Novel Object Exploration as a Potential Assay for Higher Order Repetitive Behaviors in Mice

Summary

Higher order restricted, repetitive behaviors (RRBs) disrupt the lives of affected individuals. These behaviors are challenging to model in rodents, making basic biomedical research into potential treatments or interventions for RRBs difficult. Here we describe novel object exploration as a potential assay for higher order RRBs in mice.

Abstract

Restricted, repetitive behaviors (RRBs) are a core feature of autism spectrum disorder (ASD) and disrupt the lives of affected individuals. RRBs are commonly split into lower-order and higher-order components, with lower order RRBs consisting of motor stereotypies and higher order RRBs consisting of perseverative and sequencing behaviors. Higher order RRBs are challenging to model in mice. Current assays for RRBs in mice focus primarily on the lower order components, making basic biomedical research into potential treatments or interventions for higher-order RRBs difficult. Here we describe a new assay, novel object exploration. This assay uses a basic open-field arena with four novel objects placed around the perimeter. The test mouse is allowed to freely explore the arena and the order in which the mouse investigates the novel objects is recorded. From these data, patterned sequences of exploration can be identified, as can the most preferred object for each mouse. The representative data shared here and past results using the novel object exploration assay illustrate that inbred mouse strains do demonstrate different behavior in this assay and that strains with elevated lower order RRBs also show elevated patterned behavior. As such, the novel object exploration assay appears to possess good face validity for higher order RRBs in humans and may be a valuable assay for future studies investigating novel therapeutics for ASD.

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental disorder consisting of three core symptoms: social impairment, difficulty communicating through language, and repetitive patterned behaviors¹. Since 2000, the number of individuals who have been diagnosed with ASD has increased from 1 in 150 to 1 in 68 in the span of ten years ². Though the prevalence of the disorder continues to increase, the cause of the disorder is not yet known. There has been a rise in efforts to identify appropriate mouse models for the core and associated symptoms of ASD, as these models could lead to an increased understanding of the underlying symptoms and causes of ....

Protocol

The protocol described here was approved by the Institutional Animal Care and Use Committee at the University of Redlands. The C58, C57, and FVB mice used in these studies were bred at the University of Redlands vivarium from stock originally obtained from the Jackson Laboratory (Bar Harbor, ME).  Sentinels from this vivarium were screened every six months and found to be pathogen free.

1. Equipment and Room Set Up

Note: We used two different arenas for novel object testing: a clear plastic rectangular cage (45 cm x 24 cm x 20 cm) or an opaque circular cage with a base diameter of 41 cm; however, any cage may be used. Pearson et al. used....

Results

The representative data²² show that female C58/J mice displayed a higher number of sequenced patterns than the other strains in the round arena (Figure 2, panel A), but not in the rectangular arena (Figure 2, panel C). None of the three male strains differed from each other (Figure 2, panels B and D). The representative data show that both male and female C58/J mice display a stronger preference for their most visited object (a.......

Discussion

Here, we present a recently developed assay that may be useful for quantifying mouse behaviors with face validity for higher order repetitive behaviors in humans. Unlike more established assays like the Barnes or T-maze, this novel object exploration assay does not require any mouse training nor is it particularly anxiety provoking. Additionally, novel object exploration does not require any food or social stimuli, allowing for more focus on the behaviors of interest, RRBs, and decreasing the likelihood of confounding va.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Standard Polycarbonate Rodent Cage (45 cm x 24 cm x 20 cm)			Multiple cages are desirable to facilitate testing of multiple mice
Plastic Opaque Circular Testing Arena (41 cm base diameter)	United States Plastic Corp.	13931	Multiple arenas are desirable to facilitate testing of multiple mice
Standard Corn-Cob Rodent Bedding
Novel Object - red monkey	Hasbro, Pawtucket RI		from Barrel of Monkeys
Novel Object - rectangular 2 x 4 LEGO
Novel Object - tile	Thinkfun Inc., Alexandria VA		from Toot and Otto
Novel Object - standard white die
Video Camera
Behavioral Logging Software - The Observer	Noldus, Wageningen, The Netherlands	other programs may be used
Video Tracking Software - EthoVision	Noldus, Wageningen, The Netherlands	other programs may be used
X-Keys input keyboard	P.I. Engineering, Williamstown MI	829484
MacroWorks II	P.I. Engineering, Williamstown MI