fMRI of the sheep auditory cortex: its ups & downs

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Localizing the sheep auditory cortex using functional magnetic resonance imaging: The sheep auditory cortex is located in the anterior part of the posterior ectosylvian gyrus.Sheep voluntarily participate in awake and unrestrained fMRI sessions.

The precise 3D location of the sheep auditory cortex is unknown. A single neuronal tracer study highlighted that a small region of the rostral most part of the posterior ectosylvian gyrus may constitute the sheep auditory cortex (Michaloudi et al., 1986). More evidence is required to accurately localize and understand the anatomical and functional properties of the sheep auditory cortex. To precisely map its 3D location, we use fMRI to acquire functional brain images from a group of anesthetized sheep. However, anesthesia can be detrimental to health, disrupt neurovascular coupling (Aksenov et al., 2015) and does not permit the study of higher-level cognition. Thus we also present a proof of concept that positive reinforcement training in sheep is sufficient to be able to acquire MRI of their brain

Acquiring MRI brain images in awake unrestrained sheep: Sheep voluntarily participate in awake andunrestrained MRI sessions after positive reinforcement-based training.

International audienceMagnetic Resonance Imaging (MRI) is a non-invasive technique that requires participants to be completely motionless. MRI in awake, unrestrained animals has only been achieved with humans and dogs. For other species, alternatives such as anesthesia, restraint and/or sedation have been necessary. MRI with sheep has only been conducted under anesthesia. This ensures the absence of movement and allows long experiments. However, it can be detrimental to health, disrupt neurovascular coupling and doesn’t permit the study of higher-level cognition. We present a proof of concept that positive reinforcement training in sheep is sufficient to acquire brain MRI. Training involved two phases: 1) in the sheepfold using a mock MRI and 2) in the real MRI environment. Each phase consisted of successive steps during which sheep learnt a behavior necessary to participate in an MRI experiment. To successfully complete this training protocol, sheep must remain motionless lying on the MRI table for the minimum time required for an acquisition. At present all 10 sheep actively participate and place their head inside the MRI coil for a minimum duration of ~1 min 30 sec. Six have done so long enough to acquire T1-weighted (~2 min 30 sec) and EPI functional images (~4 min 30 sec). These promising results show that MRI can be acquired with awake and unrestrained sheep; opening the door to conducting animal welfare friendly functional MRI studies with them. We are currently preparing a first awake functional MRI study investigating their auditory system

Acquiring MRI brain images in awake unrestrained sheep: Sheep voluntarily participate in awake andunrestrained MRI sessions after positive reinforcement-based training.

Magnetic Resonance Imaging (MRI) is a non-invasive technique that requires the participant to be completely motionless. To date, MRI in awake and unrestrained animals has only been achieved with humans and dogs (Andics et al., 2014). For other species, alternative techniques such as anesthesia (Barrière et al., 2019), restraint (Stefanacci et al., 1998) and/or sedation (Behroozi et al., 2018) have been necessary. MRI studies with sheep have only been conducted under general anesthesia. This ensures the absence of movement and allows relatively long MRI experiments. However, it can also be detrimental to health, disrupt neurovascular coupling (Aksenov et al., 2015) and does not permit the study of higher-level cognition. Here we present a proof of concept that positive reinforcement training in sheep is sufficient to be able to acquire MRI of their brain.We developed a step-by-step training protocol based on positive reinforcement (food reward, social reward) and human – animal cooperation with 10 lambs from birth. This training method involved two phases: 1) training in the sheepfold using a mock MRI and 2) training in the real MRI environment. Each phase consisted of successive steps during which sheep learnt a behavior necessary for them to be able to participate in an MRI experiment. To successfully complete this training protocol, sheep must remain motionless lying on the MRI table for the minimum time required for an acquisition. At present all 10 sheep actively participate in training and place their head inside the MRI coil for a minimum duration of ~1 min 30 sec. Six have done so long enough to acquire both T1-weighted structural (~2 min 30 sec, Figure 1) and EPI functional images (~4 min 30 sec).These promising early results clearly show that MRI data can be acquired with awake and unrestrained sheep. The innovative training protocol opens the door to the possibility of conducting animal welfare friendly functional MRI studies with sheep. We are currently preparing a first awake functional MRI study investigating their auditory system

Acquiring MRI brain images in awake unrestrained sheep: Sheep voluntarily participate in awake andunrestrained MRI sessions after positive reinforcement-based training.

International audienceMagnetic Resonance Imaging (MRI) is a non-invasive technique that requires the participant to be completely motionless. To date, MRI in awake and unrestrained animals has only been achieved with humans and dogs. For other species, alternative techniques such as anesthesia and/or restraint have been necessary. MRI studies with sheep have only been conducted under anesthesia. This ensures the absence of movement and allows relatively long MRI experiments. However, it can be detrimental to health, disrupt neurovascular coupling and does not permit the study of higher-level cognition. Here we present a proof of concept that positive reinforcement training in sheep is sufficient to be able to acquire both T1-weighted structural and EPI functional images. These promising early results show that MRI data can be acquired with awake and unrestrained sheep. This innovative training protocol opens the door to the possibility of conducting animal welfare friendly functional MRI studies with sheep

Maternal deprivation and milk replacement affect the integrity of gray and white matter in the developing lamb brain

The psychoendocrine evaluation of lamb development has demonstrated that maternal deprivation and milk replacement alters health, behavior and endocrine profiles. While lambs are able to discriminate familiar and non-familiar conspecifics (mother or lamb), only lambs reared with their mother develop such clear social discrimination or preference. Lambs reared without mother display no preference for a specific lamb from its own group. Differences in exploratory and emotional behaviours between mother-reared and mother deprived lambs have also been reported. As these behavioural abilities are supported by the brain, we hypothesize that rearing with maternal deprivation and milk replacement leads to altered brain development and maturation. To test this hypothesis, we examined brain morphometric and microstructural variables extracted from in-vivo T1-weighted and diffusion-weighted magnetic resonance images acquired longitudinally (1 week, 1.5 months and 4.5 months of age) in mother-reared and mother-deprived lambs. From the morphometric variables the caudate nuclei volume was found to be smaller for mother-deprived than for mother-reared lambs. T1-weighted signal intensity and radial diffusivity were higher for mother-deprived than for mother-reared lambs in both the white and gray matters. The fractional anisotropy of the white matter was lower for mother-deprived than for mother-reared lambs. Based on these morphometric and microstructural characteristics we conclude that maternal deprivation delays and affects lamb brain growth and maturation

Maternal deprivation and milk replacement affect the integrity of gray and white matter in the developing lamb brain

International audienceThe psychoendocrine evaluation of lamb development has demonstrated that mater-nal deprivation and milk replacement alters health, behavior, and endocrine pro-files. While lambs are able to discriminate familiar and non-familiar conspecifics(mother or lamb), only lambs reared with their mother develop such clear social dis-crimination or preference. Lambs reared without mother display no preference for aspecific lamb from its own group. Differences in exploratory and emotional behav-iors between mother-reared and mother-deprived lambs have also been reported.As these behavioural abilities are supported by the brain, we hypothesize that rear-ing with maternal deprivation and milk replacement leads to altered brain develop-ment and maturation. To test this hypothesis, we examined brain morphometric andmicrostructural variables extracted from in vivo T1-weighted and diffusion-weightedmagnetic resonance images acquired longitudinally (1 week, 1.5 months, and 4.5months of age) in mother-reared and mother-deprived lambs. From the morphometricvariables the caudate nuclei volume was found to be smaller for mother-deprived thanfor mother-reared lambs. T1-weighted signal intensity and radial diffusivity werehigher for mother-deprived than for mother-reared lambs in both the white and graymatters. The fractional anisotropy of the white matter was lower for mother-deprivedthan for mother-reared lambs. Based on these morphometric and microstructuralcharacteristics we conclude that maternal deprivation delays and affects lamb braingrowth and maturation