Wednesday, 23 July 2014

Olfactory Fun: The Seriously Underrated Science of Your Schnoz

When you sit down, as everyone does at some point in their life, to rank the importance of the holes in your head you are likely to get caught up on deciding which is more important, the mouth or the ears. Human beings are among the most communicative animals to ever evolve of this ball of rock and water, so it makes sense that we would consider the tools that let us talk to one another to be of the utmost importance. But to think of these organs as the sensory dream team is to overlook a potential MVP in the world of things that help us perceive the world. The true star of the show might already be front and centre.

Your nose is surprisingly important in your experience of the world. Humans are by no means powerful smellers in a world that includes heavyweights like blood hounds, sharks, and grizzly bears but that hunk of bone and cartilage in the middle of your face serves a very important purpose, possibly even more important than we can currently appreciate.

First off, without a serious leg-up from your nose, your mouth would be significantly impaired in one of it’s most enjoyable functions: taste. Our senses of taste and smell are so intertwined that some scientists believe it would be more accurate to just combine them and call the whole experience flavour. You see, when you take a bite of pizza, or cake, or seven-layer lasagna your mouth and nose initiate a sensory alley-oop, bouncing the chemical components of your meal back and forth and interpreting them in different ways.

In your mouth, receptors that cover your taste buds respond to chemicals called tastants to provide the experience of the five principle tastes: sweet, sour, bitter, salty, and umami/savoury. Contrary to popular belief, different regions of your tongue do not specialize in any of these tastes, you can experience any of the big five on any part of your tongue. Your taste buds also lead the charge in your experience of spicy foods. That is because each oral nub is generously packed with pain receptors that are triggered by capsaicin, the key chemical in foods that make you sweat.

You may also be fortunate enough to be what scientists call a “super-taster” if you were born with an unusually dense network of taste buds. It is estimated that one in four people fall into this camp (most are women), and their experience of food is the gustatory equivalent of front row seats for a cage match between the Loch Ness Monster and the Kraken.

However, beyond the five key tastes and your experience of spice, your tongue plays a surprisingly small role in the overall flavour of food. As you chew you force air to circulate into you nasal cavity, carrying with it odorants that trigger the hair-like receptor cells in your nose (cilia) to set off a neuronal fireworks show. Each type of odorant has its own pattern of activation but all the input gets shot directly into the brain’s olfactory bulb and is then distributed throughout the brain to form your overall impression of flavour. In fact, no other sense gets such direct access to the brain. The axons coming from the neurons in the olfactory bulb actual end in the cilia. Effectively, your brain’s root system is hanging from the ceiling of your nose.

As you probably already know, smell is also very closely tied to memory. If I showed you a picture of your grandmother’s kitchen, you would pretty quickly be able to put yourself into a nice memory possibly involving some delicious chocolate chip cookies. However, if instead of the picture I gave you a whiff of the cookies, you would be a sticky fingered 6-year old again before you even knew what hit you. The response is automatic and lightning fast, but it might be even more complicated a relationship than you can imagine.

Research has shown that your sense of smell might actually be able to predict if you will develop neurological disorders like Parkinson’s Disease or Alzheimer’s later in life. In one study, researchers evaluated the ability to smell in a group of people and sorted the best and the worst among them into two groups. They followed up with their participants many years later and all of the people who developed Parkinson’s Disease came from the bottom 10% of smellers. Scientists don’t completely understand the link between smell and memory quite yet, but it is theorized that brain degeneration could be caused by environmental factors, and those environmental factors might be coming in through the nose.

Clearly your nose contains mysteries far beyond what we currently know. Who know’s what scientific treasures could be hidden beneath you next dried-up booger?