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

Abstract

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