Distinct Enriched Environment Components Differentially Shape the Temporal Dynamics of Anxiety-Like Behavior in Rats

Enriched environments (EEs) are known to improve anxiety-like and related emotional behaviors in rodents. However, EEs comprise multiple components providing distinct sensory and motor stimuli. It remains unclear how these qualitative differences in behavioral experience shape the temporal dynamics of anxiety-like and related emotional responses. Male rats were housed for 4 weeks in one of four conditions: standard environment (SE), EE with a running wheel and objects (EE), EE with a running wheel only (EER), or EE with objects only (EEO). We monitored physical activity and locomotor behaviors during the housing period. Anxiety-like behavior was evaluated using a 10-min elevated plus maze (EPM) test, which was divided into five consecutive phases to enable time-resolved analysis. Physical activity was consistently higher in the wheel-containing groups (EE and EER) than in the SE group. While rearing behavior increased in all enriched groups, object interaction time was significantly higher in the EEO group than in the EE group. In the EPM test, the EE and EER groups spent significantly more time in the open arms during the early phases (p < 0.05). Conversely, the EEO group showed greater open-arm exploration at later phases than the SE group (p = 0.0068). These findings indicate that the nature of the environmental stimuli distinctively determines the onset and progression of anxiolytic effects. Our findings demonstrate that different components of EE differentially shape the temporal profile of anxiety-like and related emotional behavior. Voluntary exercise and object-based exploration influence not only the magnitude of anxiety reduction but also the temporal trajectory of these effects. Time-resolved behavioral analysis highlights the importance of environmental quality and specific sensorymotor experiences beyond total physical activity levels.