Primary maternal preoccupation revisited: circuits, genes, and the crucial role of early life experience

James Leckman, Linda Mayes, Donald Cohen, James Leckman
Point-of-view and initial caveats Before reviewing any specific findings, it may be useful to articulate our evolutionary point-of-view concerning developmental psycho-pathology. The human brain is a remarkable product of evolution. While the basic machinery of the vertebrate brain has been in place for more than 450 million years, the exploration of variations leads to the appearance of our species less than 100,000 years ago. In the struggle for life, certain traits have come to predominate.
more » ... me to predominate. Elements in our mental and behavioral repertoire related to successful reproduction were certainly the focus of the greatest selective pressures. The selection of a mate, bearing of viable offspring, and the formation of parental commitments that will sustain an infant through a lengthy period of dependency are just a few of the crucial complex, interdependent processes needed for individual survival and hence, species viability. Although most of our biological and behavioral potentialities are likely called upon at one point or another in the service of these goals, there must be highly conserved brain-based systems that are specifically activated at developmentally appropriate moments to achieve and sustain these processes. We hypothesize that a thorough understanding of these "normal" processes will also lead to deeper insights into our vulnerability to develop a range of psychopathological outcomes. 17 Despite the intuitive appeal of evolutionary explanations, it is also worth noting a few caveats. First, these explanations typically are population-based and fail to account for why a particular individual is affected. Any adequate account of disease pathogenesis requires that environmental events that impinge on CNS development be considered. Second, species and strain differences can be pronounced so that generalizations across species can be misleading. Finally, the empirical testing of specific evolutionary theories may prove to be difficult, if not impossible. Early Parental Love For the most part, empirical studies of the early parent-child relationship have been child centered. Most reports have focused on the Abstract Parental caregiving includes a set of highly conserved set of behaviors and mental states that may reflect both an individual's genetic endowment and the early experience of being cared for as a child. This review first examines the mental and behavioral elements of early parental caregiving in humans. Second, we consider what is known of the neurobiological substrates of maternal behaviors in mammalian species including some limited human data. Third, we briefly review the evidence that specific genes encode proteins that are crucial for the development of the neural substrates that underlie specific features of maternal behavior. Fourth, we review the literature on the "program-ming" role of epigenetic factors in shaping subsequent maternal behavior. We conclude that there are critical developmental windows during which the genetically determined microcircuitry of key limbic-hypothalamic-midbrain structures are susceptible to early environmental influences and that these influences powerfully shape an individual's responsivity to psychosocial stressors and their resiliency or vulnerability to various forms of human psychopathology later in life.