Sense of Smell

The sense of smell is complicated and remains largely unexplained. What we know of taste, smell and touch is miniscule in comparison to the knowledge we have amassed about vision and hearing. Smell is unique in that it is perhaps the most deep-seated of the senses. It was originally concerned with prey-localization, mating, feeding, and the formation of memories that would help facilitate future success in those areas. The sense of smell is closely associated with the Limbic System. Initially evolved for the purpose of evaluating smells, the Limbic System is situated deep in the brain and conducts experience and expression of emotions. What began as a “smell brain” evolved into an “emotional brain”. Smell is located in an area of the cortex that is important for learning, storing new memories, and processing episodes that have been experienced. Early evolution of the brain was dominated by olfactory input and function. Olfactory receptor cells in humans occupy an area about the size of a postage stamp, allowing us to distinguish between about 10,000 different odors. However, we lack a linear scale or extended vocabulary to describe them. The odorant molecules that surround us are widely varied in chemical composition and shape, defying a comprehensive scale.

How does the brain know what the nose is smelling and how does it process the olfactory information? Most odors are a mixture of odorant molecules and can be identified through different combinations, posing potential problems for the expression of the smell experience. Though olfactory neurons only have a 60-day lifespan, the memories of these smells survive because each specific smell is transmitted to its unique place in the brain, where it can be retained and remembered. Memory triggered by odor is more evocative and intense than a memory triggered by any other sensory clue. Each new aroma we experience can be recalled. By contrast, repeated exposure to the same aromas decreases olfactory sensitivity, thereby limiting important sensory input to the brain. The more chemosensory experiences we have, the more we steel our mental abilities against the onslaught of daily repetition of place and environment. In an increasingly homogenized world, it will be a battle to continue developing our sense of smell in a world that is quickly moving toward a monoculture.

There are even entire branches of medicine now that believe in the medical benefits of holistic aromatherapy.  The powers of the sense of smell are amazing.