The Scent of Memory [Thesis]

At the confluence of the Hoyoux and the Meuse, in Belgium, the limestone becomes the setting for a particular smell: humid, spicy, as if emanating from an archaic paradise. I said to my colleague Yannick who showed me the town of my ancestors: " Do you smell how good it smells? Do you smell? "

You can be carried away as I was by a smell of memory. But what makes " memories recalled by smells more detailed and emotional than those evoked by other sensory modalities "?

So, "He who masters smells masters the heart of humanity."
Patrick Süskind, The Scent.

My colleague had thought I had a good "nose ", but perhaps I had more of a good memory?

In her thesis, Anne-Lise Saive was interested in " brain and cognitive processing of olfactory information " with the Lyon neuroscience research team: " Olfaction, from coding to memory ".

The smell of memories, sometimes for better, sometimes for worse, but always in a strong way. What happens " from the detection of smell to the retrieval of memetic representations "?

A Subtle Force

Memory " is conjugated in all tenses ". Its fundamental malleability allows us to finely tune our behavior to what is happening in our environment. Psychologist Daniel L. Schacter called it a " fragile power " that participates in our identity and allows us to nurture lasting human relationships.

As research has progressed, memory has been mapped into increasingly refined systems (with different scientific theories about how they are organized). In 1972, psychologist Endel Tulving isolated episodic memory and semantic memory, which had previously been referred to as declarative memory (the memory of " knowing that ").

" Episodic memory corresponds to the conscious recall of a past personal event, anchored in a specific spatio-temporal context. [...]

Semantic memory represents the memory of words, concepts, knowledge about the world and the self. Its content is abstract and detached from the context of acquisition. "

I Remember Therefore I Am

Memory is made up of hollows and fulls that are arranged and rearranged to form a coherent narrative of ourselves that relates to autobiographical memory.

This " corresponds to the memory of personal past events, unique to each individual, encoded since childhood."

The memories are consolidated. They can be set in motion again by a process of reactivating the memory, which can be changed and then reconsolidated. Memory is a dynamic movement.

Researchers have isolated three broad categories of imperfections that mesh with the processes of memory reconsolidation and participate in its proper functioning:

1. Forgetting,
2. Distortions,
3. Persistence.
   

Breathing, Sniffing, Smelling

Volatile chemical molecules, called " odorants ", are carried through the air to our olfactory system.

Rhythmic by our breathing, scented information reaches our consciousness: at different points depending on the breathing motion, the molecules reach " the olfactory epithelium that lines the upper and posterior part of our nasal cavities. From there, an electrical message is sent to the central olfactory areas[olfactory bulb and cortex] "and we " smell ".

On inspiration, odorants reach the nasal cavity directly through the nostrils; on exhalation and when chewing food, odors pass through the nasopharyngeal junction and up to the nasal cavity.

On page 44, there is a sagittal (arrow-shaped) representation of the organization of the olfactory system, showing the passages and proximities of information. The olfactory epithelium " touches " the olfactory bulb, which " rests on the floor of the cranium ".

The Olfactory System

While olfactory stimulation is variable, slow, and discontinuous, "the sensation of odor persists[...] longer than other sensory perceptions ". The olfactory system interacts with other systems: that of taste and that of pungent, irritating, or toxic sensations.

When you come into contact with a toxic scent, such as a strong volatile organic compound (VOC), you have responses from all of these systems; you may be surprised that an odor stings the tongue long after exposure to the smell.

In a more pleasant register, you will similarly have this multisystem feeling, upon approaching, for example, a bakery, pastry shop, or waffle shop (or whatever you like)!

Our olfactory abilities are trained and developed with learning.

Some professions are known for their olfactory mastery like perfume makers, " noses ". And some mind-body practices such as sophrology work on developing sensory experiences and perceptions, including the sense of smell, which support a work of self-transformation.

" Unlike untrained participants, perfumers [and trained participants!] attest to being able to mentally smell a scent and thus be able to generate the same sensations as the actual olfactory experience evoked by a scent stimulus. "

The Limestone Mosan

Olfactory memories originate very early in our existence. Even though we, outside of scent practitioners, have fewer words and education in this sensoriality, smells are felt more deeply and are more resistant to time and forgetting. It is an archaic, fluid, and dynamic affair.

" An important feature of olfactory memory is the power of its associations. The meaning of odors is acquired by associations between the odor and the context in which we smell them: semantic, social, and emotional. "

The Scent of Memory

How does this happen? So what are " the cognitive and brain processes underlying olfactory episodic memory "? Five studies examined this question, they were conducted with laboratory and autobiographical memory approaches.

" Conceptually, the laboratory approach tests episodic memory; [whereas] the autobiographical approach tests both episodic and semantic components of autobiographical memory. "

The pleasure and familiarity of smells, as well as slower breathing, promote rich and complex episodic memory recall. Depending on the accuracy or otherwise of the recalled memories, cognitive processes differ.

Also, the ability to associate with other elements of an episode will engage different cognitive modalities depending on the links that have been established between them. When the dimensions of an episode are linked, recall of the spatial and contextual environment is activated and the memory is complete.

" Finally, this work suggests that experiences and knowledge gained over our lifetime modulate our memory and may promote the recall of certain episodic memories. "

Smells are a dynamic and subtle modality for recalling specific rich events and memories. These memories are more detailed and emotional and their richness can be developed through training, through sensory associative practices, and by breathing more slowly.

Illustration: Дмитрий Хрусталев-Григорьев from Unsplash.

To read:

Anne-Lise Saive. Les odeurs, une passerelle vers les souvenirs : caractérisation des processus cognitifs et des fondements neuronaux de la mémoire épisodique olfactive. Neurosciences. Université
Claude Bernard – Lyon I, 2015.

Thesis available at: https://www.theses.fr/2015LYO10078

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