What is olfactory memory and how it works: when scents evoke memories

The aroma of a freshly baked cake, the smell of rain on the asphalt or that of an old brand of sunscreen and “boom”, we are instantly catapulted into a precise moment in the past. This phenomenon, often referred to as “Proust syndrome” in honor of the writer who described the evocation of childhood memories, is not a simple poetic suggestion, but a precise neurobiological mechanism. Science has proven that the ability of smells to reactivate vivid and emotional memories, especially those related to first decade of lifeit depends on direct connection between olfactory receptors and brain areas linked to the processing of emotions and memory, via a truly privileged neural pathway.

Olfactory memory: childhood and the seal of the first impression

Autobiographical memories triggered by words or images tend to concentrate in youth and early adulthood (between 10 and 30 years old, the so-called “reminiscence bump”), while memories evoked by smells mainly take us back to the first decade of life, that is, thechildhood. Why does this happen? The answer lies in a phenomenon known as “proactive interference“.

Olfactory memory is particularly overwrite resistant: it is difficult to change olfactory associations once they have formed. When we associate a smell with an event for the first time, that link becomes extremely solid and difficult to undermine or replace with subsequent associations. Childhood being the period in which we encounter most smells for the first time (the scent of our grandparents’ house, the smell of school desks, our favorite food), these olfactory “first impressions” remain indelibly imprinted. The hippocampus assigns a privileged representation to these early associations, probably for evolutionary reasons: quickly learning to identify and locate food sources or dangers and keeping this information stable over time was crucial for survival. This explains why, decades later, a simple whiff can bypass adult logic and instantly bring us back to being children.

Scents are the key to memories and emotional memory

The main reason why a smell has the power to trigger such an immediate emotional response lies in the structure of our brain. Unlike other senses, such as sight or hearing, which must pass through a sorting station called thalamus before being processed by the cerebral cortex, thesense of smell enjoys an anatomical “shortcut”.. Olfactory signals travel from the nose directly to the limbic system, the oldest areas of the brain that govern emotions and memory. In particular, the olfactory bulb has direct connections with the amygdalaresponsible for emotional processing, andhippocampusfundamental for episodic memory.

This neural architecture explains why memories evoked by odors are perceived as more emotional and “vivid” compared to those aroused by images or sounds, with that typical sensation of being “Take yourself back in time” also found in experimental studies. Neuroimaging confirms that, when we think about our memory triggered by a specific smell, theactivity in the amygdala is significantly greater compared to when the same memory is recalled by visual stimuli. Some researchers use theacronym LOVER (Limbic, Old, Vivid, Emotional, Rare) to describe these memoriesunderlining how they are deeply rooted in the limbic system and often linked to rare and distant events in time.

Smelling isn’t enough: how the brain decides what to remember

While it is true that emotion plays a key role, recent findings suggest that the process is more complex than a simple instinctive reaction. Episodic olfactory memory is divided into two distinct phases: the odor recognition (“I’ve smelled this perfume before”) and the associative recovery (“This perfume reminds me of that day at the seaside”). A recent study revealed that these two processes are driven by different factors. The simple recognition of a smell is often driven by emotional strength, especially if the smell is unpleasantand by the verbal richness with which we are able to describe it. In other words, if a smell disgusts us or if we can describe it in many words, we are more likely to recognize it as familiar in the future.

However, to make the leap from simple recognition to mental time travel, other factors come into play, particularly the familiarity and the “semantic distinctiveness“. The relationship between familiarity and episodic memory follows a U-shaped curve: we tend to better remember the context of odors that are either extremely familiar or, conversely, completely new, while those that are on average familiar are less evocative. Even more fascinating is the role of language: smells that we are able to describe in a unique and specific way (semantic distinctiveness) are more likely to unlock a precise episodic memory. This suggests that, contrary to popular belief that smell is a “mute” and pre-verbal sense, our ability to conceptualize and name a scent helps the brain fixate on it in memory together with its spatial and temporal context.