July 10, 1998 CHAMPAIGN, Ill. -- A traumatic event in a child's preschool years may disrupt a key period when the brain is collecting and storing massive amounts of information, researchers say. A review of studies on animals, however, suggests that extensive corrective experiences can help over time.
The report, "How a Child Builds Its Brain," was based on studies that measured neural plasticity -- the molding of the brain -- in animals as they underwent training and learning experiences. It was one of several studies published in the March-April issue of Preventive Medicine, which was devoted to the proceedings of a 1996 conference on the "Critical Period of Brain Development."
Researchers at the conference agreed that a critical period exists when brain development is most ready for stimulation and synapse formation, and that a deprived child may never fully or healthily develop without careful and expensive intervention. They suggest mandatory preschool for all children.
The brain stores new information in systems -- one tied to its own developmental timetable and another that extracts potentially useful information for later use, said James E. Black, a physician and professor of clinical psychiatry at the University of Illinois at Chicago and visiting professor at the Beckman Institute for Advanced Science and Technology at the U. of I. at Urbana-Champaign.
In essence, Black said, "Experience alters brain structure to form persisting memories, not in a monolithic or rigid fashion, but rather utilizing multiple, flexible brain systems that can encode different types of experience and often on different developmental schedules."
Animal studies -- particularly experiments on rats by Black and William T. Greenough, a neuroscientist and psychologist at the Beckman Institute -- suggest "positive, enriching experience will likely produce more synaptic connections in human children," Black wrote.
While young mammals learn, an overproduction of synaptic connections is followed by a substantial decrease when information is stored or pruned and organized. If a species relies on the quality and timing of experience, Black said, the organization becomes vulnerable to disruption. On the other hand, unique and individualized experience-dependent input -- where a squirrel hides a nut or a child's mastery of a second language -- is stored in new neural connections. When a rat is exposed to an enriched environment, brain weight and thickness increase, and new synapses and new blood vessels form.
"While adults certainly retain neural plasticity and can be traumatized by experience, children are likely to be far more vulnerable to pathological experience, either abuse or deprivation, particularly during periods of rapid creation or modification of synaptic connections," Black said.
The animal studies, he said, suggest that extensive and caring intervention can often break the cycle and heal the damage. Even if a critical period is misused or neglected, humans retain the potential to use corrective experience to make up for their early loss. By the same reasoning, he said, failure to help abused or neglected children can lead to lifelong patterns of distress and dysfunction.
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