ReviewEnvironmental enrichment in female rodents: Considerations in the effects on behavior and biochemical markers

- Lack of standardized methods in the study of EE leads to mixed results on female rodents' emotionality and hormone secretion.
- EE leads to reduced body weight in enriched female rodents but more rapid weight gain in offspring.
- Maternal enrichment appears most beneficial to offspring and mother when implemented during gestation.
- The communal nest paradigm provides an alternative to standard EE housing but is highly sensitive to birth order manipulations.
- The inclusion of both genders in studies of EE, when behavioral and emotional parameters are investigated, is recommended.

Environmental enrichment (EE) exposes laboratory animals to novelty and complexity through alterations in the physical and social environment, which lead to enhanced sensory, cognitive and physical stimulation. Housing rodents in an EE is a highly recommended practice by governing bodies regulating animal welfare due to a growing body of evidence suggesting its benefits on rodents' wellbeing and the more naturalistic environment that such housing conditions provide. However, most paradigms and hypotheses rely on information currently available from studies performed on male subjects and the information regarding the effects of EE on female rodents' behavior and physiology is limited. Given the variety of EE paradigms described, it is increasingly difficult to ascertain the benefits or possible consequences of enriched housing strategies in females, let alone aid at establishing standardized environments in rodents. This review evaluates the female rodent literature that has examined the outcome of EE on behavior and neurochemistry and aims at identifying key elements to be addressed by future studies. Specifically, results from cognitive behavioral tests as well as commonly used tests of emotionality will be discussed, while also evaluating their relation to changes in neurochemistry and hormones brought on by various EE paradigms. Lastly, the impact of maternal enrichment on both offspring and maternal behavior and physiology will be reviewed.