Impact of early rearing experience on brain development in sheep infant
Résumé
The psychoendocrine evaluation of infant attachment recently demonstrated that early rearing experience
modifies the endocrine profiles and the social interaction between a lamb and its attachment figure. 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 displayed no
preference for a specific lamb from its own group. Other differences were reported in exploratory and emotional
behaviours. Moreover, lambs reared with their mother only present lower plasma cortisol and higher plasma
oxytocin levels than lambs reared with same age conspecifics only. Because these behavioural and endocrine
responses are supported by brain organisation, we decided to describe and compare the brain development of
lambs reared in group with and without mother by using T1-weigthed- and diffusion tensor MRI at 1 week, 1, 2
and 4 months of age. Using texture analysis of the T1w MRI, we showed that the differentiation of the pituitary
differed between the two groups. The extraction of diffusion parameters allowed to show that the white matter
fractional anisotropy increased from 1 week to 4 months, whatever the group. Moreover, some differences were
noticed between groups in specific brain areas. The impact of early rearing experience found in our study could
reflect the consequences of social environment.
