Persistence of visual cortex dendritic alterations induced by postweaning exposure to a "superenriched" environment in rats.

To assess the relative permanence of dendritic alterations induced by postweaning housing conditions, dendritic field parameters in the occipital cortex were compared among rats that had spent 30 days, beginning at 23-25 days of age, in a "superenriched" environment, rats that had the same treatment followed by 30 days of housing in individual cages, and rats that spent either 30 or 60 days in individual cages. The superenriched environment consisted of two large toy-filled cages, one containing water and one containing food, which were attached to opposite ends of a maze in which the pattern of barriers was changed daily. Aspinous stellate neurons of layer IV and pyramidal neurons of layer III both exhibited increases in total dendritic length and number of branches in response to superenriched environment exposure. In a factorial analysis of initial experience condition by age of subject, the consistent presence of experience effects combined with the relatively rare appearance of either age effects or interactions indicated that the dominant result was for the dendritic effects of the initial superenriched environment exposure to persist through the subsequent period of individual housing.