Non-scents:  New research about the overlooked sense of smell.

Dr. Shai Keeviti published his article “Follow the Smell” in the September 2009 issue of Maccabiton.  I have translated it from Hebrew.  Enjoy…

If you think that the primary purpose of your nose is to help you choose the right perfume, you are wrong.  The hidden potential in your sense of smell is much more than that.  This sense is crucial to our survival and influences everything from our partners (pheromones), to our social status, to the foods we eat.  But that’s not all:  New research discovered that the sense of smell is likely to pave the way for diagnosing diseases such as Alzheimer’s, schizophrenia, and depression. 

Evolution equipped us with approximately 1000 receptors for a variety of scents, but only about 350 of them work.  The drive of smell increases their number, and personal feelings and individual associations that accompany them also add to the shades of scents.  Medical studies and MRIs of the central nervous system prove that the sense of smell is intimately connected to the experiences of perception and feeling.  A possible explanation for this phenomenon is that the areas of the brain connected to smell are indeed an integral part of the limbic system-known to be directly responsible for mood and memories.

Mood and Smell

One of the characteristics of depression is difficulty experiencing daily enjoyment, a phenomenon called anhedonia.  Among those stricken with severe depression it was found that there is a weakened sense of smell, and many of them (primarily women) tend to put on larger quantities of perfume than those who are not depressed.  More findings indicate that anti-depression drugs like prozac improve the sense of smell in individuals suffering from depression.  

Impaired sense of smell is also a first sign of Alzheimer’s.  And possibly we will be able to predict by way of this sense, who from the immediate family will develop the disease in the subsequent years. 

Also, with neuropsychiatric diseases like Parkinson’s or schizophrenia, the loss of smell precedes the onset of the first signs by a year or two.  Recently it was found that individuals with multiple sclerosis and lupus (autoimmune diseases whereby the immune system attacks the body’s cells and tissue) there is an impaired sense of smell.  In an effort to characterize depression and psychosis that accompany autoimmune diseases the following experiment was conducted:  From the blood of lupus sufferers a unique antibody was isolated which enabled identification and diagnosis of the disease.  The antibody was injected into the ventricles of healthy mice.  The results showed that the antibody itself induced depression in mice.  The outcome implies removal of the group (because they changed the psychiatric situation-in this case depression) by way of the antibody.  In order to see how these antibodies are connected to the brain they were dyed with a special agent which helped to identify the specific bonds to the olfactory system (which is also part of the limbic system).  It was found that in the same depressed mice there was indeed a blow to the sense of smell.  MRIs showed that areas connected to smell were working less in depressed mice than in the healthy mice.

It’s not clear if the reductions in the sense of smell in diseases of the central nervous system are related due to the anatomical connection between the limbic areas and the olfactory system, or perhaps the cascading mechanism is more complex. 

A possible explanation is the elevated excretion of the hormone cortisol.  In stressful situations our body excretes large quantities of this hormone.  Excess dosage of cortisol could lead to atrophy of parts of the olfactory system and principally of brain organelles called amygdale.  Combine the organic diseases (Alzheimer’s, multiple sclerosis) and psychiatric disorders (depression) and the disabled sense of smell paves new ways to diagnose the diseases.  The transition therefore is to open new windows to treatment that on the surface looks new but actually was recognized in ancient Egypt and Greece more than 4000 years ago.  This treatment forms the basis for the instruction of aeromatherapy.

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Tags: Jordana Kagan, research

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