Task optimization and ontogenetic profile of the object-in-Place task in mice

Remembering the identity and the location of distinct spatial elements is crucial for an animal's successful exploration of their environment. Locating food and shelter are but a few behaviors that rely on forming effective associations between the identity and location of spatial elements. Object-in-place (OiP) tasks are commonly used in rats to assess this identity-location association. While the availability of genetic resources has made the mouse an increasingly used animal model in neuroscience research, very few studies have successfully assessed OiP in mice. To address this limitation, we tested three distinct experimental designs of the spontaneous OiP preference task in adult C57/129 J and C57BL/6 J mice. C57BL/6 J, but not C57/129 J mice, displayed OiP preference in the four-object version of the OiP task. In contrast, mice of both strains successfully performed the two-object OiP task design, with retention intervals of five minutes and one hour. To broaden our task validation, we uncovered the ontogenetic profile of two-object OiP in C57/129 J mice, which emerges between postnatal day (P)25 and P28 in this mouse strain. Our data establish robust guidelines for successful assessment of OiP preference in mice across the lifespan, expanding the available behavioral toolbox for spatial memory research in mice.