For the inexperienced traveler, Aubrey Gilbert’s “whirlwind tour of your nervous system” blows past the hippocampus and cortex of the frontal lobes like a five-day package excursion through the great cities of Europe. Looking back, there’s no doubt it's been a remarkable trip, but you’re unsure in which region of the brain you encountered Broca’s area, or the precise location of the olfactory bulb; your most vivid take-home memory is apt to be Gilbert's admonition never, ever to order brains for lunch.