| Smell, explainedHumans may be able to distinguish between more than a trillion different odors—extending our awareness beyond our immediate surroundings to enable us to detect gas leaks or pick up the scent of someone who just left the room. Smell is one of our most powerful senses. It’s better than sight at evoking strong memoriesbecause of the anatomy of the olfactory system, which allows neural signals about smell to bypass an area of the brain called the thalamus so that the olfactory bulb in the forebrain connects directly to brain areas that manage emotion and memory. When we smell something, we are actually breathing in tiny molecules that stimulate specialized olfactory neurons high inside the nose. Our olfactory system allows us to detect and discriminate between these substances, and our brain assigns these scents an emotional tag that influences our thoughts and actions—eat this, avoid this, flee. The anatomy of the nose and throat makes it possible to decipher complex flavor profiles because chemicals from the foods we eat travel from our mouths and throat to the olfactory neurons high inside the nose. Then, the brain attaches labels to those scents, just as it does with scents from the external environment. Partial or total loss of the sense of smell—hyposmia and anosmia, respectively—cansignificantly impact quality of life, and typically occurs due to disease or trauma. Anosmia occurs among roughly 3% of the US adult population over age 40. Sometimes this issue resolves on its own, but steroids and long-term smell retraining can often help. Phantom odor perception—smelling odors that aren’t actually present—occurs in roughly 7% of Americans over the age of 40. |
