Frontal Brain Activity and Behavioral Indicators of Affective States are Weakly Affected by Thermal Stimuli in Sheep Living in Different Housing Conditions.

Sabine Vã¶Geli,Lorenz Gygax,Beat Wechsler,Martin Wolf

doi:10.3389/fvets.2015.00009

Abstract

Many stimuli evoke short-term emotional reactions. These reactions may play an important role in assessing how a subject perceives a stimulus. Additionally, long-term mood may modulate the emotional reactions but it is still unclear in what way. The question seems to be important in terms of animal welfare, as a negative mood may taint emotional reactions. In the present study with sheep, we investigated the effects of thermal stimuli on emotional reactions and the potential modulating effect of mood induced by manipulations of the housing conditions. We assume that unpredictable, stimulus-poor conditions lead to a negative and predictable, stimulus-rich conditions to a positive mood state. The thermal stimuli were applied to the upper breast during warm ambient temperatures: hot (as presumably negative), intermediate, and cold (as presumably positive). We recorded cortical activity by functional near-infrared spectroscopy, restlessness behavior (e.g., locomotor activity, aversive behaviors), and ear postures as indicators of emotional reactions. The strongest hemodynamic reaction was found during a stimulus of intermediate valence independent of the animal’s housing conditions, whereas locomotor activity, ear movements, and aversive behaviors were seen most in sheep from the unpredictable, stimulus-poor housing conditions, independent of stimulus valence. We conclude that, sheep perceived the thermal stimuli and differentiated between some of them. An adequate interpretation of the neuronal activity pattern remains difficult, though. The effects of housing conditions were small indicating that the induction of mood was only modestly efficacious. Therefore, a modulating effect of mood on the emotional reaction was not found.

Highlights

Research on affective states, that is, short-term emotions [1] and long-term mood [2] is of interest because of their basic influence on behavior in humans and other animals
Behavioral Indicators: Locomotor Activity and Ear Postures Locomotor activity was elevated during the stimulus compared with the pre- and post-stimulus phases, and sheep living under unpredictable, stimulus-poor housing conditions exhibited a higher locomotor activity than the sheep living under predictable, stimulus-rich housing conditions
An additional effect of phase could only weakly be supported, but resulted in an increased amount of ear movements during the stimulus phase compared with the pre- and post-stimulus phases

Summary

Introduction

That is, short-term emotions [1] and long-term mood [2] is of interest because of their basic influence on behavior in humans and other animals. Sheep’s reactions on thermal stimuli can be characterized by their valence ranging from negative to positive and by their arousal ranging from low to high, as described by dimensional models of emotion [2]. In our previous studies with sheep [3, 4], we investigated physical and social stimuli that varied in their presumed valence to examine the emotional reactions of sheep. It seemed that the sensory channel, that is, physical touch [3] or video images [4] through which the sheep experienced the stimuli influenced their reactions. If temperature is very high, pain may be induced at least in humans [9]

Methods

Results

Conclusion