Do fawn-footed mosaic-tailed rats experience age-related cognitive decline in novel object recognition?

Abstract

Ageing is associated with a reduction in cognitive function and numerous studies have focused on age-related cognitive decline in laboratory rodent models to provide insight into human ageing and neurogenerative disease. However, fewer studies have focused on age-related cognitive decline in captive wild animals, which typically live longer than their free-roaming wild counterparts. In this study, we investigated whether recognition memory, measured using a novel object recognition (NOR) task, declines with age in a captive population of native Australian fawn-footed mosaic-tailed rats (Melomys cervinipes). Adult individual mosaic-tailed rats were tested for NOR twice, 4.6 years apart. Both younger and older mosaic-tailed rats took longer to approach the novel object, while intermediate-aged rats responded the fastest. Interestingly, rats were also less discriminatory when at an intermediate age, although this was not statistically significant. Sex affected the number of interactions with the novel object, with female mosaic-tailed rats interacting more with the unfamiliar object than males. This is the first study exploring age-related cognitive decline in NOR in a native Australian rodent, indicating that recognition abilities of mosaic-tailed rats do not diminish over time. Instead, some intrinsic biological factors affect NOR and there may be a trade-off in energetic investment associated with neophobia and other factors during the prime-of-life.