The fourth chapter of “Train Your Mind, Change Your Brain” by Sharon Begley is concerned with the neuroplasticity of young brains. It reviews an enormous amount of research that can best be summarized in the following paragraphs taken from the text.
“…the key sensory cortices are, for the first decade of life and perhaps longer, like a flighty new college gradate hopscotching from job to job, responding to the best offer. No signals from the eyes arriving? No problem; the visual cortex will handle a different sense and even a non sensory job such as language. No transmission from the ears? The auditory cortex will be happy to help out with peripheral vision. By the early years of the millennium, it was clear that these structures should really be referred to as he “visual cortex” and the “auditory cortex” in quotation marks. “Visual information is going into the auditory cortex and auditor information is going into the visual cortex,” the researcher Neville told the Dalai Lama as she ended her presentation. “This isn’t supposed to be how our brain is wired. But what the research has shown is that the primary visual cortex is not inherently different from the primary auditory cortex. Brain specialization is not a function of anatomy or dictated by genes. It is a result of experience. Who we are and how we work comes from our perceptions and experiences. It is the outside world that determines the functions properties of the brain’s neurons. And that’s what our work has been about: how experience shapes the functional capabilities of the brain.”
“Usually, the pathways from the ears to the visual cortex and from the eyes to the visual cortex remain scarcely traveled if traveled at all, like back roads. In people with normal vision and hearing, superhighways carry signals from the eyes to the visual cortex and from the ears to he auditory cortex just fine, swamping any activity along the back roads of he brain. As a result, the wayward connections all away soon after birth , when the brain figures out where signals are supposed to go. But in the absence of normal sensory input, as when neurons from the retina are unable to carry signals to the visual cortex or neurons from the ears to carry signals to the auditory cortex, the preexisting but little-used connections become unmasked and start carrying traffic. The “visual” cortex hears, and the “auditory cortex sees, enabling the brain to hear the lightning and see the thunder. (“In Buddhism,” Thupten Jinpa added, “there is a claim that an advanced meditator can transfer sensory functions to different organs, so that visual activity can be performed by something other than the ears. In this case, a meditator can read with “closed eyes.”) In what Alvaro Pascual -Leone and colleagues call “the intrinsically plastic brain,” more permanent structural changes then kick in, as neurons grow and sprout more connections to other neurons. This may be how the visual cortex adds higher cognitive function to its repertoire, too.”