Reconsidering anhedonia in depression: lessons from translational neuroscience

Early protein restriction in rats induces anhedonia in adult offspring: A key role of BDNF-TrkB signaling in the nucleus accumbens shell

Clinical evidence suggests that early malnutrition promotes symptoms related to psychiatric disorders later in life. Nevertheless, the molecular mechanisms underpinning nutritional injury induce depression remains unknown. The purpose of the present study was to evaluate whether perinatal protein restriction increases vulnerability to developing depressive-like behavior in adulthood by focusing on anhedonia, a core symptom of depression. To this, male adult Wistar rats submitted to a protein restriction schedule at perinatal age (PR-rats), were subjected to the sucrose preference test (SPT), the novel object recognition test (NORT), the forced swim test (FST), and the elevated plus maze (EPM), and compared to animals fed with a normoprotein diet. To investigate neurobiological substrates linked to early protein undernutrition-facilitated depressive-like behavior, we assessed the levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the nucleus accumbens (NAc), and evaluated the reversal of anhedonic-like behavior by infusing ANA-12. We found that early malnutrition decreased sucrose preference, impaired performance in the NORT and increased immobility time in the FST. Furthermore, perinatal protein-restriction-induced anhedonia correlated with increased BDNF and p-TrkB protein levels in the NAc, a core structure in the reward circuit linked with anhedonia. Finally, bilateral infusion of the TrkB antagonist ANA-12 into the NAc shell ameliorated a reduced sucrose preference in the PR-rats. Altogether, these findings revealed that protein restriction during pregnancy and lactation facilitates depressive-like behavior later in life and may increase the risk of developing anhedonia by altering BDNF-TrkB in the NAc shell.

Antidepressant-like effect of riparin I and riparin II against CUMS-induced neuroinflammation via astrocytes and microglia modulation in mice

Depression is a common mood disorder and many patients do not respond to conventional pharmacotherapy or experience a variety of adverse effects. This work proposed that riparin I (RIP I) and riparin II (RIP II) present neuroprotective effects through modulation of astrocytes and microglia, resulting in the reversal of depressive-like behaviors. To verify our hypothesis and clarify the pathways underlying the effect of RIP I and RIP II on neuroinflammation, we used the chronic unpredictable mild stress (CUMS) depression model in mice. Male Swiss mice were exposed to stressors for 28 days. From 15 th to the 22 nd day, the animals received RIP I or RIP II (50 mg/kg) or fluoxetine (FLU, 10 mg/kg) or vehicle, by gavage. On the 29 th day, behavioral tests were performed. Expressions of microglia (ionized calcium-binding adaptor molecule-1 - Iba-1) and astrocyte (glial fibrillary acidic protein - GFAP) markers and levels of cytokines tumor necrosis factor alfa (TNF-α) and interleukin 1 beta (IL-1β) were measured in the hippocampus. CUMS induced depressive-like behaviors and cognitive impairment, high TNF-α and IL-1β levels, decreased GFAP, and increased Iba-1 expressions. RIP I and RIP II reversed these alterations. These results contribute to the understanding the mechanisms underlying the antidepressant effect of RIP I and RIP II, which may be related to neuroinflammatory suppression.

Common and separable neural alterations in adult and adolescent depression - Evidence from neuroimaging meta-analyses

Depression is a highly prevalent and debilitating mental disorder that often begins in adolescence. However, it remains unclear whether adults and adolescents with depression exhibit common or distinct brain dysfunctions during reward processing. We aimed to identify common and separable neurofunctional alterations during receipt of rewards and brain structure in adolescents and adults with depression. A coordinate-based meta-analysis was employed using Seed-based d mapping with permutation of subject images (SDM-PSI). Compared with healthy controls, both age groups exhibited common activity decreases in the right striatum (putamen, caudate) and subgenual ACC. Adults with depression showed decreased reactivity in the right putamen and subgenual ACC, while adolescents with depression showed decreased activity in the left mid cingulate, right caudate but increased reactivity in the right postcentral gyrus. This meta-analysis revealed shared (caudate) and separable (putamen and mid cingulate cortex) reward-related alterations in adults and adolescents with depression. The findings suggest age-specific neurofunctional alterations and stress the importance of adolescent-specific interventions that target social functions.

Examining the Factor Structure of the Posttraumatic Checklist for Civilians

The Posttraumatic Checklist for Civilians (PCL-C) is one of the most common tools used to assess PTSD among civilian populations. However, the underlying factor structure of the PCL-C remains under examined, with the most recent research relying on small samples with limited generalizability. Thus, the present study used exploratory and confirmatory techniques in a large North American college student sample to investigate the factor structure of the PCL-C. Results supported a 3-factor model for the PCL-C accounting for 59% of the total variance and represented by Suppression (M = 11.2, SD = 5.0); Hyperarousal (M = 6.5, SD = 3.2); and Diminished Reward Processing (M = 5.9, SD = 2.9). Regarding gender differences, females tended to score higher on suppression and avoidance related symptoms, while males scored higher on symptoms related to Diminished Reward Processing. Results also showed that embedded within college campuses are trauma exposed students experiencing distressingly high levels of posttrauma symptoms. In sum, the results revealed three factors in the PCL-C, that could be used to offer insight into assessing and treating posttrauma symptoms on a college campus.

Transdiagnostic Mood, Anxiety, and Trauma Symptom Factors in Alcohol Use Disorder: Neural Correlates Across 3 Brain Networks

BACKGROUND

Alcohol use disorder (AUD) is associated with high rates of trauma, mood, and anxiety disorders. Across these diagnoses, individual symptoms substantially overlap, highlighting the need for a transdiagnostic approach. Furthermore, there is limited research on how transdiagnostic psychopathology impacts the neural correlates of AUD. Thus, we aimed to identify symptom factors spanning diagnoses and examine how they relate to the neurocircuitry of addiction.

METHODS

Eighty-six veterans with AUD completed self-report measures and reward, incentive salience, and cognitive control functional magnetic resonance imaging tasks. Factor analysis was performed on self-reported trauma, depression, anxiety, and stress symptoms to obtain transdiagnostic symptom compositions. Neural correlates of a priori-defined regions of interest in the 3 networks were assessed. Independent sample t tests were used to compare the same nodes by DSM-5 diagnosis.

RESULTS

Four symptom factors were identified: Trauma distress, Negative affect, Hyperarousal, and Somatic anxiety. Trauma distress score was associated with increased cognitive control activity during response inhibition (dorsal anterior cingulate cortex). Negative affect was related to lower activation in reward regions (right caudate) but higher activation in cognitive control regions during response inhibition (left dorsolateral prefrontal cortex). Hyperarousal was related to lower reward activity during monetary reward anticipation (left caudate, right caudate). Somatic anxiety was not significantly associated with brain activation. No difference in neural activity was found by posttraumatic stress disorder, major depressive disorder, or generalized anxiety disorder diagnosis.

CONCLUSIONS

These hypothesis-generating findings offer transdiagnostic symptom factors that are differentially associated with neural function and could guide us toward a brain-based classification of psychiatric dysfunction in AUD. Results warrant further investigation of transdiagnostic approaches in addiction.

PI3K/AKT signaling pathway: Molecular mechanisms and therapeutic potential in depression

Depression is a serious global mental disorder. Numerous studies have found that depression may be closely related to decreased neurogenesis, neuroinflammation, neurotransmitter imbalance, and synaptic plasticity dysfunction. The pathogenesis of depression is complex and involves multiple signal transduction pathways and molecular changes. The PI3K/AKT pathway is an essential signaling pathways in neurons, which is widely expressed in emotion-related regions of the brain. Therefore, the PI3K/AKT pathway may play a moderating role in mood disorders. However, the role and mechanism of the PI3K/AKT signaling pathway in depression have not been fully described. This review systematically summarized the role of the PI3K/AKT signaling pathway in the pathogenesis of depression and discussed its potential in the treatment of depression. This will help in the treatment of depression and the development of antidepressants.

The Use of Ketamine for the Treatment of Anhedonia in Depression

Anhedonia, a complex symptom rooted in deficits across reward processes, is primarily linked to depression and schizophrenia but transcends diagnostic boundaries across various mental disorders. Its presence correlates with poorer clinical outcomes, including an increased risk of suicide and diminished response to treatment. The neurobiological underpinnings of anhedonia remain incompletely understood despite advancements in biomarkers and imaging that contribute to deeper insights. Ketamine, known for its rapid-acting antidepressant properties, appears to possess antianhedonic effects through a mechanism of action not fully elucidated. This effect appears to be independent of its antidepressant properties. Explorations into alternative antianhedonic treatments have been underway, yet lingering questions persist, underscoring the imperative need for ongoing research to advance the field.

Treating Depression to Improve Survival in Coronary Heart Disease: What Have We Learned?

Major depressive disorder is a well-established risk factor for cardiac events in patients with coronary heart disease, but clinical trials have produced little evidence that treating depression reliably improves cardiac event-free survival in these patients. In this review, we offer evidence that certain symptoms that commonly remain after otherwise successful treatment of depression-insomnia, fatigue, and anhedonia-independently predict cardiac events. This may help to explain the failure of previous depression treatment trials to improve cardiac event-free survival even when other symptoms of depression improve. We thus propose that adverse cardiovascular effects that have long been attributed to syndromal depression may be instead caused by persistent fatigue, insomnia, and anhedonia, regardless of whether other symptoms of depression are present. We also identify interventions for these symptoms and call for more research to evaluate their effectiveness in depressed patients with coronary heart disease.

Understanding the role of early life stress and schizophrenia on anxiety and depressive like outcomes: An experimental study

BACKGROUND

Adverse experiences due to early life stress (ELS) or parental psychopathology such as schizophrenia (SZ) have a significant implication on individual susceptibility to psychiatric disorders in the future. However, it is not fully understood how ELS affects social-associated behaviors as well as the developing prefrontal cortex (PFC).

OBJECTIVE

The aim of this study was to investigate the impact of ELS and ketamine induced schizophrenia like symptoms (KSZ) on anhedonia, social behavior and anxiety-like behavior.

METHODS

Male and female Sprague-Dawley rat pups were allocated randomly into eight experimental groups, namely control, gestational stress (GS), GS+KSZ, maternal separation (MS), MS+KSZ pups, KSZ parents, KSZ parents and Pups and KSZ pups only. ELS was induced by subjecting the pups to GS and MS, while schizophrenia like symptoms was induced through subcutaneous administration of ketamine. Behavioral assessment included sucrose preference test (SPT) and elevated plus maze (EPM), followed by dopamine testing and analysis of astrocyte density. Statistical analysis involved ANOVA and post hoc Tukey tests, revealing significant group differences and yielding insights into behavioral and neurodevelopmental impacts.

RESULTS

GS, MS, and KSZ (dams) significantly reduced hedonic response and increased anxiety-like responses (p < 0.05). Notably, the presence of normal parental mental health demonstrated a reversal of the observed decline in Glial Fibrillary Acidic Protein-positive astrocytes (GFAP+ astrocytes) (p < 0.05) and a reduction in anxiety levels, implying its potential protective influence on depressive-like symptoms and PFC astrocyte functionality.

CONCLUSION

The present study provides empirical evidence supporting the hypothesis that exposure to ELS and KSZ on dams have a significant impact on the on development of anxiety and depressive like symptoms in Sprague Dawley rats, while positive parenting has a reversal effect.

Experiential processing increases positive affect and decreases dampening appraisals during autobiographical memory recall in an anhedonic sample

Anhedonia is characterized by diminished reward processing, which may be explained in part by dampening appraisals, or thoughts that blunt positive emotions. Experiential processing, or attending to sensory and bodily experience, may curb dampening appraisals, as compared to analytical processing, or conceptually thinking about an event. In this study, 96 participants with elevated anhedonia completed writing tasks, in which they recalled positive autobiographical memories. Participants recalled the first memory as they naturally would to assess spontaneous use of processing mode and were then randomized to recall the second positive memory using either experiential, analytical, or control instructions. Both spontaneous and instructed experiential processing were associated with greater positive affect and less dampening compared to analytical processing. Clinical implications include savoring pleasant sensations to reduce dampening and enhance positive affect in anhedonia.

Association of anhedonia with brain-derived neurotrophic factor and interleukin-10 in major depressive disorder

BACKGROUND

Anhedonia, a core symptom of major depressive disorder (MDD), manifests in two forms: anticipatory and consummatory, reflecting a diminished capacity to anticipate or enjoy pleasurable activities. Prior studies suggest that brain-derived neurotrophic factor (BDNF) and interleukin-10 (IL-10) may play key roles in the emergence of anhedonia in MDD. The specific relationships between these biomarkers and the two forms of anhedonia remain unclear. This study investigated the potential links between BDNF, IL-10, and both forms of anhedonia in MDD patients.

METHODS

This study included 43 participants diagnosed with MDD and 58 healthy controls. It involved detailed assessments of depression and anxiety levels, anticipatory and consummatory pleasure, cognitive functions, and a broad spectrum of plasma biomarkers, such as C-reactive protein, various interleukins, and BDNF. Using partial correlation, variables related to pleasant experiences were identified. Stepwise multiple linear regression analysis was applied to pinpoint the independent predictors of anhedonia in the MDD group.

RESULTS

Demographically, both groups were comparable in terms of age, sex, body mass index, educational year, and marital status. Individuals with MDD displayed markedly reduced levels of anticipatory and consummatory pleasure, higher anxiety, and depression scores compared to healthy controls. Additionally, cognitive performance was notably poorer in the MDD group. These patients also had lower plasma diamine oxidase levels. Analysis linked anhedonia to impaired delayed memory. Regression results identified IL-10 and BDNF as independent predictors of anticipatory and consummatory anhedonia, respectively.

CONCLUSION

These findings demonstrate that anticipatory and consummatory anhedonia are influenced by independent factors, thereby providing critical insights into the distinct neuroimmunological mechanisms that underlie various forms of anhedonia. Clinicl Trial Registration Number: NCT03790085.

Platelet Levels of Brain-Derived Neurotrophic Factor in Adults with Autism Spectrum Disorder: Is There a Specific Association with Autism Spectrum Psychopathology?

To date, although several studies have investigated the circulating levels of brain-derived neurotrophic factor (BDNF) in children with autism spectrum disorder (ASD), only a few authors have addressed their evaluation in adults. Furthermore, an important limitation of these studies lies in the fact that circulating BDNF is stored in platelets and released into the circulation when needed. To the best of our knowledge, a very limited number of studies have related peripheral BDNF values to platelet counts, and yet no study has evaluated intra-platelet BDNF levels in adults with ASD. In this framework, the aim of the present work is to pave the way in this field and evaluate platelet BNDF levels in adult ASD patients, as well as their correlation with autistic symptoms and related psychopathological dimensions. We recruited 22 ASD and 22 healthy controls, evaluated with the Adult autism subthreshold spectrum (AdAS Spectrum), the Social Anxiety Spectrum-self report (SHY-SR), the Trauma and loss spectrum-self report (TALS-SR), the Work and Social Adjustment Scale (WSAS), and the Mood Spectrum-self report for suicidality. Intra-platelet BDNF levels were also assessed. The results highlighted lower BDNF levels in the ASD group; moreover, AdAS Spectrum and WSAS total score as well as AdAS Spectrum Restricted interest and rumination, WSAS Private leisure activities, TALS-SR Arousal, and SHY-SR Childhood domains were significant negative predictors of platelet BDNF levels.

From movement to motivation: a proposed framework to understand the antidepressant effect of exercise

Depression is the leading cause of disability worldwide, exerting a profound negative impact on quality of life in those who experience it. Depression is associated with disruptions to several closely related neural and cognitive processes, including dopamine transmission, fronto-striatal brain activity and connectivity, reward processing and motivation. Physical activity, especially aerobic exercise, reduces depressive symptoms, but the mechanisms driving its antidepressant effects are poorly understood. Here we propose a novel hypothesis for understanding the antidepressant effects of exercise, centred on motivation, across different levels of explanation. There is robust evidence that aerobic exercise decreases systemic inflammation. Inflammation is known to reduce dopamine transmission, which in turn is strongly implicated in effort-based decision making for reward. Drawing on a broad range of research in humans and animals, we propose that by reducing inflammation and boosting dopamine transmission, with consequent effects on effort-based decision making for reward, exercise initially specifically improves 'interest-activity' symptoms of depression-namely anhedonia, fatigue and subjective cognitive impairment - by increasing propensity to exert effort. Extending this framework to the topic of cognitive control, we explain how cognitive impairment in depression may also be conceptualised through an effort-based decision-making framework, which may help to explain the impact of exercise on cognitive impairment. Understanding the mechanisms underlying the antidepressant effects of exercise could inform the development of novel intervention strategies, in particular personalised interventions and boost social prescribing.

Developmental exposure to 17-α-hydroxyprogesterone caproate disrupts decision-making in adult female rats: A potential role for a dopaminergic mechanism

The synthetic progestin, 17α-hydroxyprogesterone caproate (17-OHPC), is administered to pregnant individuals at risk for preterm birth and is likely transferred from mother to fetus. Yet, there is little information regarding the potential effects of 17-OHPC administration on behavioral and neural development in offspring. In rats, neonatal 17-OHPC exposure altered dopaminergic fiber distribution and density in the prelimbic medial prefrontal cortex (mPFC) in neonates and adolescents, respectively. Additionally, neonatal 17-OHPC exposure in male rats increased response omissions in a delay discounting task of impulsive decision-making. Because developmental 17-OHPC exposure has differential effects in males and females, investigating the effects of 17-OHPC on impulsive decision-making in female rats is necessary. The present study tested the effects of developmental 17-OHPC exposure (P1-P14) in a delay discounting task in which female rats chose between a small immediate reward and a larger delayed (0, 15 30, or 45 s) reward. 17-OHPC-exposed females made more omissions than controls. There was no effect of 17-OHPC on large reward preference nor on response time, and omissions were similar during both free- and forced-choice trials. The present study also aimed to investigate the neural mechanisms underlying omissions in 17-OHPC-exposed female rats. The dopamine transporter inhibitor, methylphenidate (MPH), was administered prior to delay discounting testing. MPH treatment did not reduce omissions in 17-OHPC-exposed females. If anything, MPH increased omissions in control females nearly fourfold during the longest delays. These results suggest that developmental 17-OHPC exposure increased omissions without affecting impulsivity or slowing decision-making. Furthermore, omissions may be regulated, at least in part, by dopaminergic mechanisms.

PET/CT study of dopamine transporter (DAT) binding with the triple reuptake inhibitor toludesvenlafaxine in rats and humans

PURPOSE

Toludesvenlafaxine is a recently developed antidepressant that belongs to the triple reuptake inhibitor class. Despite the in vitro evidence that toludesvenlafaxine inhibits the reuptake of serotonin (5-HT), norepinephrine (NE) and dopamine (DA), there is no in vivo evidence that toludesvenlafaxine binds to DAT and increases DA level, a mechanism thought to contribute to its favorable clinical performance.

METHODS

Positron emission tomography/computed tomography (PET/CT) was used to examine the DAT binding capacity in healthy rats and human subjects and microdialysis was used to examine the striatal DA level in rats. [18F]FECNT and [11C]CFT were used as PET/CT radioactive tracer for rat and human studies, respectively.

RESULTS

In rats, 9 mg/kg of toludesvenlafaxine hydrochloride (i.v.) followed by an infusion of 3 mg/kg via minipump led to the binding rate to striatum DAT at 3.7 - 32.41% and to hypothalamus DAT at 5.91 - 17.52% during the 45 min scanning period. 32 mg/kg oral administration with toludesvenlafaxine hydrochloride significantly increased the striatal DA level with the AUC0 - 180 min increased by 63.9%. In healthy volunteers, 160 mg daily toludesvenlafaxine hydrochloride sustained-release tablets for 4 days led to an average occupancy rates of DAT at 8.04% ± 7.75% and 8.09% ± 7.00%, respectively, in basal ganglion 6 h and 10 h postdose.

CONCLUSION

These results represent the first to confirm the binding of toludesvenlafaxine to DAT in both rats and humans using PET/CT, and its elevation of brain DA level, which may help understand the unique pharmacological and functional effects of triple reuptake inhibitors such as toludesvenlafaxine.

CLINICALTRIALS

GOV IDENTIFIERS

NCT05905120. Registered 14 June 2023. (retrospectively registered).

Everyday emotion, naturalistic life stress, and the prospective prediction of adolescent depression

BACKGROUND AND OBJECTIVES

Increasing research underscores low positive emotion (PE) as a vital component of depression risk in adolescence. Theory also suggests that PE contributes to adaptive coping. However, it is unclear whether naturalistic experiences of emotions contribute to long-term depression risk, or whether daily PE levels equip adolescents to cope with later naturalistic stressors, reducing risk for depression. The current study examines whether PE (and negative emotion [NE]) assessed via ecological momentary assessment (EMA) (a) predict prospective increases in depression, and (b) moderate the association between later life stressors and depression.

DESIGN

Longitudinal study of community-recruited adolescents, with EMA at baseline.

METHOD

Adolescents (n = 232) completed contextual threat life stress interviews, interview and self-report measures of depression at baseline and 1.5 year follow-up. At baseline, they completed a seven-day EMA of emotion.

RESULTS

Preregistered analyses showed that daily NE, but not PE, predicted increased depression over time and moderated the association between interpersonal episodic stress and self-reported depression.

CONCLUSIONS

Results did not support daily PE as a buffer against depressogenic effects of life stress, but point to daily NE as a marker of depression risk.

Behavioral Activation and Brain Network Changes in Depression

Behavioral activation (BA) is a well-established method of evidence-based treatment for depression. There are clear links between the neural mechanisms underlying reward processing and BA treatment for depressive symptoms, including anhedonia; however, integrated interpretations of these two domains are lacking. Here we examine brain imaging studies involving BA treatments to investigate how changes in brain networks, including the reward networks, mediate the therapeutic effects of BA, and whether brain circuits are predictors of BA treatment responses. Increased activation of the prefrontal and subcortical regions associated with reward processing has been reported after BA treatment. Activation of these regions improves anhedonia. Conversely, some studies have found decreased activation of prefrontal regions after BA treatment in response to cognitive control stimuli in sad contexts, which indicates that the therapeutic mechanism of BA may involve disengagement from negative or sad contexts. Furthermore, the decrease in resting-state functional connectivity of the default-mode network after BA treatment appears to facilitate the ability to counteract depressive rumination, thereby promoting enjoyable and valuable activities. Conflicting results suggest that an intact neural response to rewards or defective reward functioning is predictive of the efficacy of BA treatments. Increasing the benefits of BA treatments requires identification of the unique individual characteristics determining which of these conflicting findings are relevant for the personalized treatment of each individual with depression.

Brain stimulation over the left DLPFC enhances motivation for effortful rewards in patients with major depressive disorder

BACKGROUND

Amotivation is a typical feature in major depressive disorder (MDD), which produces reduced willingness to exert effort. The dorsolateral prefrontal cortex (DLPFC) is a crucial structure in goal-directed actions and therefore is a potential target in modulating effortful motivation. However, it remains unclear whether the intervention is effective for patients with MDD.

METHODS

We employed transcranial magnetic stimulation (TMS), computational modelling and event-related potentials (ERPs) to reveal the causal relationship between the left DLPFC and motivation for effortful rewards in MDD. Fifty patients underwent both active and sham TMS sessions, each followed by performing an Effort-Expenditure for Rewards Task, during which participants chose and implemented between low-effort/low-reward and high-effort/high-reward options.

RESULTS

The patients showed increased willingness to exert effort for rewards during the DLPFC facilitated session, compared with the sham session. They also had a trend in larger P3 amplitude for motivated attention toward chosen options, larger CNV during preparing for effort exertion, and larger SPN during anticipating a high reward. Besides, while behavior indexes for effortful choices were negatively related to depression severity in the sham session, this correlation was weakened in the active stimulation session.

CONCLUSIONS

These findings provide behavioral, computational, and neural evidence for the left DLPFC on effortful motivation for rewards. Facilitated DLPFC improves motor preparation and value anticipation after making decisions especially for highly effortful rewards in MDD. Facilitated DLPFC also has a potential function in enhancing motivated attention during cost-benefit trade-off. This neuromodulation effect provides a potential treatment for improving motivation in clinics.

Non-invasive vagus nerve stimulation conditions increased invigoration and wanting in depression

BACKGROUND

Major depressive disorder (MDD) is often marked by impaired motivation and reward processing, known as anhedonia. Many patients do not respond to first-line treatments, and improvements in motivation can be slow, creating an urgent need for rapid interventions. Recently, we demonstrated that transcutaneous auricular vagus nerve stimulation (taVNS) acutely boosts effort invigoration in healthy participants, but its effects on depression remain unclear.

OBJECTIVE

To assess the impact of taVNS on effort invigoration and maintenance in a sample that includes patients with MDD, evaluating the generalizability of our findings.

METHODS

We used a single-blind, randomized crossover design in 30 patients with MDD and 29 matched (age, sex, and BMI) healthy control participants (HCP).

RESULTS

Consistent with prior findings, taVNS increased effort invigoration for rewards in both groups during Session 1 (p = .040), particularly for less wanted rewards in HCP (pboot < 0.001). However, invigoration remained elevated in all participants, and no acute changes were observed in Session 2 (Δinvigoration = 3.3, p = .12). Crucially, throughout Session 1, we found taVNS-induced increases in effort invigoration (pboot = 0.008) and wanting (pboot = 0.010) in patients with MDD, with gains in wanting maintained across sessions (Δwanting = 0.06, p = .97).

CONCLUSIONS

Our study replicates the invigorating effects of taVNS in Session 1 and reveals its generalizability to depression. Furthermore, we expand upon previous research by showing taVNS-induced conditioning effects on invigoration and wanting within Session 1 in patients that were largely sustained. While enduring motivational improvements present challenges for crossover designs, they are highly desirable in interventions and warrant further follow-up research.

Cross-Sectional and Longitudinal Association of Clinical and Neurocognitive Factors With Apathy in Patients With Parkinson Disease

BACKGROUND AND OBJECTIVES

A robust understanding of the natural history of apathy in Parkinson disease (PD) is foundational for developing effective clinical management tools. However, large longitudinal studies are lacking while the literature is inconsistent about even cross-sectional associations. We aimed to determine the longitudinal predictors of apathy development in a large cohort of people with PD and its cross-sectional associations and trajectories over time, using sophisticated Bayesian modeling techniques.

METHODS

People with PD followed up in the longitudinal New Zealand Parkinson's progression project were included. Apathy was defined using the neuropsychiatric inventory subscale ≥4, and analyses were also repeated using a less stringent cutoff of ≥1. Both MoCA and comprehensive neuropsychological testing were used as appropriate to the model. Depression was assessed using the hospital anxiety and depression scale. Cross-sectional Bayesian regressions were conducted, and a multistate predictive model was used to identify factors that predict the initial onset of apathy in nonapathetic PD, while also accounting for the competing risk of death. The relationship between apathy presence and mortality was also investigated.

RESULTS

Three hundred forty-six people with PD followed up for up to 14 years across a total of 1,392 sessions were included. Apathy occurrence did not vary significantly across the disease course (disease duration odds ratio [OR] = 0.55, [95% CI 0.28-1.12], affecting approximately 11% or 22% of people at any time depending on the NPI cutoff used. Its presence was associated with a significantly higher risk of death after controlling for all other factors (hazard ratio [HR] = 2.92 [1.50-5.66]). Lower cognition, higher depression levels, and greater motor severity predicted apathy development in those without motivational deficits (HR [cognition] = 0.66 [0.48-0.90], HR [depression] = 1.45 [1.04-2.02], HR [motor severity] = 1.37 [1.01-1.86]). Cognition and depression were also associated with apathy cross-sectionally, along with male sex and possibly lower dopaminergic therapy level, but apathy still occurred across the full spectrum of each variable (OR [cognition] = 0.58 [0.44-0.76], OR [depression] = 1.43 [1.04-1.97], OR [female sex] = 0.45 [0.22-0.92], and OR [levodopa equivalent dose] = 0.78 [0.59-1.04].

DISCUSSION

Apathy occurs across the PD time course and is associated with higher mortality. Depressive symptoms and cognitive impairment in particular predict its future development in those with normal motivation.

Ketamine treatment for anhedonia in unipolar and bipolar depression: a systematic review

Ketamine, an N-methyl-D-aspartate receptor antagonist, is a racemic mixture of esketamine and arketamine used to treat unipolar and bipolar depression. Preliminary reports indicate that it may be beneficial for depressed patients reporting symptoms of anhedonia. In this systematic review we aim to assess and analyze the existing body of evidence regarding the therapeutic effects of ketamine on the domain of anhedonia. Electronic databases (PubMed, APA Psycinfo and Web of Science) were searched from inception to November 2023. Protocol was registered in PROSPERO under the identifier CRD42023476603. A total of twenty-two studies, including four randomized-controlled trials and eighteen open-label trials were included. All studies reported alleviation of anhedonia symptoms following ketamine or esketamine administration, regardless of the number of infusions. Several important limitations were included, first and foremost low number of placebo-controlled randomized-controlled trials. This review indicates a potential anti-anhedonic effect of ketamine in patients with depression. Several trials used neuroimaging techniques which confirm ketamine's effect on functional connectivity correlating with the improvement in anhedonia. Despite considerable variations in methodology and the specific brain regions investigated, these studies collectively point towards ketamine's neuroplastic effects in mitigating anhedonia.

Prenatal Iodine Intake and Maternal Pregnancy and Postpartum Depressive and Anhedonia Symptoms: Findings from a Multiethnic US Cohort

Objective: Emerging evidence suggests that essential trace elements, including iodine, play a vital role in depressive disorders. This study investigated whether prenatal dietary iodine intake alone and in combination with supplemental iodine intake during pregnancy were associated with antepartum and postpartum depressive and anhedonia symptoms. Methods: The study population included 837 mothers in the PRogramming of Intergenerational Stress Mechanisms (PRISM) study. The modified BLOCK food frequency questionnaire was used to estimate prenatal dietary and supplemental iodine intake, while the 10-item Edinburg Postpartum Depression Scale (EPDS) ascertained depressive symptoms. Analyses considered the global EPDS score and the anhedonia and depressive symptom subscale scores using dichotomized cutoffs. Logistic regression estimating odds ratios and 95% confidence intervals (CIs) assessed associations of iodine intake in the second trimester of pregnancy and 6-month postpartum depressive and anhedonia symptoms considering dietary intake alone and combined dietary and supplementary intake in separate models. Results: Most women were Black/Hispanic Black (43%) and non-Black Hispanics (35%), with 39% reporting a high school education or less. The median (interquartile range, IQR) dietary and supplemental iodine intake among Black/Hispanic Black (198 (115, 337) µg/day) and non-Black Hispanic women (195 (126, 323) µg/day) was higher than the overall median intake level of 187 (116, 315) µg/day. Relative to the Institute of Medicine recommended iodine intake level of 160-220 µg/day, women with intake levels < 100 µg/day, 100-<160 µg/day, >220-<400 µg/day and ≥400 µg/day had increased adjusted odds of 6-month postpartum anhedonia symptoms (aOR = 1.74 (95% CI: 1.08, 2.79), 1.25 (95% CI: 0.80, 1.99), 1.31 (95% CI: 0.82, 2.10), and 1.47 (95% CI: 0.86, 2.51), respectively). The corresponding estimates for postpartum global depressive symptoms were similar but of smaller magnitude. Conclusions: Prenatal iodine intake, whether below or above the recommended levels for pregnant women, was most strongly associated with greater anhedonia symptoms, particularly in the 6-month postpartum period. Further studies are warranted to corroborate these findings, as dietary and supplemental iodine intake are amenable to intervention.

The computational structure of consummatory anhedonia

Anhedonia is a reduction in enjoyment, motivation, or interest. It is common across mental health disorders and a harbinger of poor treatment outcomes. The enjoyment aspect, termed 'consummatory anhedonia', in particular poses fundamental questions about how the brain constructs rewards: what processes determine how intensely a reward is experienced? Here, we outline limitations of existing computational conceptualisations of consummatory anhedonia. We then suggest a richer reinforcement learning (RL) account of consummatory anhedonia with a reconceptualisation of subjective hedonic experience in terms of goal progress. This accounts qualitatively for the impact of stress, dysfunctional cognitions, and maladaptive beliefs on hedonic experience. The model also offers new views on the treatments for anhedonia.

Effect of venlafaxine on anhedonia and amotivation in patients with major depressive disorder

OBJECTIVE

Serotonin norepinephrine reuptake inhibitors (SNRIs) have been postulated to afford benefits in alleviating anhedonia and amotivation. This post hoc pooled analysis evaluated the effect of venlafaxine XR, an SNRI, on these symptoms in patients with major depressive disorder (MDD).

METHODS

Data was pooled from five short-term randomized, placebo-controlled studies of venlafaxine XR for the treatment of MDD, comprising 1087 (venlafaxine XR, n = 585; placebo, n = 502) adult subjects. The change from baseline score in the MADRS anhedonia factor (based on items 1 [apparent sadness], 2 [reported sadness], 6 [concentration difficulties], 7 [lassitude], and 8 [inability to feel]) for anhedonia, and in motivational deficits (based on 3 items of HAM-D17: involvement in work and activities, psychomotor retardation, and energy level [ie, general somatic symptoms]) for amotivation, were measured through 8 weeks. Mixed model repeated measures (MMRMs) were used to analyze changes over time and ANCOVA to analyze the change from baseline at week 8 with LOCF employed to handle missing data.

RESULTS

At the end of 8 weeks, the change from baseline was significantly greater in patients on venlafaxine XR in both anhedonia (mean, 95% CI: -2.73 [-3.63, -1.82], p < 0.0001) and amotivation scores (mean, 95% CI: -0.78 [-1.04, -0.52], p < 0.0001) than those on placebo. For both measures, the between-group separation from baseline was statistically significant starting from week 2 onwards, and it increased over time.

CONCLUSION

This analysis demonstrates that venlafaxine XR is effective in improving symptoms of anhedonia and motivational deficits in patients with MDD.

Reward motivation adaptation in people with negative schizotypal features: development of a novel behavioural paradigm and identifying its neural correlates using resting-state functional connectivity analysis

Reward motivation in individuals with high levels of negative schizotypal traits (NS) has been found to be lower than that in their counterparts. But it is unclear that whether their reward motivation adaptively changes with external effort-reward ratio, and what resting-state functional connectivity (rsFC) is associated with this change. Thirty-five individuals with high levels of NS and 44 individuals with low levels of NS were recruited. A 3T resting-state functional brain scan and a novel reward motivation adaptation behavioural task were administrated in all participants. The behavioural task was manipulated with three conditions (effort > reward condition vs. effort < reward condition vs. effort = reward condition). Under each condition were rated 'wanting' and 'liking' for rewards. The seed-based voxel-wise rsFC analysis was conducted to explore the rsFCs associated with the 'wanting' and 'liking' ratings in individuals with high levels of NS. 'Wanting' and 'liking' ratings of individuals with high levels of NS significantly declined in the effort > reward condition but did not rebound as high as their counterparts in the effort < reward condition. The rsFCs in NS group associated with these ratings were altered. The altered rsFCs in NS group involved regions in the prefrontal lobe, dopaminergic brain regions (ventral tegmental area, substantia nigra), hippocampus, thalamus and cerebellum. Individuals with high levels of NS manifested their reward motivation adaptation impairment as a failure of adjustment adaptively during effort-reward imbalance condition and altered rsFCs in prefrontal, dopaminergic and other brain regions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Modulation of habenular and nucleus accumbens functional connectivity by ketamine in major depression

INTRODUCTION

Major depressive disorder (MDD) is associated with dysfunctional reward processing, which involves functional circuitry of the habenula (Hb) and nucleus accumbens (NAc). Since ketamine elicits rapid antidepressant and antianhedonic effects in MDD, this study sought to investigate how serial ketamine infusion (SKI) treatment modulates static and dynamic functional connectivity (FC) in Hb and NAc functional networks.

METHODS

MDD participants (n = 58, mean age = 40.7 years, female = 28) received four ketamine infusions (0.5 mg/kg) 2-3 times weekly. Resting-state functional magnetic resonance imaging (fMRI) scans and clinical assessments were collected at baseline and 24 h post-SKI. Static FC (sFC) and dynamic FC variability (dFCv) were calculated from left and right Hb and NAc seeds to all other brain regions. Changes in FC pre-to-post SKI, and correlations with changes with mood and anhedonia were examined. Comparisons of FC between patients and healthy controls (HC) at baseline (n = 55, mean age = 32.6, female = 31), and between HC assessed twice (n = 16) were conducted as follow-up analyses.

RESULTS

Following SKI, significant increases in left Hb-bilateral visual cortex FC, decreases in left Hb-left inferior parietal cortex FC, and decreases in left NAc-right cerebellum FC occurred. Decreased dFCv between left Hb and right precuneus and visual cortex, and decreased dFCv between right NAc and right visual cortex both significantly correlated with improvements in mood ratings. Decreased FC between left Hb and bilateral visual/parietal cortices as well as increased FC between left NAc and right visual/parietal cortices both significantly correlated with improvements in anhedonia. No differences were observed between HC at baseline or over time.

CONCLUSION

Subanesthetic ketamine modulates functional pathways linking the Hb and NAc with visual, parietal, and cerebellar regions in MDD. Overlapping effects between Hb and NAc functional systems were associated with ketamine's therapeutic response.

Web-Based Imagery Behavioral Activation (WIMBA): Study Protocol for a Randomized Controlled Trial Testing the Effects, Acceptability, and Feasibility of a Mental Imagery Activity Scheduling Training Delivered Online

Background

Behavioral activation (BA) is an effective and efficacious treatment for depression. Activity scheduling is the central treatment component of BA and involves planning of potentially enjoyable and rewarding activities. Evidence from non-clinical studies suggests that mental imagery simulations of planned activities can increase motivation and anticipated pleasure for these activities.

Method

We describe a randomized controlled trial testing a mental imagery activity scheduling training delivered online in four weekly sessions (total training duration approximately 90 minutes) in a sample meeting diagnostic criteria of a major depressive episode, as indicated by the Diagnostic Short-Interview for Mental Disorders (Mini-DIPS), and not currently receiving treatment. Participants (N = 140) will be randomized to either mental imagery activity scheduling or a wait-list control condition. Depressive symptoms (BDI-II) and behavioral activation (BADS) are the primary outcomes; BDI-II will be measured at Session 1, Session 4, and at two-week follow-up, BADS at Sessions 1-4 and at two-week follow-up.

Discussion

It is discussed how the expected results may reflect mechanisms and effects of a mental imagery activity scheduling training delivered online in a sample of individuals with depression. Concluding we outline next steps for future research and highlight the potential of this novel treatment for dissemination in the wider community and integration into routine care.

Beyond the serotonin deficit hypothesis: communicating a neuroplasticity framework of major depressive disorder

The serotonin deficit hypothesis explanation for major depressive disorder (MDD) has persisted among clinicians and the general public alike despite insufficient supporting evidence. To combat rising mental health crises and eroding public trust in science and medicine, researchers and clinicians must be able to communicate to patients and the public an updated framework of MDD: one that is (1) accessible to a general audience, (2) accurately integrates current evidence about the efficacy of conventional serotonergic antidepressants with broader and deeper understandings of pathophysiology and treatment, and (3) capable of accommodating new evidence. In this article, we summarize a framework for the pathophysiology and treatment of MDD that is informed by clinical and preclinical research in psychiatry and neuroscience. First, we discuss how MDD can be understood as inflexibility in cognitive and emotional brain circuits that involves a persistent negativity bias. Second, we discuss how effective treatments for MDD enhance mechanisms of neuroplasticity-including via serotonergic interventions-to restore synaptic, network, and behavioral function in ways that facilitate adaptive cognitive and emotional processing. These treatments include typical monoaminergic antidepressants, novel antidepressants like ketamine and psychedelics, and psychotherapy and neuromodulation techniques. At the end of the article, we discuss this framework from the perspective of effective science communication and provide useful language and metaphors for researchers, clinicians, and other professionals discussing MDD with a general or patient audience.

New clues for the role of cerebellum in schizophrenia and the associated cognitive impairment

Schizophrenia (SZ) is a complex neuropsychiatric disorder associated with severe cognitive dysfunction. Although research has mainly focused on forebrain abnormalities, emerging results support the involvement of the cerebellum in SZ physiopathology, particularly in Cognitive Impairment Associated with SZ (CIAS). Besides its role in motor learning and control, the cerebellum is implicated in cognition and emotion. Recent research suggests that structural and functional changes in the cerebellum are linked to deficits in various cognitive domains including attention, working memory, and decision-making. Moreover, cerebellar dysfunction is related to altered cerebellar circuit activities and connectivity with brain regions associated with cognitive processing. This review delves into the role of the cerebellum in CIAS. We initially consider the major forebrain alterations in CIAS, addressing impairments in neurotransmitter systems, synaptic plasticity, and connectivity. We then focus on recent findings showing that several mechanisms are also altered in the cerebellum and that cerebellar communication with the forebrain is impaired. This evidence implicates the cerebellum as a key component of circuits underpinning CIAS physiopathology. Further studies addressing cerebellar involvement in SZ and CIAS are warranted and might open new perspectives toward understanding the physiopathology and effective treatment of these disorders.

Aticaprant: (a κ-opioid receptor antagonist) for major depressive disorder

INTRODUCTION

Major depression is a common, disabling mental health condition associated with the highest disease burden for any neuropsychiatric disorder worldwide, according to the WHO. Due to the imperfect efficacy and tolerability profiles of existing treatments, investigational compounds in novel treatment classes are needed. Opioid-receptor antagonists are a potential new class of treatments currently under investigation.

AREAS COVERED

Major depressive disorder is first overviewed. Existing treatments, both their mechanisms of action and their place within the antidepressant space, are discussed herein. Then, the profile of Aticaprant and the wider context of kappa-opioid antagonism for depression are discussed in focus.

EXPERT OPINION

Early evidence indicates that Aticaprant may possess desirable pharmacodynamic and pharmacokinetic properties. A lack of convincing efficacy data at the time of writing precludes any definitive statement on its potential as an antidepressant.

Using Drift Diffusion and RL Models to Disentangle Effects of Depression On Decision-Making vs. Learning in the Probabilistic Reward Task

The Probabilistic Reward Task (PRT) is widely used to investigate the impact of Major Depressive Disorder (MDD) on reinforcement learning (RL), and recent studies have used it to provide insight into decision-making mechanisms affected by MDD. The current project used PRT data from unmedicated, treatment-seeking adults with MDD to extend these efforts by: (1) providing a more detailed analysis of standard PRT metrics-response bias and discriminability-to better understand how the task is performed; (2) analyzing the data with two computational models and providing psychometric analyses of both; and (3) determining whether response bias, discriminability, or model parameters predicted responses to treatment with placebo or the atypical antidepressant bupropion. Analysis of standard metrics replicated recent work by demonstrating a dependency between response bias and response time (RT), and by showing that reward totals in the PRT are governed by discriminability. Behavior was well-captured by the Hierarchical Drift Diffusion Model (HDDM), which models decision-making processes; the HDDM showed excellent internal consistency and acceptable retest reliability. A separate "belief" model reproduced the evolution of response bias over time better than the HDDM, but its psychometric properties were weaker. Finally, the predictive utility of the PRT was limited by small samples; nevertheless, depressed adults who responded to bupropion showed larger pre-treatment starting point biases in the HDDM than non-responders, indicating greater sensitivity to the PRT's asymmetric reinforcement contingencies. Together, these findings enhance our understanding of reward and decision-making mechanisms that are implicated in MDD and probed by the PRT.

Aberrant effort-based reward dynamics in anhedonia

Anhedonia is a transdiagnostic symptom and associated with a spectrum of reward deficits among which the motivational dysfunction is poorly understood. Previous studies have established the abnormal cost-benefit trade-off as a contributor to motivational deficits in anhedonia and its relevant psychiatric diseases. However, it remains elusive how the anhedonic neural dynamics underlying reward processing are modulated by effort expenditure. Using an effort-based monetary incentive delay task, the current event-related potential study examined the neural dynamics underlying the effort-reward interplay in anhedonia using a nonclinical sample who scored high or low on an anhedonia questionnaire. We found that effort prospectively decreased reward effect on the contingent variation negativity and the target-P3 but retrospectively enhanced outcome effect on the feedback-P3 following effort expenditure. Compared to the low-anhedonia group, the high-anhedonia group displayed a diminished effort effect on the target-P3 during effort expenditure and an increased effort-enhancement effect for neutral trials during the feedback-P3 period following effort expenditure. Our findings suggest that anhedonia is associated with an inefficient control and motivation allocation along the efforted-based reward dynamics from effort preparation to effort production.

Studying the social mind: An updated summary of findings from the Vietnam Head Injury Study

Lesion mapping studies allow us to evaluate the potential causal contribution of specific brain areas to human cognition and complement other cognitive neuroscience methods, as several authors have recently pointed out. Here, we present an updated summary of the findings from the Vietnam Head Injury Study (VHIS) focusing on the studies conducted over the last decade, that examined the social mind and its intricate neural and cognitive underpinnings. The VHIS is a prospective, long-term follow-up study of Vietnam veterans with penetrating traumatic brain injury (pTBI) and healthy controls (HC). The scope of the work is to present the studies from the latest phases (3 and 4) of the VHIS, 70 studies since 2011, when the Raymont et al. paper was published (Raymont et al., 2011). These studies have contributed to our understanding of human social cognition, including political and religious beliefs, theory of mind, but also executive functions, intelligence, and personality. This work finally discusses the usefulness of lesion mapping as an approach to understanding the functions of the human brain from basic science and clinical perspectives.

The Swedish version of the Motivation and Pleasure Scale self-report (MAP-SR): psychometric properties in patients with schizophrenia or depression

PURPOSE

Negative symptoms are commonly regarded as a symptom dimension belonging to schizophrenia spectrum disorders but are also present in depression. The recently developed Clinical Assessment Interview for Negative Symptoms (CAINS) has shown to be reliable and valid. A corresponding self-report questionnaire has also been developed, named the Motivation and Pleasure Scale - Self Report (MAP-SR). The purpose was to evaluate the psychometric properties of the Swedish version of the MAP-SR in patients with either schizophrenia or depression.

MATERIALS AND METHODS

The MAP-SR was translated to Swedish. Participants were 33 patients with schizophrenia spectrum disorders and 52 patients with a depressive disorder and they completed the MAP-SR, the CAINS and other measures assessing adjacent psychopathology, functioning and cognition.

RESULTS

The internal consistency for the MAP-SR was adequate in both groups (schizophrenia spectrum α = .93, depressive disorder α = .82). Furthermore, the MAP-SR had a large correlation to the motivation and pleasure subscale of the CAINS in patients with schizophrenia disorders (r = -0.75, p < .001), however among patients with depression this correlation was medium-to-large (r = -0.48, p < 0.001).

CONCLUSIONS

Findings suggest that the Swedish version of the MAP-SR shows promise as a useful measure of motivation and pleasure, especially in patients with schizophrenia spectrum disorders. Furthermore, results also suggest that the MAP-SR does not assess negative symptoms specifically, but that there is an overlap between depressive and negative symptoms.

Hypoactivation of ventromedial frontal cortex in major depressive disorder: an MEG study of the Reward Positivity

Background

The Reward Positivity (RewP) is sensitive and specific electrophysiological marker of reward receipt. These characteristics make it a compelling candidate marker of dysfunctional reward processing in major depressive disorder. We previously proposed that the RewP is a nexus of multiple aspects of reward variance, and that a diminished RewP in depression might only reflect a deficit in some of this variance. Specifically, we predicted a diminished ventromedial contribution in depression in the context of maintained reward learning.

Methods

Here we collected magnetoencephalographic (MEG) recordings of reward receipt in 43 individuals with major depressive disorder (MDD group) and 38 healthy controls (CTL group). MEG allows effective source estimation due to the absence of volume conduction that compromises electroencephalographic recordings.

Results

The MEG RewP analogue was generated by a broad set of cortical areas, yet only right ventromedial and right ventral temporal areas were diminished in MDD. These areas correlated with a principal component of anhedonia derived from multiple questionnaires. Compellingly, BA25 was the frontal region with the largest representation in both of these effects.

Conclusions

These findings not only advance our understanding underlying the computation of the RewP, but they also dovetail with convergent findings from other types of functional source imaging in depression, as well as from deep brain stimulation treatments. Together, these discoveries suggest that the RewP may be a valuable marker for objective assessment of reward affect and its disruption in major depression.

Annual Research Review: Neuroimmune network model of depression: a developmental perspective

Depression is a serious public health problem, and adolescence is an 'age of risk' for the onset of Major Depressive Disorder. Recently, we and others have proposed neuroimmune network models that highlight bidirectional communication between the brain and the immune system in both mental and physical health, including depression. These models draw on research indicating that the cellular actors (particularly monocytes) and signaling molecules (particularly cytokines) that orchestrate inflammation in the periphery can directly modulate the structure and function of the brain. In the brain, inflammatory activity heightens sensitivity to threats in the cortico-amygdala circuit, lowers sensitivity to rewards in the cortico-striatal circuit, and alters executive control and emotion regulation in the prefrontal cortex. When dysregulated, and particularly under conditions of chronic stress, inflammation can generate feelings of dysphoria, distress, and anhedonia. This is proposed to initiate unhealthy, self-medicating behaviors (e.g. substance use, poor diet) to manage the dysphoria, which further heighten inflammation. Over time, dysregulation in these brain circuits and the inflammatory response may compound each other to form a positive feedback loop, whereby dysregulation in one organ system exacerbates the other. We and others suggest that this neuroimmune dysregulation is a dynamic joint vulnerability for depression, particularly during adolescence. We have three goals for the present paper. First, we extend neuroimmune network models of mental and physical health to generate a developmental framework of risk for the onset of depression during adolescence. Second, we examine how a neuroimmune network perspective can help explain the high rates of comorbidity between depression and other psychiatric disorders across development, and multimorbidity between depression and stress-related medical illnesses. Finally, we consider how identifying neuroimmune pathways to depression can facilitate a 'next generation' of behavioral and biological interventions that target neuroimmune signaling to treat, and ideally prevent, depression in youth and adolescents.

Sex differences in anhedonia in bipolar depression: a resting-state fMRI study

Previous studies about anhedonia symptoms in bipolar depression (BD) ignored the unique role of gender on brain function. This study aims to explore the regional brain neuroimaging features of BD with anhedonia and the sex differences in these patients. The resting-fMRI by applying fractional amplitude of low-frequency fluctuation (fALFF) method was estimated in 263 patients with BD (174 high anhedonia [HA], 89 low anhedonia [LA]) and 213 healthy controls. The effects of two different factors in patients with BD were analyzed using a 3 (group: HA, LA, HC) × 2 (sex: male, female) ANOVA. The fALFF values were higher in the HA group than in the LA group in the right medial cingulate gyrus and supplementary motor area. For the sex-by-group interaction, the fALFF values of the right hippocampus, left medial occipital gyrus, right insula, and bilateral medial cingulate gyrus were significantly higher in HA males than in LA males but not females. These results suggested that the pattern of high activation could be a marker of anhedonia symptoms in BD males, and the sex differences should be considered in future studies of BD with anhedonia symptoms.

Rodent tests of depression and anxiety: Construct validity and translational relevance

Behavioral testing constitutes the primary method to measure the emotional states of nonhuman animals in preclinical research. Emerging as the characteristic tool of the behaviorist school of psychology, behavioral testing of animals, particularly rodents, is employed to understand the complex cognitive and affective symptoms of neuropsychiatric disorders. Following the symptom-based diagnosis model of the DSM, rodent models and tests of depression and anxiety focus on behavioral patterns that resemble the superficial symptoms of these disorders. While these practices provided researchers with a platform to screen novel antidepressant and anxiolytic drug candidates, their construct validity-involving relevant underlying mechanisms-has been questioned. In this review, we present the laboratory procedures used to assess depressive- and anxiety-like behaviors in rats and mice. These include constructs that rely on stress-triggered responses, such as behavioral despair, and those that emerge with nonaversive training, such as cognitive bias. We describe the specific behavioral tests that are used to assess these constructs and discuss the criticisms on their theoretical background. We review specific concerns about the construct validity and translational relevance of individual behavioral tests, outline the limitations of the traditional, symptom-based interpretation, and introduce novel, ethologically relevant frameworks that emphasize simple behavioral patterns. Finally, we explore behavioral monitoring and morphological analysis methods that can be integrated into behavioral testing and discuss how they can enhance the construct validity of these tests.

Annual Research Review: Puberty and the development of anhedonia - considering childhood adversity and inflammation

Anhedonia, or diminished pleasure and motivation, is a symptom of severe mental illness (e.g., depressive disorder, bipolar disorder, schizophrenia) that emerges during adolescence. Anhedonia is a pernicious symptom that is related to social impairments, treatment resistance, and suicide. As the mechanisms of anhedonia are postulated to include the frontostriatal circuitry and the dopamine neuromodulatory system, the development and plasticity of these systems during the vulnerable period of adolescence, as well as their sensitivity to pubertal hormones, suggest that pubertal maturation could play a role in the development of anhedonia. This review takes a developmental perspective, considering the possibility that anhedonia emerges in the context of pubertal maturation and adolescent development, with childhood adversity and chronic inflammation influencing neural reward systems to accelerate anhedonia's progression. Here, we review the relevant extant literature on the components of this model and suggest directions for future research.

Specific mechanisms underlying executive and emotional apathy: A phenotyping study

Apathy is a behavioral symptom prevalent both in neuropsychiatric pathologies and in the healthy population. However, the knowledge of the cognitive and neural mechanisms underlying apathy is still very limited, even if clinical and fMRI data support the existence of three forms of apathy (executive, emotional, initiative). These forms could be explained by the alteration of specific mechanisms. This present study's aim is to specify the cognitive and neuronal mechanisms of executive and emotional apathy. We used an EEG study conducted on 68 subjects comprising two groups of young people with specific executive or emotional phenotypes of apathy and one group with no apathy. Despite having symptom of apathy, participants were free of any neurological, metabolic, or psychiatric diagnoses and with high education. Two tasks were used: the DPX for cognitive control and the MID for motivation. Our results showed that distinct mechanisms underlie these two forms of apathy, and, for the first time, we specified these mechanisms. A deficit of the proactive control mode, reflected by a reduced probe-N2 amplitude in AY trials, underlies the executive form of apathy (p < .03), whereas liking motivational blunting, highlighted by a reduced LPP amplitude for financial loss, characterizes the emotional form (p < .04). The main limit of the results is that generalizability to the general population may be reduced since the apathetic samples were chosen for having a specific form of apathy. To conclude, better knowledge of these mechanisms informs new, more targeted treatments, both pharmacological and non-pharmacological, necessary for reducing the debilitating consequences of apathy.

The effect of noninvasive brain stimulation on anhedonia in patients with schizophrenia and depression: A systematic review and meta-analysis

Anhedonia is a transdiagnostic symptom found in patients with schizophrenia and depression. Current pharmacological interventions for anhedonia are unsatisfactory in a considerable proportion of patients. There has been growing interest in applying noninvasive brain stimulation (NIBS) to patients with anhedonia. However, evidence for the efficacy of NIBS for anhedonia remain inconsistent. This study systematically identified all studies that measured anhedonia and applied NIBS in patients with schizophrenia or depression. We conducted a search using the various databases in English (PubMed, EBSCOHost (PsycInfo/PsycArticles), Web of Science) and Chinese (China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform) languages, and reviewed original research articles on NIBS published from January 1989 to July 2023. Our search had identified 15 articles for quantitative synthesis, with three concerning schizophrenia samples, 11 concerning samples with depression, and one concerning both clinical samples. We conducted a meta-analysis based on the 15 included studies, and the results suggested that NIBS could improve anhedonia symptoms in schizophrenia patients and patients with depression, with a medium-to-large effect size. Our findings are preliminary, given the limited number of included studies. Future NIBS research should measure anhedonia as a primary outcome and should recruit transdiagnostic samples.

There is no happiness in positive affect: the pervasive misunderstanding of the rotated circumplex model

Research on positive affect (PA) and negative affect (NA) is often guided by the rotational variant of the circumplex model of affect (RCMA). According to the RCMA, PA and NA are posited to be orthogonal, with PA ranging from the union of positive valence and high activation (e.g., excited) to the union of negative valence and low activation (e.g., sluggish), and NA ranging from the union of negative valence and high activation (e.g., distressed) to the union of positive valence and low activation (e.g., relaxed). However, many authors incorrectly interpret the RCMA as positing that positively valenced affect (i.e., pleasure) and negatively valenced affect (i.e., displeasure)-rather than PA and NA, as defined in the RCMA-are orthogonal. This "received view" of the RCMA has led to significant confusion in the literature. The present paper articulates the "received view" of the RCMA and characterizes its prevalence in psychological research. A random sample of 140 empirical research articles on affect published in 14 high-impact journals covering a range of psychological subdisciplines were reviewed. Over half of the articles subscribing to the RCMA showed evidence of the "received view," demonstrating that misuse of the terms PA and NA in the context of the RCMA is rampant in the psychological literature. To reduce continued confusion in the literature, we recommend abandoning use of the terms positive affect and negative affect. We further recommend referring to the two dimensions of the RCMA as positive activation and negative activation, and the two poles of the valence dimension as positive valence and negative valence (or pleasure and displeasure).

How are irritability and anhedonia symptoms linked? A network approach

BACKGROUND

Anhedonia and irritability are two prevalent symptoms of major depressive disorder (MDD) that predict greater depression severity and poor outcomes, including suicidality. Although both symptoms have been proposed to result from paradoxical reward processing dysfunctions, the interactions between these symptoms remain unclear. Anhedonia is a multifaceted symptom reflecting impairments in multiple dimensions of reward processing (e.g., pleasure, desire, motivation, and effort) across distinct reward types (e.g., food, sensory experiences, social activities, hobbies) that may differentially interact with irritability. This study investigated the complex associations between anhedonia and irritability using network analysis.

METHOD

Participants (N = 448, Mage = 33.29, SD = 14.58) reported their symptoms of irritability on the Brief Irritability Test (Holtzman et al., 2015) and anhedonia (i.e., pleasure, desire, motivation, and effort dimensions across four reward types) on the Dimensional Anhedonia Rating Scale (Rizvi et al., 2015). A regularized Gaussian Graphical Model was built to estimate the network structure between items.

RESULTS

Irritability was negatively related to willingness to expand effort to obtain food/drinks (estimate = -0.18), social activities (-0.13), and hobbies (-0.12) rewards. Irritability was positively associated with a desire for food/drinks (0.12).

LIMITATIONS

Only a small proportion (5.8%) of our sample was clinical and the study design was cross-sectional.

CONCLUSION

A specific link between irritability and the effort dimension of the hedonic response across three reward types was identified. Investigating effort expenditure deficits with experimental paradigms may help us understand the mechanisms underlying the comorbidity between irritability and anhedonia in the context of MDD.

Measurement invariance of the Personality Inventory for DSM-5 across sex

Introduction

There has been an international movement towards dimensional models of personality disorders (PDs) in the last decades, which culminated in the publication of the Alternative Model of Personality Disorders (AMPD) in the Emerging Measures and Models section of the DSM-5. This model was accompanied by a APA-sanctioned Personality Inventory for DSM-5 (PID-5) for the assessment of the AMPD pathological personality traits. One major issue with the assessment of personality disorders pertains to sex differences, and measurement invariance across sex in assessment instruments for PDs is necessary in order to ensure non-biased evaluations and to make valid comparisons between men and women. This study aimed to provide more information on measurement invariance across sex for the PID-5, using both the original scoring approach provided by the authors of the instrument and the scoring approach suggested by the APA in the published version of the PID-5.

Methods

This study was conducted with a sample of 2273 participants from the general Québec (Canada) adult population aged 18 to 90 years (M = 46.59; SD = 16.32; 51.8% women).

Results

The original scoring approach model showed good fit to data after freeing paths between certain traits and reached strict invariance. The APA scoring approach also showed good fit to data and reached strict invariance, but needed an adjustment (path freed between Emotional lability and Impulsivity in men) to reach scalar invariance.

Discussion

In line with previous research, the PID-5 is invariant across sex and the five-factor structure adjusts well to data. The APA scoring approach appears to attenuate the cross-loading problem observed with the original scoring approach. In light of these results, we recommend using the APA scoring approach to derive domain scores.

A randomized proof-of-mechanism trial of TNF antagonism for motivational anhedonia and related corticostriatal circuitry in depressed patients with high inflammation

Chronic, low-grade inflammation has been associated with motivational deficits in patients with major depression (MD). In turn, impaired motivation has been linked to poor quality of life across psychiatric disorders. We thus determined effects of the anti-inflammatory drug infliximab-a potent tumor necrosis factor (TNF) antagonist-on behavioral and neural measures of motivation in 42 medically stable, unmedicated MD patients with a C-reactive protein > 3mg/L. All patients underwent a double-blind, placebo-controlled, single-dose, randomized clinical trial with infliximab (5mg/kg) versus placebo. Behavioral performance on an effort-based decision-making task, self-report questionnaires, and neural responses during event-related functional magnetic resonance imaging were assessed at baseline and 2 weeks following infusion. We found that relative to placebo, patients receiving infliximab were more willing to expend effort for rewards. Moreover, increase in effortful choices was associated with reduced TNF signaling as indexed by decreased soluble TNF receptor type 2 (sTNFR2). Changes in effort-based decision-making and sTNFR2 were also associated with changes in task-related activity in a network of brain areas, including dmPFC, ventral striatum, and putamen, as well as the functional connectivity between these regions. Changes in sTNFR2 also mediated the relationships between drug condition and behavioral and neuroimaging measures. Finally, changes in self-reported anhedonia symptoms and effort-discounting behavior were associated with greater responses of an independently validated whole-brain predictive model (aka "neural signature") sensitive to monetary rewards. Taken together, these data support the use of anti-inflammatory treatment to improve effort-based decision-making and associated brain circuitry in depressed patients with high inflammation.

Emotion dynamics in current and remitted depression: an ecological momentary assessment study

BACKGROUND

Individuals in a depressive episode and healthy controls exhibit robust differences on affect dynamics captured with ecological momentary assessment (EMA). However, few studies have explored affect dynamics in individuals in remission from depression, and results have been mixed.

METHODS

A community sample of 18-year-olds (N = 345) completed diagnostic interviews and EMA probing emotions and low interest/motivation 5× daily for 2 weeks. Affect home base, variability, and inertia were compared across currently depressed, remitted, and never-depressed groups.

RESULTS

Both depression groups had a higher negative affect (NA) and low interest/motivation home base, lower positive affect (PA) home base, greater variability of NA, PA, and low interest/motivation, and greater NA and low interest/motivation inertia than never-depressed participants. Additionally, the currently depressed group had a higher sad home base specifically, greater variability across most negative emotions and low interest/motivation, and greater low interest/motivation inertia than the remitted group. The currently depressed and remitted groups did not differ in anxious, upset, or PA home base, anxious or PA variability, and inertia of all negative emotions and PA.

CONCLUSIONS

Findings suggest that a number of abnormalities in emotion and reward functioning persist after a depressive episode resolves, however, the tendency to experience higher levels of sadness, greater range of a variety of negative emotions, and more variable and persistent low interest/motivation are exacerbated during depressive episodes. Conversely, greater intensity and persistence of some negative emotions (anxiety, upset) and blunted positive emotions appear to equally characterize depression in both the symptomatic and remitted state.

Smartphone keyboard dynamics predict affect in suicidal ideation

While digital phenotyping provides opportunities for unobtrusive, real-time mental health assessments, the integration of its modalities is not trivial due to high dimensionalities and discrepancies in sampling frequencies. We provide an integrated pipeline that solves these issues by transforming all modalities to the same time unit, applying temporal independent component analysis (ICA) to high-dimensional modalities, and fusing the modalities with linear mixed-effects models. We applied our approach to integrate high-quality, daily self-report data with BiAffect keyboard dynamics derived from a clinical suicidality sample of mental health outpatients. Applying the ICA to the self-report data (104 participants, 5712 days of data) revealed components related to well-being, anhedonia, and irritability and social dysfunction. Mixed-effects models (55 participants, 1794 days) showed that less phone movement while typing was associated with more anhedonia (β = -0.12, p = 0.00030). We consider this method to be widely applicable to dense, longitudinal digital phenotyping data.

Hippocampal and gut AMPK activation attenuates enterocolitis-like symptoms and co-occurring depressive-like behavior in ulcerative colitis model mice: Involvement of brain-gut autophagy

Patients with inflammatory bowel disease, including ulcerative colitis (UC) and Crohn's disease, have a high incidence of psychiatric disorders, including depression and anxiety. However, the underlying pathogenic mechanism remains unknown. Dextran sulfate sodium (DSS)-treated mice, a model of UC, exhibit depressive-like behavior and reduced adenosine monophosphate-activated protein kinase (AMPK) activity, which regulates various physiological functions in the brain and gut. However, comprehensive studies on UC pathophysiology with co-occurring depression focused on brain-gut AMPK activity are lacking. Therefore, we aimed to investigate whether resveratrol (RES), an AMPK activator, prevented DSS-induced UC-like symptoms and depressive-like behavior. DSS treatment induced UC-like pathology and depressive-like behavior, as assessed via the tail suspension test. Moreover, western blotting and immunohistochemical studies revealed that DSS increased p-p70S6 kinase (Thr389), p62, tumor necrosis factor-α, interleukin (IL)-1β, IL-18, NLR family pyrin domain containing 3 (NLRP3), cleaved caspase-1, cleaved Gasdermin-D (GSDMD), and cleaved caspase-3 expression levels in the rectum and hippocampus, and increased CD40, iNOS, and Kelch-like ECH-associated protein 1 expression levels, and the number of Iba1-positive cells in the hippocampus, and decreased p-AMPK and LC3II/I expression levels, and the number of NF-E2-related factor 2 (Nrf2)-positive cells, and reduced neurogenesis in the hippocampus. These changes were reversed by the RES administration. RES also enhanced PGC1α and SOD1 expression in the hippocampus of DSS-treated male mice. Moreover, NLRP3 staining was observed in the neurons and microglia, and cleaved GSDMD staining in neurons in the hippocampus of DSS-treated mice. Notably, RES prevented UC-like pathology and depressive-like behavior and enhancement of autophagy, decreased rectal and hippocampal inflammatory cytokines and inflammasome, and induced the Nrf2-PGC1α-SOD1 pathway in the hippocampus, resulting in neurogenesis in the hippocampal dentate gyrus. Our findings suggest that brain-gut AMPK activation may be an important therapeutic strategy in patients with UC and depression.

Enhanced Punishment Responses in Patients With Schizophrenia: An Event-Related Potential Study

It is well known that abnormal reward processing is a characteristic feature of various psychopathologies including schizophrenia. Reduced reward anticipation has been suggested as a core symptom of schizophrenia. The Monetary Incentive Delay Task (MID) is frequently used to detect reward anticipation. The present study aims to evaluate the amplitude and latency of event-related potential (ERP) P300 in patients with schizophrenia (SCH) compared to healthy controls during the MID task. Twenty patients with SCH and 21 demographically matched healthy controls (HC) were included in the study. ERP P300 amplitude and latency values were compared between groups using an MID task in which reward and loss cues were presented. Relations between P300 and clinical facets were investigated in the patient group. SCH group had enhanced mean P300 amplitudes and delayed peak latency in the punishment condition compared with HC. These higher responses were also associated with negative symptoms. SCH group showed altered reward processing as being more sensitive to loss of reward conditions as firstly evidenced by electrophysiological methods, possibly due to abnormality in various systems including social withdrawal, social defeat, and behavioral inhibition system.