Why is the sense of smell so linked to memory and how can a smell that we haven't smelled for years have the capacity to move us so much? What are the mechanisms behind this incredible sensory teleportation?  

A brief reminder of how olfaction works.

If we have all experienced the memory/smell link, it is because anatomically there is an explanation. An olfactory molecule, once inhaled, will first dissolve in the mucus and then rise to the level of the olfactory epithelium. There it is picked up by olfactory cilia. It will then join the olfactory bulb in the form of nerve impulses passing through olfactory neurons. From the olfactory bulb, the information goes up to the olfactory cortex. For now, and despite all the progress made by our small olfactory molecule, we have still not become aware of the smell. A crucial step is missing: the transition from the olfactory cortex to the orbito-frontal cortex. It is only when the information reaches this area that you will be able to become aware of the existence of the smell and potentially recognize it. What is incredible, apart from the almost instantaneousness of the process: between 300 and 500 milliseconds, is that even before having perceived and intellectualized it, your brain, unconsciously, has already given the smell a hedonic value. 

It is in the penultimate stage that the answer is hidden, at the level of the olfactory cortex. The latter is located in a specific area of ​​the brain: the limbic region. Our limbic system, which also includes the amygdala and the hippocampus, is the center of emotion and memory. The amygdala processes emotions, pleasant or unpleasant while the hippocampus plays a major role in encoding and recalling memories. Add to this that smell is the only sense that is in direct contact with our limbic system and you have a connection so close that the slightest smell, however insignificant it may seem, has the potential to revive with strength and power. , memory and emotion. 

Ultimately, olfactory information is processed at the heart of emotions and memory. We understand better why smells are tinged with emotions and nostalgia.

They whisper, memories speak and feelings howl.