Memory enhancement in aged rats: The differential outcomes effect

Aged (23 months) and young (3 months) rats were trained on an operant Match ing-To-Position (MTP) task that had either (a) specific outcomes (reinforce rs) correlated (differential groups), or (b) outcomes uncorrelated (nondiff erential groups) for each correct sample-choice sequence. The traditional v ersion of MTP uses a common outcome and is thought to assess spatial workin g memory. Aged rats are impaired on the traditional version of MTP. However , aged animals trained with the Differential Outcomes Procedure (DOP) did n ot display the typical age-related decline in spatial working memory. Diffe rences in choice accuracy between old and young rats reached significance o nly if the subjects were trained with a nondifferential outcomes procedure (NOP)-similar to when a common outcome is used. These data demonstrate that employing behavioral procedures to tap intact cognitive functions is an ef fective means of enhancing spatial working memory in normal as well as aged subjects. (C) John Wiley & Sons, Inc.