Impact of early rearing experience on brain development in sheep infant

The psychoendocrine evaluation of infant attachment recently demonstrated that early rearing experiencemodifies the endocrine profiles and the social interaction between a lamb and its attachment figure. While lambsare 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 displayed nopreference for a specific lamb from its own group. Other differences were reported in exploratory and emotionalbehaviours. Moreover, lambs reared with their mother only present lower plasma cortisol and higher plasmaoxytocin levels than lambs reared with same age conspecifics only. Because these behavioural and endocrineresponses are supported by brain organisation, we decided to describe and compare the brain development oflambs reared in group with and without mother by using T1-weigthed- and diffusion tensor MRI at 1 week, 1, 2and 4 months of age. Using texture analysis of the T1w MRI, we showed that the differentiation of the pituitarydiffered between the two groups. The extraction of diffusion parameters allowed to show that the white matterfractional anisotropy increased from 1 week to 4 months, whatever the group. Moreover, some differences werenoticed between groups in specific brain areas. The impact of early rearing experience found in our study couldreflect the consequences of social environment