Renner M J, Rosenzweig M R
Dev Psychobiol. 1987 Jan;20(1):19-24. doi: 10.1002/dev.420200106.
It has been proposed that the brain effects induced by laboratory environmental enrichment may be a product of the social stimulation inherent in the standard enriched environment. This experiment was conducted in order to study the suitability of the golden-mantled ground squirrel Spermophilus lateralis (a solitary-living species) for studies attempting to dissociate social factors from other effects in brain and behavioral effects of environmental enrichment. Juvenile Spermophilus lateralis, born in the laboratory of mothers wild-caught while pregnant, were assigned singly to individual enriched conditions (I-EC) or impoverished (IC) conditions at 55-62 days (an age at which wild individuals would disperse from the natal burrow and live alone). After 30 days, the subjects were videotaped in two 10-min opportunities for exploration; following this, they were sacrificed and their brains dissected. Multiple indications of isolation stress were observed, including unusual difficulty in handling, stereotyped pacing behavior, and escape behaviors in the exploration arena. Comparisons between I-EC and IC showed no differences in whole-brain weight or weights of several brain regions. These results indicate that S. lateralis is not suitable for this type of study; in addition, this species' reported nonsociality is questioned, based on these subjects' reactions to isolation housing and field observations of social interactions in this species.
