AGE-RELATED CHANGES AND COGNITIVE PERFORMANCE LEVELS IN WORKING MEMORY ACROSS THE LIFESPAN OF MALE FISCHER 344 RATS

Abstract

Loss of cognitive function is a very common symptom of aging in humans. This decline has also been observed across several different rat models and these models can be used to gain an insight into cognitive decline. This study looked at how working memory changes in male Fischer 344 (F344) rats throughout their lifespan. Three age groups of young, (6mo), middle aged (15mo) and old (23mo) rats underwent the Morris water maze protocol for working memory using inter-trial intervals of 30 seconds, 30 minutes, and 2 hours. The old rats were significantly worse at performing the working memory tasks were than the young and middle-aged rats for the 30 minute (p=0.0028) delay, but none of the other inter-trial intervals revealed significant differences. These rats were initially tested on a reference memory water maze protocol and categorized into high performers, average performers, and low performers within each age group. These categorizations were then used to see if the level of cognitive functionality from the spatial reference memory task match the performance of the rats on the working memory task. Results show that the working memory categorization for performance level does not match the performance level categorization for reference memory. The spatial reference memory task relies on the hippocampus while the working memory task primarily relies on the prefrontal cortex. Although there are connections between these two structures that interact, the differences in level of cognitive performance between the two tasks suggests that the mental operations engaged by these tasks work independently such that impairment in one does not predict impairment in the other.