Download SRCD Abstract 01 - University of Illinois Archives

Development is, ultimately, a product of the interaction of genes with the
environment. By looking at this process in the brain and behavior, we can see how genes
and experience interact. The initial development of the basic pattern of organization of
the brain, positioning cells and forming initial connections, occurs under substantial
control of orchestrated patterns of gene expression that run forward relatively rigidly in
the absence of major disruptive environmental influences (which if they disrupt
development are called teratogens). In humans, developmentally-acquired characteristics
such as communication skills, social skills, cognitive skills and motor skills all depend
heavily upon experience. The genetically-guided processes of neural development are
designed to capture information from experience and to incorporate the effects of
experience into the architecture of the nervous system. This occurs in at least two ways.
Experience-expectant brain development takes advantage of information reliably present
in the environments of all species members, generally in relatively basic processes; one
example is the utilization of patterned visual experience in tuning the visual system to
analyze visual patterns. In this and other basic sensory and motor development, synapses
are often “overproduced,” such that experience selects a functional subset of them and the
remainder are lost. There has been some “use it or lose it” frenzy about this loss of
connections, but it is a normal process and failure to lose excess connections, or losing
the wrong connections, impairs behavior. During periods after eye opening in animals,
visual experience modulates patterns of brain gene expression, driving this synapse
selection process. Critical or sensitive periods of this sort, where specific experiences
must occur at relatively specific times, are more the exception than the rule in overall
human brain development. Throughout life, new experiences trigger new brain growth,
enhancing and refining existing brain structures. New experience-dependent
connections form and supportive cells, such as astrocytes, myelinating cells and
vasculature are also added and modified by the demands placed on the brain as the
ultimate organ of adaptation to the environment and the organism’s needs. The “soft
underbelly” of development comprises the hazards and risks of its disruption. Sensory
deficits or perceptual-motor delays can impair the acquisition of information during
critical periods. And teratogens and postnatal insults can disrupt development of brain
and behavioral competence. Diseases, for example rubella, can disrupt prenatal pattern
formation in rapidly-developing brain regions. Alcohol and other drugs can similarly
impair developmental generation and organization of neurons and other brain cells.
Nutritional deficiencies, such as anemia resulting from inadequate iron, can affect brain
development before and after birth. Premature birth puts infants that, until recent years,
would not have survived, at exceptional risk for aberrant brain and peripheral
development and subsequent neurological dysfunction. Stress resulting from neglect or
abuse can permanently alter brain and hormone physiology and can disrupt subsequent
social and cognitive function. The resilience of development comprises its ability to
reverse prior damage through plastic adaptation, perhaps driven by ameliorative
environments. Thus nature, genes and their intrinsic expression patterns, and nurture, the
influences of experience, are not combatants for control but partners in a near seamless
development process.