We want you to close your eyes and reimagine the smell of fresh rain, the smell of the first pizza you ever ate, and the smell of the perfume your significant other wore on your first date. Feeling relaxed yet? Maybe, or not? That awe-inspiring moment when the aroma of certain things immediately reminds you of a past experience (it could be terrible, though). How does such a thing happen? Why do we even feel like we’re living the moment again? New research could figure out exactly how and why these potent aromas produce calming physiological responses.
Related media: Taste & Smell: Crash Course A&P #16
Your Smelling Anatomy
First thing first: let’s take a crash course of how your sense of smell gets activated in your brain. Your sense of smell is triggered when fragrance molecules attach to special cilia-covered olfactory receptors in the nasal cavity, carry electrical pulses directly to your olfactory cortex in your brain. This also relays that signal to your memory and emotion centers of your brain — that’s the hippocampus and the amygdala (respectively) and also the frontal cortex.
In a 2018 Japanese study published in the Journal Frontiers in Behavioral Neuroscience, researchers threw more light on the idea that certain smells can indeed act as natural anti-depressant medication — in similar ways just as painkillers does with aches. The researchers conducted a series of experiments with mice in running in mazes or some other rodent stress tests while exposed to an aroma called linolool — the organic compound that gives lavender its sweet floral scent.
Previously, they suspected that linolool would cause lower anxiety levels in the mice, of which it did. But the scientists also wanted to test their hypothesis: does lavender have calming effects on the mice neurons.
To find out how, they included mice that were “asonmic” — mice with no sense of smell. Obviously, these mice showed no effects of linolool exposure, a strong evidence that prove that the olfactory system is definitely behind the mechanism of soothing scents and their after effects. Later on, they wanted to find out if linolool had effects on the same receptors in the brain similar to some common anti-depressant medications.
The Smell Of You
Several anti-depressant drugs like diazepam, klonopin, and valium all belong to the chemical family of benzodiazepines. The causes of clinical anxiety is mainly due to the overactive neural activity in your brain. Benzodiazepines does the job of inhibiting or calming down the neural activity by binding certain parts on neurons known as gamma-aminobutyric acid (GABA) receptors. When an anti-depressant drug like valium, for instance, binds to a GABA receptor, it increases the flow of certain chemicals into the neuron that mellow the brain out.
The scientists predicted that the smell of lavender acts the same on those very same GABA receptors. To test such an idea, they treated some mice with flumazenil — a drug that prevent GABA receptors — and made the mice sniff the linolool, and (you guessed it) didn’t exhibit any soothing effects afterwards. However, lavender isn’t the only fragrance that’s associated with the same neuron receptors as potent anti-depressant drugs.
Some years back, another team of German scientists test hundreds of fragrance on GABA receptors in both rodent and humans, jasmine emerged as the most effective depressant — it delivered a GABA effect as powerful as sleeping pills and sedatives. Interestingly, both lavender and jasmine were the first ancient soothing remedies tested, though several others might possess similar nasal-to-neuron mechanism.
Just Sniff It All In
According to the Japanese study, fragrances like limonene, citrus peels, and the pinene (the scent of pine trees) are all organic compounds that have seeming signs of anti-depressant effects. Fragrances aren’t universally soothing, though; since every scent that you’d ever sniff has a close neurological connection to your memories and feelings, their physiological effects is somewhat subjective to your personal experiences.
Let’s consider Pavlov’s dog: your brain stands the chance of being conditioned to like or dislike certain scents depending on your encounter with it. For instance, if one of your “horrible-boss-like” math teachers back in elementary school wore a kind of perfume, you’re more likely never going to like that perfume, ever. Research has shown that the olfactory system is directly in line to the hippocampus and the amygdala — the memory and emotional centers of your brain, respectively.
This explains why some scents can evoke such powerful memories and feelings of nostalgia. The smell of a fragrance could carry you way back to a specific time and even place in such an amazing way that your conscious thinking and recall cannot. That might explain why petrichor (the smell of fresh rain) seems so soothing, and the smell of whatever scent you remember from your childhood just reminds you of your wonderful days as a youth.
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Written by: Nana Kwadwo, Thu, Jun 27, 2019.