How we perceive such chemical substances as odours is a mystery that, until recently, defeated most attempts to solve it. Anatomical studies showed that signals from the olfactory cells in the nose reach the olfactory area of the cortex (the higher functioning part of the brain) after only a single relay within the brain. Situated at the back and very top of our nasal cavity is a small area called the olfactory epithelium, an area of mucus-covered nerve cells that sense smell. When airborne molecules are released by substances around you, like foods, hot drinks or nature, those molecules dissolve in the mucus. Your smell receptors then send a message to your brain, which will search your memory bank to identify the smell.
The olfactory cortex, in turn, connects directly with a key structure called the hypothalamus, which is functionally associated with the whole limbic system (which also includes such brain areas as the amygdala and hippocampus), which is increasingly recognised to be crucial in determining and regulating the entire emotional ‘tone’. Excitation of this, by whatever means, produces heightened emotions and an intensification of all the senses. It is thought that smell is the key sense to detect danger and therefore has the ability to activate the other senses, emotions and the physical body.
One of the great pleasures in life is eating and drinking and just the thought of biting into your favourite treat will get the saliva flowing. We divide our day by the meal and refreshment breaks we take and rapidly succumb to a ‘naughty’ treat when we want to comfort ourselves.
Smell and taste are closely linked and although we will more often comment on the wonderful taste rather than on the smell of a meal, it is actually the sensory smell information that determines 80 to 90 % of our taste experience. Smell is also more sensitive than taste; according to some estimates smell is no less than 10,000 times more sensitive than taste. But humans define the world around them largely through the eyes and ears. We neglect the sense of smell and often suppress our awareness of what our nose tells us. However, mothers can recognise their babies by smell, and newborns recognise their mothers in the same way. The smells that surround us affect our well-being on a daily basis. Everyone has a unique smell, except identical twins – dogs can distinguish between non-identical twins, but not identical twins using their sense of smell. We give out a happiness odour which we can detect though our sense of smell.
Smell strongly influences the retention and recall of memories and smells can evoke ‘long lost’ memories. Odour memory falls off less rapidly than other sensory memory and will last a long time. The so called “Proust effect” is when a smell recalls a memory of an experience in the past. Smell is better at this memory cue effect than any of the other senses as it goes straight to the brain without intermediate processing. Whole memories, complete with all associated emotions, can thus be prompted by smell. You can use this effect to your advantage by associating an odour to, for instance, a revision session and using the same odour at exam time – you can use natural smells such as apples, mandarins, strawberries or chocolate.
We can be over or under sensitive to certain smells, or even have a combination of both. This will affect eating habits, but also concentration and emotional well-being. The strong link of smell to our emotional world can have a profound influence on our ability to perform to our full potential. Although it is not easy to retrain our sense of smell directly, we have found that the intricate link between all five senses can be used to good effect. Retraining our hearing and vision senses will often lead to changes in smell and taste.