Ishikawa et al 2014: Effects of early social isolation (gray bars) and enriched environment (white bars-running wheel) on anxious like phenotypes demonstrated in adult rats undergoing the elevated plus maze test. Rats exposed to social isolation demonstrated more closed arms entries attesting to greater anxiety levels.
References:
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Ishikawa J, Ogawa Y, Owada Y, Ishikawa A (2014) Hyperlocomotor activity and stress vulnerability during adulthood induced by social isolation after early weaning are prevented by voluntary running exercise before normal weaning period. Behav Brain Res 264C:197-206