Scientists talked about human stereoscopic

(ORDO NEWS) — The volumetric perception of odors affects how we perceive the direction of movement of objects.

It is generally accepted that people have an underdeveloped sense of smell. Oriented in space, we primarily rely on sight and hearing. The brain uses differences in the spatial arrangement of paired organs – eyes and ears – to create a three-dimensional picture of the world.

Although the nasal canals in humans are also two, it is widely believed among scientists that differences in the concentration of olfactory stimuli in the nostrils do not provide information about the location of the smell source. Exceptions are observed in cases when stimuli affect the ends of trigeminal nerve branches, which are able to perceive individual chemical stimuli.

However, in the strict sense of the word, this cannot be called a sense of smell, since this nerve does not transmit signals to the cortical centers of smell in the brain.

However, scientists from the Institute of Psychology of the Chinese Academy of Sciences claim that this is not so. In their article published in the publication Proceedings of the National Academy of Sciences, they described a series of experiments with olfactory stimuli that are not perceived by the ends of the trigeminal nerve.

The experiments involved 216 healthy non-smoking volunteers. For half a second they were shown on the screen an array of flickering dots. This flicker created the effect of the movement of points on a person. The subject should have answered where the place from which the dots move is on the screen — right, left, or center. A second after the answer he was shown a new array of twinkling dots.

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Screen showing flickering dots (A) and olfactory stimulus (B) supply pattern / Yuli Wu, Wen Zhou et al., Proceedings of the National Academy of Science, 2020.

Along with visual stimuli, volunteers were exposed to olfactory stimuli. Watching the dots on the screen, people inhaled through the tube the contents of containers filled with an aqueous solution of vanillin or phenylethyl alcohol in propylene glycol. Moreover, the tubes for each nostril were individual, and the concentration of the same substance in different containers was different; thus, different numbers of odorous substance molecules got into different nostrils.

It turned out that the concentration of alcohol or vanillin influenced the subjects’ perception of the location of the point from which the points supposedly moved. At the same time, the experiment participants could not determine exactly which side the smell was stronger. Also, the shift in perception of the visual stimulus was associated not with the absolute concentration of odorous substances, but with the difference in their concentration between the two nostrils. So, the concentration ratio in 4: 1 containers shifted the perception of movement more than the concentration of 3: 2, and at the same time it was stronger than the ratio of 5: 0 (when a tube came from the vessel into the second nostril, where there was neither alcohol, nor vanillin) .

From these experiments, we can conclude that the stereoscopic (volumetric) sense of smell in a person is provided not only by the trigeminal, but also by the olfactory nerve. The authors of the article also believe that information from the visual and olfactory systems is correlated in the cerebral cortex, which is processed in the medial temporal and entorhinal cortex, respectively. But in order to finally find out, additional experiments will be needed.

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