Novel Object Recognition Test for the Investigation of Learning and Memory in Mice

Summary

The object recognition test (ORT) is a simple and efficient assay for evaluating learning and memory in mice. The methodology is described below.

Abstract

The object recognition test (ORT) is a commonly used behavioral assay for the investigation of various aspects of learning and memory in mice. The ORT is fairly simple and can be completed over 3 days: habituation day, training day, and testing day. During training, the mouse is allowed to explore 2 identical objects. On test day, one of the training objects is replaced with a novel object. Because mice have an innate preference for novelty, if the mouse recognizes the familiar object, it will spend most of its time at the novel object. Due to this innate preference, there is no need for positive or negative reinforcement or long training schedules. Additionally, the ORT can also be modified for numerous applications. The retention interval can be shortened to examine short-term memory, or lengthened to probe long-term memory. Pharmacological intervention can be used at various times prior to training, after training, or prior to recall to investigate different phases of learning (i.e., acquisition, early or late consolidation, or recall). Overall, the ORT is a relatively low-stress, efficient test for memory in mice, and is appropriate for the detection of neuropsychological changes following pharmacological, biological, or genetic manipulations.

Introduction

The object recognition test (ORT), also known as the novel object recognition test (NOR), is a relatively fast and efficient means for testing different phases of learning and memory in mice. It was originally described by Ennaceur and Delacour in 1988 and used primarily in rats¹; however, since then, it has been successfully adapted for use in mice^2,3,4,5,6,7. The test relies on as few as three sessions: one habituation session, one training sessio....

Protocol

All procedures performed here were submitted to and approved by the Animal Care and Use committee and were conducted following NIH guidelines.

1. Object Selection and Experimental Setup

1. Select objects that are different enough to be easily discriminated by mice, but have a similar degree of complexity (texture, shape, color patterning and brightness, etc.) in order to minimize any potential induced object preference that may bias the results (see Ennaceur 2010 for a comprehensive description of object choice⁷).
   1. Test for innate preference and discrimination (see Steps ....

Results

A general experimental setup for the ORT is shown in Figure 2. On habituation day (T0) mice are placed in the empty arena for 5 min. Twenty-four hours later, mice are placed back in the chamber with 2 identical objects and allowed to freely explore for up to 10 min (T1). On testing day (T2), the mice are again placed in the arena, but with one familiar object and one novel object, and allowed to explore for up to 10 min. The retention interval, the time betwe.......

Discussion

The ORT is an efficient and flexible method for studying learning and memory in mice. When setting up an experiment, it is important to consider a number of variables that may affect the outcome. As discussed in the representative results, the strain of mouse will affect both exploration time and retention interval. A decrease in exploration time may skew or mask results in an absolute discrimination analysis^2,3,5,

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Open Field Box	Panlab/Harvard Apparatus	LE800SC	Available in grey, white, or black
ANY-maze	Stoelting Co.	60000	Behavior tracking system
EthoVisionXT 12	Noldus		Behavior tracking system; requires 3 point tracking
Video Camera	Any		Video camera should be mounted directly overhead of the apparatus
70% Ethanol	Fisher Scientific	BP2818-4	Prior to starting testing and in between trials, each object should be carefully cleaned. The floor and walls of the apparatus should also be cleaned.