Behavioral and physiological effects of an infant neglect manipulation in a bi-parental, twinning primate: Impact is dependent on familial factors

Experimental animal studies and epidemiological. and clinical human studies demonstrate that atypical infant-caregiving can exert short- and long-term effects on offspring phenotype, including increased long-term risk of affective disorders. Whilst the early environment is therefore a major determinant of behavioral, physiological and neurobiological phenotypes, the effects of early adversity exhibit individual variation, presumably due to differences in environment-genotype interactions. Twin studies provide a powerful model. with which to study such interactions. However, human twin studies rarely include analysis of genotype-environment interactions or of individuals exposed to extreme environments, and rat studies have rarety attempted to utilize littermates (i.e. dizygotic twins) to investigate environrrient-genotype interactions. Here, we report on the effects of repeated deprivation of caregiving in the common marmoset, a primate that exhibits dizygotic twinning and bi-parental care. Breeding pairs each contributed early deprived (ED) twins and control (CON) twins, thereby allowing for the study of effects of ED, parentage and ED-parentage interaction. Significant ED x parentage interaction effects were obtained for basal urinary, plasma and cerebrospinal-fluid cortisol titers (infancy-adolescence), and basal Levels of social, and maintenance behaviors (juveniles); basal urinary cortisol titers during a 2-week period of repeated psychosocial challenge (juveniles), and social and exploratory behavior during psychosocial challenge (juveniles). Significant main effects of ED were obtained for: basal levels of time spent in contact with parents (ED > CON; juveniles) and in locomotor activity (ED < CON; adolescents); basal and psychosocial-stress-related systolic blood pressure (ED > CON; juveniles); time spent in locomotor activity (ED < CON), contact calling (ED < CON) and exploring novelty (ED > CON)