Evaluation of Sheep Anticipatory Response to a Food Reward by Means of Functional Near-Infrared Spectroscopy
by
, , , and
Matteo Chincarini
1,*
,
Lina Qiu
2,
Lorenzo Spinelli
3, 
Alessandro Torricelli
2,3, 
Michela Minero
4,
Emanuela Dalla Costa
4,
Massimo Mariscoli
1,
Nicola Ferri
5,
Melania Giammarco
1 and
Giorgio Vignola
1 1
Università degli Studi di Teramo, Facoltà di Medicina Veterinaria, Località Piano d’Accio S.P. 18, 64100 Teramo, Italy
2
Politecnico di Milano, Dipartimento di Fisica, piazza Leonardo da Vinci 32, 20133 Milano, Italy
3
Consiglio Nazionale delle Ricerche, Istituto di Fotonica e Nanotecnologie, piazza Leonardo da Vinci 32, 20133 Milano, Italy
4
Università degli Studi di Milano, Dipartimento di Medicina Veterinaria, via Celoria 10, 20133 Milano, Italy
5
Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise G. Caporale, Campo Boario, 64100 Teramo, Italy
*
Author to whom correspondence should be addressed.
Animals 2019, 9(1), 11; https://doi.org/10.3390/ani9010011
Submission received: 22 November 2018
/
Revised: 21 December 2018
/
Accepted: 24 December 2018
/
Published: 29 December 2018
(This article belongs to the Section Animal Welfare)
Simple Summary
Anticipatory behaviour to an oncoming food reward can be triggered via classical conditioning, implies the activation of neural networks, and may serve to study the emotional state of animals. This work aimed to investigate how the anticipatory response affects cerebral cortex activity in sheep. Eight ewes were conditioned to associate a neutral auditory stimulus (water bubble) to a food reward (maize grains). Then, sheep were trained to wait 15 s before accessing the food (anticipatory phase). Behavioural reaction and changes in cortical oxy-haemoglobin ([ΔO2Hb]) and deoxy-haemoglobin ([ΔHHb]) concentration were recorded by functional near infrared spectroscopy (fNIRS). During the anticipatory phase, sheep increased their active behaviour together with a cortical activation (increase of [ΔO2Hb] and a decrease of [ΔHHb]) compared to baseline. Sheep showed a greater response of the right hemisphere compared to the left hemisphere, possibly indicating frustration. Behavioural and cortical changes observed during anticipation of a food reward reflect a learnt association and an increased arousal, but no clear emotional valence of the sheep subjective experience.
Abstract
Anticipatory behaviour to an oncoming food reward can be triggered via classical conditioning, implies the activation of neural networks, and may serve to study the emotional state of animals. The aim of this study was to investigate how the anticipatory response to a food reward affects the cerebral cortex activity in sheep. Eight ewes from the same flock were trained to associate a neutral auditory stimulus (water bubble) to the presence of a food reward (maize grains). Once conditioned, sheep were trained to wait 15 s behind a gate before accessing a bucket with food (anticipation phase). For 6 days, sheep were submitted to two sessions of six consecutive trials each. Behavioural reaction was filmed and changes in cortical oxy- and deoxy-hemoglobin concentration ([ΔO2Hb] and [ΔHHb] respectively) following neuronal activation were recorded by functional near infrared spectroscopy (fNIRS). Compared to baseline, during the anticipation phase sheep increased their active behaviour, kept the head oriented to the gate (Wilcoxon’s signed rank test; p ≤ 0.001), and showed more asymmetric ear posture (Wilcoxon’s signed rank test; p ≤ 0.01), most likely reflecting a learnt association and an increased arousal. Results of trial-averaged [ΔO2Hb] and [ΔHHb] within individual sheep showed in almost every sheep a cortical activation during the anticipation phase (Student T-test; p ≤ 0.05). The sheep showed a greater response of the right hemisphere compared to the left hemisphere, possibly indicating a negative affective state, such as frustration. Behavioural and cortical changes observed during anticipation of a food reward reflect a learnt association and an increased arousal, but no clear emotional valence of the sheep subjective experience. Future work should take into consideration possible factors affecting the accurateness of measures, such as probe’s location and scalp vascularization.
