Why Do Humans Have Weak Sense of Smell

Compared to nearly all other animals, humans have the weakest sense of smell. You would think that humans and our closest evolutionary cousins (chimpanzees, apes, etc) would have similar sense of smell, but humans still have a much weaker olfactory sense.

Why might that be?

Well, research from Karolinska Institutet have discovered that humans are the ONLY mammals whereby no new neurons are formed in the olfactory bulb after birth. Or if there is any, it is VERY little.

In all other mammals including apes, new neurons are constantly being formed in the olfactory bulb which might explain why all mammals with the exception of humans have a superb sense of smell.

How did scientists figure out the absence of neuron growth in humans?

They looked at Carbon-14 levels within the DNA of the olfactory bulb. Carbon-14 levels in the atmosphere increased significantly due to nuclear bomb testing during the Cold War.

As such, IF new neurons were being formed, one would expect Carbon-14 levels which gets incorporated into developing DNA, to be similar to current atmospheric levels. Or at least find a certain turn-over percentage of both "old" and "new" neurons reflective of the Carbon-14 atmospheric levels at time of neuron development.

However, what researchers have found was Carbon 14 concentrations that corresponded to the atmospheric levels at the time of birth of the individuals establishing that there is very limited, if any, postnatal neuron development in the human olfactory bulb.

Reference:
The age of olfactory bulb neurons in humans. Neuron. May 24, 2012, 10.1016/j.neuron.2012.03.030

Sedated Anesthesia for Kids Under 2 Years May Cause Learning Disability

There is mounting evidence in animals and in humans that general anesthesia might damage developing young brains.

Researchers at Mayo Clinic compared the learning skills of 350 kids who underwent 1 or more general anesthesia before age 2 to 700 kids who have never been under sedated (general) anesthesia. What they found was that before the age of 19 (after statistical normalization):

No significant difference in learning disability between kids who have been under anesthesia once (23 out of 100) with kids who have never been under anesthesia (21 out of 100).  

However, those kids who have been under anesthesia 2 or more times had increased rate of learning disability (36 out of 100). 

Based on animal studies, anesthetics are known to cause accelerated loss of brain cells during development which leads to learning and behavior problems later in life. Whether that's also true for humans has not been studied.

However, further study is required as the results were obtained based on observation and did not account for other variables (type of surgery for example).

This information, though not definitive, does warrant extra circumspection by parents and surgeons when deciding to pursue surgery in kids under age 2 years, no matter how minor the surgery including ear tubes, tonsillectomy, adenoidectomy, and turbinate reduction.

IF surgery pursued, one should perform as much as required to minimize need for a 2nd procedure at a later date. That means multiple procedures under one anesthesia would be preferable than multiple procedures at different times.

Of course, surgery should only be done if the benefits outweigh the risks including anesthetic risks.

Read the MSNBC report here.

Reference:
Cognitive and Behavioral Outcomes After Early Exposure to Anesthesia and Surgery. Published online in Pediatrics October 3, 2011. doi: 10.1542/peds.2011-0351

Our Practice Website Completely Renovated (www.FauquierENT.net)

Recently, readers may have noticed that I have not been as prolific with blog articles as I have been in the past. The reason is because I've been in the process of overhauling the our practice's official website (www.FauquierENT.net) to the latest and greatest in webpage coding incorporating HTML5 and CSS3 standards.

Given the official practice website contains over 200 webpages... it just took a very long time and I required the assistance of Chris Ferrell with Pettygrove Full Creative Agency to make it a reality. BTW... I highly recommend him if you need a website or extensive website rework.

The website is best viewed using the most recent version of your browser whether it be Internet Explorer, Safari, or Firefox. Older browser versions will work, but just won't be as pretty and formatting may be slightly off.

Also new to the website is its ability to automatically detect and adjust appearance of the webpages based on whether you are on a regular computer vs tablet vs smartphone. Very cool...

Check it out here!