Showing posts with label Sense of Smell. Show all posts
Showing posts with label Sense of Smell. Show all posts

Tuesday, December 8, 2009

Smelly Facts: Sense of Smell & Pregnancy


A few years ago, in 2007, I had reported here on Fragrance Bouquet on the mistaken, yet still propagated belief that the adult brain does not produce new neurons. In that post I explained that one of the two identified areas in the brain that constantly see the birth of new neurons is the olfactory system (the other is the hippocampus). As I reported back then, neurons in the olfactory system constantly die off, mostly due to their constant exposure to harmful agents and thankfully, they are constantly replaced. Recently, while reading the astonishingly interesting and very humorously written Why Zebras don’t Get Ulcers by Robert M. Sapolsky as part of the obligatory books to be learned for my exams in Health Psychology, I came across the following related excerpt which I provide here for your pleasure:

“It turns out that there is a huge burst in the production of those new olfactory neurons early during pregnancy. They are fully on line just around the time of birth, and the scientists who discovered this speculated that these new olfactory neurons are tagged for the task of imprinting forever on the smell of your offspring (a critical event for mothers of most mammals). And what happens early in pregnancy, when those new olfactory neurons are showing up, but not quite making sense yet? I bet this has something to do with the famed nausea of pregnancy, the food aversions and olfactory sensitivities.”


- Sapolsky, R. M., 2004. Why Zebras don’t Get Ulcers. New York, NY: Henry Holt and Company, LLC

Image: Flickr by Raphael Goetter

Monday, December 1, 2008

Ghost Scents

You wouldn’t guess it from the interior, with its pretty fountain, the enormous, suspended mosaic of two gigantic eyes following you everywhere in the main hall, the artwork in the hallways, the throngs of students happily chattering away between classes but… Many, many years ago, the Psychology building of my University used to be a Hospital. Nowadays, the building has acquired the familiar smell of Academic buildings everywhere, without a doubt, a special smell itself: The smell of students, library books, computers and a faint whiff of food and coffee from the cafeteria. It is a smell as instantly recognizable as that of high schools, as anyone who has visited their old high school for a reunion and has been hit in the face by a smell that is truly a blast from the past can attest. But there are times when one really comes to realize that this building’s current scent is actually the intruder, a smell that is trying hard to banish the previous occupant. The previous occupant sometimes strikes back, desperate, aggravated; running down the stairs to catch a class students are sometimes – in fact rarely enough so that it always remains a huge surprise- assaulted by the Ghost Scent: The smell of the Hospital. Where does it come from? How does it resurface? How does it manage to remain hidden the rest of the time? Why does it make our heart skip a beat when we smell it? I am not surprised we react to the smell with aversion and dread – we are, after all, socialized from an early age to fear hospitals, and their smell is a strong reminder of all the negative associations related to them. I am however surprised at the tenacity of the scent, seemingly becoming an entity that lives on and on, long after one would expect it to.

Ghost Scents are not always unpleasant however. Have you ever worn a loved one’s clothes and found yourself living with their smell all day long? I have a friend with whom I exchange clothes. She lives in Greece and I live in the Netherlands… We send each other packets of things that do not quite work in our wardrobes any longer. When her packets arrive, I open them to find myself surrounded by her presence. What’s most surprising is that even after several wears and subsequent washes, her clothes retain her own unique smell - the fibers completely drenched in her essence as it were. When finally the harsh detergents manage to strip away every last bit of her slightly vanilla scented skin, I always feel distinctly disappointed…

From clothes, to cars and houses, the smell of ownership is present, slightly different each time, mingling with the scent of fibers and materials. None are as distinctive and as potent as the smells created by diverse, unrelated individuals sharing a common goal. The smell of the gym, the same in every country you visit, decade after decade: Muscle and sweat, enough to make your adrenaline levels rise and your heart to start pumping the moment you walk in. Even more evocative, the smell of dance. A recent visit to the Ballet Academy to sign up for a class made me feel like I was about to faint from wistfulness the moment I walked in, recently. It smelled of learning, almost like elementary school and high school combined, and its familiar scent was mingled with that of sweat. Not the sweat of a single person, but that of many. It smelled of collective effort and art, of broken toes, blissful misery and hope. There is no way this smell could ever be eradicated, even if the Academy became something else. Like the smell of the Hospital, the ghosts of a thousand dancers’ smell would come back to haunt this place, claim it as their own.

Some ghosts are living, living through the ages. When I travel back to Thessaloniki Greece, I am always greeted by the scent of this ancient city the moment I step out of the airport. Air that’s slightly thicker than I’m used to over here, humid and salty, smelling of the sea and the people, the vague smell of herbs and woods. The smell of a particular sort of energy reverberating in the air. It makes me want to fall down on my knees, Pope-like, and kiss the ground that bore me.

Some scents are truly gone from this earth however. I am lucky to have them living in my head, and I am even luckier to have this strange ability to call them forth and smell them again whenever I wish to. The scent of my maternal grandmother, recently gone from this world, is probably the most precious such Ghost. It smells of her skin, scented like fresh dough after working her capable hands on each and everything that needed attention in the house. That slight smell of sweet and sour dough, the smell of light sweat over clean, soapy skin, calls forth an image of her working in her old kitchen, turning to smile down at me. And all I can do is wish I could run and hug her again. But at least I have her smell. Ghost of a scent.

Images: www.sxc.hu, www.morguefile.com

Monday, November 26, 2007

Smelly Facts: A Collection of Little Facts

Do we take our sense of smell for granted? Do we lament the fact that it is nowhere near as sensitive as that of many other animals? It is still pretty remarkable. A few random facts today to remind us how special our sense of smell is.

· “We can smell smoke at concentrations well below that needed to trigger even the most sensitive of household smoke detectors.”
· “We can distinguish among roughly 10.000 different chemicals by their smell.” (Axel, 1995)
· “Blind people regularly identify other individuals by each person’s unique odor, and sighted people can do that too when they try.” Where does our special, identifiable odor come from? “In humans, specialized scent-producing glands (apocrine glands) are concentrated most highly in the axillary region (underarms) and also exist in high concentrations in the genital area, the alveolar area (around the nipples), the navel area, on the top of the head, and on the forehead and cheeks.” (Stoddart, 1990)
· “Much, if not most of what we call the flavor of foods is actually smell, not taste.”
· “As we get older, our sense of smell declines. By age 65, about 25 percent of people have serious olfactory impairment, and by age 80 the number is 75 percent." (Doty et al., 1984)


Note: All of the above facts are direct quotes from Peter Gray’s Psychology, 4th Edition, Worth Publishers

Image of navel: commons.wikimedia.org

Friday, October 12, 2007

Smelly Facts: A Glance at Anosmia

Anosmia, the general lack of olfaction, can be congenital – that is, a person can be born anosmic. Alternatively, anosmia can occur later in life, either due to brain damage or because of vitamin A deficiency. In contrast, Specific Anosmia is the inability to detect the smell of a single chemical. A small percentage (2%-3%) of the general population for example, is unable to detect the smell of isobutyric acid – the component that makes sweat smelly. (Next time you find yourself suffering next to someone who has forgone the use of deodorant in the bus, you can perhaps distract yourself by wondering whether the reason behind their thoughtless behavior is the fact that they are anosmic to sweat and thus unable to detect their own funk!) Among perfume enthusiasts, the most commonly cited specific anosmia is of course musk anosmia, but in reality, specific anosmias span a much wider range of odors. To give a few examples aside from the aforementioned sweat and musk, other specific anosmias include fish, urine, sperm, camphor, mint and malt.

References: Amoore, 1977, Pelosi & Viti, 1978 and Kalat, 2007.

Thursday, October 4, 2007

Smelly Facts : Neuron Renewal

Have you ever heard others say that the adult brain has a fixed number of neurons and is unable to generate new ones once these die out? Indeed it was traditionally believed among scientists that the adult vertebrate brain could only lose neurons, never gain. (Kalat, 2007) Recently though, a small number of exceptions have been found. Among them, and of special interest to us of course, are the olfactory receptors. Indeed, these only tend to survive a couple of months at best, due to the fact that they constantly come into contact with harmful chemicals, as well being subjected to natural wear and tear, exposed as they are to the natural world. Thankfully, the dying olfactory receptors are constantly replaced by new developing cells! Too, adult stem cells within the brain have the ability to propagate daughter cells. These “migrate to the olfactory bulb and transform into glia cells or neurons" (Gage, 2000).


References: Graziadei & de Han, 1973, Gogos et al., 2000 and Kalat, 2007.

Image: Coronal section of olfactory bulb, http://commons.wikimedia.org