What about your phone? In a 2022 American study, smell was compared to other senses (sight and hearing) and to personally valued goods (including money, a pet, or hair) to see what people valued more.
The researchers found that smell is perceived as much less important than sight and hearing and is valued less than many goods. For example, half of the women surveyed said they would prefer to keep their hair over their sense of smell.
Smell often remains under the radar as one of the least valued senses. But it was one of the first sensory systems developed by vertebrates, and is linked to mental health, memory and more.
Here are five interesting facts about your olfactory system.
1. The sense of smell is linked to memory and emotions
Why can the smell of freshly baked bread trigger happy childhood memories? And why can a certain perfume bring you back to a painful breakup?
Smell is directly linked to both memory and your emotions. This connection was first established by American psychologist Donald Laird in 1935 (although French writer Marcel Proust had already made it famous in his musings on the scent of baking madeleines - French sweets).
Smells are first picked up by special olfactory nerve cells in the nose. These cells extend upward from the roof of the nose to the odor processing center in the brain called the olfactory bulb.
From the olfactory bulb, they establish a direct connection to the brain's limbic system. It includes the amygdala, where emotions are generated, and the hippocampus, where memories are created.
The other senses - such as vision and hearing - are not directly connected to the limbic system.
In a 2004 study, functional magnetic resonance imaging was used to prove that smells trigger a much stronger emotional and memory response in the brain than visual cues.
2. Your sense of smell is constantly recovering
You can lose your ability to sense smells due to injury or infection - for example, during and after a Covid infection. This is known as olfactory dysfunction. In most cases, it is temporary and recovers within a few weeks.
This is due to the fact that every few months your olfactory nerve cells die and are replaced by new ones.
We are not entirely sure how this happens, but it probably involves the stem cells of your nose, the olfactory bulb and other olfactory nerve cells.
Other areas of your nervous system - including your brain and spinal cord - cannot regenerate and repair after injury.
Permanent regeneration may be a protective mechanism, as olfactory nerves are vulnerable to damage caused by the external environment, including toxins (such as cigarette smoke), chemicals, and pathogens (such as the influenza virus).
However, some people may continue to experience a loss of sense of smell after an infection with Kovid. Studies suggest that the virus and the prolonged immune response damage the cells that allow the olfactory system to regenerate.
3. Olfaction is linked to mental health
About 5% of the world's population suffers from anosmia - a complete loss of sense of smell. Approximately 15-20% suffer a partial loss known as hyposmia.
Given that loss of sense of smell is often a major and long-lasting symptom of COPD, these figures are likely to be higher post-pandemic.
However, in Australia, the prevalence of olfactory dysfunction remains surprisingly poorly understood.
Loss of sense of smell has been shown to affect your personal and social relationships. For example, it may mean you miss out on shared experiences at mealtimes, or cause changes in sexual desire and behaviour.
In older people, a decline in the ability to smell is associated with a higher risk of depression and even death, although we don't yet know why.
4. Loss of sense of smell may help identify neurodegenerative diseases
Partial or complete loss of sense of smell is often an early indicator of a number of neurodegenerative diseases, including Alzheimer's and Parkinson's diseases.
Patients often report that they have lost their sense of smell years before any symptoms appear in the body or brain. However, many people do not know they are losing their sense of smell.
There are ways to determine if you have a loss of sense of smell and to what degree. It is possible to visit an official smell testing center or do a self-test at home that evaluates your ability to recognize household items such as coffee, wine or soap.
5. You can train your nose to sense smells
"Odor learning" is emerging as a promising experimental option for the treatment of olfactory dysfunction. For people who experience olfactory loss after Kovid, it has been shown to improve the ability to detect and discriminate odors.
Olfactory training (or "olfactory learning") was first tested in 2009 in a German psychological study. It involves sniffing strong smells - such as floral, citrus, aromatic or fruity scents - at least twice a day for 10-20 seconds, usually for 3-6 months.
Participants are asked to focus on the memory of the smell as they sniff and recall information about it and its intensity. This is thought to help reorganize neural connections in the brain, although the exact mechanism behind it is unclear.
Some studies recommend using one set of smells, while others recommend switching to a new set of smells after a period of time. However, both methods show significant improvement in olfaction.
This training has also been shown to alleviate depressive symptoms and improve cognitive decline in both elderly and dementia sufferers.
Similar to physical therapy after physical injury, olfactory training is thought to act as a rehabilitation of the sense of smell. It realigns the nerves in the nose and the connections it forms in the brain, allowing you to properly detect, process and interpret smells. | BGNES
