Oliver Sacks

We have long known, from observation of people with specific injuries or strokes, that different aspects of visual perception (color perception, face recognition, movement perception, etc.) depend on highly specialized areas of the brain. Thus, for example, damage to a tiny area of the visual cortex called V4 may knock out color perception but nothing else.

While humans can detect and identify perhaps ten thousand distinct smells, the number of possible smells is far greater, for there are more than five hundred different odorant receptor sites in the nasal mucosa, and stimulation of these (or their cerebral representations) may be combined in trillions of ways.

Thus one man who said he had “an intracranial jukebox” found that he could switch at will from one “record” to another, provided there was some similarity of style or rhythm, though he could not turn on or turn off the “jukebox” as a whole.