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Sex- and light cycle-based differences in spontaneous object recognition performance


The spontaneous object recognition (SOR) task is a test of recognition memory, drawing on the innate tendency for rats to explore novel objects and images more than those that are familiar. This task involves multiple brain areas including the perirhinal cortex (PER), which is necessary for identifying novelty. While many studies support the role of the PER in visual recognition memory, there are two common issues: only male rodents are tested and they are only tested during the light phase.\n\nFemales are generally not used for behavioral experiments due to the possible effects of circulating hormone levels. Effects of sex differences on memory in rodents, however, have not been thoroughly investigated. Whereas males often outperform females in spatial navigation tasks, females often outperform males in fear conditioning tasks. Additionally, while rats are nocturnal and demonstrate higher locomotor activity during their dark phase, most behavioral experiments are run during the light phase. This leads to additional confounding variables such as a lack of alertness or motivation during testing. To date, there have been no studies on sex or light cycle differences in the SOR task. Therefore, we set out to elucidate whether these differences existed. We tested six females in the light phase, six males in the light phase, and six males in the dark phase on the SOR task. Our results show that sex did not impact cognitive performance in the SOR task, but suggest that the phase of the light cycle in which the rats were tested may impact recognition memory. Rats tested during the light phase spent more time exploring the novel objects than the familiar objects, resulting in a positive discrimination ratio. Rats tested during the dark phase, however, spent equal time exploring the novel and familiar objects. The discrimination ratios for rats tested in the light were not significantly different from those of the rats tested during the dark, but a power analysis suggests these results would reach significance if the number of subjects were doubled.


Udawatta, Methma, "Sex- and light cycle-based differences in spontaneous object recognition performance" (2015). Summer Research Symposium. Brown Digital Repository. Brown University Library.



  • Summer Research Symposium

    Each year, Brown University showcases the research of its undergraduates at the Summer Research Symposium. More than half of the student-researchers are UTRA recipients, while others receive funding from a variety of Brown-administered and national programs and fellowships and go …