As you smell a fresh pine tree, cookies baking, bayberry or orange, do flashes of past Christmas holidays come flooding through your mind? This very aromatic season is an easy way to describe the phenomenon of scent and memory.
The process of smelling is a thing of beauty. Smell is a chemical sense detected by sensory cells called chemoreceptors in the nose that detect smell and pass on electrical impulses to the brain. The brain then interprets patterns in electrical activity as specific odors and olfactory sensation becomes perception – we recognize this as smell. The only other chemical system that can quickly identify, make sense of, and memorize new molecules is the immune system (Sarah Dowdy, How Stuff Works).
Where is this amazing olfactory system located? It is positioned in each of the two nasal cavities below and between the eyes, containing approximately fifty million primary sensory receptor cells. The olfactory sense can distinguish an almost infinite number of chemical compounds at very low concentrations and is over 10,000 times more sensitive than the sense of taste. Scents stimulate multiple areas and systems in the brain, influence the endocrine system, modulate immunological responses, and affect emotional states through their impact on the limbic system (Fragrance and Consciousness, Oct. 29, 2010).
So how does scent influence memory? Smell, more than any other sense, is intimately linked to parts of the brain that process emotion and associative learning. The olfactory bulb is part of the brain. It is part of the limbic system – a system that includes the hippocampus and amygdala, structures that are critical to our behavior, mood, and memory. The olfactory sense has a direct connection to the amygdala – the emotional center of our brain. And, just as important, is the relationship between the olfactory and the hippocampus, the center for new learning and memory. The close interaction of scent with the learning and memory centers of the brain may explain why a scent might get tied to a vivid memory.
“Interestingly, visual and auditory (sound), and tactile (touch) information do not pass through these brain areas. This may be why olfaction, more than any other sense, is so successful at triggering emotions and memories.” (Mercola.com, August 6, 2015)
The scent makes its way through the areas of the hippocampus and amygdala before you have any awareness of the scent itself. Because your body has far more receptors for scent (at least 1,000) than it does for other senses like sight (four) and touch (at least four) and travels through the hippocampus and amygdala, odor-cued memories are more poignant and different from other memories. Researcher Maria Larsson of Stockholm University concentrated on whether smell does release emotional memories. Autobiographical memory peaks between the ages of 15 and 30. Larsson stated “For visual and verbal cues, people’s memories came from their teens and 20s, as expected. But for smells, the peak was around age 5. It was clear that when they recollected a specific memory, that memory was localized to the childhood period. The memories were also more emotional and more vivid than memories brought up by visual and verbal cues.”
It is this physiological pathway that sets olfaction separate from the other senses: For every sense, the message travels first to the brain stem and the thalamus before going out to the primary sensory areas. “Olfaction is completely differently wired,” says Johan Lundsrtom, an APS Fellow at the Monell Chemical Senses Center in Philadelphia. First, odor molecules bind to receptors in the nose -> signals for the receptors travel up to the olfactory bulb -> some signals go to the primary olfactory cortex and onto higher-order parts of the brain. But there are also connections from the olfactory bulb directly to the amygdala -> an area relevant to emotions -> and the hippocampus -> which is involved in memory.
Separate research also revealed that both young and old adult were able to recall more than twice as many memories when they are associated with an odor. This suggests that “evidence for substantial olfactory cuing that is remarkably intact in old age.” (mercola.com) I went back to graduate school when I was fifty years old. If you know me – you know this story. I am also a certified clinical aromatherapist and I had to call on that skill to help get me through the academic challenges I faced. I used olfactory cuing to prepare for examinations. I had a scent that I only smelled when I was studying. It had to be different from an everyday scent - like coffee. On exam day, I brought my little bottle of essential oils with me. As was stated, I could recall twice as many memories with the scent – which was great for me. My classmates (half my age) saw what I was doing, and they asked for their study scent. As we took exams as a group, you could see many people around the table sniffing their bottles of essential oils! Luckily our professor was all about this and so we excelled in our studies with the help of olfactory cuing.
To summarize: we recall older memories when we smell an ambient scent that triggered that memory. And we can embed more memories when we purposely study with a scent. From the past to the present – scent plays a major role in memory.
References:
Crow, D. (October 29, 2010). Fragrance and consciousness. Retrieved March 29, 2016 from http://www.paraveda.org/readings/fragrances-and-consciousness/
Dowdey, S. How smell works. Retrieved November 28, 2016 from http://health.howstuffworks.com/mental-health/human-nature/perception/smell.htm
Fields, H. (April 12, 2012). Fragrant flashbacks. Retrieved March 30, 2016 from http://psychologicalscience.org/index.php/publications/observer/2012/april-12/fragrant-flashbacks.html
Holohan, M. (July 19, 2012). Smells like nostalgia: Why do scents bring back memories? Retrieved March 30, 2016 from http://www.nbcbews.com/pages/print
Dr. Mercola. (August 5, 2016) Why smells can trigger strong memories. Retrieved November 28, 2016 from http://articles.mercola.com/sites/articles/archive/2015/08/06/smells-trigger-memories.aspx
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