Sense of smell has roles in memory, taste, and emotions
Smell: It’s one of the five senses that you probably took for granted, until you came down with a case of this year’s cold. Unfortunately, when you drink a hot bowl of homemade soup, your severe nasal congestion prevents you from inhaling the delicious aroma. Furthermore, you lament your inability to taste your favorite, cold-weather treat.
So how does smell work? According to howstuffworks.com, smell is a chemical sense. You are able to detect odor when airborne molecules are given off by some source and float into the top of your nasal passage. Once they reach a small patch of thin mucus lining, the odor molecules come into contact with nerve cells called olfactory receptors. On the tip of the olfactory receptors are hair-like projections called cilia, which can bind to the odorants.
The binding event triggers signals that get passed along bundles of small nerve fibers, called axons, which make up the olfactory nerve. The signals are processed once they reach the olfactory bulb, a structure located in the forebrain. Afterwards, the information becomes transmitted to other parts of the brain, activating the sensation of smell.
The more concentrated the odor, the greater the signals being relayed into the olfactory bulb from the receptors. In humans, there are about 12 million olfactory receptor cells, which possess the ability to detect about 10,000 odors.
Scientists have discovered the mechanism by which the brain differentiates and memorizes the many odors we encounter.
In 2004, the Nobel Prize in Physiology or Medicine was awarded to Richard Axel and Linda Buck, who discovered that each olfactory receptor cell is genetically encoded to respond to a particular set of odors. Furthermore, their research showed that receptors send impulses to particular regions in the olfactory bulbs, known as glomeruli. They claimed that our brain’s interpretation of the activity in the thousands of different glomeruli allows us to sense a variety of odors.
Axel and Buck’s research was challenged, however, by biophysicist Luca Turin. He developed a theory that it was the quantum vibrations of the atoms in the odor molecules, rather than the shape of those molecules, that allow humans to detect an almost endless list of odors.
Regardless of how smell is actually brought about, scientists have been the most fascinated by the way smell is linked to our memories and emotions, which are associated with a part of the brain called the limbic system.
A component within the limbic system, the olfactory bulb is linked to areas of the brain responsible for processing emotion as well as for learning. Your brain is responsible for making the link between a smell and an event. Hence, people are able to use smell to jog their memories.
Besides memory, smell has also been found to enhance our sense of taste. 70 to 75 percent of what we taste actually comes from our sense of smell.
So when you are experiencing nasal congestion, thick mucus linings in your nasal passages are preventing odor molecules from binding with your olfactory receptor cells. In turn, the olfactory bulbs are hampered in their ability to process smell.
Additionally, smell can play an essential role in our survival. The unpleasant odor of fire or rotten food can prompt us to avoid potential danger.
While our ability to smell is considered to be one of our most primal senses, its complexities and significant role in our well-being is often overlooked.