" People fluent in two languages can lose either one after trauma, since first and second languages* draw on distinct neural circuits. Language deficits can even interfere with math. We seem to have a natural “number circuit” in the parietal lobe that handles comparisons and magnitudes—the basis of most arithmetic. But we learn some things (like the times tables) linguistically, by rote memorization. So if language goes kaput, so too will those linguistically based skills. More strikingly, some people who struggle to string even three words together can sing just fine. "

― Sam Kean , The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery