Depression and Approach Motivation: Differential Relations to Monetary, Social, and Food Reward

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.

Neural activation and connectivity in offspring of depressed mothers during monetary and social reward tasks

Multiple previous studies show associations between history of and familial risk for depression and reward function. These previous studies have predominantly focused on neural activation during monetary tasks. Fewer studies of have examined functional connectivity and social reward tasks, particularly in offspring of mothers with depression. This study examined brain function in older children (aged 9-14 years) through both regional activation and functional connectivity during monetary (n = 103) and social reward (n = 115) tasks. Overall, our study failed to find significant differences between offspring of mothers with and without depression on monetary (65 offspring of mothers without and 38 offspring of mother with depression) and social reward (73 offspring of mothers without and 42 offspring of mother with depression) tasks on task activation and functional connectivity. We discuss possibilities for developmental timing of finding differences between offspring of mothers with and without depression on monetary and social reward tasks.

Parsing patterns of reward responsiveness: Initial evidence from latent profile analysis

Variation in reward responsiveness has been linked to psychopathology. Reward responsiveness is a complex phenomenon that encompasses different temporal dimensions (i.e., reward anticipation or consumption) that can be measured using multiple appetitive stimuli. Furthermore, distinct measures, such as neural and self-report measures, reflect related but distinct aspects of reward responsiveness. To understand reward responsiveness more comprehensively and better identify deficits in reward responsiveness implicated in psychopathology, we examined ways multiple measures of reward responsiveness jointly contribute to distinct psychological problems by using latent profile analysis. Specifically, we identified three profiles of reward responsiveness among 139 female participants based on their neural responses to money, food, social acceptance, and erotic images and self-reported responsiveness to reward anticipation and consumption. Profile 1 (n = 30) exhibited blunted neural responses to social rewards and erotic images, low self-reported reward responsiveness, but average neural responses to monetary and food rewards. Profile 2 (n = 71) showed elevated neural response to monetary rewards, average neural responses to other stimuli, and average self-reported reward responsiveness. Profile 3 (n = 38) showed more variable neural responses to reward (e.g., hypersensitivity to erotic images, hyposensitivity to monetary rewards), and high self-reported reward responsiveness. These profiles were differentially associated with variables generally linked to aberrations in reward responsiveness. For example, Profile 1 was most strongly associated with anhedonic depression and social dysfunction, whereas Profile 3 was associated with risk-taking behaviors. These preliminary findings may help to elucidate ways different measures of reward responsiveness manifest within and across individuals and identify specific vulnerabilities for distinct psychological problems.

Estrogen administration and withdrawal in a model of hormone-simulated pregnancy lead to alterations in behavior and gene expression but do not induce depression-like phenotypes in mice

Pregnancy and the post-partum period are associated with substantial fluctuations in hormone levels and are frequently associated with significant stress. Many individuals also experience affective disturbances during the peri‑partum period, including anxiety, the 'baby blues,' and post-partum depression. However, the extent to which these affective changes result from rapidly altering hormone levels, increased stress, or the combination of both remains largely unknown. The current study sought to evaluate the consequences of pregnancy-like hormonal changes on behavior and gene expression in c57BL/6 mice in the absence of stress using a hormone-simulated pregnancy model. Our results reveal that animals receiving hormone injections to simulate the high levels of estrogen observed in late pregnancy and animals withdrawn from estrogen to mimic the rapid decline in this hormone following parturition both exhibit increased anxiety-like behavior compared to ovariectomized controls in the novel open field test. However, no other significant anxiety- or depression-like alterations were observed in either hormone-treated group compared to ovariectomized controls. Both hormone administration and estrogen withdrawal were shown to induce several significant alterations in gene expression in the bed nucleus of the stria terminalis and the paraventricular nucleus of the hypothalamus. In contrast to the estrogen withdrawal hypothesis of post-partum depression, our results suggest that this method estrogen withdrawal following hormone-simulated pregnancy in the absence of stress does not induce phenotypes consistent with post-partum depression in c57BL/6 mice. However, given that estrogen withdrawal does lead to significant gene expression changes in two stress-sensitive brain regions, it remains possible that estrogen withdrawal could still contribute to affective dysregulation in the peri-partum period by influencing susceptibility to stress. Future research is required to evaluate this possibility.

Sucrose Preference Test as a Measure of Anhedonic Behavior in a Chronic Unpredictable Mild Stress Model of Depression: Outstanding Issues

Despite numerous studies on the neurobiology of depression, the etiological and pathophysiological mechanisms of this disorder remain poorly understood. A large number of animal models and tests to evaluate depressive-like behavior have been developed. Chronic unpredictable mild stress (CUMS) is the most common and frequently used model of depression, and the sucrose preference test (SPT) is one of the most common tests for assessing anhedonia. However, not all laboratories can reproduce the main effects of CUMS, especially when this refers to a decrease in sucrose preference. It is also unknown how the state of anhedonia, assessed by the SPT, relates to the state of anhedonia in patients with depression. We analyzed the literature available in the PubMed database using keywords relevant to the topic of this narrative review. We hypothesize that the poor reproducibility of the CUMS model may be due to differences in sucrose consumption, which may be influenced by such factors as differences in sucrose preference concentration threshold, water and food deprivation, and differences in animals’ susceptibility to stress. We also believe that comparisons between animal and human states of anhedonia should be made with caution because there are many inconsistencies between the two, including in assessment methods. We also tried to offer some recommendations that should improve the reproducibility of the CUMS model and provide a framework for future research.

Differential Neural Substrates for Responding to Monetary, Sexual Humor, and Erotic Rewards

Sexual humor involves neural mechanisms related to both humor and sexual arousal. However, evidence on the role of the amygdala in processing sexual humor is lacking. Unlike erotic stimuli that directly involve a biological drive, sexual humor gains its value through learned associations. Processes related to responding to erotic versus monetary rewards have been identified in the lateral orbitofrontal cortex (lOFC) along a postero-anterior axis, but it is less clear whether these processes are also active during the appreciation of sexual humor. Results showed the processing of sexual humor appreciation in the amygdala. Psychophysiological interaction (PPI) analysis further identified functional connectivity in the amygdala-midbrain coupling during sexual humor versus monetary gains appreciation. The present study provides evidence demonstrating roles for the posterior OFC (pOFC) and anterior OFC (aOFC) in distinguishing between sexual (sexual humor and erotic) and non-sexual (monetary) rewards. The experience of sexual pleasure induced by erotic rewards involves phylogenetically and ontogenetically older regions in the pOFC, while the experience of receiving monetary gains involves the aOFC. This study also provides additional insights into sexual humor appreciation in the pOFC, with findings of a postero-anterior dissociation in the processing of sexual humor appreciation. PPI analysis revealed functional connectivity in the pOFC-amygdala coupling in response to both types of sexual rewards versus monetary rewards. Together, our results suggest that the amygdala serves as a reward hub, especially in processing sexual humor versus monetary gains appreciation. Functional connectivity analysis showed amygdala-midbrain and pOFC-amygdala coupling during the appreciation of sexual humor. DATA AVAILABILITY STATEMENT: The data underlying this article is available from the corresponding author upon request.

Social anhedonia as a Disrupted-in-Schizophrenia 1-dependent phenotype

Deficits in social interaction or social cognition are key phenotypes in a variety of chronic mental diseases, yet, their modeling and molecular dissection are only in their infancy. The Disrupted-in-Schizophrenia 1 (DISC1) signaling pathway is considered to play a role in different psychiatric disorders such as schizophrenia, depression, and biopolar disorders. DISC1 is involved in regulating the dopaminergic neurotransmission in, among others, the mesolimbic reward system. A transgenic rat line tgDISC1 has been introduced as a model system to study behavioral phenotypes associated with abnormal DISC1 signaling pathways. Here, we evaluated the impact of impaired DISC1 signaling on social (social interaction) and non-social (sucrose) reward preferences in the tgDISC1 animal model. In a plus-maze setting, rats chose between the opportunity for social interaction with an unfamiliar juvenile conspecific (social reward) or drinking sweet solutions with variable sucrose concentrations (non-social reward). tgDISC1 rats differed from wild-type rats in their social, but not in their non-social reward preferences. Specifically, DISC1 rats showed a lower interest in interaction with the juvenile conspecific, but did not differ from wild-type rats in their preference for higher sucrose concentrations. These results suggest that disruptions of the DISC1 signaling pathway that is associated with altered dopamine transmission in the brain result in selective deficits in social motivation reminiscent of phenotypes seen in neuropsychiatric illness.

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

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

Poorer mental health and sleep quality are associated with greater self-reported reward-related eating during pregnancy and postpartum: an observational cohort study

BACKGROUND

Depression, stress, and poor-quality sleep are common during pregnancy and postpartum, but the relationship of these factors with reward-related eating is not well understood. This observational cohort study examines associations of depression, stress, and sleep quality with self-reported reward-related eating in pregnancy and postpartum.

METHODS

Participants were enrolled at < 12 weeks gestation and followed through 1 year postpartum. Self-reported measures obtained at baseline and 23-31 weeks postpartum included the Edinburgh Postnatal Depression Scale, Perceived Stress Scale, Pittsburgh Sleep Quality Index; reward-related eating measures included the Power of Food Scale (assessing hedonic hunger), modified Yale Food Addiction Scale (assessing addictive-like eating), and frequency and intensity of cravings. Linear and logistic regression models estimated associations of depressive symptoms, stress, and sleep quality with reward-related eating during pregnancy and postpartum, as well as change in each predictor with change in outcome.

RESULTS

During pregnancy, greater depressive symptoms (β ± SE = 0.03 ± 0.01, p < .01), higher stress (0.03 ± 0.01, p < .01), and worse sleep quality (0.03 ± 0.01, p = 0.03) were associated with greater hedonic hunger. Similarly, greater depressive symptoms (OR = 1.08, 95% CI: 1.02, 1.14, p = .01), higher stress (OR = 1.09, 95% CI: 1.04, 1.14, p = <.01), and worse sleep quality (OR = 1.09, 95% CI: 1.00, 1.18, p = .04) were associated with greater odds of addictive-like eating. These associations were also significant in postpartum except that sleep quality was not associated with hedonic hunger. Greater depressive symptoms (β ± SE = 0.06 ± 0.02, p < .01; 0.08 ± 0.02, p = <.01), higher stress (0.04 ± 0.01, p < .01; 0.06 ± 0.02, p < .01), and worse sleep quality (0.11 ± 0.03, p < .01; 0.13 ± 0.03, p < .01) during pregnancy were associated with stronger and more frequent cravings, respectively. Increased depressive symptoms from pregnancy to postpartum was associated with increased hedonic hunger (β ± SE = 1.17 ± 0.57, p = 0.01) and addictive-like eating (0.88 ± 0.33, p = 0.01), and increased stress was associated with increased hedonic hunger (1.71 ± 0.76, p = 0.02). Change in stress was not associated with change in addictive-like eating and change in sleep quality was not associated with change in either hedonic hunger or addictive-like eating.

CONCLUSIONS

Greater depressive symptoms, perceived stress, and poorer sleep quality are associated with greater self-reported reward-related eating during pregnancy and postpartum, suggesting that efforts to improve diet during and after pregnancy may benefit from addressing mental health and sleep.

TRIAL REGISTRATION

Clinicaltrials.gov Registration ID - NCT02217462 . Date of registration - August 13, 2014.

Stepwise Noise Elimination for Better Motivational and Advisory Texts Classification

There is little research into designing artificial motivational agents. The end-goal of our studies is therefore to create a dialogue system that would motivate users to do their everyday tasks using natural language. In this paper, we present a method of distinguishing texts containing motivational advice from regular texts to sort out noise in training data for our dialogue system. We implemented a novel method of chaining two shallow networks together by utilizing the output results of the first network to determine the input for the second one. We achieved F-score of 0.94 and 0.97 with our proposed method. The contributions of this paper are threefold: first, we successfully identified 14 hand-crafted features that make a text motivational/advisory. Secondly, we were able to create a classifying algorithm that distinguishes motivational/advisory texts from regular ones. Finally, our proposed method can be applied to other text classification tasks.

Sluggish cognitive tempo and positive valence systems: Unique relations with greater reward valuation but less willingness to work

BACKGROUND

Research has started conceptualizing sluggish cognitive tempo (SCT) within the Research Domain Criteria (RDoC), but no study has tested SCT symptomatology in relation to the positive valence systems.

METHODS

Participants (N = 4,679; 18-29 years; M = 19.08, SD = 1.36; 69% female; 80.9% White) enrolled in six universities in the United States completed self-reported measures of positive valence systems, SCT, and psychopathology dimensions.

RESULTS

SCT symptoms were uniquely associated with greater reward valuation and expectancy of reward, but less willingness to work for reward. SCT symptoms were not uniquely related to initial and sustained response to reward. Conversely, depressive symptoms remained uniquely associated with greater reward valuation but less expectancy, willingness to work, initial, and sustained response to reward.

LIMITATIONS

The present study included a relatively homogenous sample of college-age students, solely relied on self-report measures of the positive valence systems, and analyses were conducted cross-sectionally.

CONCLUSIONS

Findings demonstrated that SCT has unique relations with various components of the positive valence system while controlling for commonly co-occurring psychopathology dimensions. Future research should continue investigating relations between SCT and positive valence systems to understand whether these domains may be targets for prevention and intervention.

Peer Victimization and Dysfunctional Reward Processing: ERP and Behavioral Responses to Social and Monetary Rewards

Peer victimization (or bullying) is a known risk factor for depression, especially among youth. However, the mechanisms connecting victimization experience to depression symptoms remains unknown. As depression is known to be associated with neural blunting to monetary rewards, aberrant responsiveness to social rewards may be a key deficit connecting socially stressful experiences with later depression. We, therefore, sought to determine whether adolescents’ experiences with social stress would be related to their current response to social rewards over less socially relevant monetary rewards. Neural responses to monetary and social rewards were measured using event-related potentials (ERPs) to peer acceptance and rejection feedback (Island Getaway task) and to monetary reward and loss feedback (Doors task) in a sample of 56 late adolescents/emerging young adults followed longitudinally since preschool. In the Island Getaway task, participants voted whether to “keep” or “kick out” each co-player, providing an index of prosocial behavior, and then received feedback about how each player voted for the participant. Analyses tested whether early and recent peer victimization was related to response to rewards (peer acceptance or monetary gains), residualized for response to losses (peer rejection or monetary losses) using the reward positivity (RewP) component. Findings indicated that both experiencing greater early and greater recent peer victimization were significantly associated with participants casting fewer votes to keep other adolescents (“Keep” votes) and that greater early peer victimization was associated with reduced neural response to peer acceptance. Early and recent peer victimization were significantly more associated with neural response to social than monetary rewards. Together, these findings suggest that socially injurious experiences such as peer victimization, especially those occurring early in childhood, relate to two distinct but important findings: that early victimization is associated with later reduced response to peer acceptance, and is associated with later tendency to reject peers. Findings also suggest that there is evidence of specificity to reward processing of different types; thus, future research should expand studies of reward processing beyond monetary rewards to account for the possibility that individual differences may be related to other, more relevant, reward types.

Factors Affecting Consumer Food Preferences: Food Taste and Depression-Based Evoked Emotional Expressions with the Use of Face Reading Technology

In this study, several factors (social status, age, gender, education, knowledge about healthy eating, and attitude to food) affecting consumer food choices (FC), including the relationship between the taste of food, FC, and depression, were analysed by using sensory traits and face reading technology. The first stage of the experimental scheme was the analysis of factors affecting consumer food preferences by using a questionnaire, while the second stage was evaluation of emotional expressions evoked by different food tastes in individuals with and without depressive disorders (DD), using the FaceReader 6 software. We show that gender is a significant factor for most emotional motivations, with a higher effect in females where there was an indication of increased cravings for sweets when feeling depressed. Age was a significant factor in the motivation to eat for positive feelings, while education had a significant influence on perceptions regarding healthy eating. Face reading technology was found to be sufficiently accurate to detect differences in facial expressions induced by different tastes of food, for groups with and without DD. In conclusion, many factors are of high importance in the analysis of food choices, and the results obtained using the FaceReader 6 technique are very promising for food-mood relation analysis. We suggest that mood has a strong link with the choice of food.