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Birth of the Brain Cells
The formation of human brain cells or neurons starts at about 10 weeks of gestational age and completed after 8 more weeks of gestation. By 18 weeks of gestation, virtually all neurons in the human cerebral cortex have been generated and have settled to their designated locations.
The precursors of neurons are born near the cerebral ventricles (open cave like passage way of the brain). From there they travel to the cortical plate in an orderly manner. The early starters form the lower cortical layer, and the later-arriving neurons by-pass the lower layers to form an upper layers of laminar columns until a multilayered cortex is completed.
The next major event in the formation of the human cortex into a thinking organ is the connections of these neurons to each other. This developmental phase is called synaptogenesis, when the axons and dendritic trees establish synaptic circuits. This activities start during the second trimester of gestation and continue after birth.
At birth the volume of the newborns cerebral cortex is only about one third of the adult brain. The rapid increase in size of an infant’s cerebral cortex occurs during the first year because of the growth of neurons and of their connections (synaptogenesis).
This is the reason why parents and other primary caregivers should talk, sing, massage, play, interact, demonstrate, explain, draw, act, make faces, etc. to infants especially during newborn and infancy period till their brain has reached to almost the adult size.
Leo Leonidas, MD, FAAP, Assistant Clinical Professor in Pediatrics, Tufts University School of Medicine, Boston; Attending Pediatrician, Eastern Maine Medical Center, Bangor, Maine.
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