Spontaneous stereotypy and environmental enrichment in deer mice (Peromyscus maniculatus): Reversibility of experience

Spontaneous and persistent stereotypies exhibited by deer mice appear to be prevented by post-weaning rearing in a larger, more complex environment. We sought to determine: (1) if exposure to an enriched environment later in development would still be efficacious in reducing stereotypy, and (2) if exposure to an enriched environment would prevent the development of stereotypy after animals were returned to standard laboratory cages. Enriched housing (24–84 days of age) was associated with substantially lower levels of stereotypy. Moreover, environmental enrichment experienced later in development (84–124 days of age) was as effective as early enrichment. This was not the case, however, for older animals (11–14 months of age) that experienced the same duration of enriched housing. The beneficial effects of early enrichment were found to persist as mice placed in standard cages following enrichment exhibited lower levels of stereotypy than controls. These findings support a sensitive period for the amelioration of abnormal repetitive behavior and suggest a neuroprotective effect of this form of early experience.