Pigs' brain responses to stroking after long-term positive human interactions: An fMRI exploratory study
Positive interactions with humans can induce pleasurable experiences in animals, but their underlying neurobiology mechanisms are unknown. We investigated the brain responses (Functional Magnetic Resonance Imaging) to stroking by a human in 20 pigs under general anaesthesia. Ten pigs received positive human contacts over 9 weeks post-weaning (POS) and 10 pigs did not (CTL). Images from CTL pigs showed peaks of activation in the primary somatosensory cortex, caudate nucleus, anterior prefrontal cortex, and dorsal anterior cingulate cortex during stroking. Greater peaks of activation in the anterior prefrontal, ventral anterior cingulate, primary somatosensory and somatosensory association cortices were observed in POS pigs; whereas greater peaks of activation in the amygdala were observed in CTL pigs. Therefore, stroking is perceived and possibly elicited positive emotions in anesthetised pigs, and it may be perceived as more pleasant by experienced pigs than naive pigs, which may rather perceive it as a novel stimulus.