Have you ever had a flood of memories triggered by a smell? If so, you are far from alone.
There’s a reason for how smells can pull up specific memories, and it starts with the structure of the brain itself. Unlike sound, for example, which travels from our ears to the brainstem, then up to the thalamus, and finally to the auditory cortex, smells take a more direct route. Smell-sensing neurons in the nose extend directly to the brain’s olfactory bulb. From there they can be passed on to other brain regions, including areas involving memory.
Further, our sense of smell is specific, which helps explain the accuracy of our smell memories. Our olfactory receptors come in more than 400 types, which provide a huge amount of detail, and our nervous system needs to categorize all that input. In 2013, a group of scientists hypothesized that just as there are five senses of taste (sweet, salty, sour, bitter and umami), there are ten basic dimensions of smell.
But there is a lot we still don’t know, like why smells and memory evolved to be so intertwined. Did scent memories provide an evolutionary advantage?
Also, this is a condition that should be exploited to our advantage. Could smells be used to help informational recall? Might certain smells be used to calm people who are being treated for trauma?
Fortunately, new technologies for faster and more-refined genetic sequencing and brain imaging are helping yield new insights. Eventually, we may be able to understand why past smells linger in the brain so long.
Taken from “Unpicking the Link Between Smell and Memories” by Roxanne Khamsi (https://www.nature.com/articles/d41586-022-01626-x?).