Abstract
The perirhinal cortex (PRh) is a critical mediator of recognition memory, and a wealth of evidence points to impairment in PRh function with age. Despite this evidence, age-related deficits in recognition memory are not consistently observed. This may be partially due to the fact that older animals also have well-established deficits in hippocampal function, and many protocols that assess perirhinal function are also sensitive to hippocampal damage. When using one of these protocols, spontaneous object recognition in an open field, we are able to replicate published age-related deficits using pairs of complex objects. However, when using zero-delay object recognition, a task that is more resistant to the influence of changes in hippocampal function, we find no significant age-related differences in recognition memory in the same animals. These data highlight the importance of the protocol used for testing recognition memory, and may place constraints on the role of the PRh in age-related recognition memory impairment as it is typically tested in much of the literature.
Highlights
Normal aging is associated with changes in many cognitive functions, including memory
The majority of previous work showing age-related deficits in spontaneous object recognition (SOR) has been done under circumstances in which the hippocampus may contribute – with testing conducted in open fields and with delay intervals during which animals are removed from the environment
The current results provide a potential explanation for the equivocal results seen among studies of age-related differences in recognition memory
Summary
Normal aging is associated with changes in many cognitive functions, including memory. Testing in a more confined space with high walls can reduce contextual cues and minimize the hippocampal contribution to performance Testing under these circumstances results in tasks, such as zero-delay object recognition (ZOR), that are sensitive to damage to the perirhinal cortex and not the hippocampus (e.g., [27]). Tasks with at least some of the features of ZOR ( having the task occur in a Y-maze and with little or no delay) are commonplace in the “basic” literature on recognition memory, while these types of tests are relatively rare in the context of ageing research This is only problematic, if these variations in testing protocol produce meaningful differences in results. Spatial learning was assessed using the Morris water maze [28]
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