Grippo, A. J., Ihm, E., Wardwell, J. et al. 2014. The effects of environmental enrichment on depressive and anxiety-relevant behaviors in socially isolated prairie voles. Psychosomatic Medicine 76(4), 277-284.

Social isolation is associated with depression, anxiety and negative health outcomes. Environmental enrichment, including environmental and cognitive stimulation with inanimate objects and opportunities for physical exercise, may be an effective strategy to include in treatment paradigms for affective disorders as a function of social isolation. In a rodent model – the socially monogamous prairie vole – we investigated the hypothesis that depression- and anxiety-related behaviors following social isolation would be prevented and remediated with environmental enrichment. Experiment 1 investigated the preventive effects of environmental enrichment on negative affective behaviors when administered concurrently with social isolation. Experiment 2 investigated the remediating effects of enrichment on negative affective behaviors when administered following a period of isolation. Behaviors were measured in 3 operational tests: open field; forced swim test; and elevated plus maze. In isolated prairie voles, enrichment prevented depression- (immobility in FST, group × housing interaction, P=0.049) and anxiety-relevant behaviors (exploration in open field, group × housing interaction, P=0.036; exploration in elevated plus maze, group × housing interaction, P=0.049). Delayed enrichment also remediated these behaviors in isolated animals (immobility in forced swim test, main effect of housing, P=0.001; exploration in open field, main effect of housing, P=0.047; exploration in elevated plus maze, main effect of housing, P=0.001), and was slightly more effective than physical exercise alone in remediating anxiety-relevant behaviors. These findings provide insight into the beneficial effects of an enriched environment on depression- and anxiety-relevant behaviors using a translational rodent model of social isolation.