An excerpt from an article written by journalist Paola Totaro (who tested positive to Covid-19 and lost her sense of smell, published in the Weekend Australian Magazine January 30-31, 2021
‘Since Covid-19 unleashed its devastation upon the world, neuroscientists estimate that as many as 68 percent of people affected by Covid-19 have experienced some form of olfactory and taste dysfunction. These patients have enabled a growing number of scientists to study aspects of human olfactory physiology and perception that have remained mysterious. So the sense of smell, which is triggered when airborne particles inhaled through the nose attach to the receptor cells that line the mucus membranes at the top of the nasal bridge. There are about six million of these receptor cells on an area the size of a postage stamp but only 400 or so different types of sensory receptors. Some respond to the odorant they switch on, sending signals upwards to the olfactory bulb and into the brain for interpretation.
Unlike hearing and sight, which can be measured and mapped physiologically, the olfactory sense is the product of a complex neurological process and science still cannot explain in absolute detail how humans code odours.
Many Covid-19 patients have also begun a phase of recovery characterised by ‘parosmia’, a less reported condition in which smells are terribly distorted, often sparking nausea and disgust. Some even described experiencing ‘phantosmia’, in which sufferers detect a smell that simply isn’t there.
Professor Annie Sophie Barwich, a German born cognitive scientist and philosopher, has described smell as the Cinderella of the senses because it has been dismissed by philosophers and scientists throughout history as the most dispensable. She writes, ‘the characteristics of odour perception and its neural bases are key to understanding the mind’.
The nose is deeply wired into the limbic system, the area of the brain that controls and regulates both conscious and unconscious functions. Smell is the only sense that completely bypasses the thalamus, the part that relays motor, visual and auditory signals, and travels straight to the amygdala, where emotions and memories are given meaning. The olfactory senses are related to instinctive behaviours, gatekeepers not just for health (detecting smoke and fire is fundamental) but for intimate relationships too. Mothers and babies are profoundly linked by smell, while perceiving chemical signals or odours can define who we find attractive. Smells can also trigger powerful memories and emotions: the smell of the sea, freshly cut grass, our mother’s perfume.
Professor Barry Smith, the UK lead for the Global Chemosensory Group, believes that the experiences reported by the vast new patient cohort is integral to the campaign for knowledge. “The odours we perceive are not predictable from the mixtures of molecules we inhale,” Smith says. “There is no equivalent of primary colours or musical scales. We respond to each molecule with many receptors and each receptor responds to different molecules. Odour mixtures are much more mysterious and that’s what we mostly smell. For all that we do know, science still struggles to work out how we code odours.”
Dr Federica Genovese, a young Italian neuro-scientist explores the role of the trigeminal nerve, the system that triggers protective responses against powerful stimuli such as wasabi, mustard or chillies. For years, she says, scientists have believed that the olfactory and trigeminal systems are independent and work in parallel. Recently, this has been questioned with the sudden loss of both functions together in the wake of Covid-19 infections, which seems to confirm they work in tandem. Scientists first thought Covid-19 was killing the olfactory neurons themselves, but now they understand that the special protein needed by the virus to invade the cells isn’t in the olfactory neurons but on the scaffolding that supports them, known as sustentacular cells.
“We have now realised that there is a giant gap in our knowledge about what maintains health in the olfactory epithelium (tissue) and the role of these cells, which are like scaffolding structurally.” Genovese says, “They create order but if you knock them out, the whole system goes nuts. So far the most credited thesis is that parosmia is part of the recovery process from anosmia. During the regeneration and rewiring of the neurons from nose to brain there is mistargeting, but the more we use the network, keep smelling, training and retraining, the more it will redefine.” Anosmia sufferers are training the nose daily with essences such as eucalyptus, citrus and rose oils.
Professor Smith, who is also director of the University of London’s Institute of Philosophy Centre for the Study of Senses, says smell not only governs food intake but regulates our interactions with the environment and others. “It constantly modulates our everyday experience in a way we mostly fail to recognise,” he says. “We don’t know what we have got until it’s gone.”
In 2017 I attended a lecture by Sissel Tolaas, held at the NGV as part of the Triennial exhibition. This was an incredibly insightful wonderful, intelligent and authentic exhibit.
“Smell is a crucial sense, used and understood (often unconsciously) by people to trigger their memories of time and place." Stemming from a desire to counter the ‘continuous wholesale deodorisation’ of the world, Tolaas composes provocative smells to stimulate memory, recreate place, capture the seasons and arouse emotional and intellectual responses.
For the NGV Triennial 2017, Sissel Tolaas created a ‘smell landscape’ of Melbourne composed of twenty unique smells to touch and smell – building a picture of the city in your mind, made up by smells both pleasant and unpleasant. Through this project Tolaas aimed to stimulate stories about time and place to enhance our understanding of our surroundings and to enable us to reconnect with our sense of smell – a sense she believes is being lost.” from NGV website
The Re_Search Lab founded in January 2004 as a laboratory for research on smell, the olfactory and smell communication. Situated in Berlin, the Re-Search Lab is part of the Tolaas studio, a workspace where interdisciplinary projects are developed, researched and executed. These projects all involve smell, odour and fragrance in various ways, shapes or forms, and can be conceptual, scientific and creative in nature. Click this link to discover more https://www.researchcatalogue.