Girl smelling lily valley

Have you ever wondered why some scents can take you back to a place in time? Or indeed how do essential oils affect memory? Scent is the least understood of our senses, however, scientists are now beginning to explore this arcane aspect of our limbic system to help people with dementia and those living with the effects of PTSD.

Why Do We Know So Little About Smell? 

One of the key problems around fragrance associations in the brain is the research around it is very new. This is because of historic connotations of bad smells being associated with the devil and certain types of malintent. This derives from the early church adapting pagan practices around incense to bring ideas that things that smelt emitted the odor of sanctity or godlike properties. So if Christlike wonders smelt of wondrous scents then the opposite must be true that rotting things reeked of death, evil, and decay. Over time then, this anxiety around things that were smelt became more religious and less scientific. Nonetheless, who wants to be associated with dealing with the devil? So attention was diverted elsewhere.

Scent and Memory: Correctly Termed Olfactory Memory

This knowledge deficit not only pertains to scent and memory but about how we understand smell as a whole. However fundamentally, olfactory memory is harder to study than memories associated with visual or auditory cues, for example. So far most studies into human olfaction have been limited to tests that prove how many one can recognize which is a little different from understanding how and why we recall them.

This time travel aspect of smelling something that immediately transports you through space and time to the past is commonly known as the Proust Effect. It’s not an exact representation because the example that inspired the name involves both smell and taste, but of course, the two are intrinsically linked. 

Scent and Memory Travel: The Proust Effect

In the book In Search of Lost Time,  Marcel Proust dips a madeleine cake into his tea and enjoys a strange sense of being transported straight back to Sunday mornings staying with his aunt. 

No sooner had the warm liquid mixed with the crumbs touched my palate than a shudder ran through me and I stopped intent upon the extraordinary thing that was happening to me. An exquisite pleasure had invaded my senses, something isolated, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory – this new sensation having had on me the effect which love has of filling me with a precious essence; or rather this essence was not in me it was me…
Whence did it come? What did it mean? How could I seize and apprehend it? ... And suddenly the memory revealed itself. The taste was that of the little piece of madeleine which on Sunday mornings at Combray (because on those mornings I did not go out before mass), when I went to say good morning to her in her bedroom, my aunt Léonie used to give me, dipping it first in her own cup of tea or tisane. The sight of the little Madeleine had recalled nothing to my mind before I tasted it. And all from my cup of tea.” ― Marcel Proust, In Search of Lost Time

Proust’s astute note that the effects had not happened when he had looked at the cake, but that the alchemy took place when he tasted it is fascinating.

Nostalgic Scent and Memory

Scent and memory have a unique correspondence that evokes emotional memories,  rather than spatial ones, which visual memories do. In other words, we might see something that reminds us of something or somewhere else, but it is the smell of it that reminds us how it felt to be there or with that person. (Hertz, 2016)

Scent and Memory Physiology

It could be that this is down to how the brain is constructed.

Information about scent is sent to the brain via the olfactory nerve. Data career along electrical pathways, but there are junctions between nerves, over which electrical pulses cannot pass. We call these synapses (The way that information gets across then, is via neurotransmitters - chemicals messengers traversing the gap)

Just two synapses exist between the olfactory nerve and the amygdala, the part of the brain that recognizes certain types of emotions including joy and fear.  The amygdala also connects emotions to other brain abilities, like your senses - so the sense of smell - but also learning and memory. 

So two synapses between the olfactory nerve - the bit that initially accepts the fragrance into the body and then turns that information - and the amygdala - the part that then turns that into a functional behavior like a fear response if we sense smoke, for example. This is a fast and dependable system, with few places where the process might be adapted. 

But then there are just three synapses between the olfactory nerve and the hippocampus which is responsible for us being able to commit things to long-term memory. Again, a very fast and reliable system.

Examples of Scent and Memory Adaptations

Let’s think of that in two ways then, healthy and not-so-healthy. Let’s begin with the first…

Imagine a soldier who witnesses a suicide bomber. Many are later triggered by the smell of burning flesh. The simple act of placing hamburgers on a barbeque transports them right back to Helmand Province. It’s not only the smell, but that smell also triggers the horror of the emotional response when the initial trauma is witnessed. Smell accesses not only the location and moment but also the intensity of the emotion experienced. Studies now show us this intensity can have a large bearing on the development of PTSD.

A more palatable example might be someone priming themselves with essential oils for an exam. Lavender and rosemary both have excellent results for improving recall, but it's not only the memory of information that is recalled but also the calm planning and preparation to tackle the exam with ease.

Can You Change Scent and Memory? 

Excellent question and one that scientists are trying very hard to understand.

What we do know is that, like visual and auditory memory, one's recall might not be so good if there have been distractions. Thus, a person might not remember the details of a conversation as well if there has been music or more chatter around them, for example. The same applies to recalling the details of an accident if your brain is trying to process other things you have seen at the same time. But if you have sat quietly focusing on a jigsaw for hours, you are likely to be able to recall tiny details about the picture. Likewise, other smells can be distractions to recalling a fragrance, although you are likely to remember more if the scents are all quite similar. 

But perhaps most interesting is that olfactory memory greatly resists forgetting.

Numerous studies have demonstrated that if a person is asked if they can recognize a fragrance 30 seconds after their first exposure, and then they are asked again a year later, the remembering only drops about 5%. Again, that has both good implications and bad ones, right?

New Scent and Memory Associations Vs Old

Related to this, is the discovery that these memories also resist change when a researcher tries to introduce new smells. In other words, retroactive interference of trying to cancel out memories by trying to create new associations does not work. But proactive interference - associations that happened before the event, can seriously impede the olfactory memory.

Understanding what went before - in terms of autobiographical memory, especially from childhood and from homeland, can be tremendously powerful. This could be part of the urge to “just go home for a while”. After all, smelling mom is the first association we have. Scent and memory can perhaps be adapted by taking fragrance memories right back to childhood.

Autobiographical Memory

An interesting component is that fragrance may be behind the success of my writing. Something I had never considered before. My books often talk about my personal experiences working with oils. Since I am also a Melissa bee priestess, I can often wander into the mythic, particularly about recollections of dreamwork and things that happened to me as a child being brought up by another aromatherapist. Studies reveal that autobiographical memories are better accessed using scent than any other retrieval cue.

A 2017 study of 170 participants, done by Tilburg University in the Netherlands compared scent versus images as a means of recollecting childhood memories. They were then asked to rate how much detail was involved in the memory, what the emotional intensity of it was, and how vivid. Odor created a much richer landscape for each of the participants. (de Bruijn, 2018)

Scientists have also proved that it is possible to improve mood by using scents to promote nostalgia for a happier time gone by as well as theoretically improving both spatial and working memory. (de Bruijn, 2018)

Find out more about using essential oils for PTSD.

Scent and Memory for Alzheimer’s

It may also be that autobiographical scents can improve future memory. When a person initially develops Alzheimer's disease, olfactory neurons are the first to decline. Work is underway to try to develop protocols to access happier memories through scent. (El Haj, 2022)

I always wonder what these might be.  I think for me though, they might not even be essential oils. How about marmalade? Palmolive soap? Bread and butter pudding? Parma violet sweets. The role of loved ones around you would be fundamental for the success of this I think.

Essential Oils for Memory

That said, the work into understanding what essential oils can do for memory is also interesting.

Importantly, inhaling lavender makes extinction learning easier, so there is a gradual deconditioning of the fear response to certain triggers, whether that is scent, sound, or other. It’s not only useful for PTSD but also for overcoming other conditioned fear responses. (Manganiello-Terra, 2022)

Inhalation is a vital tool here. Find out more at Inhalation of Essential Oils.

Quick Memory

Peppermint enhances memory whereas ylang-ylang impairs it and makes processing speed slower. If you have a math exam, you don’t want to be wearing ylang-ylang. However, the opposite is also true of using peppermint for someone who is already a little hyper because  Peppermint increases alertness. (Moss, 2008)

Efficient Memory

Salvia officinalis improves how efficiently you recall memories, but this is really more useful for people who are sitting exams than actual autobiographical memories. Not only do they improve cognition, but also mood. (Tildesley, 2005)

Find out more at Essential Oils to Improve Memory

Final Word on Scent and Memory

This is but a tiny snapshot of the work being done to understand the associations of scent and memory. It stands at the very forefront of aromatherapy, but of course also in the background of all of our everyday lives. It will be interesting to watch how the research develops and hopefully develops into a whole new meaning for the term Aromatherapy.

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