Children who suffer brain injury at an early age usually recover language and cognitive abilities rapidly, contributing to the conventional view that the brain manifests its greatest plasticity at younger ages.
But time often reveals impairment in the ability of brain-injured children to make inferences - to summarize a paragraph in a sentence, or to respond appropriately to subtle social cues - and this may hamper their performance in school as well as their ability to interact with others, according to a neurologist who has studied such children.
"These kids have incredible learning deficits even when the IQ returns to normal," Dr. Sandra Bond Chapman, of the University of Texas at Dallas, said at the annual meeting of the American Association for the Advancement of Science. Dr. Chapman noted that 1 in 30 children will experience a brain injury before age 21, and that 70% of these injuries will affect the frontal cortex.
She noted that injuries to this region are especially detrimental to the developing brain. Myelination of the sensory and motor regions of the brain is completed by age 2, but myelination of the frontal regions continues throughout young adulthood.
A frontal lesion in a developing child interrupts myelination, which may be prevented from further formation, inhibiting adaptability of the developing brain, Dr. Chapman explained.
Functional brain imaging scans in a series of eight patients with a history of severe brain injury 3 years prior, but before age 9, revealed hyperactive brains, Dr. Chapman said. That is, when compared with eight normal, age-matched controls, the scans revealed increased regional blood flow in the left mesial frontal cortex, the globus pallidus-putamen-thalamus, and the right visual cortex, with decreased regional blood flow in the right cerebellum.
In a pilot study of cognitive communication intervention involving two patients with histories of severe brain injury and two normal, age-matched controls, Dr. Chapman's group provided 10 hours of training in making inferences over a 2-week period. Brain scan evidence suggests that the training causes a marked increase in the neuronal recruitment for the task, she reported.