Research comparing brain development in humans and our closest nonhuman primate relatives, chimpanzees, reveals how quickly myelin in the cerebral cortex grows, shedding light on the evolution of human cognitive development and the vulnerability of humans to psychiatric disorders. Myelin is the fatty insulation surrounding axon connections of the brain.
Recent research by Chet Sherwood, associate professor of anthropology in Columbian College of Arts and Sciences, along with Daniel Miller, a former GW graduate student, and other colleagues, reveals this key difference in brain development between human and chimpanzee. The findings were recently published in the September 24th edition Proceedings of the National Academy of Sciences (PNAS).
In the article, Dr. Sherwood and co-authors write that the development of myelin from birth to adulthood in humans is protracted in comparison to chimpanzees. In humans, myelin develops slowly during childhood, followed by a delayed period of maturity beyond adolescence and into early adulthood. In contrast, in chimpanzees, the development of myelin already starts at a relatively more mature level at birth and ceases development long before puberty.
“These observations indicate that a marked delay in the development schedule of the human neocortex may play an important role in the growth of connections that contribute to our species-specific cognitive abilities,” wrote Dr. Sherwood and co-authors.
The developmental timing of myelination is important because it establishes connectivity among parts of the growing brain, which is essential to higher-order cognitive functions, such as decision-making and emotional regulation. These cognitive functions are known to mature relatively late in humans, after the time of adolescence. Also, this period of persistent myelin development during early adulthood in humans is a time of particular vulnerability to neuropsychiatric diseases, including schizophrenia, bipolar disorder, and depression.
- D. J. Miller, T. Duka, C. D. Stimpson, S. J. Schapiro, W. B. Baze, M. J. McArthur, A. J. Fobbs, A. M. M. Sousa, N. Sestan, D. E. Wildman, L. Lipovich, C. W. Kuzawa, P. R. Hof, C. C. Sherwood. Prolonged myelination in human neocortical evolution. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1117943109
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