In this tip, Coyle is referencing his earlier book, The Talent Code. In it he looks at research into the way the brain works with particular reference to myelin (you may have read about the "myelin sheath") that surrounds the axon of a neuron in the brain. It is an electrical insulator and as you repeat actions, the myelin sheath grows (myelination) and increases the speed with which electrical impules flow from one neuron to another. In essence, it's the way practice—repetition—makes those repeated actions easier, more automatic, and better. In the appendix of The Little Book of Talent Coyle quotes Dr. George Bartzokis, a scientist at UCLA: "What do good athletes do when they train? They send precise impulses along wires that give the signal to myelate that wire. They end up, after all that training, with a super-duper wire—lots of bandwidth, a T-3 line. That's what makes them different from the rest of us."
To get back to Tip #24, Coyle suggests, "When you practice, it's useful and motivating to visualize the pathways of your brain being transformed from simple copper wires to high-speed broadband, because that's what's really happening."
In much the same way as telling my choir about the difference between "drill" and "scrimmage," and increasing what I've called the "density" of their rehearsals, I suspect that their understanding of myelination and what's really happening in their brains as we practice (or they practice individually in the practice room) could also increase the focus and effectiveness of their work.
Something to think about—and also useful for us individually as we work to improve our own rehearsal and conducting skills.