In vivo functional near-infrared spectroscopy measures mood-modulated cerebral responses to a positive emotional stimulus in sheep
ABSTRACT The affective state of an animal, which is thought to reflect its welfare, consists of both short-term emotional reactions and long-term general mood. Because this state is generated and processed by the brain, we used non-invasive measurement of such brain activity as a novel indicator variable and investigated the interplay of mood and short-term emotional reactions in animals. We developed a wireless sensor for functional near-infrared spectroscopy (fNIRS), which assesses cortical perfusion changes, and consequently neuronal activity. Mood differences were induced by barren and enriched housing in a total of nine sheep and we observed their brain reaction in response to the positive situation of being groomed. We detected a decrease in cerebral oxyhaemoglobin concentration ([O(2)Hb]) which persisted during grooming. The localisation of the decrease in the brain did not depend on the site where the stimulus was applied. Also, the intensity of the response did not depend on the intensity of the grooming stimulus and a sham stimulus did not evoke an [O(2)Hb] response as seen with a grooming stimulus. Thus, we conclude that the observed haemodynamic brain response was unlikely to reflect pure somato-sensory information. We then found that the amplitude of the [O(2)Hb] response was larger if sheep were in a supposedly more negative mood. This contradicts the common assumption that negative mood generally taints reactions to emotional stimuli. Our results also demonstrate the potential of fNIRS for assessing affective states in freely moving animals.
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ABSTRACT: We have designed, built and successfully tested a prototype portable and wireless near-infrared spectroscopy system. It takes forward the well-established series of NIRO spectroscopy instruments made by Hamamatsu Photonics (Hamamatsu City, Japan). It uses an identical optical probe, and has a data acquisition rate of 10Hz. It illuminates the tissue with laser diode sources at 3 wavelengths of 775, 810 and 850nm, and detects the reflected light with 2 silicon photodiode detectors at 2 different separations, enabling spatially resolved spectroscopy to be performed. We have tested it with both in vitro and in vivo experiments to establish its basic functionality for use in studies of both brain and muscle.Medical Engineering & Physics 05/2013; · 1.78 Impact Factor
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ABSTRACT: Modulation of short-term emotions by long-term mood is little understood but relevant to understand the affective system and of importance in respect to animal welfare: a negative mood might taint experiences, whilst a positive mood might alleviate single negative events. To induce different mood states in sheep housing conditions were varied. Fourteen ewes were group-housed in an unpredictable, stimulus-poor and 15 ewes in a predictable, stimulus-rich environment. Sheep were tested individually for mood in a behavioural cognitive bias paradigm. Also, their reactions to three physical stimuli thought to differ in their perceived valence were observed (negative: pricking, intermediate: slight pressure, positive: kneading). General behaviour, activity, ear movements and positions, and haemodynamic changes in the cortical brain were recorded during stimulations. Generalised mixed-effects models and model probabilities based on the BIC (Bayesian information criterion) were used. Only weak evidence for mood difference was found. Sheep from the unpredictable, stimulus-poor housing condition had a somewhat more negative cognitive bias, showed slightly more aversive behaviour, were slightly more active and moved their ears somewhat more. Sheep most clearly differentiated the negative from the intermediate and positive stimulus in that they exhibited more aversive behaviour, less nibbling, were more active, showed more ear movements, more forward ear postures, fewer backward ear postures, and a stronger decrease in deoxyhaemoglobin when subjected to the negative stimulus. In conclusion, sheep reacted towards stimuli according to their presumed valence but their mood was not strongly influenced by housing conditions. Therefore behavioural reactions and cortical brain activity towards the stimuli were hardly modulated by housing conditions.Behavioural brain research 03/2014; 267:144-155. · 3.22 Impact Factor
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ABSTRACT: This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy- and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Lambert-Beer law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects.NeuroImage 05/2013; · 6.25 Impact Factor