Introducing Clicker Training as a Cognitive Enrichment for Laboratory Mice

Summary

The development of new refinement strategies for laboratory mice is a challenging task that contributes towards fulfilling the 3R principle. This protocol introduces clicker training as a cognitive enrichment program for laboratory mice.

Abstract

Establishing new refinement strategies in laboratory animal science is a central goal in fulfilling the requirements of Directive 2010/63/EU. Previous research determined a profound impact of gentle handling protocols on the well-being of laboratory mice. By introducing clicker training to the keeping of mice, not only do we promote the amicable treatment of mice, but we also enable them to experience cognitive enrichment. Clicker training is a form of positive reinforcement training using a conditioned secondary reinforcer, the "click" sound of a clicker, which serves as a time bridge between the strengthened behavior and an upcoming reward. The effective implementation of the clicker training protocol with a cohort of 12 BALB/c inbred mice of each sex proved to be uncomplicated. The mice learned rather quickly when challenged with tasks of the clicker training protocol, and almost all trained mice overcame the challenges they were given (100% of female mice and 83% of male mice). This study has identified that clicker training for mice strongly correlates with reduced fear in the mice during human-mice interactions, as shown by reduced anxiety-related behaviors (e.g., defecation, vocalization, and urination) and fewer depression-like behaviors (e.g., floating). By developing a reliable protocol that can be easily integrated into the daily routine of the keeping of laboratory mice, the lifetime experience of welfare in the mice can be improved substantially.

Introduction

The development of new refinement strategies for laboratory mice is a challenging task that contributes to the fulfillment of the 3Rs (replacement, reduction, and refinement) of laboratory animal science¹. Improvements in the field of refinement can further contribute to the well-being of the millions of animals that are used for experimental purposes. Therefore, intensive research is needed in the field. This is also a defined aim of Directive 2010/63 of the European Union. Directive 2010/63/EU points out that the lifetime experience of laboratory animals has to be enhanced and that "establishments shall set up habituation and training pro....

Protocol

Ethics Statement: The handling of the mice and the experimental procedures were conducted in accordance with European, national, and institutional guidelines for animal care.

NOTE: The protocol includes five days of interventions (Monday to Friday), with breaks on the weekends (Saturday and Sunday). The protocol can be easily adapted to meet specific needs.

1. Determining a Reward Suitable as a Second Reinforcer

NOTE: Use food rewards, such as vacuum-packed food or animal feed that meets food safety standards. For example, different kinds of nuts, chocolate, gummy bears, or dried fruits are suitable.

1. Insert a small Petri dish with diff....

Results

The first and also one of the most important steps was the determination of an appropriate food reward. Therefore, the mice were offered different kinds of nuts, a sugar solution, marmalade, and different kinds of chocolate in a Petri dish (Figure 1). In our experience, the mice showed an obvious preference for white chocolate. Hence, we used white chocolate for all further training processes.

The actual trainin.......

Discussion

The effective implementation of the clicker training protocol with a cohort of 12 BALB/c inbred mice of each sex proved to be uncomplicated. Previous studies have confirmed the effectiveness of clicker training with several species, and we extended this to mice. As mice are the lowest developed mammals among laboratory animals, their abilities are often underestimated. Therefore, the most surprising aspect of the data is that training success could be achieved with almost all mice.

One critica.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Lid for open housing	Tecniplast	GM500LID117
SealSAfe Plus top for open housing	Tecniplast	GM500400SU
Type II long, filter top cages	Tecniplast	GM500PFSPC
Aspen bedding material	Lab & Vet Service GmbH	H0234-300	Environmental enrichment
Red polycarbonate Mouse House	Tecniplast	ACRE011	Environmental enrichment
Tissue papers	Tork, SCA Hygiene Products GmbH	290179	Environmental enrichment
Food - ssniff M-H Extrudat	ssniff	V1126-000	ad libitum
Target Stick with Clicker	Trixie	2282
PVC Tube (Tunnels)	Thyssen Krupp	RTPVCU04003005
White Chocolate/ white chocolate cream			Company doesn't matter, preferable organic quality
Forceps	FineScienceTools	e.g. 11150-10	Or any other tool to fixate chocolate
Prism Version 6.0 for Windows	GraphPad Software