Word: myelination
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...that most teens' gray-matter structures - including those involved in decision-making - are less advanced than those of adults, as you would expect, until now no one had studied teens' white matter, which works along with gray matter to produce decisions. The key part of white matter is called myelin, a fatty substance that coats the individual neural strands, or axons, that make up white matter. Myelination of axons begins during childhood and is completed at the end of adolescence, around the mid-20s. Myelination in the frontal lobe - the brain region responsible for decision-making - happens last...
...which point a serious round of pruning is under way. Gray matter is thinned out at a rate of about 0.7% a year, tapering off in the early 20s. At the same time, the brain's white matter thickens. The white matter is composed of fatty myelin sheaths that encase axons and, like insulation on a wire, make nerve-signal transmissions faster and more efficient. With each passing year (maybe even up to age 40) myelin sheaths thicken, much like tree rings. During adolescence, says Giedd, summing up the process, "you get fewer but faster connections in the brain...
...between their 20s and 40s. Since 1990, thanks to work done in Hafler's lab, however, they've known that MS sufferers have hyperactive T cells - cells that cruise the body looking for bacteria, viruses and other pathogens - a condition that triggers an inflammatory response and destroys the protective myelin sheath around nerve cells in the central nervous system, which connects the brain and body. This can lead to gradual nerve damage and weakening of the muscles in the arms as legs, as well as problems with vision...
...closest to human trials are in the biotech industry, which operates without government funds. Geron claims it is close to filing for permission to conduct the first human trials relying on ESC-based therapy. It is using stem cells to create oligodendroglial progenitor cells, which produce neurons and provide myelin insulation for the long fingers that extend out from the body of a nerve cell. Lanza's group is also close to filing for FDA permission to begin clinical trials on three cell-based therapies: one for macular degeneration, one for repairing heart muscle and another for regenerating damaged skin...
...study the volume and distribution of white matter in 300 healthy subjects from 18 to 75 years old as well as in hundreds of older people suffering from such brain-related ills as Alzheimer's and Parkinson's diseases. As he suspected, the healthy adults had the most myelin in the frontal and temporal lobes--where big thoughts live. The quantity of sheathing reached its peak around 45 or 50, exceeding the amount in unhealthy older subjects and healthy younger ones...