Observational Fear as a Model of Affective Empathy in Mice

Summary

The observational fear paradigm assesses vicarious freezing in rodents as a model for affective empathy. This procedure entails exposing observer rodents to conspecific demonstrators receiving aversive foot shocks to elicit empathic freezing responses. By employing observational fear assays, researchers can investigate the neural mechanisms underlying affective empathy.

Abstract

Empathy, characterized by the ability to recognize and share the emotions of others, plays a fundamental role in shaping social interactions. It allows individuals to respond to the emotional states of others, promoting prosocial behaviors and social bonding. Observational fear is a fundamental aspect of affective empathy, where an observer witnesses a demonstrator undergoing aversive experiences and subsequently exhibits fear behaviors. This socially induced vicarious freezing response in observers, known as emotional contagion or affect sharing, is regarded as an indicator of empathy-like traits in rodents. Here, we present a protocol that delineates the assessment of vicarious freezing responses in observers exposed to conspecific demonstrators receiving aversive foot shocks. The utilization of observational fear assays in rodents has become a widely adopted method for studying the neural mechanisms underlying affective empathy. Given the universality of observational fear across mammals, this methodology further contributes to advancing our understanding of the neural substrates of empathy in humans.

Introduction

Empathy -- the capacity to recognize and share the feelings of others -- is crucial for our emotional and social interactions¹. This protocol aims to investigate affective empathy in rodents through the observational fear conditioning assay, designed to assess vicarious fear responses in an observer rodent. Empathic ability has deep neurobiological underpinnings, with evolutionary continuity from rodents to humans². Converging lines of evidence demonstrate that rodents exhibit significant affective sensitivity to the emotional states of their social counterparts³ and display empathy-related behavi....

Protocol

All procedures using live animals described here were approved by the Institutional Animal Care and Use Committee (IACUC) of the Institute for Basic Science (IBS). Male or female C57BL/6J mice (observers and demonstrators), aged 10-12 weeks, were housed separately. Mice were housed 2-5 animals per cage and maintained at a constant temperature of 23-25 °C with a 12-h light/dark cycle. The mice were provided with mouse chow and water ad libitum. No handling was performed prior to testing. Details of the reagents and equipment used in this study are listed in the Table of Materials.

1. Preparation for the o....

Results

As described in the behavioral diagram (Figure 1A), the session starts with habituation (5 min), followed by an observational fear conditioning period (4 min). In this experiment, the demonstrator mice in the observational fear (OF) group were subjected to aversive foot shocks during the conditioning period, while those in the control (Con) group did not receive foot shocks. Only the observer mouse in the OF group witnessed the distress responses of a demonstrator mouse receiving repetitive .......

Discussion

The contextual observational fear conditioning (OFC) test, described in this behavioral protocol, is employed to study affective empathy in mice^4,16. To successfully execute this paradigm, careful consideration should be given to experimental conditions and practical details, particularly factors that influence the subjects' emotional responses, including familiarity, social isolation, social hierarchy, prior shock experience, and the strength of the foot sho.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Precision animal shocker	Coulbourn Instruments	H13-15
Grid floor	Coulbourn Instruments	H13-15
Ribbon cable for grids	Coulbourn Instruments	H93-01-25
FreezeFrame	ACTIMETRICS	ACT-100A
FreezeView software	ACTIMETRICS
Stimulator	ACTIMETRICS	ACT-712
Observational fear chamber	Coulbourn Instruments		height 32.7 cm × width 19.1 cm × length 37.8 cm
Video recording system	ACTIMETRICS
Sound attenuating cubicle
70% ethanol			Widely available.
Sanitizer			Widely available.
paper towel			Widely available.
Plexiglas divider	Custom	N/A	width 18 cm × length 32.2 cm
GraphPad Prism 8	GraphPad Software Inc.