Our sense of smell serves as a warning

Which of our senses helps us most to ward off danger – sight, hearing? Apparently, it’s smell. Our sense of smell serves as an immediate warning of danger. The associated nerves trigger a quick response from our body. An experiment by researchers at the Karolinska Institute in Sweden proves it.

Our sense of smell serves as a super-fast alert for the body.
Our sense of smell serves as a super-fast alert for the body.

Table of Contents

Quick response

Studies were done in rodents. The set of nerves that detects odors is the olfactory bulb. It processes information in a very similar way to the brain. Actively classifies stimuli based on learned and innate responses.

This is a very important thing in potentially dangerous situations. What if a harmful food is detected? Or perhaps the presence of toxic fumes? The brain must respond immediately.

Nineteen non-smokers who reported being healthy were recruited. They quickly smelled six different scents. Some were pleasant, others not so pleasant. The reactivity of the olfactory bulb was measured by electroencephalography. This gave a balance of two different types of “brain waves” produced by the nerves.

One was gamma waves, fast processing. Attention and memory depend on them. The second was beta waves, slightly slower. It’s used in deliberate decision-making processes. Both are close to our nasal neurons.

If odors do not arouse alertness, the body delays responding.
If odors do not arouse alertness, the body delays in responding.
Smells alarm

In a second experiment with 21 volunteers, the body’s response to a dangerous smell was measured. Faced with an unpleasant smell, we only take half a second to turn away. But a lot happens in that half second. In the 250 milliseconds following the arrival of a smell in the nose, the two brain waves coordinate the response.

If the odor is considered a threat, the signal is sent earlier. It takes about 150 milliseconds to reach the motor cortex. If the smell is not so bad, we take our time.

“The bulb reacts to negative odors. It sends a direct signal to the motor cortex in about 300 milliseconds,” says Johan Lundström. He is a biologist at the Department of Clinical Neuroscience at the Karolinska Institute.

Our sense of smell serves as a warning. It detects dangers in our proximity. Much of this ability is more unconscious than that mediated by our senses of sight and hearing,” says Lundström.

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