Editor's Note: The second installment of this five-part series, on hearing, will appear in the Oct. 1 issue.
Freshly cut lilac, fingernails on a chalkboard, just-baked apple pie, satin and silk, the vivid hues of a sunset. Such sensory stimuli shape people's lives. They arouse and change, elate or sadden, calm or agitate. They tap memories of yesterday or years ago. Information that travels through the eyes, nose, ears, mouth, and skin define the world: what the senses don't perceive, the brain will never know.
René Descartes, the famous 17th century French mathematician, philosopher, and physiologist, postulated that all information reaches the brain through the senses. He has since been proven correct: all sensory cues do end up there, arriving as electrical impulses in nerve fibers. But understanding how this happens and how this process can be manipulated is still being decoded.
"At some level, everyone who works on...