ENVIRONMENTAL ENRICHMENT REVERSES THE DETRIMENTAL ACTION OF EARLY INCONSISTENT STIMULATION AND INCREASES THE BENEFICIAL-EFFECTS OF POSTNATAL HANDLING ON SHUTTLEBOX LEARNING IN ADULT-RATS

Certain types of environmental stimulation administered during critica l periods of neural development can enduringly modify adult behavior. The present experiments show that postnatal handling of Sprague-Dawley rats (administered from postnatal days 1 to 22) and/or living in an e nriched environment (EE; from weaning until the age of 100 days) clear ly improved the ability to learn a two-way active avoidance task in ad ulthood. In addition the results demonstrated that postnatal inconsist ent stimulation (from postnatal days 1 to 22) impaired avoidance acqui sition in the same task. This detrimental effect of inconsistent stimu lation was reversed by EE. Our findings provide evidence that differen t types of early experience can influence learning abilities in distin ct directions and with different strenghts.