Have you ever stopped to think if drowsiness or sleep affects your sense of smell?
I know that I went almost 40 years of my life without ever arriving at that peculiar thought. But, once my mind went there I couldn’t believe I’d never thought of it before!
I mean, it’s rather obvious how drowsiness and sleep can affect your other senses, but it is not immediately apparent how feeling sleepy or being asleep affects your ability to perceive and recognize smells.
I know that you are probably thinking that you don’t smell anything when you are fully asleep, therefore, drowsiness must reduce your capacity to smell. Except, there is plenty of scientific evidence that this is not the case. So is it true or false?
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Does Drowsiness Affect Your Sense Of Smell?
No. Being drowsy does not affect your sense of smell. However, sleep and smell have a very interesting relationship. Let’s learn more…
How Do We Smell?
The sense of smell is essential. Not as much as in primitive times, where the smell of predators in the air would send our ancestors into fight or flight frenzies, but still extremely important.
Even though we have lost to a great degree our ability to detect and recognize a vast number of scents, we still use our smell every day of our lives.
Our strong sense of smell helps us bond with our family and loved ones, it allows us to truly appreciate the taste of delicious foods and drinks, or it lets us notice when food products have spoiled, and it can even save our lives in varied situations, such as if we are caught in a gas leak.
But How Does It Work?
The brain, as with all other senses, is in charge of the sense of smell.
Stimuli from the environment are quickly and thoroughly gathered and processed through the central nervous system, where they are interpreted.
The human sense of smell is thousands of times more sensitive than the rest of our senses, and it has the pleasure of being the only aspect of our central nervous system that is in direct contact with the environment around us.
Other senses such as touch and taste, must filter their corresponding sensory input through different organs and channel them through the spinal cord towards the brain. However, the olfactory response is immediate and extends directly to the brain.
This is why drowsiness and sleep do not turn off the sense of smell. The brain never turns off during sleep, and so it continues to be able to perceive odors.
Scents Can Influence Sleep
Repeated research suggests that the smells we perceive before or during sleep have the power to influence our dreams.
A professional study, carried out by scientists at the University Hospital in Manheim, Germany, tested volunteers as they fell asleep. The test subjects were exposed to the scent of roses and questioned about the content of their dreams.
Almost unanimously, test subjects reported that their dreams were pleasant after exposure to the pleasant odor. However, when they were exposed to unpleasant types of smells, such as that of rotten eggs, the opposite would occur. Their dreams were riddled with disturbing imagery and unpleasant sensations.
This medical study, one of many, demonstrates that drowsiness or sleep does not negatively affect the sense of smell.
The nose continues to collect and process smells as it is falling asleep, and through the duration of sleep. This is because, as mentioned above, scent stimuli reach the brain’s limbic system unimpeded.
This does not happen with other senses, as they must be fed through to the brain via the thalamus, which shuts off completely when a person sleeps.
Nevertheless, it is important to note that the sensitivity of our sense of smell wavers throughout the day, following our circadian rhythm. Therefore, most people will reach the peak of their sense of smell late in the evening. Early in the morning, when our noses are often stuffy after a long rest, our sense of smell is weakest.
This is why the smell of coffee is so darned invigorating in the morning!