Get a Whiff of This!
The sense of smell is the least understood and perhaps the least appreciated of all our senses, and in the future may become a key to unlocking many of our body-mind's most sensual mysteries.
Researchers have found that even if we soon forget things we see or hear, we remember odors for a lifetime. Our sense of smell is our most enduring and powerful of all our senses. It is linked with emotions which are stored in our limbic brain. Our memory of scent is longer lasting and more accurate than our sight or reasoning memory. Scent triggers our emotions affecting the autonomic system (controls nerves leading to your body's glands and organs).
Smell is the most sensitive of our senses, and perhaps the most primitive. We can distinguish literally thousands of odors and fragrances, and somehow remember them for the rest of our lives. Studies have shown that infants can identify their mothers on the basis of smell, and that mothers also can pick out their babies on smell alone. It requires only four scent-bearing molecules for us to recognize a particular smell, yet scientists still do not know exactly how odors are discerned or remembered.
We all have a unique reaction to particular smells, because we've all had a personal history of exposure to aromas with associated emotional connections. Choosing aromas is very much a matter of personal taste. No single perfume will have the same appeal to everyone.
Much of our experience is associated with smell, even when we are unconscious of those smells in our environment. Consequently, memories and their related emotions can be called forth instantly by the right odor or fragrance. We can be consumed by our immediate problems while walking to work one day when suddenly after passing a bakery, we are distracted by childhood memories of the smell of fresh bread baking in the oven. The secret of aromatherapy lies in human experience; that is, how we relate fragrance to specific experiences even if we cannot recall the details of that experience.
In practical terms there are many examples of this intimate connection between fragrance and memory, both positive and negative. In terms of positive reinforcement, if a fragrance once worn resulted in a successful intimacy between a young woman and her lover, then that fragrance sticks in her memory as the one she would like to wear on any date or socially important occasion. The odor of a fir tree at Christmas or the odor of a turkey cooking at Thanksgiving may engender memories and feelings of each holiday and bring satisfaction related to the holiday based upon memories of these powerful odors. On the other hand, in terms of negative reinforcement, if you were to drink coffee for the first time before having a life threatening car accident, the odor of Starbucks brewing may engender the olfactory memory of fear, embarrassment, discomfort and pain associated with the accident.
The reason that smell evokes such powerful memories and emotions is that our olfactory sense is linked directly with the brain's limbic system, one of the most primitive parts of the central nervous system. The limbic system plays a central role in our ability to experience emotion and retain those experiences. It is literally a storehouse of memories, emotions, and their related odor, any set of which can be released by the right fragrance.
Stress level, heart rate, respiratory and digestive systems are all influenced by our emotional states. Aromatherapists believe essential oils can be greatly beneficial to our emotional healing. Essential oils known for their anti-depressant, sedative, or tranquilizing characteristics may trigger the release of endorphins and encephalin (neurochemical analgesics and tranquilizers) and, by other studies of odorant effects upon mood, how they may also influence other endogenous opiates within the brain.
Your Nose Smells
Your nose draws odors and fragrances to itself by inhalation. At the roof of the nose, just below the eyes, lies a closely bunched set of specialized nerve endings called smell receptors. These olfactory nerves protrude downward into the nose canal. The tips of these nerves have tiny hairs, called cilia, extending from them. A mucous membrane covers the surface of the nerves and serves to dissolve molecules that carry scent, thus making the odor accessible to the nerves, triggering electrical nerve transmission to the olfactory bulb. The olfactory bulb is lined on both sides with a special tissue consisting of approximately ten million nerve cells covered with a thin layer of mucous. These nerve cells are replaced every twenty eight days. Each nerve cell has six to eight tiny hairs acting as receptors by electrical impulse to the olfactory membrane (actual brain cells). The nerve signal entering the bulb then travels along the olfactory tract into the brain. The smell centers in the brain are located in the limbic system, just above the brain stem, and the frontal lobe.
Physiologically, odor and memory are linked anatomically and functionally. Once fragrance enters the nose, the odor is perceived through three major initial brain pathways, (1) the prefrontal cortex, (2) the temporal cortex and (3) olfactory pathways leading to the hypothalamus. You can think of your hypothalamus as your personal "mind/body laboratory." It takes thought and emotional impulses from the storage banks in your brain and transforms them into the chemicals you need for response. The chemicals that are thus formed determine our perceptions. This is the only place on the body where the central nervous system is directly exposed to the environment. Our other nerves or senses must travel through our sensory path of neurons and spinal cord before reaching the brain. So far, scientists have not been able to determine any microscopic distinctions in the smell receptors. So, no one knows how smells can be differentiated.
Each of these systems contributes to the general functional anatomical brain region called the limbic system. It is this general limbic system which is intimately involved with memory. Indeed, 80% of the brain is called the paleocortex or "old cortex" whose major function in the primitive and modern world is to perceive odors in order for us to (1) seek and find food, (2) seek and find an appropriate mate and (3) stay out of trouble by avoiding enemies who smell different and who could injure us.
By using our aroma sense which could assist in performance of these three important activities we can expend the least amount of energy, conserve our precious endogenous resources and survive in a hostile world environment. However, in order to accomplish these tasks and survive successfully our brains have to "remember" the character of these odors, since if they were forgotten, each of these critical functions could not be performed successfully.
Some believe that the 'sixth sense' that often keeps us out of trouble may have a lot to do with smell. The ability to smell varies widely among people. Some have a talent for smells, while the capacity to smell in others is relatively dull. Neither end of the spectrum is regarded as a disorder, but rather a genetic trait.
My favorite theory on the human sense of smell was introduced by Luca Turin, that the smell of substances is based upon the frequencies of vibration of their molecules. If you have further interest, I strongly recommend you read Chandler Burr's very engaging The Emperor of Scent: A True Story of Perfume and Obsession, a biography of Luca Turin.