Dissecting novel object exploration in a fully automated homecage-based novel object recognition test

TL;DR

A fully automated homecage-based test reliably measures object memory in mice, improving reproducibility and reducing experimental variability.

Contribution

A novel, fully automated homecage-based NOR test that enhances reproducibility and reduces human error in object memory studies.

Findings

Mice reliably preferred novel objects after 24-h and 7-day delays, even from a distance.

Recognition after 24 h depends on prior object interactions, but not after 7 days.

External biases in exploration can be mitigated using relative discrimination measures.

Abstract

The novel object recognition (NOR) test is widely used to assess memory in rodents, offering strong ethological validity, cross-species relevance, and specificity for hippocampal-parahippocampal function. However, standard implementations are often confounded by uncontrolled factors. Here, we present a fully automated, homecage-based NOR test for evaluating long-term object memory in mice. Our empirically informed computational model demonstrates the robustness of this approach despite uncertainties in defining exploratory behavior. Mice reliably preferred novel over familiar objects after both 24-h and 7-day delays, with recognition emerging already at a distance. Results were replicated across two facilities. Notably, recognition after 24 h depended on prior interactions with the replaced object, but not after 7 days. We also show that external factors can bias exploration, which can be mitigated using relative discrimination measures. This automated paradigm enhances standardization, reproducibility, and our understanding of the factors influencing object exploratory behaviors and object memory.

•Fully automated homecage NOR test reliably measures long-term object memory in mice•Recognition occurs at both 24-h and 7-day delays, even from a distance•External biases can be mitigated using relative discrimination measures for accuracy•Pipeline enhances reproducibility in object exploratory behavioral studies

Fully automated homecage NOR test reliably measures long-term object memory in mice

Recognition occurs at both 24-h and 7-day delays, even from a distance

External biases can be mitigated using relative discrimination measures for accuracy

Pipeline enhances reproducibility in object exploratory behavioral studies

Recognition of objects as novel or familiar is an important cognitive memory function with cross-species relevance. Extensive work has provided a good understanding of the brain regions involved. Despite the apparent simplicity of novel object recognition (NOR) tests, they remain challenging due to their sensitivity to various uncontrolled experimental factors and differences in study design. Here, we report a fully automated standardized NOR test carried out in a mouse’s homecage, which minimizes previously reported variability in NOR tests.

Ho et al. develop homecage-based fully automated novel object recognition test to measure object memory in mice. The test is consistent across laboratories and removes human error, helping scientists study memory and brain function more accurately and reliably.

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