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Sense of smell ‘can be improved through training’

BBC Online:
The sense of smell can be improved through training, a study on rats suggests. The study, published in Nature Neuroscience, also suggests if we do not use our sense of smell, we begin to lose it. The New York University Langone Medical Center team says their work also raises hopes of reversing loss of smell caused by ageing or disease.
But a UK expert thought that was unlikely.
Impairment in the sense of smell is associated with Alzheimer's disease, Parkinson's disease, schizophrenia, and even normal ageing.
Exactly why smell weakens remains a mystery, but the Langone team have pinpointed a half-inch-sized area of the rat brain called the piriform (olfactory) cortex where the problems appear to occur.
The researchers placed thirsty rats in boxes with a snout-sized hole in each of three walls and exposed them to brief blasts of odours through the middle hole. There were three different smells: a mix of 10 chemicals from fruits, oils, and cleaning agents; the same mixture with one chemical replaced by another; and the same mixture minus one of the chemicals.
When the rodents identified one smell, they were rewarded with a sip of water by going to the hole in the left side wall, for another smell they received water by going to the right side wall. Rats could readily distinguish between odours when a chemical had been replaced in one mixture, but when one component had simply been removed, they could not differentiate.