Women's finer sense of smell may be due to more brain cells

Date: Nov-06-2014 New research shows that women have more cells in the olfactory bulb

- the area of the brain that is dedicated to sense of smell - than men. The

authors of the study - published in PLOS ONE - suggest this may

explain why women are reported to have a better sense of smell than

men.

Women often outperform men in odor-sensing tests.

The study was led by a team from the Federal University of Rio de

Janeiro in Brazil, where another group of researchers had developed the

"isotropic fractionator" - a fast and reliable method of measuring the

number of cells in a given brain region such as the olfactory bulb.

The olfactory bulb is the first region of the brain to receive signals

about odors sensed via the nostrils. The ability to discriminate among

odors and scents varies widely among individuals. Also, studies show marked

differences between men and women, with women often outperforming men in

many kinds of odor-sensing tests.

There are theories that sex differences in smell are due to cognitive

and emotional influences rather than perceptual ability.

Previous studies that have looked for biological explanations for

women's apparent superior sense of smell have used brain scans to look for

structural and volume differences. These have led to mixed results and left

many questions still unanswered.

So Roberto Lent, a professor in the Institute of Biomedical Sciences at

Rio's Federal University, and colleagues set out to measure the biological

evidence more directly - by counting the number of cells in women's and

men's olfactory bulbs.

To this end they examined post-mortem brains from seven men and 11 women

who were all healthy and aged over 55 when they died. None of the subjects

had worked in jobs that required them to have exceptional sense of smell

such as cookery or coffee-tasting.

Study found women's brains have up to 50% more olfactory neurons

Using the isotropic fractionator, the team calculated the number of

cells in the olfactory bulbs of these individuals and found that, on

average, the women had 43% more cells in this brain region than the men.

When they included only neurons in the count - that is leaving out other

cells like glial or structural cells - this figure went up to nearly

50%.

The olfactory bulb is the first region of the brain to receive signals about odors sensed via the nostrils.
Image credit: Roberto Lent

The authors acknowledge that just finding this difference is not enough

to prove that women have a superior sense of smell - it is not even enough

to explain the findings of previous studies about differences in ability to

differentiate, identify and remember scents and odors. However, Prof. Lent

suggests:

"Generally speaking, larger brains with larger numbers of neurons

correlate with the functional complexity provided by these brains. Thus, it

makes sense to think that more neurons in the female olfactory bulbs would

provide women with higher olfactory sensitivity."

Since the brain does not accumulate many more cells as we grow, it would

seem that women are equipped with these extra olfactory cells from the day

they are born.

There are still many questions to explore, including why women should

have this ability hard-wired into their brains, and what mechanism

produces this greater quantity of olfactory cells in the female brain.

One theory is that a superior sense of smell helps mother and child to

bond after birth; another is it also influences females' selection of

potential mates.

In October 2012, Medical News Today learned of another PLOS

ONE study from the University of Pennsylvania that suggested losing sense of smell could be an early sign of

Parkinson's or Alzheimer's disease, or another neurodegenerative

disorder.

Written by Catharine Paddock PhD

Not to be reproduced without permission.

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.