Do early interactions determine adult social skills, BDNF and oxytocin brain levels? Psychoneuroendo.April.2013

16.04.2013

Mother-infant attachment/interaction is conceptualised as an emotional bond that influence the behaviour “from the cradle to the grave” ( Bowlby,1969).Interactions with peers early in life is also considered important in shaping future relationships.Most animal studies have focused on the  role of maternal care.

Igor Branchi , James P. Curley ,D’Andrea I, Cirulli F, Champagne FA and  Alleva E ( Italy &  USA) report the results of a novel study that addressed the relative contributions of maternal and peer relatiosnhips.They used the communal nest paradigm in which three lactating females ( mice) place their litters ( each with 3 days differing in age)  together in a single nest and engage in shared care-giving from birth to weaning. The standard condition was one dam rearing her own litter. Maternal behaviour and  pup social interactions were monitored. When they reached adulthood, social behaviour was assessed using  a social interaction test where in a neutral venue, after two weeks of isolation,  each was exposed to a standard opponent and behaviour ( aggression, subordination, affiliation,nonsocial etc) was recorded. Brain BDNF and Oxytocin receptor levels were also measured in adulthood.

Findings

Early interactions with mother and peers independently shape social skills, brain BDNF expression and Oxytocin receptor binding in the amygdala at adulthood.High levels of interactions with mother and peers predicted  elaborate social competencies and with elevated brain BDNF levels.

High levels of peer interactions in the nest were selectively associated with high adult affiliative behaviour  (the display of behavioral patterns aimed at reducing aggressive behavior and increasing social tolerance) and  increased OTR binding in different nuclei of the amygdala.Enhanced affiliative behavior emerged only in those groups who displayed high levels of early peer interactions during infancy — and independently from the amount of maternal care — suggesting that different adult social domains are structured through diverse early social experience.

Those having received a combination of both high levels of maternal care and peer interactions during infancy displayed  rapid social learning and social plasticity.The  groups exposed to high levels of both social components showed significantly higher hippocampal, frontal cortical and hypothalamic BDNF protein levels compared to the other two groups, which were exposed to high levels of only one component.

Both components  are critical for the development of the adult social agonistic competencies (the ability to manage social interactions, playing either the dominant or the subordinate role ).

These findings would help future studies aiming to investigate the neurobiological mechanisms underlying how pathological aggressive behavior can lead to an escalation of violence without inhibitory control associated to affiliative behavior and reconciliation.

The study highlights the importance of  early life relationships. Impoverished early relationships can lead to dysfunctional neurobiological systems .This can set  the ground for maladaptive behavior and disability.

Another interesting observation was that the amount of maternal care received changed according to birth order, with the Middle group receiving the least amount of care. This might be probably  the case in humans as well.

Summary of the article:

Early interactions with mother and peers independently build adult social skills and shape BDNF and oxytocin receptor brainlevels.

Branchi I, Curley JP, D’Andrea I, Cirulli F, Champagne FA, Alleva E.Psychoneuroendocrinology. 2013 Apr;38(4):522-32.

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