Why women can smell better

Female olfactory bulb contains twice as many brain cells as men

Women have a more sensitive sense of smell © freeimages
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Sensitive nipples: women perceive smells more sensitively than men. Why this is so, now Brazilian researchers have revealed. Although both sexes have almost the same number of olfactory receptors in their noses, women have almost twice as many neurons in the olfactory bulb of their brains. Their odor processing is therefore significantly better, as the researchers report in the trade magazine "PloS ONE".

Observations and experiments show that women are more sensitive to smells than most men. Why this is so, has remained a mystery. Because men and women have about the same number of olfactory receptors in the nose, as studies have shown. Therefore, it can not actually be due to a better absorption of the scent stimuli. In addition, the volume of the olfactory bulb in men is even greater than in women, as brain scans show - so at first glance, there seems to be no explanation for the finer nibble.

Cells count in the olfactory bulb

Or maybe yes? Brain scans can only portray rough structures, as explained by Ana Oliveira-Pinto from the University of Rio de Janeiro and her colleagues. The number of cells in a brain area can not be determined - and this usually gives a better picture of the complexity and performance of a brain area.

To solve the mystery of female olfactory sensibility, Oliveira-Pinto and her colleagues therefore took the Reichkolben of real brains. For this purpose, they asked the relatives of 18 deceased - seven men and eleven women - to dissect the brains of the dead. For their study, they released the olfactory bulbs of the dead and first determined the volume of this area. Then they dissolved the tissue so that the individual cells could float in a solution and be counted.

The stimuli of the receptors in the nose go to the olfactory bulbs in the brain. © Patrick J. Lynch / CC-by-sa 2.5 gen

Twice as many brain cells

The result was surprisingly clear: Although the olfactory bulb was even slightly lighter in women than in men, contained as female variant significantly more cells. The researchers found 16.2 million cells per olfactory bulb for women, only 9.2 million in the men. And the difference was even clearer among the neurons, the brain cells important for processing: the 6.9 million neurons in women were only 3.5 million neurons in the men compared to this corresponds to a difference of 49.3 percent, as the scientists report. display

Although the size and mass of the olfactory bulb were taken into account, this picture did not change: the cell density was almost twice as high in women. But that also means that girls are born with this olfactory advantage. Because in the course of life, the number of cells in the olfactory bulb hardly changed, as the researchers explain.

Same nose, but more differentiated processing

But does the higher cell count also explain the finer nose of women? In the opinion of Oliveira-Pinto and her colleagues, that is quite the case. "In general, brains with a larger number of cells have a higher functional complexity, " they explain. And just with the Reichkolben, the number of brain cells is very closely linked to its function. "It therefore seems plausible that a larger number of neurons in the olfactory bulb also give women greater sensitivity to smell, " says senior author Roberto Lent of the University from Rio de Janeiro.

The intake of the odor stimuli and their transmission to the brain is probably the same for both genders. Because both have the same number of olfactory receptors. But the processing of these stimuli is more differentiated in women than in men, the researcher explains. (PloS ONE, 2014; doi: 10.1371 / journal.pone.0111733)

(Publicase Comunica o Cient fica, 07.11.2014 - NPO)