DIFFERENTIAL ENVIRONMENTAL MODULATIONS ON LOCOMOTOR-ACTIVITY, EXPLORATION AND SPATIAL-BEHAVIOR IN YOUNG AND OLD RATS

The effects of environmental enrichment on motor activity, exploration and spatial performances were studied in young and old rats. Both you ng (4 mo old) and old (22 mo old) rats were housed from weaning to tes ting either in standard or in enriched conditions. All rats were submi tted successively to spontaneous alternation test and to object explor ation test. Results show that locomotion is decreased by age and enric hment but that the quality of exploration expressed by corrected alter nation scores or by the response to spatial change is improved by enri chment sometimes in old, sometimes in young rats. Enrichment tends to accelerate the acquisition of spatial informations in young rats, but it does not succeed to restore the reactivity to spatial change of old rats in the object exploration test. These results, although they do not rule out a persistance of a continued behavioural plasticity durin g aging, also support the idea that the beneficial effects of environm ental stimulations do not succeed to restore high cognitive function, such as the capacity to have a spatial representation, in old animals.