Prenatal Central Nervous System Development

Central Nervous System development plays the central role in the primary argument. That argument is that the prenatal nervous system is particularly vulnerable to environmenttal perturbations because it is rapidly developing during that time period. Futher, many of the learning and behavioral problems that occur in childhood and adolescence have their origins in these prenatal perturbation on central nervous system development.

To help conceptualize fetal central nervous system development, metaphorically link the development of the central nervous system to the construction of a house. In the same way that a blueprint guides house construction, an individual's genome serves as ablueprint for the brain. Some of the DNA in the genome creates proteins that buid structures, while others are"timing genes" that manage the sequencing of the building process, Neurons and glial cells function as the foundational materials of bricks, wood and cement. Axons, dendrites and synaptic connections among neurons serve as the wiring for electricity and the telephone.

The construction of this elaborate communication structure we call the brain is complex, but there are general principles that guide that process. First, while genes provide the blueprint, central nervous system development is a complex process that results from the interplay of genetically governed biological processess and a number of experential,environtmental factors. Second, despite this complex genetic and environtmental interaction, the formation of brain regions occurs according to precisety sequenced schedule with more phylogenetically primitive region (e.g, lymbic system, forebrain) developing before more complex structure (e.g, cerebral cortex). Third, within these regions, brain development is most vulnerable to insult during periods of most rapid growth and development. Thus, the timing of an insult may be more important than the dose or nature of the insult in fluencing the pattern of malformation. The fourth guiding principle is that of all organs in the body, the brain is most vulnerable to teratogenic disruptionbecause of the extended amount of time it requires for development. Fifth, birth does not mark a particular milestone in the development of the brain. The brain continues to develop throughout the lifespan, although the most significant development occurs early in the development during the fetal period and the first years of life.