The Novel Object Recognition Task

Introduction

Maternal separation (MS) has been used in mice and rats as an animal model of early life adversity (ELA) in human children to examine its effects on sociability, stress reactivity, learning, and memory. In a previous study, MS C57BL/6 mice, an inbred strain of mice, were found to have a deficit in novel object recognition, which is demonstrated by a lack of novel object exploration time compared to that of a familiar object during the novel object recognition test (NORT). For this experiment, they used an MS procedure consisting of removing the rodent pups from their mother for 4h/day from postnatal day 2 (P2) until P20 (Shin & Lee, 2023). In this study, we use CD-1 mice, an outbred strain of mice, for more generalizability of results due to their genetic variation. Our MS procedure consists of removing the pups for 3h/day from P1-P14. In this experiment, we examined the effects of MS on object recognition memory in the novel object recognition test in adolescent CD-1 mice.

General Experimental Design

Rearing Conditions: 

Control and MS litters are housed in a vivarium with a reversed 12/12hr light/dark cycle. From postnatal day 1 (PND 1) to PND 14, MS mice were separated from their mothers for 3 hours a day in a different room away from the vivarium at a temperature of 27 °C. From  P15-P20 the mice were housed continuously with their mother. Control Litters were housed continuously with their mother from birth until all litters were weaned on P21.

The Novel Object Recognition Test

On P38-P44, the NORT was conducted in a standard housing cage, consisting of three trials: habituation, training, and testing.

• Habituation

  • Mouse was left to habituate in the cage they will be trained and tested in for 10 minutes, 24 hours prior to training.

• Training

  • Mouse was placed in the center of the cage, in which Objects A and Object A' (two black spools) were placed equidistant from the center and allowed to freely explore the cage and objects for 5 minutes.

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• Testing

  • Mouse was placed in the center of the cage, in which Object A and Object B (a clear card container with a piece of paper inside) were placed equidistant from the center and allowed to freely explore the cage and objects for 5 minutes.

More information about the Novel Object Recognition Task to come soon!