The smell, which is associated with pain, causes a more acute reaction in the future
Last reviewed: 16.10.2021
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Pain sensations, in which a person felt a certain smell, makes the olfactory neurons in the future react to this aroma more intensively. American experts came to such conclusions during several experiments on laboratory mice.
The fact that unpleasant sensations have an associative connection with smells or sounds has been known for a long time. It is believed that such a reaction is determined by changes in some parts of the brain responsible for processing information coming from the senses.
However, a research group at the University of New Jersey, led by Marley Kass, determined after a series of experiments that in the case of odors, changes do not occur in the brain but directly in the nasal mucosa, or rather in the olfactory epithelium, consisting of olfactory neurons.
Scientists conducted the experiment using specially selected laboratory mice that were placed in a special box, in the floor of which an electric current was conducted. With each electric discharge there was a release of a harmless gas with a certain odor, after each "procedure" the box with mice was weathered from the remains of gas and after a while the session was repeated. The experiment lasted three days, for which the rodents had to survive 15 aromo-electric workouts, the duration of which was 15 seconds.
After that, the fluorescent protein was injected into the rodents so that it would be possible to judge the activation of neurons by its luminescence, and the protein attached to the olfactory neurons started to glow even with the slightest excitation. After that, the specialists removed a part of the cranium to the experimental animals and directly observed changes in the activity of the neurons. Before the animals, a source with a "painful" smell already familiar to them was installed. In comparison with the control group of rodents, mice that participated in the experiment by electric current had a stronger signal of olfactory neurons.
The results obtained allow specialists to assume pain sensations accompanied by a certain odor, in the future develop a greater sensitivity of the receptors to it, even if there is already no source of pain. Scientists noted that this kind of regularity has no connection with the departments in the brain, all changes occur in the epithelium of the nasal mucosa, in which neurons are present. This is how the sensitivity to aromas is developed, which proves that the olfactory epithelium has a susceptibility to pain.
Previously, experts established the fact that people are not susceptible to pain, are not able to distinguish smells. The reason for this is that the channels for conveying smells and feelings of pain in the human brain are the same. In the course of the research, the susceptibility to the aromas of patients whose functioning of the ion channel of the sensory cells, responsible for the transmission of pain from the skin to the corresponding parts of the brain, was studied. As it turned out, the same channel is involved in the perception of odors, so people who participated in the experiment did not perceive smells.