The olfactory bulb sends signals to the brain (somehow) and our brain tells us there is an odor. We remember them and recognize them. I had a patient who started to smell the ocean, 75 miles away from Houston, as the first sign of her brain tumor. Smell recognition get built in as we become adults from infants. It is just like sight, an amazing capacity of brain interpretation.-http://medicalxpress.com/news/2013-05-temporal-olfactory.html