Wait What Was That Smell? Connecting the Scents Around Us With Our Brain

By: Kallon Crowther  

November 2024

www.evitasherman.com/graph text

Imagine this: you pass a stranger on the street, and you get a strong whiff of their perfume. Suddenly, you are transported to the last time you felt your grandmother pulling you in for a warm embrace. The image is so clear even though your grandmother is nowhere to be seen. You find yourself immersed in the memories of the past. Nostalgia, warmth and a bit of sadness wash over you. How and why did your brain make such a connection between two seemingly unrelated events? Why did the shortest exposure to a simple scent evoke such a strong emotional response? Something smells fishy. Let’s dive deeper into your brain’s abilities to tie memories with your sense of smell. 

Your brain is a master of many things and storing complex memories is one of them. To understand this we first have to figure out how our brain processes smell, also known as olfaction. When you encounter a scent, such as a stranger’s perfume, that ‘smell molecule’, or odorant, travels into your nostrils. There, it interacts with small hair-like protrusions attached to your brain cells (aka neurons) known as cilia (1,2). This interaction activates the cell so it can send an electrical signal all the way to a different area of your brain known as the olfactory bulbs (1,2). Here, a decision is made on where this information should go next. Is this scent we are experiencing important enough to transport to long-term memory, or can it be forgotten just as quickly as it happened? An important memory such as a warm embrace from your late grandmother is clearly an impactful moment in your life. However, something irrelevant, like the smell of drying cement while walking to work, may not be important enough to be remembered. 

Our brain developed this special skill of advanced scent memory due to evolution (3). In a survival setting, remembering a certain smell can indicate danger, which could be the difference between life and death. The other senses, such as touch and taste, take a pit stop at the sensory relay center of our brain, known as the thalamus (3). Scent can bypass this relay system so we can react as quickly as possible to dangerous situations such as a toxic gas leak. 

Olfaction is unique from our other senses because it is the only sense that can be linked directly from our environment to memory and emotional processing centers of the brain known as the hippocampus and amygdala (4). An interesting research study found that when participants were shown visual versus scent-like cues from their childhood, they reported richer or more profound memory retrieval from familiar scents rather than familiar sights (5). Additionally, Alzheimer’s/dementia patients who have been provoked with a particular smell experienced enhanced memory recollection (6). In a “sense,” our sense of smell can be linked to our deepest memories stronger than any of our other senses. 

Our brain can use scent as a stronger memory trigger than any other cue from our environment. Thishelps us survive dangerous scenarios, but our brain also uses this skill to remember important momentsin our lives. Whether it be a memory involving the warmth of your grandmother's embrace or somethingas silly as a trigger that reminds you of your college days, scent and memory go hand in hand. So, the next time a scent transports you back in time, think about how your brain is working behind the scenes to make that happen. 

References: 

1.  Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. The Transduction of Olfactory Signals.

2. Patel, A., & Peralta-Yahya, P. (2023, January 17). Olfactory Receptors as an Emerging Chemical Sensing Scaffold. Biochemistry. American Chemical Society.

3. Sullivan, R. M., Wilson, D. A., Ravel, N., & Mouly, A. M. (2015). Olfactory memory networks: from emotional learning to social behaviors. Frontiers in behavioral neuroscience, 9, 36.

4. Mouly AM, Sullivan R. Memory and Plasticity in the Olfactory System: From Infancy to Adulthood. In: Menini A, editor. The Neurobiology of Olfaction. Boca Raton (FL): CRC Press/Taylor & Francis; 2010. Chapter 15.

5. de Bruijn, M. J., & Bender, M. (2018). Olfactory cues are more effective than visual cues in experimentally triggering autobiographical memories. Memory (Hove, England), 26(4), 547–558.

6. Mohamad El Haj, Odor-evoked Autobiographical Memory in Alzheimer’s disease?, Archives of Clinical Neuropsychology, Volume 37, Issue 2, March 2022, Pages 513–520.