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FOOTNOTES

1 In September, as part of an ongoing effort to revive American tennis, the United States Tennis Association plans to centralize its player development program at the Evert Tennis Academy in Boca Raton, Fla., a new complex that will feature 23 courts (14 lighted), dormitories, a state-of-theart video lounge and a staff of 30, including a mental-conditioning coach. Tuition with room and board will cost as much as $42,000 a year. By comparison, the Russian Tennis Federation's total youth-development budget is estimated to be between $300,000 and $400,000.

2 Timing is vital because neurons are binary: either they fire or they don't — no gray areas. Their firing depends solely on whether the incoming impulse is strong enough to exceed the neuron's threshold of activation. To explain the implications of this effect, Fields had me imagine a skill circuit in which two neurons need to combine their impulses to make a third, high-threshold neuron fire — for, say, a golf swing. In order to combine properly, those two incoming impulses must arrive at nearly exactly the same time — sort of like two people running at a heavy door to push it open. The time window turns out to be about four milliseconds, or roughly the time it takes a bee to flap its wings once. If the first two signals arrive more than four milliseconds apart, the door stays shut, the crucial third neuron doesn't fire and the golf ball soars into the rough (or, as I was reflexively picturing, Zoe swings and misses the purple ball). "Your brain has so many connections and possibilities that your genes can't code the neurons to time things so precisely," Fields said. "But you can build myelin to do it."

3 These studies shine a new light on the neuro-anatomist Marian C. Diamond's 1985 finding that the left, inferior parietal lobe of Albert Einstein's brain, though it had a typical number of neurons, had significantly more glial cells than her other samples, a study that neurologists at the time considered so meaningless as to be nearly comical but that now seems to make sense, bandwidth-wise.

4 The list of myelin-related pathologies is long and, Bartzokis believes, includes multiple sclerosis and Alzheimer's as well as a wider range of conditions, like schizophrenia, dyslexia, attention-deficit/hyperactivity disorder and autism, all of which can be understood as disorders of impulse timing.

5 Venezuela is a more recent example of this phenomenon. In 1989, the Houston Astros opened the first of what are now nine major-league academies there, and a few years later, the number of Venezuelans in the big leagues started to rise. Since 1995, 125 Venezuelans have broken into Major League Baseball, 51 more than had appeared in all the years up to that point.

6 In children, myelin arrives in a series of waves, some of them determined by biological code, some of them dependent on activity. These waves last into young adulthood. Until this time, the brain is extraordinarily receptive to learning new skills. Though adults retain the ability to myelinate throughout life (thankfully, 5 percent of our oligos remain immature, ready to answer the call), anyone who has tried to learn a language or musical instrument late in life can testify that it costs a lot more time and sweat to build the requisite circuitry. The effortlessness is the first thing to go.

7 Replicating the Spartak system in the United States (or, for that matter, installing Dominican-style baseball academies or forcing young golfers to practice only at driving ranges) would likely not create a sudden wellspring of stars. The reasons that the United States is losing ground on the talent map have less to do with training mechanisms and more to do with bigger factors: a highly distractive youth culture, a focus on the glamour of winning rather than on the brickwork of building technique and a sporting environment that is gentler than those found in many of the world's harder corners.

"You can't keep breast-feeding them all the time," Robert Lansdorp, a tennis coach in Los Angeles, told me. "You've got to make them an independent thinker." Lansdorp, who is in his 60s, has coached Sharapova, along with the former No. 1-ranked players Pete Sampras, Tracy Austin and Lindsay Davenport, all three of whom grew up in the same area and played at the same run-of-the-mill tennis clubs near Los Angeles. "You don't need a fancy academy," he said. "You need fundamentals and discipline, and in this country nobody gives a damn about fundamentals and discipline." Lansdorp also mentioned that he'd visited Spartak last year to teach a clinic. "It was a pretty different place," he said. "But that Larisa, she sure knows her stuff."