Aged rodents have been used as preclinical models of age-associated cognitive decline. Most of those models displayed substantial impairments in learning and memory. The initial, more subtle changes that precede more severe losses in cognitive abilities have not been well characterized. Here, we established a model detecting initial subtle cognitive changes by comparing the performance of moderately aged Oncins France Strain A Sprague Dawley rats with young rats in the Morris water maze (MWM) and the Open Field (OF) test. Both age groups improved their performance during the training period at a similar rate; however, the older rats performed worse in several parameters measured in the MWM. Our results suggest that already at the age of 18-20 months rats show changes in their approach to solve the spatial memory task while their ability to learn is not yet diminished. The disparate spatial information processing of the moderately aged rats provides a novel animal model for early age-related cognitive alterations that could be useful to test the effect of early intervention strategies. Moreover, our results suggest that the sensitivity of cognitive tests in the elderly could be substantially enhanced if they assess both the improvement after several trials, and the strategy used to solve a certain task.
Keywords: Aged rat; Cognition; MCI; Mild cognitive impairment; Spatial learning, memory.
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