The Influence of Environmental Enrichment on Affective and Neural Consequences of Social Isolation Across Development

Protective effects of exercise on responses to combined social and environmental stress in prairie voles

The combination of social and environmental stressors significantly influences psychological and physical health in males and females, and contributes to both depression and cardiovascular diseases. Animal models support these findings. Voluntary exercise may protect against some forms of stress; however, the protective effects of exercise against social stressors require further investigation. This study evaluated the influence of exercise on the impact of combined social and environmental stressors in socially monogamous prairie voles. Following a period of social isolation plus additional chronic environmental stress, prairie voles were either allowed access to a running wheel in a larger cage for 2 weeks or remained in sedentary conditions. A behavioral stress task was conducted prior to and following exercise or sedentary conditions. Heart rate (HR) and HR variability were evaluated after exercise or sedentary conditions. Group-based analyses indicated that exercise prevented elevated resting HR and promoted autonomic control of the heart. Exercise was also effective against social and environmental stress-induced forced swim test immobility. Some minor sex differences in behavior were observed in response to exercise intensity. This research informs our understanding of the protective influence of physical exercise against social and environmental stressors in male and female humans.

Association Between the Enriched Environment Level and Serum Brain-Derived Neurotrophic Factor (BDNF) in Patients with Major Depressive Disorder

Major Depressive Disorder (MDD) is a neuropsychiatric condition whose neurobiological characteristics include alterations in brain plasticity, modulated by Brain-Derived Neurotrophic Factor (BDNF). In animal models, environmental enrichment promotes neuroplasticity and reduces depressive-like behaviors. In humans, we proposed to assess the level of Enriched Environment (EE) using a questionnaire that includes different domains of the EE (cognitive, social, and physical), which we named the EE Indicator (EEI).

OBJECTIVE

To determine the relationship between the level of EE and serum BDNF in participants with MDD and healthy controls.

MATERIALS

Participants with MDD without antidepressant treatment and healthy controls were recruited, and their EE level and serum BDNF concentration were determined looking for correlations between their clinical characteristics and the cognitive, social, and physical activities according to the EEI.

RESULTS

A total of 25 participants were recruited, of which 6 participants with MDD and the same number of controls were selected in a paired manner. Although no differences were found in the concentration of BDNF between the groups, positive correlations were observed between cognitive EE and BDNF (r = 0.62, p = 0.035), as well as negative social EE and the Hamilton Depression Rating Scale (HDRS) (r = -0.86, p = 0.001). The sum between cognitive and social EE showed a positive correlation with the serum concentration of BDNF (r = 0.34, p = 0.0451).

CONCLUSIONS

The level of EE is potentially modulating the presence and severity of MDD at a clinical level, but it can also influence at a neuroplastic level through promoting or limiting the concentration of BDNF.

Attachment across the lifespan: Examining the intersection of pair bonding neurobiology and healthy aging

Increasing evidence suggests that intact social bonds are protective against age-related morbidity, while bond disruption and social isolation increase the risk for multiple age-related diseases. Social attachments, the enduring, selective bonds formed between individuals, are thus essential to human health. Socially monogamous species like the prairie vole (M. ochrogaster) form long-term pair bonds, allowing us to investigate the mechanisms underlying attachment and the poorly understood connection between social bonds and health. In this review, we explore several potential areas of focus emerging from data in humans and other species associating attachment and healthy aging, and evidence from prairie voles that may clarify this link. We examine gaps in our understanding of social cognition and pair bond behavior. Finally, we discuss physiologic pathways related to pair bonding that promote resilience to the processes of aging and age-related disease. Advances in the development of molecular genetic tools in monogamous species will allow us to bridge the mechanistic gaps presented and identify conserved research and therapeutic targets relevant to human health and aging.

Introduction to Special Issue on Affective Science in Animals: Toward a Greater Understanding of Affective Processes in Non-Human Animals

How should we characterize the affective lives of non-human animals? There is a large body of work studying affective processes in non-human animals, yet this work is frequently overlooked. Ideas about the affective lives of animals have varied across culture and time and are reflected in literature, theology, and philosophy. Our contemporary ideas about animal affect are philosophically important within the discipline of affective science, and these ideas have consequences in several domains, including animal husbandry, conservation, and human and veterinary medicine. The articles contained within this special volume cover several levels of analysis and broad representation of species, from the non-mammalian, to rodents, to primates; but together, these articles are collectively concerned with the topic of affective processes in non-human animals.