PNAS: The sense of smell is our fastest warning system

The ability to detect potential threats and response to odors is a prerequisite for the survival of us and other mammals

The first author of the study, Behzad Iravani, a researcher in the Department of Clinical Neurosciences of Karolinska Institutet, said: "For a long time, human avoidance of unpleasant smells related to danger has been regarded as a conscious cognition.

The olfactory organ accounts for about 5% of the human brain, allowing us to distinguish millions of different smells

The survival of all living things depends on their ability to avoid danger and seek rewards

The neural mechanism by which humans transform unpleasant odors into escape behavior has long been a mystery

Researchers at Karolinska Institute have now developed a method that makes it possible for the first time to measure signals from the human olfactory bulb

Their results are based on three experiments

Johan Lundstrm, the last author of the study and an associate professor in the Department of Clinical Neurosciences at Karolinska Institutet, said: “It is clear that the olfactory bulb responds very quickly to negative odors and sends a direct signal to the motor cortex within about 300 milliseconds

He continued:

"Research results show that our sense of smell is important to our ability to detect nearby dangers, and this ability is largely unconscious, rather than a visual and auditory response to danger

Published papers:

"The human olfactory bulb processes odorvalence representation and cues motor avoidance behavior", Behzad Iravani, Martin Schaefer, Donald A.