well known that the mOFC becomes dysfunctional in depression and schizophrenia. Our data point to the possibility that reduced mOFC DA activity could contribute to effort-related motivational symptoms in these disorders and support the notion that the DA system may be a drug target to treat effort-related motivational symptoms.

Striatal reactivity to reward under threat-of-shock and working memory load in adults at increased familial risk for major depression: A preliminary study

INTRODUCTION

Anhedonia, a core symptom of Major Depressive Disorder (MDD), manifests as a lack or loss of motivation as reflected by decreased reward responsiveness, at both behavioral and neural (i.e., striatum) levels. Exposure to stressful life events is another important risk factor for MDD. However, the mechanisms linking reward-deficit and stress to MDD remain poorly understood. Here, we explore whether the effects of stress exposure on reward processing might differentiate between Healthy Vulnerable adults (HVul, i.e., positive familial MDD) from Healthy Controls (HCon). Furthermore, the well-described reduction in cognitive resources in MDD might facilitate the stress-induced decrease in reward responsiveness in HVul individuals. Accordingly, this study includes a manipulation of cognitive resources to address the latter possibility.

METHODS

16 HVul (12 females) and 16 gender- and age-matched HCon completed an fMRI study, during which they performed a working memory reward task. Three factors were manipulated: reward (reward, no-reward), cognitive resources (working memory at low and high load), and stress level (no-shock, unpredictable threat-of-shock). Only the reward anticipation phase was analyzed. Imaging analyses focused on striatal function.

RESULTS

Compared to HCon, HVul showed lower activation in the caudate nucleus across all conditions. The HVul group also exhibited lower stress-related activation in the nucleus accumbens, but only in the low working memory (WM) load condition. Moreover, while stress potentiated putamen reactivity to reward cues in HVul when the task was more demanding (high WM load), stress blunted putamen reactivity in both groups when no reward was at stake.

CONCLUSION

Findings suggest that HVul might be at increased risk of developing anhedonic symptoms due to weaker encoding of reward value, higher difficulty to engage in goal-oriented behaviors and increased sensitivity to negative feedback, particularly in stressful contexts. These findings open new avenues for a better understanding of the mechanisms underlying how the complex interaction between the systems of stress and reward responsiveness contribute to the vulnerability to MDD, and how cognitive resources might modulate this interaction.

Inflammation and Negative Symptoms of Schizophrenia: Implications for Reward Processing and Motivational Deficits

Negative symptoms of schizophrenia are debilitating and chronic in nature, are difficult to treat, and contribute to poor functional outcomes. Motivational deficits are a core negative symptom and may involve alterations in reward processing, which involve subcortical regions such as the basal ganglia. More specifically, dopamine-rich regions like the ventral striatum, have been implicated in these reward-processing deficits. Inflammation is one mechanism that may underlie negative symptoms, and specifically motivational deficits, via the effects of inflammatory cytokines on the basal ganglia. Previous work has demonstrated that inflammatory stimuli decrease neural activity in the ventral striatum and decrease connectivity in reward-relevant neural circuitry. The immune system has been shown to be involved in the pathophysiology of schizophrenia, and inflammatory cytokines have been shown to be altered in patients with the disorder. This paper reviews the literature on associations between inflammatory markers and negative symptoms of schizophrenia as well as the role of anti-inflammatory drugs to target negative symptoms. We also review the literature on the role of inflammation and reward processing deficits in both healthy controls and individuals with depression. We use the literature on inflammation and depression as a basis for a model that explores potential mechanisms responsible for inflammation modulating certain aspects of negative symptoms in patients with schizophrenia. This approach may offer novel targets to treat these symptoms of the disorder that are significant barriers to functional recovery and do not respond well to available antipsychotic medications.

Dimensional anhedonia and the adolescent brain: reward and aversion anticipation, effort and consummation

BACKGROUND

Given the heterogeneity of depression the Research Domain Criteria Framework suggests a dimensional approach to understanding the nature of mental illness. Neural reward function has been suggested as underpinning the symptom of anhedonia in depression but how anhedonia is related to aversion processing is unclear.

AIMS

To assess how the dimensional experience of anhedonia and depression severity relate to reward and aversion processing in the human brain.

METHOD

We examined adolescents and emerging adults (n = 84) in the age range 13-21 years. Using a dimensional approach we examined how anhedonia and depression related to physical effort to gain reward or avoid aversion and neural activity during the anticipation, motivation/effort and consummation of reward and aversion.

RESULTS

As anhedonia increased physical effort to gain reward decreased. As anhedonia increased neural activity decreased during effort to avoid in the precuneus and insula (trend) and increased in the caudate during aversive consummation. We found participants with depression symptoms invested less physical effort than controls and had blunted neural anticipation of reward and aversion in the precuneus, insula and prefrontal cortex and blunted neural activity during effort for reward in the putamen.

CONCLUSIONS

We show for the first time that both physical effort and neural activity during effort correlate with anhedonia in adolescents and that amotivation might be a specific deficit of anhedonia irrespective of valence. Future work will assess if these neural mechanisms can be used to predict blunted approach and avoidance in adolescents at risk of depression.

Affective biases and their interaction with other reward-related deficits in rodent models of psychiatric disorders

Major depressive disorder (MDD) is one of the leading global causes of disability. Symptoms of MDD can vary person to person, and current treatments often fail to alleviate the poor quality of life that patients experience. One of the two core diagnostic criteria for MDD is the loss of interest in previously pleasurable activities, which suggests a link between the disease aetiology and reward processing. Cognitive impairments are also common in patients with MDD, and more recently, emotional processing deficits known as affective biases have been recognised as a key feature of the disorder. Studies in animals have found similar affective biases related to reward. In this review we consider these affective biases in the context of other reward-related deficits and examine how affective biases associated with learning and memory may interact with the wider behavioural symptoms seen in MDD. We discuss recent developments in how analogues of affective biases and other aspects of reward processing can be assessed in rodents, as well as how these behaviours are influenced in models of MDD. We subsequently discuss evidence for the neurobiological mechanisms contributing to one or more reward-related deficits in preclinical models of MDD, identified using these behavioural assays. We consider how the relationships between these selective behavioural assays and the neurobiological mechanisms for affective bias and reward processing could be used to identify potential treatment strategies.

Thimet Oligopeptidase (EC 3.4.24.15) Key Functions Suggested by Knockout Mice Phenotype Characterization

Thimet oligopeptidase (THOP1) is thought to be involved in neuropeptide metabolism, antigen presentation, neurodegeneration, and cancer. Herein, the generation of THOP1 C57BL/6 knockout mice (THOP1^−/−) is described showing that they are viable, have estrus cycle, fertility, and a number of puppies per litter similar to C57BL/6 wild type mice (WT). In specific brain regions, THOP1^-/- exhibit altered mRNA expression of proteasome beta5, serotonin 5HT2a receptor and dopamine D2 receptor, but not of neurolysin (NLN). Peptidomic analysis identifies differences in intracellular peptide ratios between THOP1^-/- and WT mice, which may affect normal cellular functioning. In an experimental model of multiple sclerosis THOP1^-/- mice present worse clinical behavior scores compared to WT mice, corroborating its possible involvement in neurodegenerative diseases. THOP1^-/- mice also exhibit better survival and improved behavior in a sepsis model, but also a greater peripheral pain sensitivity measured in the hot plate test after bradykinin administration in the paw. THOP1^-/- mice show depressive-like behavior, as well as attention and memory retention deficits. Altogether, these results reveal a role of THOP1 on specific behaviors, immune-stimulated neurodegeneration, and infection-induced inflammation.

Rigidity in Motor Behavior and Brain Functioning in Patients With Schizophrenia and High Levels of Apathy

The aim of this study was to investigate whether apathy in schizophrenia is associated with rigidity in behavior and brain functioning. To this end, we studied associations between variability in dynamic functional connectivity (DFC) in relevant functional brain networks, apathy, and variability in physical activity in schizophrenia. Thirty-one patients with schizophrenia, scoring high on apathy, were included and wore an actigraph. Activity variability was calculated on the activity counts using the root of the Mean Squared Successive Difference (MSSD). Furthermore, we calculated DFC on resting-state data as phase interactions between blood oxygen-level dependent (BOLD) signals of 270 brain regions per volume. Variability (MSSD) in DFC was calculated for 3 networks, including the default-mode network (DMN), frontoparietal network, and salience-reward network (SRN). Finally, we calculated correlations between these DFC estimates and apathy and activity variability. First, lower activity variability was associated with higher levels of apathy. Second, higher levels of apathy were associated with lower variability in DFC in the DMN and SRN. Third, higher activity variability was associated with higher variability in DFC in the SRN. In conclusion, patients with schizophrenia and more severe levels of apathy showed less variability in their physical activity and more rigid functional brain network behavior in the DMN and SRN. These networks have been shown relevant for self-reflection, mental simulation, and reward processing, processes that are pivotal for self-initiated goal-directed behavior. Functional rigidity of these networks may therefore contribute to reduced goal-directed behavior, which is characteristic for these patients.

Inefficient Involvement of Insula in Sensorineural Hearing Loss

The insular cortex plays an important role in multimodal sensory processing, audio-visual integration and emotion; however, little is known about how the insula is affected by auditory deprivation due to sensorineural hearing loss (SNHL). To address this issue, we used structural and functional magnetic resonance imaging to determine if the neural activity within the insula and its interregional functional connectivity (FC) was disrupted by SNHL and if these alterations were correlated clinical measures of emotion and cognition. Thirty-five SNHL subjects and 54 Controls enrolled in our study underwent auditory evaluation, neuropsychological assessments, functional and structure MRI, respectively. Twenty five patients and 20 Controls underwent arterial spin labeling scanning. FC of six insula subdivisions were assessed and the FC results were compared to the neuropsychological tests. Interregional connections were also compared among insula-associated networks, including salience network (SN), default mode network (DMN), and central executive network (CEN). Compared to Controls, SNHL subjects demonstrated hyperperfusion in the insula and significantly decreased FC between some insula subdivisions and other brain regions, including thalamus, putamen, precentral gyrus, postcentral gyrus, mid-cingulate cortex, dorsolateral prefrontal cortex, rolandic operculum. Anxiety, depression and cognitive impairments were correlated with FC values. Abnormal interactions among SN, DMN, and CEN were observed in SNHL group. Our result provides support for the "inefficient high-order control" theory of the insula in which the auditory deprivation caused by SNHL contributes to impaired sensory integration and central deficits in emotional and cognitive processing.

Reward systems and cognitions in Major Depressive Disorder

A lack of motivation and anhedonia represent frequent and pervasive symptoms in depression, although with poor specificity. Historically described as a response bias, reward-related impairments in depression may account for the important aspects of the cognitive impairments associated with diagnosis of major depressive disorder. Reward processing is a broad psychological construct that can be parsed into 3 distinct components known as "reinforcement learning" (learning), "reward responsiveness" (liking), and "motivation to obtain a reward" (wanting). Depressed patients respond hyposensitively to reward and maladaptively to punishment: this pattern is related to a dysfunction in the frontostriatal systems modulated by the monoamine systems; seems to be observed in medicated and unmedicated patients with depression and in healthy individuals with high levels of anhedonia; and could be observed in patients with a history of depression, even when in full remission. Considered to be cognitive impairments, reward-related-impairments may also constitute part of an underlying neurobiological vulnerability to major depressive disorder (MDD). For example, the reward-related impairment is state dependent and, more or less, correlated with symptom severity in some studies but has also been proposed as being trait like, with endophenotype characteristics, possibly contributing to the persistence of the disease or treatment resistance. The 3 core aspects of reward processing have specific neurobiological correlates that involve the ventral and dorsal striatum, lateral habenula, ventral tegmental area, orbitofrontal cortex, anterior cingulate cortex, and ventromedial and dorsolateral prefrontal cortex. These structures underline the important role of the dopaminergic mesolimbic pathway, but glutamate and serotonin could also have an important role, at least in some aspects of reward-related impairments.

Impaired Expected Value Computations in Schizophrenia Are Associated With a Reduced Ability to Integrate Reward Probability and Magnitude of Recent Outcomes

BACKGROUND

Motivational deficits in people with schizophrenia (PSZ) are associated with an inability to integrate the magnitude and probability of previous outcomes. The mechanisms that underlie probability-magnitude integration deficits, however, are poorly understood. We hypothesized that increased reliance on "valueless" stimulus-response associations, in lieu of expected value (EV)-based learning, could drive probability-magnitude integration deficits in PSZ with motivational deficits.

METHODS

Healthy volunteers (n = 38) and PSZ (n = 49) completed a learning paradigm consisting of four stimulus pairs. Reward magnitude (3, 2, 1, 0 points) and probability (90%, 80%, 20%, 10%) determined each stimulus's EV. Following a learning phase, new and familiar stimulus pairings were presented. Participants were asked to select stimuli with the highest reward value.

RESULTS

PSZ with high motivational deficits made increasingly less optimal choices as the difference in reward value (probability × magnitude) between two competing stimuli increased. Using a previously validated computational hybrid model, PSZ relied less on EV ("Q-learning") and more on stimulus-response learning ("actor-critic"), which correlated with Scale for the Assessment of Negative Symptoms motivational deficit severity. PSZ specifically failed to represent reward magnitude, consistent with model demonstrations showing that response tendencies in the actor-critic were preferentially driven by reward probability.

CONCLUSIONS

Probability-magnitude deficits in PSZ with motivational deficits arise from underutilization of EV in favor of reliance on valueless stimulus-response associations. Confirmed by our computational hybrid framework, probability-magnitude integration deficits were driven specifically by a failure to represent reward magnitude. This work provides a first mechanistic explanation of complex EV-based learning deficits in PSZ with motivational deficits that arise from an inability to combine information from different reward modalities.

Effort-Based Decision-Making in Schizophrenia

Motivational impairment has long been associated with schizophrenia but the underlying mechanisms are not clearly understood. Recently, a small but growing literature has suggested that aberrant effort-based decision-making may be a potential contributory mechanism for motivational impairments in psychosis. Specifically, multiple reports have consistently demonstrated that individuals with schizophrenia are less willing than healthy controls to expend effort to obtain rewards. Further, this effort-based decision-making deficit has been shown to correlate with severity of negative symptoms and level of functioning, in many but not all studies. In the current review, we summarize this literature and discuss several factors that may underlie aberrant effort-based decision-making in schizophrenia.

Impaired Expected Value Computations Coupled With Overreliance on Stimulus-Response Learning in Schizophrenia

BACKGROUND

While many have emphasized impaired reward prediction error signaling in schizophrenia, multiple studies suggest that some decision-making deficits may arise from overreliance on stimulus-response systems together with a compromised ability to represent expected value. Guided by computational frameworks, we formulated and tested two scenarios in which maladaptive representations of expected value should be most evident, thereby delineating conditions that may evoke decision-making impairments in schizophrenia.

METHODS

In a modified reinforcement learning paradigm, 42 medicated people with schizophrenia and 36 healthy volunteers learned to select the most frequently rewarded option in a 75-25 pair: once when presented with a more deterministic (90-10) pair and once when presented with a more probabilistic (60-40) pair. Novel and old combinations of choice options were presented in a subsequent transfer phase. Computational modeling was employed to elucidate contributions from stimulus-response systems (actor-critic) and expected value (Q-learning).

RESULTS

People with schizophrenia showed robust performance impairments with increasing value difference between two competing options, which strongly correlated with decreased contributions from expected value-based learning (Q-learning). Moreover, a subtle yet consistent contextual choice bias for the probabilistic 75 option was present in people with schizophrenia, which could be accounted for by a context-dependent reward prediction error in the actor-critic.

CONCLUSIONS

We provide evidence that decision-making impairments in schizophrenia increase monotonically with demands placed on expected value computations. A contextual choice bias is consistent with overreliance on stimulus-response learning, which may signify a deficit secondary to the maladaptive representation of expected value. These results shed new light on conditions under which decision-making impairments may arise.

Effort-cost decision-making in psychosis and depression: could a similar behavioral deficit arise from disparate psychological and neural mechanisms?

Motivational impairment is a common feature of both depression and psychosis; however, the psychological and neural mechanisms that give rise to motivational impairment in these disorders are poorly understood. Recent research has suggested that aberrant effort-cost decision-making (ECDM) may be a potential contributor to motivational impairment in both psychosis and depression. ECDM refers to choices that individuals make regarding the amount of 'work' they are willing to expend to obtain a certain outcome or reward. Recent experimental work has suggested that those with psychosis and depression may be less willing to expend effort to obtain rewards compared with controls, and that this effort deficit is related to motivational impairment in both disorders. In the current review, we aim to summarize the current literature on ECDM in psychosis and depression, providing evidence for transdiagnostic impairment. Next, we discuss evidence for the hypothesis that a seemingly similar behavioral ECDM deficit might arise from disparate psychological and neural mechanisms. Specifically, we argue that effort deficits in psychosis might be largely driven by deficits in cognitive control and the neural correlates of cognitive control processes, while effort deficits in depression might be largely driven by reduced reward responsivity and the associated neural correlates of reward responsivity. Finally, we will provide some discussion regarding future directions, as well as interpretative challenges to consider when examining ECDM transdiagnostically.

Subcortical Local Functional Hyperconnectivity in Cannabis Dependence

BACKGROUND

Cannabis abuse (CA) has been associated with psychopathology, including negative emotionality and higher risk of psychosis, particularly with early age of initiation. However, the mechanisms underlying this association are poorly understood. Because aberrant dopamine signaling is implicated in cannabis-associated psychopathology, we hypothesized that regular CA would be associated with altered resting-state functional connectivity in dopamine midbrain-striatal circuits.

METHODS

We examined resting-state brain activity of subcortical regions in 441 young adults from the Human Connectome Project, including 30 subjects with CA meeting DSM-IV criteria for dependence and 30 control subjects matched on age, sex, education, body mass index, anxiety, depression, and alcohol and tobacco usage.

RESULTS

Across all subjects, local functional connectivity density hubs in subcortical regions were most prominent in ventral striatum, hippocampus, amygdala, dorsal midbrain, and posterior-ventral brainstem. As hypothesized, subjects with CA showed markedly increased local functional connectivity density relative to control subjects, not only in ventral striatum (where nucleus accumbens is located) and midbrain (where substantia nigra and ventral tegmental nuclei are located) but also in brainstem and lateral thalamus. These effects were observed in the absence of significant differences in subcortical volumes and were most pronounced in individuals who began cannabis use earliest in life and who reported high levels of negative emotionality.

CONCLUSIONS

Together, these findings suggest that chronic CA is associated with changes in resting-state brain function, particularly in dopaminergic nuclei implicated in psychosis but that are also critical for habit formation and reward processing. These results shed light on neurobiological differences that may be relevant to psychopathology associated with cannabis use.