Study Finds Sense Of Smell Is Body’s Most Rapid Warning System

Health News – A new study examined what happens in the brain when the central nervous system judges a smell to represent danger. Researchers found that negative smells related to unpleasantness are processed earlier than positive smells as well as trigger a physical avoidance response.

In a new study, researchers at the Karolinska Institutet (Sweden) conducted three experiments in which the participants were asked to rate their experience of six different smells, including some positive and negative, while the electrophysiological activity of the olfactory bulb responding to each of the smell was measured.

They developed a novel technique that made it possible for the first time to measure signals from the human olfactory bulb which processes smells and transmits signals to the specific parts of the brain that control movement and avoidance behavior.

“The human avoidance response to unpleasant smells associated with danger has long been seen as a conscious cognitive process, but our study shows for the first time that it’s unconscious and extremely rapid,” said Behzad Iravani, first author of the study published in the Proceedings of the National Academy of Sciences (PNAS).

Johan Lundström, last author of the study, explained that the olfactory bulb reacts rapidly to only negative smells and sends a direct signal to the motor cortex within about 300ms. It leads to a person unconsciously leaning back and away from the source of the smell.

“The results suggest that our sense of smell is important to our ability to detect dangers in our vicinity, and much of this ability is more unconscious than our response to danger mediated by our senses of vision and hearing,” Lundström added.

To Know More You May Refer To:

Iravani, B., Schaefer, M., Wilson, D. A., Arshamian, A., & Lundström, J. N. (2021). The human olfactory bulb processes odor valence representation and cues motor avoidance behavior. Proceedings of the National Academy of Sciences, 118(42), e2101209118. https://doi.org/10.1073/pnas.2101209118