Word: cortexes
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Dates: during 1990-1999
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Tsai and her team have recently isolated a gene in mice, called p35, which appears to play an integral part in the formation of the cortex...
University of Chicago pediatric neurologist Dr. Peter Huttenlocher has chronicled this extraordinary epoch in brain development by autopsying the brains of infants and young children who have died unexpectedly. The number of synapses in one layer of the visual cortex, Huttenlocher reports, rises from around 2,500 per neuron at birth to as many as 18,000 about six months later. Other regions of the cortex score similarly spectacular increases but on slightly different schedules. And while these microscopic connections between nerve fibers continue to form throughout life, they reach their highest average densities (15,000 synapses per neuron...
Scientists are also beginning to identify some of the genes that guide neurons in their long migrations. Consider the problem faced by neurons destined to become part of the cerebral cortex. Because they arise relatively late in the development of the mammalian brain, billions of these cells must push and shove their way through dense colonies established by earlier migrants. "It's as if the entire population of the East Coast decided to move en masse to the West Coast," marvels Yale University neuroscientist Dr. Pasko Rakic, and marched through Cleveland, Chicago and Denver to get there...
This profusion of connections lends the growing brain exceptional flexibility and resilience. Consider the case of 13-year-old Brandi Binder, who developed such severe epilepsy that surgeons at UCLA had to remove the entire right side of her cortex when she was six. Binder lost virtually all the control she had established over muscles on the left side of her body, the side controlled by the right side of the brain. Yet today, after years of therapy ranging from leg lifts to math and music drills, Binder is an A student at the Holmes Middle School in Colorado Springs...
...those behavioral mileposts that never cease to delight and awe parents. Around the age of two months, for example, the motor-control centers of the brain develop to the point that infants can suddenly reach out and grab a nearby object. Around the age of four months, the cortex begins to refine the connections needed for depth perception and binocular vision. And around the age of 12 months, the speech centers of the brain are poised to produce what is perhaps the most magical moment of childhood: the first word that marks the flowering of language...