Image from: pixabay.com
Ok, last week's TIL post was about a study that revealed how their partner's smell helps women feel safer and reduce cortisol levels. The study claimed women's more acute sense of smell to be the reason for using them as guinea pigs. I was intrigued to look further into it and so I did.
According to another research from the Institute of Biomedical Sciences at the Federal University of Rio de Janeiro, which took place in 2014, women's brain region in charge of smell is more advanced than in men.
The "guinea pigs"
The scientists studied the brain of 11 dead women and 7 dead men. The subjects were all 55-94 years old, had lived in the same environment of moderate to high environmental pollution levels, were neurologically healthy and had never worked in positions requiring high olfactory abilities (like a professional cook). According to a past genomic DNA analysis, "Brazilians subjects can be considered representative of many different ethnic ancestries".
The method
The technique used in order to count the absolute cell number of a specific brain structure (in the present study: the olfactory system) is called isotropic fractionator. Up untill then, imaging methods would reveal a gross number of cells and lacked in accuracy (leaving questions as to whether the discrepancies measured were due to biological or social and cognitive differences.
The findings
There were no significant differences regarding mean mass of the olfactory bulb between men and women, age groups or brain hemisphere. The measurements revealed that women have 43.2% more cells than men in the specific brain structure. For neurons, the difference would reach almost 50% (49.3%). The non-neuronal number was also 38.7% higher in women. Coming to density, the differences were as notable as above, with women showing higher density of total cells, neurons and non-neurons compared with men.
Image from: maxpixel.freegreatpicture.com
The questions that rose
Why do women have such an advanced olfactory bulb system? What purposes does it serve?
One possible explanation is evolution, bigger brains serve greater and more complex functions (as shown by a study on elephants). A second one is based on reproduction. Both sexes seem to have equal amount of smell receptors. In neuro-imaging experiments, women showed higher activity in the frontal and temporal lobes than men. Moreover, in odor evaluating tests, women also seem to process odors differently, which implies a possible role of estrogen levels in smell recognition.
Some studies have shown women have certain odor sensitivity, while others failed to produce such results. According to this study, women exhibit greater odor sensitivity due to repetitive exposure to certain odors but only after puberty. This is suggested to serve reproduction, as greater sensitivity in smell aids in pair bonding and kin recognition, a trait that has been maintained through centuries of evolution.
There is still a definite answer pending as to whether the higher number of neurons is responsible for the enhanced sense of smell in women. Another question that hasn't been answered with certainty is whether women are born equipped with more olfactory bulb cells or acquire them afterwards. But since the accute smell does not abandon women even after menopause, then it cannot necessarily be hormone-regulated.
Are reproductive hormones to blame?
A study has indicated that estrogens increase olfactory performance, whereas androgens decrease it. But there have been contradicting results from other studies that have revealed a teenage girls' outperformance over boys in odor identification. Accordingly, analogous results were revealed in experiments with post-menopause women and same-age men. All these lead to the conclusion that reproductive hormones ang aging cannot have a great role in women's better smelling abilities.
Adult neurogenesis and aging have a part?
Although in many mammals neurogenesis occurs during lifetime, in humans this is not the case. The addition of new neurons is insignificant. Therefore, scientists can conclude that the more advanced olfactory bulb system in women is due to "embryonic proliferation and/or to postnatal cell death controlled by hormones or by inhibitory neurotransmitters".
Aging does not seem to influence women's outperformance, although there are conflicting studies in this field. However, the decrease in neurons due to aging does not seem to affect women as much as men, since they still maintain their "superiority" even after the deterioration that comes with old age.
TL;DR
Women's part of the brain that is responsible for smell is more advanced and equipped with more cells than men's. Therefore, women can detect and identify odors easier. Women are probably born bearing more cells in the specific part of their brains and this could be driven by reproductive reasons.
There has been a wide bibliography and studies on the field that reveal fascinating results. The more you look into it the more amazed you will be by human nature.
References
journals.plos.org
sciencedaily.com
livescience.com
scientificamerican.com
scielo.br
frontiersin.org
nature.com
academic.oup.com
Thank you so much for your time!
Until my next post,
Steem on and keep smiling, people!
