Chronic Stress Shifts Effort-Related Choice Behavior in a Y-Maze Barrier Task in Mice

A pilot exploration of the relationships between optimism, affect, and cardiovascular reactivity

Introduction

Cardiovascular reactivity refers to changes in blood pressure and heart rate in response to internal or external stimuli. Previous research has shown that excessively high and low cardiovascular reactivity are associated with an increased risk of cardiac problems. Dispositional optimism has been associated with numerous health benefits, including better cardiovascular responses to stressors, and reduced mortality risk. Conversely, pessimism has been associated with negative health outcomes and worse cardiovascular reactivity to stress. Mood, comprising positive and negative affect, can significantly impact psychological adjustment and physical health. Therefore, it is important to consider mood as a potential confounding variable in the link between optimism and cardiovascular reactivity. The study hypothesized that optimism and pessimism would still influence cardiovascular reactivity even when mood variables were controlled for.

Methods

A within-subjects correlational design with 107 young adult participants was used. Sociodemographic and clinical questionnaires were administered to collect information on participants' characteristics. The Dispositional Optimism Scale (LOT-R) and the Positive and Negative Affect Scale (PANAS) were used to assess participants' levels of optimism, pessimism, and mood. Measures of cardiovascular reactivity, including systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR), were taken during a stressor task (PASAT).

Results

There is a moderate positive correlation between dispositional optimism and positive affect, while pessimism demonstrated a moderate positive association with negative affect. Linear regression analyses were conducted, controlling baseline reactivity variables, gender, and body mass index. The results showed that pessimism had a significant negative effect on SBP reactivity, suggesting that higher levels of pessimism decreased SBP response. Optimism had a significant positive effect on DBP reactivity, while pessimism had a significant negative effect.

Discussion

Overall, these results suggest that dispositional optimism and pessimism are related to cardiovascular reactivity, even after controlling for positive and negative affect. Pessimism was associated with lower SBP reactivity, while both optimism and pessimism influenced DBP reactivity. These findings are consistent with previous research indicating that optimism enables more effective stress management during challenging events, whereas pessimism can serve as a risk factor, heightening the likelihood of experiencing future cardiac issued caused by blunted cardiovascular reactivity.

Critical review of RDoC approaches to the study of motivation with animal models: effort valuation/willingness to work

The NIMH research domain criteria (RDoC) approach was instigated to refocus mental health research on the neural circuits that mediate psychological functions, with the idea that this would foster an understanding of the neural basis of specific psychiatric dysfunctions (i.e. 'symptoms and circuits') and ultimately facilitate treatment. As a general idea, this attempt to go beyond traditional diagnostic categories and focus on neural circuit dysfunctions related to specific symptoms spanning multiple disorders has many advantages. For example, motivational dysfunctions are present in multiple disorders, including depression, schizophrenia, Parkinson's disease, and other conditions. A critical aspect of motivation is effort valuation/willingness to work, and several clinical studies have identified alterations in effort-based decision making in various patient groups. In parallel, formal animal models focusing on the exertion of effort and effort-based decision making have been developed. This paper reviews the literature on models of effort-based motivational function in the context of a discussion of the RDoC approach, with an emphasis on the dissociable nature of distinct aspects of motivation. For example, conditions associated with depression and schizophrenia blunt the selection of high-effort activities as measured by several tasks in animal models (e.g. lever pressing, barrier climbing, wheel running). Nevertheless, these manipulations also leave fundamental aspects of hedonic reactivity, food motivation, and reinforcement intact. This pattern of effects demonstrates that the general emphasis of the RDoC on the specificity of the neural circuits mediating behavioral pathologies, and the dissociative nature of these dysfunctions, is a valid concept. Nevertheless, the specific placement of effort-related processes as simply a 'sub-construct' of 'reward processing' is empirically and conceptually problematic. Thus, while the RDoC is an excellent general framework for new ways to approach research and therapeutics, it still needs further refinement.

Association of Optimism with Cardiovascular Events and All-Cause Mortality: Systematic Review and Meta-Analysis

BACKGROUND

The effect of psychological health on cardiovascular disease is an underappreciated yet important area of study. Understanding the relationship between these two entities may allow for more comprehensive care of those with cardiovascular disease. The primary objective of this meta-analysis is to evaluate the relationship between optimism and risk of developing adverse events such as all-cause mortality or fatal and non-fatal cardiovascular disease in community-based populations.

METHOD

A systematic search of electronic databases was conducted from inception through November 2021 for prospective studies evaluating optimism and adverse outcomes. Two reviewers independently selected prospective cohort studies that evaluated optimism and either all-cause mortality or cardiovascular disease and reported hazard ratios of these outcomes between optimistic and non-optimistic groups. Studies that reported odds ratio or other risk assessments were excluded. Pooled hazard ratios were calculated in random-effects meta-analyses.

RESULTS

Pooled analysis of six studies (n = 181,709) showed a pooled hazard ratio of 0.87 (95% confidence interval [CI], 0.82-0.92) for all-cause mortality among those with more optimistic mindset. Analysis of seven studies (n = 201,210) showed a pooled hazard ratio of 0.59 (95% CI, 0.37-0.93) for cardiovascular disease and pooled hazard ratio of 0.57 (95% CI, 0.07-4.56) for stroke.

CONCLUSIONS

In this pooled meta-analysis, optimism was associated with a reduced risk of all-cause mortality and of cardiovascular disease. These results suggest an important relationship between psychological health and cardiovascular disease that may serve as an area for intervention by clinicians.

Environmental Contributions to Anhedonia

Anhedonia is a core feature of psychopathological conditions that have recent exposure to stress and trauma as central to their etiology. Indeed, evolutionary accounts of depression suggest that decreased motivation to pursue reward may be an adaptive strategy in the face of social stress, in particular, as it may serve to defuse interpersonal conflict. Through a review of rodent models and research with humans, we show that exposure to stress, particularly when it is chronic, repeated, and/or involves themes of social rejection or defeat, is consistently associated with reduced hedonic capacity ("liking"), motivation to pursue reward ("wanting"), and ability to learn from reward ("reward learning"). Further, across rodent and human research, there is evidence that females show greater stress-induced blunting of reward processing than males. In humans, this sex difference emerges most strongly when examining individual differences in the stress response rather than group differences in stress exposure. We discuss the implications of these findings for understanding the etiology of, and sex differences in, stress-related psychopathology, including depression and addiction.

Chronic Distress in Male Mice Impairs Motivation Compromising Both Effort and Reward Processing With Altered Anterior Insular Cortex and Basolateral Amygdala Neural Activation

In humans and mammals, effort-based decision-making for monetary or food rewards paradigms contributes to the study of adaptive goal-directed behaviours acquired through reinforcement learning. Chronic distress modelled by repeated exposure to glucocorticoids in rodents induces suboptimal decision-making under uncertainty by impinging on instrumental acquisition and prompting negative valence behaviours. In order to further disentangle the motivational tenets of adaptive decision-making, this study addressed the consequences of enduring distress on relevant effort and reward-processing dimensions. Experimentally, appetitive and consummatory components of motivation were evaluated in adult C57BL/6JRj male mice experiencing chronic distress induced by oral corticosterone (CORT), using multiple complementary discrete behavioural tests. Behavioural data (from novelty suppressed feeding, operant effort-based choice, free feeding, and sucrose preference tasks) collectively show that behavioural initiation, effort allocation, and hedonic appreciation and valuation are altered in mice exposed to several weeks of oral CORT treatment. Additionally, data analysis from FosB immunohistochemical processing of postmortem brain samples highlights CORT-dependent dampening of neural activation in the anterior insular cortex (aIC) and basolateral amygdala (BLA), key telencephalic brain regions involved in appetitive and consummatory motivational processing. Combined, these results suggest that chronic distress-induced irregular aIC and BLA neural activations with reduced effort production and attenuated reward value processing during reinforcement-based instrumental learning could result in maladaptive decision-making under uncertainty. The current study further illustrates how effort and reward processing contribute to adjust the motivational threshold triggering goal-directed behaviours in versatile environments.

RNA therapeutics for mood disorders: current evidence toward clinical trials

INTRODUCTION

Mood disorders are severe yet frequent psychiatric disorders worldwide, comprising major depressive disorder (MDD) and bipolar disorders (BD). Their treatment remains poorly effective. Recently, growing evidence for epigenetic mechanisms has emerged. Consequently, a great interest in a novel pharmacological class arose: RNA therapeutics.

AREAS COVERED

We conducted a systematic review of RNA therapeutics -antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs), short hairpin RNAs (shRNAs), and micro-RNA (miRNA) therapeutics- for the treatment of mood disorders studied in pre-clinical animal models listed in PubMed, in clinical trials registered in ClinicalTrials.gov and available on the market by combining literature search and Food and Drug Administration and European Medicine Agency online databases. Eighteen pre-clinical studies investigated the antidepressant effects of RNA therapeutics. However, even though there is an increasing number of marketing authorizations and clinical trials for the past twenty years, no RNA therapeutic has reached the clinical development pipeline for the treatment of psychiatric disorders yet.

EXPERT OPINION

Several promising RNA therapeutics have been tested in pre-clinical studies for MDD, whereas no molecule has been developed for BD. There are several issues to address before reaching clinical development and new challenges include stratifying patient population and predicting therapeutic response.

Chronic non-discriminatory social defeat stress reduces effort-related motivated behaviors in male and female mice

Reward and motivation deficits are prominent symptoms in many mood disorders, including depression. Similar reward and effort-related choice behavioral tasks can be used to study aspects of motivation in both rodents and humans. Chronic stress can precipitate mood disorders in humans and maladaptive reward and motivation behaviors in male rodents. However, while depression is more prevalent in women, there is relatively little known about whether chronic stress elicits maladaptive behaviors in female rodents in effort-related motivated tasks and whether there are any behavioral sex differences. Chronic nondiscriminatory social defeat stress (CNSDS) is a variation of chronic social defeat stress that is effective in both male and female mice. We hypothesized that CNSDS would reduce effort-related motivated and reward behaviors, including reducing sensitivity to a devalued outcome, reducing breakpoint in progressive ratio, and shifting effort-related choice behavior. Separate cohorts of adult male and female C57BL/6 J mice were divided into Control or CNSDS groups, exposed to the 10-day CNSDS paradigm, and then trained and tested in instrumental reward or effort-related behaviors. CNSDS reduced motivation to lever press in progressive ratio and shifted effort-related choice behavior from a high reward to a more easily attainable low reward in both sexes. CNSDS caused more nuanced impairments in outcome devaluation. Taken together, CNSDS induces maladaptive shifts in effort-related choice and reduces motivated lever pressing in both sexes.