The Power of our Nose, and how it relates to COVID-19

            Our sense of sight, hearing, and touch are crucial to understanding our environments and in helping us perform important tasks throughout our everyday lives. However, often playing a supporting role, we also have our sense of smell, an incredibly powerful tool able to alert us to both pleasant and unpleasant odors. As we walk down the street, numerous scents flood into our nose, whether it is the smell of coffee from a café, the smell of flowers from the park, or the dangerous scent of a gas leak, we often forget exactly how much we smell each day. We can link specific scents to specific things, and these associations allow us to be reminded of previous encounters with the specific scent, and whether they were positive or negative. However, the strength of this association is still not entirely known, and research continues to discover how powerful it is.

In 2017, researchers Laura K. Shanahan and Jay A. Gottfried published a review of recent literature regarding scent influences on memory consolidation in sleeping human brains. In this review, the researchers presented recent studies that sought to understand how the presence of specific scents during human sleep affected our brain’s ability to consolidate and reinforce the memories obtained that day. One such study is Rasch et al. 2007, where the researchers had participants learn the locations of card pairs in a visuospatial learning task akin to the card game “Concentration”, in the presence of a rose odor. After learning the locations of card pairs, the subjects went to sleep, which is when the researchers presented the sleeping subjects with either a control odor vehicle or the same rose odor used during learning. What they discovered is that the participants exposed to the same rose odor during their sleep performed better on a memory post-test once they had awoken than those who were just exposed to a control odor vehicle.

However, these discoveries raise some concerns regarding the COVID-19 pandemic. One common symptom of COVID-19 infection is a loss of smell, also known as anosmia. In an article for Nature.com, Michael Marshall seeks to answer some questions regarding the effects of COVID-19 on the sense of smell. According to a study performed in Iran on 100 people infected with COVID-19, 96% of the participants had some sort of olfactory dysfunction and 18% had anosmia. However, most recover their sense of smell after a month, but some feel the effects for an extended time, and even if they do recover, there is a likelihood that their sense of smell will be altered – pleasant odors may now smell rancid, different than what the patients remember. Now that we have an idea of smell’s role in memory consolidation during sleep, we cannot be sure that anosmia resulting from COVID-19 will not affect one’s ability to retain and consolidate memories. The article for Nature.com also mentions how those suffering from anosmia are more than twice to likely to experience a hazardous event, and that smell dysfunction has been linked with depression. In the review article, we had also learned that odors have been shown to enhance declarative memories and quell fear memories, so a loss of smell as a result of COVID-19 could affect one’s mental health greatly. If odors have an important role in the association of objects to their role, and COVID-19 can harm one ability to smell, there is a possibility that COVID can affect one’s ability to remember important things, as we do not know what odors we smell when we sleep, and how these specific odors that may be familiar to us affect our development. Now, I call to you to enjoy your sense of smell, to appreciate the odors that things give off, as it can help you consolidate your memories, and you never know when you might lose it.

References:

Marshall, M. (2021, January 14). COVID's toll on smell and taste: what scientists do and don't know. Nature News. https://www.nature.com/articles/d41586-021-00055-6.

Shanahan, L.K., & Gottfried, J. (2017). Scents and Reminiscence: Olfactory Influences on Memory Consolidation in the Sleeping Human Brain.