The Smell Files

Scent, the most primal of all senses, is arguably the most complex. The human nose contains millions of odor receptors of a thousand kinds--far more variety than is required for color vision or taste. How does the brain make sense of this flurry of signals? An essential first step, two groups of neurobiologists have recently found, is an orderly filing system. As they enter the brain from the different receptors, the hundreds of signals, each one representing a distinct odor component, are sorted into little round files called glomeruli--one type of signal per file.