Kai McCormack

Effects of Maternal Maltreatment on the Development of Rhesus Macaques

Early social experiences, specifically those related to the mother-infant relationship, are important determinants of human and non-human primate development. Over the past 20 years, at the Yerkes National Primate Research Center, we have evaluated a rhesus macaque model of infant maltreatment, which consists of comorbid maternal physical abuse and infant rejection, and the associated infant developmental outcomes. Across a series of studies, we have collected behavioral, cognitive, neuroendocrine, and neurodevelopmental measures during the first 18 months of life, in groups of maltreated and non-maltreated rhesus infants. Compared to non-maltreated infants, maltreated infants demonstrate higher rates of emotional reactivity, aggression, and reduced affiliation with their peers. Maltreated infants also demonstrate higher levels of chronic stress, as measured by both hair and plasma cortisol levels, reduced serotonergic function, and alterations in the development of their prefrontal-amygdala pathways. As juveniles, maltreated animals show increased sensitivity to cocaine administration. These results suggest that early maternal care is critical for the healthy development of several behavioral, neural, and physiological systems, and that poor maternal care results in increased emotional reactivity and brain alterations in the offspring, which likely contribute to the risk for later behavioral alterations, including addiction. An overview of this animal model of early life stress will be presented, as well as a discussion of the findings and implications for human mental health.