How Perfume Affects the Brain

Most perfumers rarely delve into explaining the function of scent, but I’ll do so here so you can feel a bit more informed.  Much of this information comes from my ancient college days, where I was required to perform lab dissections, one being a human brain.  What I can tell you is that the scent of formaldehyde is probably the singular thing that put me off pursuing medical forensic science.  They say its “odor adaptive,” that you become accustomed to the smell…but for me?  Umm, no thanks. 

Everything You Ever Wanted to Know About the Olfactory Bulb

The olfactory bulb has 2 structures:  the main bulb and the accessory bulb. The main bulb connects to the amygdala (fight-or-flight structure, that part of the brain that spurs the question “Should I dodge the department store perfume spritzer or check out what they’re offering?”).  Also, you should know because I’ve actually seen it up close:  the human olfactory bulb, in all its entirety, is little more than a skinny white flap as big as a fork tine.

Its gateway to the amygdala is through the piriform cortex (the juncture of the frontal and temporal lobes.) The piriform cortex collects information from the primary olfactory cortex and the accessory olfactory bulb, which are situated on the back (dorsal posterior) of the main olfactory bulb.

In humans, the olfactory bulb is housed on the cribriform plate of the ethmoid bone. (See the graphic below.) The ethmoid bone is one of the bones that make up part of the eye socket, and it has 3 parts:  the cribriform plate, ethmoidal labyrinth and perpendicular plate. The ethmoid sinuses are the air-filled spaces located within the ethmoid bone and are lined with cells that produce mucus that keeps the nasal passages healthy.  

Cool sidebar fact:  birds carry small deposits of magnetite (ferric iron) version of this bone which allows them to sense the direction of the Earth’s magnetic field.  Humans carry some of this ferric iron here, too, but it’s believed to be more of an evolutionary trait.  I’m sure you can think of a couple people who have more directional instincts than others so believe what you will.  You can read more here. 

How the Sense of Smell Functions  

The olfactory bulb detects fragrant molecules via tentacle-like receptors, and this information is conveyed by neural synapses to the olfactory cortex and onward into the limbic system, a catch-all term for a group of structures in your brain that establish emotions and memory.  This structural group includes the aforementioned amygdala (emotion processing center), hippocampus (memory formation), hypothalamus (regulator of body temperature, hunger and thirst), thalamus (conveyor of sensory information to the limbic system and other parts of the brain), the cingulate gyrus (attention, decision-making) and basal ganglia (movement and habit formation.)

Human brains are structured to be primarily visually dominant, with the sense of smell equalling the sense of hearing.  By comparison, a dog’s olfactory bulb is about 40x larger than a human’s and is nasally structured so that scent influences their emotions more immediately than it does with humans.  Whenever dogs inhales, a portion of this inhalation goes straight to their olfactory bulb and cannot be exhaled.  Unlike humans, dogs carry nasal turbinates, a sponge-like mesh covered in scent receptors.  The remainder of their inhalation flows down their pharynx into their lungs.  A dog also has significantly more density to their scent receptors compared to the human nose, roughly 100 to 300 million receptors compared to 5 million for humans. 

If you’ve managed to read this far, then it goes to say that whenever you detect a scent, the brain processes it on several levels:  danger detection (Fire?  Spoiled food?  Sickness?) to hunger cues triggered by cooking scents to memory spurred by association with particular scents (pleasant/unpleasant).

The role of how fragrance affects the brain, as I see it, is to promote mental health and well-being.  If you enjoy a fragrance, it triggers happiness endorphins (the body’s natural stress reliever and mood booster) and increases serotonin (a neurotransmitter/hormone that helps regulate mood, sleep, appetite and digestion.).  Who hasn’t worn fragrance like a wardrobe, changing up scents to suit the mood and occasion?

And who hasn’t worn a beloved fragrance only to find that you can no longer stand to wear it due to certain memories it brings?  

Using Scent as a Tool

You might be interested to know that many film actresses, ranging from Emma Stone to Penélope Cruz to Margot Robbie and Jessica Chastain utilize fragrance to help define their character’s role as well as set parameters that make it easier for them to shed that role and leave behind once filming is done.       

Also, medical researchers have been investigating the role of how fragrance and scents can help Alzheimer’s patients retrieve memories while the patient is in the earliest stages of the disease.  

So go ahead and revel in your appreciation of fragrance!  It offers a healing modality, not just for the senses but also for the mind but also for the body.

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