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An odor that is associated with pain triggers a more acute reaction in the future
Last reviewed: 01.07.2025
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Painful sensations, when a person sensed a certain smell, make olfactory neurons react to this aroma more intensely in the future. American specialists 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, after a series of experiments determined that in the case of smells, changes occur not in the brain, but directly in the nasal mucosa, or rather in the olfactory epithelium, consisting of olfactory neurons.
Scientists conducted an experiment using specially selected laboratory mice, which were placed in a special box with an electric current running through the floor. Each electric discharge emitted a harmless gas with a certain smell, after each "procedure" the box with the mice was aired from the gas residues and after some time the session was repeated. The experiment lasted three days, during which the rodents had to endure 15 aroma-electric training sessions, the duration of which was 15 seconds.
After this, the rodents were injected with a fluorescent protein so that its glow could be used to judge the activation of neurons, and the protein attached to the olfactory neurons began to glow even with the slightest excitation. After this, the specialists removed part of the cranium of the experimental animals and directly observed the change in neuronal activity. A source with a familiar "painful" smell was installed in front of the animals. Compared to the control group of rodents, the mice that participated in the experiment with electric current had a stronger signal from the olfactory neurons.
The results obtained allow specialists to assume that pain sensations that are accompanied by a certain smell, in the future, produce greater sensitivity of receptors to it, even if there is no longer a source of pain. Scientists noted that this kind of pattern 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 sensitivity to aromas is developed, which proves that the olfactory epithelium has susceptibility to pain.
Previously, specialists established the fact that people who are not sensitive to pain are not able to distinguish smells. The reason for this is that the channels for transmitting smells and the feeling of pain to the human brain are the same. During the research, the sensitivity to aromas of patients who had a disrupted ion channel of sensory cells responsible for transmitting pain sensations from the skin to the corresponding parts of the brain was studied. As it turned out, this same channel is involved in the perception of smells, so the people who took part in the experiment did not perceive smells.