This research attempts to understand how early experience affects the development of brain and behavior. Nonhuman primates are very similar to humans in many aspects of their anatomy, physiology and behavior. Nonhuman primates offer the opportunity to conduct longitudinal studies of the effects of early experience on the development of brain and behavior in a relatively short period of time and with experimental procedures that would be difficult to use in humans. Serotonin is a brain neurotransmitter that plays an important role in the regulation of emotions and behavior. In a recent study Dr. Maestripieri discovered that rhesus monkey infants who are reared by mothers with a rejecting parenting style have lower serotonin in their brain during infancy, adolescence, and early adulthood than infants with less rejecting mothers. Some of these infants had been adopted and reared by unrelated mothers, thus showing that the low serotonin of highly rejected infants was not the result of genetic similarities with their mothers. In adulthood, highly rejected infants resembled the mothers who reared them in many aspects of their behavior. For example, female infants who were physically abused by their mothers in infancy and had low serotonin in their brain tended to become abusive mothers themselves. In this study, Dr. Maestripieri and his lab want to continue studying the relationship between early experience and the development of brain serotonin and other neurotransmitters in a different and larger population of monkeys living in a naturalistic environment. They also plan to explore whether genetic differences among individuals in the regulation of brain serotonin affect the extent to which early experience alters the development of this neurotransmitter system and adult behavior.
In humans, low serotonin in the brain has been associated with several psychopathologies including anxiety, depression, and impulsive aggression and violence. Although a great deal of effort has been devoted to the development of effective medical treatments for these psychopathologies, their causes are poorly understood. This research attempts to understand the role of early experience and genetic factors in the development of behavior and brain monoamine systems, including serotonin, in nonhuman primates. Early interactions with one’s parents are a very important aspect of early experience in both humans and other primates. The proposed study is part of the first and only research project to date investigating how natural variation in maternal care patterns affects the development of brain and behavior in nonhuman primates. This study could contribute to our understanding of how genes and early experience interact in the development of brain and behavior and how particular genes and environments may increase the vulnerability to psychological and behavioral pathologies. Understanding the developmental origins of vulnerabilities to psychopathology may increase the potential for early intervention and prevention as well as for treatment.