Object recognition tasks in rats: Does sex matter?

Abstract

Novelty recognition tasks based on object exploration are frequently used for the evaluation of cognitive abilities and investigation of neurobiological and molecular aspects of memory in rodents. This is an interesting approach because variations of the object recognition tasks focus on different aspects of the memory events such as novelty, location, context, and combinations of these elements. Nevertheless, as in most animal neuroscience research, female subjects are underrepresented in object recognition studies. When studies include females, the particularities of this sex are not always considered. For example, appropriate controls for manipulations conducted exclusively in females (such as estrous cycle verification) are not included. In addition, interpretation of data is often based on standardizations conducted with male subjects. Despite that, females are frequently reported as deficient and unable to adequately perform some memory tests. Thus, our study aims to review studies that describe similarities and differences between male and female performances in the different variations of object recognition tasks. In summary, although females are commonly described with deficits and the articles emphasize sex differences, most published data reveal similar performances when sexes are compared.

Developmental trajectory of episodic-like memory in rats

“…While our study was not designed to address the importance of sex as a determinant of object recognition memory development, we were able to explore this question in our cross-sectional experiment with LH rats. The absence of sex-dependent developmental trajectories in LH rats is consistent with recent research and meta-analyses suggesting that sex is not a significant determinant of object memory performance ( Becker et al, 2016 ; Becegato and Silva, 2022 ).…”

Hippocampal damage causes retrograde amnesia for objects' visual, but not odour, properties in male rats

“…The design of the present study included only male rats, limiting any conclusion about potential sex differences. There is considerable evidence suggesting that male and female rats may use different spatial navigation strategies (Koss & Frick, 2017; Yagi & Galea, 2019), but little evidence for sex differences in recognition or discrimination memory (Becegato & Silva, 2022). Also, hippocampal lesions similarly affect male and female rats across most memory tasks (Broadbent & Clark, 2013; Driscoll et al, 2005; Epp et al, 2008; Morris et al, 1982; Mumby et al, 1999; Sutherland et al, 2008).…”

The anterior retrosplenial cortex is required for short‐term object in place recognition memory retrieval: Role of ionotropic glutamate receptors in male and female Long–Evans rats

“…Given inconsistent findings regarding sex differences in short‐term OiP performance in rodents (Becegato & Silva, 2022; Cost et al, 2014, 2012; Howland et al, 2012) and humans (Asperholm et al, 2019), female rats were used in all experiments and considered as a statistically independent factor during analyses. In each experiment, we assessed sample exploration (Figures 1d–f, 2b–d, 3b–d), test exploration (Figures 1g–i, 2e–g, 3e–g) and DR performance (Figures 1j–l, 2h and i, 3h and i) using two‐way repeated measured (RM) analyses of variance (ANOVAs) comparing Sex by Session, Object Set and Treatment.…”

“…Given inconsistent findings regarding sex differences in short-term OiP performance in rodents (Becegato & Silva, 2022;Cost et al, 2014Cost et al, , 2012Howland et al, 2012) and humans (Asperholm et al, 2019), female rats were used in all experiments and considered as a statistically independent factor during analyses. In each experiment, we assessed sample exploration (Figures 1d-f…”

“…The objectin-place (OiP) test is a spontaneous recognition paradigm that relies on rodents' innate tendency to explore unfamiliar objects (Binder et al, 2015). Interestingly, research from our lab and others suggests that male rats exhibit an advantage in the OiP test, particularly when delays are extended beyond 30 min; however, differences seem to diminish when estrous phase is considered (Asperholm et al, 2019;Becegato & Silva, 2022;Cost et al, 2012;Herlitz & Rehnman, 2008;Howland et al, 2012;Mitchell et al, 2008). In addition to uncertainty regarding sex differences, to our knowledge, no labs have reported on the reliability of repeated OiP testing, which has obvious benefits including limiting the number of subjects required and facilitating within-subjects control comparisons.…”