The Contribution of Environmental Enrichment to Phenotypic Variation in Mice and Rats

Abstract

The reproducibility and translation of neuroscience research is assumed to be undermined by introducing environmental complexity and heterogeneity. Rearing laboratory animals with minimal (if any) environmental stimulation is thought to control for biological variability but may not adequately test the robustness of our animal models. Standard laboratory housing is associated with reduced demonstrations of species typical behaviors and changes in neurophysiology that may impact the translation of research results. Moreover, modest increases in environmental enrichment (EE) mitigate against insults used to induce animal models of disease, directly calling into question the translatability of our work and may in part underlie the disconnect between preclinical and clinical research findings. Enhancing environmental stimulation for our model organisms promotes ethological natural behaviors but may simultaneously increase phenotypic trait variability. To test this assumption, we conducted a systematic review and evaluated coefficients of variation between EE and control housed animals. Overall, animals housed in enrichment were not more variable than controls. Therefore, environmental heterogeneity introduced into the laboratory does not compromise data integrity.

Enhancing Effects of Environmental Enrichment on the Functions of Natural Killer Cells in Mice

“…Differences in outcomes may arise based on different experimental EE paradigms or different lived experiences among animals within any complex social and physical environment. This concern has been identified repeatedly, and studies addressing it frequently show reliability and reproducibility in EE (76)(77)(78). Basic standard environment features like bedding, housing density, temperature, and ambient noise all contribute to outcome variation with much less concern from the scientific audience, perhaps due to less awareness about welfare and husbandry needs (79).…”