Characterizing reward and relief/habit drinking profiles in a study of naltrexone, varenicline, and placebo.

INTRODUCTION: This study aims to clarify differences in mood, craving, and treatment response between reward and relief/habit individuals in a study of naltrexone, varenicline, and placebo. We hypothesized that relief/habit individuals would have a poorer mood during early abstinence and higher levels of alcohol craving than reward individuals. We hypothesized that reward individuals would demonstrate better drinking outcomes on naltrexone versus placebo. METHODS: Data were culled from a randomized, double-blind, placebo-controlled human trial of 53 individuals (18F/16M) with alcohol use disorder randomized to varenicline (n = 19), naltrexone (n = 15), or matched placebo (n = 19). In this 6-day practice quit trial, participants attempted to abstain from drinking and completed daily diaries. Participants were classified into reward or relief/habit subgroups based on self-reported motivation for drinking. Multilinear models tested differences in mood and alcohol craving between reward and relief/habit individuals. General linear models tested differences between reward and relief/habit individuals' drinking outcomes on each medication versus placebo. RESULTS: Relief/habit individuals showed decreases in positive mood and increases in negative mood over the quit attempt across medications, compared to reward individuals (P's < .05). Reward individuals' tension decreased on naltrexone, while relief/habit individuals' tension remained stable (F = 3.64, P = .03). Reward individuals in the placebo group had higher percent days abstinent than relief individuals in the placebo group (P < .001). DISCUSSION: This study suggests relief/habit individuals' mood worsens during early abstinence. Our finding that reward individuals' tension decreased on naltrexone and increased on placebo may suggest a clinical response to the medication.

Blunted midbrain reward activation during smoking withdrawal: a preliminary study.

Introduction: Tobacco smoking is the leading preventable cause of death, causing more than six million deaths annually worldwide, mainly due to cardiovascular disease and cancer. Many habitual smokers try to stop smoking but only about 7% are successful, despite widespread knowledge of the risks. Development of addiction to a range of substances is associated with progressive blunting of brain reward responses and sensitisation of stress responses, as described by the allostasis theory of addiction. There is pre-clinical evidence from rodents for a dramatic decrease in brain reward function during nicotine withdrawal. Methods: Here we tested the hypothesis that habitual smokers would also exhibit blunted reward function during nicotine withdrawal using a decision-making task and fMRI. Results: Our findings supported this hypothesis, with midbrain reward-related responses particularly blunted. We also tested the hypothesis that smokers with a longer duration of smoking would have more pronounced abnormalities. Contrary to expectations, we found that a shorter duration of smoking in younger smokers was associated with the most marked abnormalities, with blunted midbrain reward related activation including the dopaminergic ventral tegmental area. Discussion: Given the substantial mortality associated with smoking, and the small percent of people who manage to achieve sustained abstinence, further translational studies on nicotine addiction mechanisms are indicated.

The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents.

BORLAND, J.M., The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents, NEUROSCI BIOBEH REV 21(1) XXX-XXX, 2024.-Sociality shapes an organisms' life. The nucleus accumbens is a critical brain region for mental health. In the following review, the effects of different types of social interactions on the physiology of neurons in the nucleus accumbens is synthesized. More specifically, the effects of sex behavior, aggression, social defeat, pair-bonding, play behavior, affiliative interactions, parental behaviors, the isolation from social interactions and maternal separation on measures of excitatory synaptic transmission, intracellular signaling and factors of transcription and translation in neurons in the nucleus accumbens in rodent models are reviewed. Similarities and differences in effects depending on the type of social interaction is then discussed. This review improves the understanding of the molecular and synaptic mechanisms of sociality.

How adverse childhood experiences get under the skin: A systematic review, integration and methodological discussion on threat and reward learning mechanisms.

Adverse childhood experiences (ACEs) are a major risk factor for the development of multiple psychopathological conditions, but the mechanisms underlying this link are poorly understood. Associative learning encompasses key mechanisms through which individuals learn to link important environmental inputs to emotional and behavioral responses. ACEs may impact the normative maturation of associative learning processes, resulting in their enduring maladaptive expression manifesting in psychopathology. In this review, we lay out a systematic and methodological overview and integration of the available evidence of the proposed association between ACEs and threat and reward learning processes. We summarize results from a systematic literature search (following PRISMA guidelines) which yielded a total of 81 articles (threat: n=38, reward: n=43). Across the threat and reward learning fields, behaviorally, we observed a converging pattern of aberrant learning in individuals with a history of ACEs, independent of other sample characteristics, specific ACE types, and outcome measures. Specifically, blunted threat learning was reflected in reduced discrimination between threat and safety cues, primarily driven by diminished responding to conditioned threat cues. Furthermore, attenuated reward learning manifested in reduced accuracy and learning rate in tasks involving acquisition of reward contingencies. Importantly, this pattern emerged despite substantial heterogeneity in ACE assessment and operationalization across both fields. We conclude that blunted threat and reward learning may represent a mechanistic route by which ACEs may become physiologically and neurobiologically embedded and ultimately confer greater risk for psychopathology. In closing, we discuss potentially fruitful future directions for the research field, including methodological and ACE assessment considerations.

Severe sexual abuse in childhood and altered neurophysiological response to reward in female adults.

BACKGROUND: A relatively understudied but growing body of research indicates that individuals with a history of childhood trauma exhibit altered reward processing in adulthood. Research to date has focused on adversity broadly, with studies typically finding evidence of blunted response to rewards in adults with a history of childhood trauma. OBJECTIVE: Given the role of reward processing in risk for psychopathology and the particularly pathogenic nature of sexual abuse (SA), the present study sought to assess whether adults with a history of severe childhood SA exhibit altered neurophysiological response to rewards. PARTICIPANTS AND SETTING: Female adults (N = 105) were included from two study sites that used the same measures of childhood trauma (Childhood Trauma Questionnaire, CTQ), reward processing (Doors Task), and psychopathology (SCID). METHODS: Based on participants' CTQ and SCID responses, three groups were created: Severe SA (n = 36), Clinical Match (with comparable lifetime psychopathology but no-to-minimal SA history; n = 35), and Healthy Controls (n = 34). Group differences in RewP amplitude were assessed. RESULTS: The Severe SA group exhibited larger reward positivity (RewP) amplitude to monetary rewards than the Clinical Match and Healthy Control groups (partial ƞ2 = 0.06, p = .047). This effect remained after covarying for severity of other forms of childhood trauma. CONCLUSIONS: Our study found that severe SA in childhood was related to a heightened response to reward in adulthood. Furthermore, this was not attributable to the severity of other forms of early trauma or comorbid psychopathology. Future studies are needed to identify how heightened reward processing following severe childhood SA may be implicated in the onset and course of psychopathology.

Nutrient clustering, NOVA classification, and nutrient profiling: How do they overlap, and what do they predict about food palatability?

We compared the performance of three food categorisation metrics in predicting palatability (taste pleasantness) using a dataset of 52 foods, each rated virtually (online) by 72-224 participants familiar with the foods in question, as described in Appetite 193 (2024) 107124. The metrics were nutrient clustering, NOVA, and nutrient profiling. The first two of these metrics were developed to identify, respectively: 'hyper-palatable' foods (HPFs); and ultra-processed foods (UPFs), which are claimed to be 'made to be hyper-palatable'. The third metric categorises foods as high fat, sugar, salt (HFSS) foods versus non-HFSS foods. There were overlaps, but also significant differences, in categorisation of the foods by the three metrics: of the 52 foods, 35 (67%) were categorised as HPF, and/or UPF, and/or HFSS, and 17 (33%) were categorised as none of these. There was no significant difference in measured palatability between HPFs and non-HPFs, nor between UPFs and non-UPFs (p ≥ 0.412). HFSS foods were significantly more palatable than non-HFSS foods (p = 0.049). None of the metrics significantly predicted food reward (desire to eat). These results do not support the use of hypothetical combinations of food ingredients as proxies for palatability, as done explicitly by the nutrient clustering and NOVA metrics. To discover what aspects of food composition predict palatability requires measuring the palatability of a wide range of foods that differ in composition, as we do here.

Late Positive Potential Elicited by Monetary Reward Feedback Predicts Changes of Disordered Eating From Age 11 to Age 12 in Community-Dwelling Girls.

OBJECTIVE: Early adolescence is marked by elevated psychopathology, including disrupted eating attitudes and behaviors. Reward processing is an identified mechanism in portending eating pathology, that is, aberrant reward responsivity may contribute to disrupted reward-seeking behaviors (e.g., food consuming). This literature has focused on adults or mid-to-late adolescents, with little work done on early adolescence. We examined the linkages between reward feedback processing, indexed by event-related potentials (ERPs), and changes of emerging disordered eating in community-dwelling early adolescents. METHOD: At T1, 115 youths (66 girls, mean/SD age = 11.00/1.16 years) completed an EEG monetary reward Doors task. Youths completed the Eating Disorder Examination-Questionnaire Short at T1 and ~6 months (T2) and ~12 months (T3) after T1. In the ERP data, we isolated a reward positivity (RewP) and a late positive potential (LPP) via principal component analysis. We applied multilevel modeling to examine whether baseline ERPs interacted with Time in predicting disordered eating and whether these interactions varied by sex. RESULTS: We found a significant Time × LPP interaction in girls but not boys. Among girls, only those with a smaller LPP toward the losses (versus wins), which might reflect suboptimal evaluation and regulatory processes in undesired situations, showed increases in disordered eating from T1 to T3. DISCUSSION: We provided preliminary yet novel evidence concerning the prospective associations between reward processing and changes of disordered eating in early adolescents. Future studies along this line will be critical for understanding the early mechanisms of eating pathology, identifying youths at risk, and developing prevention strategies.

BACLOFEN PREVENTS MORPHINE REWARDING EFFECTS AND ASSOCIATED BIOCHEMICAL ALTERATIONS IN MALE AND FEMALE MICE.

Previous studies from our laboratory have shown sex differences in the behavioral, molecular, and neurochemical manifestations of morphine withdrawal and they were related to an increased sensitivity to morphine effects in males. In addition, we observed an interaction between the GABAergic and opioid systems that could also be sex-dependent. Baclofen, a GABAB receptor agonist, prevented the somatic expression and the molecular and neurochemical changes induced by morphine withdrawal syndrome in mice. On the contrary, little is known about baclofen effects in the rewarding properties of morphine in male and female mice. The present study aimed to explore the effect of baclofen (1, 2 and 3 mg/kg, i.p.) pretreatment in the rewarding effects induced by morphine (7 mg/kg, s.c.) and its effect on c-Fos and brain-derived neurotrophic factor (BDNF) expression induced by the rewarding properties of morphine in prepubertal male and female mice. Baclofen (2 mg/kg) pretreatment prevented the rewarding effects of morphine only in male mice, while baclofen (3 mg/kg) reduced these effects in both sexes. Moreover, the rewarding effects of morphine were associated with a decrease of BDNF and c-Fos expression cingulate cortex, nucleus accumbens shell, cornu ammonis 1 (CA1), and cornu ammonis 3 (CA3) areas of the hippocampus only in male mice. In addition, baclofen pretreatment prevented these changes in BDNF, but not in c-Fos expression. In conclusion, our results show that GABAB receptors have a regulatory role in the rewarding effects of morphine that could be of interest for a potential future therapeutic application in opioid use disorders.

The effects of reward and punishment on the performance of ping-pong ball bouncing.

Introduction: Reward and punishment modulate behavior. In real-world motor skill learning, reward and punishment have been found to have dissociable effects on optimizing motor skill learning, but the scientific basis for these effects is largely unknown. Methods: In the present study, we investigated the effects of reward and punishment on the performance of real-world motor skill learning. Specifically, three groups of participants were trained and tested on a ping-pong ball bouncing task for three consecutive days. The training and testing sessions were identical across the three days: participants were trained with their right (dominant) hand each day under conditions of either reward, punishment, or a neutral control condition (neither). Before and after the training session, all participants were tested with their right and left hands without any feedback. Results: We found that punishment promoted early learning, while reward promoted late learning. Reward facilitated short-term memory, while punishment impaired long-term memory. Both reward and punishment interfered with long-term memory gains. Interestingly, the effects of reward and punishment transferred to the left hand. Discussion: The results show that reward and punishment have different effects on real-world motor skill learning. The effects change with training and transfer readily to novel contexts. The results suggest that reward and punishment may act on different learning processes and engage different neural mechanisms during real-world motor skill learning. In addition, high-level metacognitive processes may be enabled by the additional reinforcement feedback during real-world motor skill learning. Our findings provide new insights into the mechanisms underlying motor learning, and may have important implications for practical applications such as sports training and motor rehabilitation.

Reward positivity moderates the association between pubertal status and social anxiety symptoms in nine-to-12-year-old youths.

The transition to adolescence is characterized by rapid development of puberty, reward processing, and internalizing psychopathology (i.e., depression and anxiety). More advanced pubertal status and altered reward processing are both known to be associated with elevated internalizing symptoms. However, it was unclear to what extent pubertal status and reward processing interacted with each other in predicting internalizing psychopathology. We examined how the puberty-psychopathology association was moderated by the reward processing indexed by ERPs, including the reward positivity (RewP) and the late positive potential (LPP). A-hundred-and-fifteen nine-to-12-year-old typically developing youths (66 girls; Mean age/SD =10.98/1.18 years) reported their pubertal status and symptoms of depression and social anxiety and completed an EEG Doors task that assessed monetary reward feedback processing. A principal component analysis of the ERP data identified a RewP, an anterior LPP, and a posterior LPP, elicited by the win and loss feedback of the task. The puberty-social anxiety relationship was moderated by the RewP, an identified neural marker of reward sensitivity. Specifically, more advanced puberty was associated with heightened social anxiety symptoms in the presence of a larger, but not smaller, RewP. We did not observe any moderating effect of the LPPs. Our study provided novel evidence that a hypersensitivity toward the reward stimuli (indexed by an enlarged RewP) further exacerbated the risks associated with more advanced pubertal status for social anxiety.

Self-reported food liking and wanting: A factor analytic study of ratings across 49 consecutive days.

Reward responses to food are thought to play an important role in highly palatable food overconsumption. In animal models, food reward responses can be decoupled into unique "liking" (in the moment enjoyment) and "wanting" (motivation/craving) components. However, research on liking and wanting has been hampered by uncertainty regarding whether liking and wanting can be reliably separated in humans. We used factor analysis to test whether ratings of liking and wanting could be empirically separated in women assessed across 49 consecutive days. Female participants (N = 688; ages 15-30) from the Michigan State University Twin Registry reported liking and wanting of foods consumed that day, and wanting of foods not consumed that day, separately for sweets (e.g., cookies), fast food (e.g., French fries), carbohydrates (e.g., bread), and whole foods (fruit, plain chicken) each evening for 49 consecutive days. We examined both average levels and daily levels of liking/wanting across the 49-day period that captured individual differences in liking/wanting over time. Across both types of analyses, liking and wanting for foods that were eaten formed a single factor rather than separate, dissociable factors, while wanting of foods not eaten formed an independent factor. At the daily level, a liking/wanting factor emerged for each individual food category (e.g., liking/wanting sweets), whereas in average analyses, a single factor emerged that collapsed across all food types (i.e., liking/wanting of all foods). Results suggest individuals have difficulty distinguishing between liking and wanting of foods they have eaten on that day but may be able to more reliably separate wanting of foods they have not consumed.

CREB-Binding Protein Regulates Cocaine- and Amphetamine-Regulated Transcript Peptide Expression in the Lateral Hypothalamus: Implication in Reward and Reinforcement.

Neuropeptide cocaine- and amphetamine-regulated transcript peptide (CARTp) is known to play an important role in reward processing. The rats conditioned to intra-cranial self-stimulation (ICSS) showed massive upregulation of CART protein and mRNA in the vicinity of the electrode implanted to deliver the electric current directly at the lateral hypothalamus (LH)-medial forebrain bundle (MFB) area. However, the underlying mechanisms leading to the upregulation of CART in ICSS animals remain elusive. We tested the putative role of CREB-binding protein (CBP), an epigenetic enzyme with intrinsic histone acetyltransferase (HAT) activity, in regulating CART expression during ICSS. An electrode was implanted in LH-MFB and the rats were conditioned to self-stimulation in an operant chamber. CBP siRNA was delivered ipsilaterally in the LH-MFB to knock-down CBP and the effects on lever press activity were monitored. While ICSS-conditioned rats showed distinct increase in CART, CBP and pCREB levels, enhanced CBP binding and histone acetylation (H3K9ac) were noticed on the CART promoter in chromatin immunoprecipitation assay. Direct infusion of CBP siRNA in the LH-MFB lowered lever press activity, CBP levels, histone acetylation at the CART promoter, and CART mRNA and peptide expression. Co-infusion of CARTp in LH-MFB rescued the waning effects of CBP siRNA on self-stimulation. We suggest that CBP-mediated histone acetylation may play a causal role in CART expression in LH, which in turn may drive the positive reinforcement of lever press activity.

Incidence of effort-reward imbalance among nurses: a systematic review and meta-analysis.

Introduction: To systematically evaluate the incidence of effort-reward imbalance among nurses. Method: PubMed, Web of Science, Embase, CNKI, WanFang Data, and VIP databases were searched to collect studies on the incidence of effort-reward imbalance among nurses. The search timeframe was from database construction to December 2023. Two researchers independently screened the literature, extracted the data, and evaluated the risk of bias in the included studies. The meta-analysis was performed using Stata 17.1 software. Results: A total of 60 studies, including 79,644 participants, were included. The prevalence of effort-reward imbalance among nurses was 52.3% (95% CI: 44.9-59.7%). In terms of time, the incidence of effort-reward imbalance among nurses before 2010 (26.6, 95%CI: 6.8-46.4%) and in 2010-2015 (42.4, 95%CI: 32.1-52.8%), 2016-2020 (60.2, 95%CI: 49.6-70.7%), and 2021-2023 (65.0, 95%CI: 51.5-78.4%) continued to increase. Geographically, Asia (57.4, 95%CI: 51.8-63.1%) nurses had a relatively higher prevalence of effort-reward imbalance. In terms of department, the incidence of effort-reward imbalance among nurses was relatively higher in operating rooms (71.8, 95%CI: 64.5-79.0%), ICU (64.6, 95%CI: 27.7-100.0%), emergency (68.7, 95%CI: 62.9-74.5%), and pediatrics (65.8, 95%CI: 32.2-99.3%). Discussion: The prevalence of nurse effort-reward imbalance is high, and there are differences in its prevalence across time, geography, department. Hospital administrators should actively take measures to effectively prevent and reduce the effort-reward imbalance for nurses, especially for nurses in Asia, operating rooms, emergency pediatrics and ICU departments. Systematic review registration: PROSPERO (CRD42023452428).

Decision-making shapes dynamic inter-areal communication within macaque ventral frontal cortex.

Macaque ventral frontal cortex is comprised of a set of anatomically heterogeneous and highly interconnected areas. Collectively these areas have been implicated in many higher-level affective and cognitive processes, most notably the adaptive control of decision-making. Despite this appreciation, little is known about how subdivisions of ventral frontal cortex dynamically interact with each other during decision-making. Here we assessed functional interactions between areas by analyzing the activity of thousands of single neurons recorded from eight anatomically defined subdivisions of ventral frontal cortex in macaques performing a visually guided two-choice probabilistic task for different fruit juices. We found that the onset of stimuli and reward delivery globally increased communication between all parts of ventral frontal cortex. Inter-areal communication was, however, temporally specific, occurred through unique activity subspaces between areas, and depended on the encoding of decision variables. In particular, areas 12l and 12o showed the highest connectivity with other areas while being more likely to receive information from other parts of ventral frontal cortex than to send it. This pattern of functional connectivity suggests a role for these two areas in integrating diverse sources of information during decision processes. Taken together, our work reveals the specific patterns of interareal communication between anatomically connected subdivisions of ventral frontal cortex that are dynamically engaged during decision-making.

Bidirectional valence coding in amygdala intercalated clusters: A neural substrate for the opponent-process theory of motivation.

Processing emotionally meaningful stimuli and eliciting appropriate valence-specific behavior in response is a critical brain function for survival. Thus, how positive and negative valence are represented in neural circuits and how corresponding neural substrates interact to cooperatively select appropriate behavioral output are fundamental questions. In previous work, we identified that two amygdala intercalated clusters show opposite response selectivity to fear- and anxiety-inducing stimuli - negative valence (Hagihara et al. 2021). Here, we further show that the two clusters also exhibit distinctly different representations of stimuli with positive valence, demonstrating a broader role of the amygdala intercalated system beyond fear and anxiety. Together with the mutually inhibitory connectivity between the two clusters, our findings suggest that they serve as an ideal neural substrate for the integrated processing of valence for the selection of behavioral output.

Effectiveness of Catch-Up Vaccination Interventions Versus Standard or Usual Care Procedures in Increasing Adherence to Recommended Vaccinations Among Different Age Groups: Systematic Review and Meta-Analysis of Randomized Controlled Trials and Before-After Studies.

BACKGROUND: To address the global challenge of vaccine hesitancy, the Strategic Advisory Group of Experts on Immunization strongly promotes vaccination reminder and recall interventions. Coupled with the new opportunities presented by scientific advancements, these measures are crucial for successfully immunizing target population groups. OBJECTIVE: This systematic review and meta-analysis aims to assess the effectiveness of various interventions in increasing vaccination coverage compared with standard or usual care. The review will cover all vaccinations recommended for different age groups. METHODS: In February 2022, 2 databases were consulted, retrieving 1850 studies. Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, 79 manuscripts were included after the assessment phase. These comprised 46 trials/randomized controlled trials (RCTs) and 33 before-after studies. A meta-analysis using a random-effects model was performed with STATA software (version 14.1.2). The selected outcome was the risk ratio (RR) of vaccination coverage improvement effectiveness. Additionally, meta-regression analyses were conducted for the included manuscripts. RESULTS: The analyses showed an overall efficacy of RR 1.22 (95% CI 1.19-1.26) for RCTs and RR 1.70 (95% CI 1.54-1.87) for before-after studies when considering all interventions cumulatively. Subgroup analyses identified multicomponent interventions (RR 1.58, 95% CI 1.36-1.85) and recall clinical interventions (RR 1.24, 95% CI 1.17-1.32) as the most effective in increasing vaccination coverage for RCTs. By contrast, educational interventions (RR 2.13, 95% CI 1.60-2.83) and multicomponent interventions (RR 1.61, 95% CI 1.43-1.82) achieved the highest increases for before-after studies. Meta-regression analyses indicated that the middle-aged adult population was associated with a higher increase in vaccination coverage (RCT: coefficient 0.54, 95% CI 0.12-0.95; before-after: coefficient 1.27, 95% CI 0.70-1.84). CONCLUSIONS: Community, family, and health care-based multidimensional interventions, as well as education-based catch-up strategies, effectively improve vaccination coverage. Therefore, their systematic implementation is highly relevant for targeting undervaccinated population groups. This approach aligns with national vaccination schedules and aims to eliminate or eradicate vaccine-preventable diseases.

Cellular and circuit architecture of the lateral septum for reward processing.

The lateral septum (LS) is composed of heterogeneous cell types that are important for various motivated behaviors. However, the transcriptional profiles, spatial arrangement, function, and connectivity of these cell types have not been systematically studied. Using single-nucleus RNA sequencing, we delineated diverse genetically defined cell types in the LS that play distinct roles in reward processing. Notably, we found that estrogen receptor 1 (Esr1)-expressing neurons in the ventral LS (LSEsr1) are key drivers of reward seeking via projections to the ventral tegmental area, and these neurons play an essential role in methamphetamine (METH) reward and METH-seeking behavior. Extended exposure to METH increases the excitability of LSEsr1 neurons by upregulating hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, thereby contributing to METH-induced locomotor sensitization. These insights not only elucidate the intricate molecular, circuit, and functional architecture of the septal region in reward processing but also reveal a neural pathway critical for METH reward and behavioral sensitization.

Linking social reward responsiveness and affective responses to the social environment: An ecological momentary assessment study.

Social support is a key predictor of well-being, but not everyone experiences mental health benefits from receiving it. However, given that a growing number of interventions are based on social support, it is crucial to identify the features that make individuals more likely to benefit from social ties. Emerging evidence suggests that neural responses to positive social feedback (i.e., social reward) might relate to individual differences in social functioning, but potential mechanisms linking these neural responses to psychological outcomes are yet unclear. This study examined whether neural correlates of social reward processing, indexed by the reward positivity (RewP), relate to individuals' affective experience following self-reported real-world positive social support events. To this aim, 193 university students (71% females) underwent an EEG assessment during the Island Getaway task and completed a 10-day ecological momentary assessment where participants reported their positive and negative affects (PA, NA) nine times a day and the count of daily positive and negative events. Experiencing a higher number of social support positive events was associated with higher PA. The RewP moderated this association, such that individuals with greater neural response to social feedback at baseline had a stronger positive association between social support positive events count and PA. Individual differences in the RewP to social feedback might be one indicator of the likelihood of experiencing positive affect when receiving social support.

Effects of acute stress on reward processing: A comprehensive meta-analysis of rodent and human studies.

Stressors can initiate a cascade of central and peripheral changes that modulate mesocorticolimbic dopaminergic circuits and, ultimately, behavioral response to rewards. Driven by the absence of conclusive evidence on this topic and the Research Domain Criteria framework, random-effects meta-analyses were adopted to quantify the effects of acute stressors on reward responsiveness, valuation, and learning in rodent and human subjects. In rodents, acute stress reduced reward responsiveness (g = -1.43) and valuation (g = -0.32), while amplifying reward learning (g = 1.17). In humans, acute stress had marginal effects on valuation (g = 0.25), without affecting responsiveness and learning. Moderation analyses suggest that acute stress neither has unitary effects on reward processing in rodents nor in humans and that the duration of the stressor and specificity of reward experience (i.e., food vs drugs) may produce qualitatively and quantitatively different behavioral endpoints. Subgroup analyses failed to reduce heterogeneity, which, together with the presence of publication bias, pose caution on the conclusions that can be drawn and point to the need of guidelines for the conduction of future studies in the field.

From anticipation to action: A RCT on mental imagery exercises in daily life as a motivational amplifier for individuals with depressive symptoms.

Encouraging engagement in rewarding or pleasant activities is one of the most important treatment goals for depression. Mental imagery exercises have been shown to increase the motivation for planned behaviour in the lab but it is unclear whether this is also the case in daily life. Therefore, we aimed to investigate the effect of mental imagery exercises on motivation and behaviour in daily life. Participants with depressive symptoms (N = 59) were randomly assigned to a group receiving mental imagery (MI) exercises or a control group receiving relaxation (RE) exercises via study phones. We employed an experience sampling design with 10 assessments per day for 10 days (three days baseline, four days with two exercises per day and three days post-intervention). Data was analysed using t-tests and multilevel linear regression analyses. As predicted, MI exercises enhanced motivation and reward anticipation during the intervention phase compared to RE. However, MI did not enhance active behaviour or strengthen the temporal association from reward anticipation (t-1) to active behaviour (t). Mental imagery exercises can act as a motivational amplifier but its effects on behaviour and real-life reward processes remain to be elucidated.