increasingly being understood as dynamic disruptions in key developmental processes that exert their effects throughout the life span. Unraveling the causes and consequences of complex MEB disorders remains an enormous challenge. However, major advances have been made not only in identifying genetic and environmental factors that play causal roles in the genesis of disorders, but also in understanding more fully the interaction between genetic and environmental influences in causing or protecting against specific diseases. In addition, advances in the emerging field of epigenetics have begun to provide information about the complex ways in which genetic traits are expressed as disease and the possible mechanisms through which environment and experience can influence gene expression.

This chapter begins with the role of genetics and the interplay of genetic and environmental factors in MEB disorders. This is followed by a discussion of brain development and its relationship to MEB disorders. Next is an examination of neural systems and their role in complex processes that underlie the cognitive and social competence that is essential to healthy emotional and behavioral development. The third section addresses the relationship between developmental neuroscience and prevention science. The final section presents conclusions and recommendations.

GENETICS

The importance of understanding genetic influences in brain development goes well beyond simply explaining the hereditary components of disorders. Genes are the basic component from which the brain’s structure and function are determined and regulated. Genes encode proteins, and proteins are the building blocks of cells, interacting with the molecular and physical features of their surroundings to determine cellular structure and function. Individual cells interact functionally with other cells within the neural circuits that make up the structure of the brain, which in turn interact with other neural circuits to determine behaviors. Behaving organisms interact with their environments, which can cause adaptive changes in neural systems, circuits, and cells and ultimately in the expression of genes—which in turn modifies brain structure and function. The complexity of the pathways connecting the genes and the environments of organisms to their behaviors has frustrated most attempts to correlate genes directly with behaviors and with specific diagnostic syndromes in the field of psychiatric genetics (Inoue and Lupski, 2003; Joober, Sengupta, and Boksa, 2005; Sanders, Duan, and Gejman, 2004; van den Bree and Owen, 2003).

Inherited or sporadic genetic mutations can profoundly affect the production, structure, or function of the protein that a gene encodes. This can have a dramatic and highly consistent effect in producing disease. However, more subtle variations in the genetic sequence can also affect protein struc-



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