Ian think of the myelin sheath as being the insulation on an electrical cable the thicker coating and wider the bore the better the current will flow and be controlled by the insulation so signalling takes place faster and also more controlled and with better reproducibility. The myelin sheath is almost complete before the end of adolescence but there is activity into adulthood. I have not and will not be reading the book as I don't read too much fiction based literature. They guy who wrote the book has made a great deal of mileage... and money out of authoring pseudo scientific books.
A couple of articles that do suggest we increase Myelin sheathing with cognitive skill development..
Good reading and not out of line with the suggestions presented in the Talent Code!
Practice is "learning" a skill. And some of the attached articles state that myelin sheathing continues to increase for those "pathways" we use even into adulthood.
It may increase exponentially faster in infants and adolescence (as you might expect for those that are also exponentially "learning").
How we learn and increasing understanding of skill development is not a wasted effort, for anyone that wishes to improve. The Talent Code suggests (even discounting any connection with myelin "building") different practice methods and types of skill mastery.
As Mr Coyle studied centers of exceptional skill development, his "cognitive" conclusions of "Myelinization"(even if WRONG) , does not automatically discount his conclusion of how we might increase talent. And how exceptional skill is learned. Deep Practice, being a term he coined for a particular type of practice.
I have no emotional attachment to the TALENT CODE, other than examining how I might improve my practice technique.
Likewise, his observations on how the BEST coaches "coach", are not dependent on his "neurological" assumptions. (Myelin formation) But Mr. Coyle's observations should be of interest to coaches with regard to methodology of the "best of the best", as in John Wooten at UCLA, and others.
http://www.sv.ntnu.no/psy/bjarne.fjeldsenden/psypro102/brainmyelin.htm
http://www.sciencedaily.com/releases/2012/09/120924152544.htm
Cheers
p.s.
I might add an aside, as a retired engineer, listening to others NEW ideas allowed me to stay current as technology progressed. (it wasn't how much I knew, as it was how much THOSE AROUND me knew! That made me better at my job.)
I also spent some time in the UK and there are cultural differences between the USA and UK with regard to change and new ideas.
That is not a "slam" on either side of the pond, just saying there are differences.