The sense of smell is man's fastest danger warning system

Our sense of smell seems to be particularly good and quick at alerting us to danger before our other senses.

Results from two experiments previously conducted by researchers at the Karolinska Institutet in Sweden show that scent-detecting nerves deep inside the nose begin processing and analyzing 'dangerous' odors as soon as possible. detected, and at the same time trigger the body's response immediately.

This is in stark contrast to our auditory and visual systems because these systems channel sensory responses into specialized areas inside the brain for processing, resulting in delayed reaction times and transference. motion.

It may surprise many people because we often rely primarily on visual and auditory responses to determine direction and make decisions. However, quickly picking up the scent can make all the difference.

Studies in rodents have demonstrated how the nerve bundles that detect scent or smell work. This set of neurons can actively orchestrate stimuli based on innate responses and through training.

This is especially true when it comes to potentially dangerous situations. When you smell something unpleasant or toxic, your body immediately reacts by covering your nose or staying away from the smell.

However, what is true in mice may not necessarily be true in humans. Millions of years of separate evolution have differentiated our sense of smell from most other mammals. The sense of smell makes up about 5% of the human brain and allows us to distinguish millions of different smells. These odors are associated with health threats such as chemical odors or rancid food.

The sense of smell makes up about 5% of the human brain.

The sense of smell is especially important in humans because it helps detect and respond to potentially harmful stimuli quickly.

Scent stimulates reactions faster than other senses?

To test, the team recruited 19 healthy non-smokers to participate in a rapid sniff test of six different odors.

Some smells like linalool or ethyl butyrate perfume are fruity and relatively pleasant. Others, such as diethyl disulfide compounds, are less attractive.

Volunteers smelled each scent multiple times, and the researchers measured olfactory reactivity non-invasively using electroencephalograms. This not only provides fast response times, but also allows for the storage of two different types of 'brain waves' produced by the nerves.

• One is a gamma wave , a fast processing wave that we often use when noticing and remembering something.
• The second is that beta waves are a bit slower and are a common brain oscillation used in deliberate decision-making.

The presence of both types of waves near our nasal neurons means that at the very moment when a scent is stimulated to smell, other parts of the brain are already responding and ordering action. physical.

In a second trial with 21 volunteers, the team tested to see if this first response translated into the body's actual response.

The two pleasant smells of strawberry and carvone (an essential oil found in mint and dill) have been compared to something unpleasant and stinky like the ethanethiol smell of rotten cabbage. After sniffing, the volunteers' movements were measured again to see how long it took the scent to trigger a response.

Putting the data together, it's clear that our sense of smell processes pleasant and threatening odors at different rates. If we accidentally inhale an unpleasant and potentially life-threatening odor, it only takes half a second for us to react. If the smell isn't too bad, the reaction will be a bit slower.

But there's a lot going on within that half-second. Within 250 milliseconds of the smell entering the nose, two different brain waves 'combine' to coordinate the response.

If the smell is identified as a threat, the signal is sent earlier, and it takes about 150 milliseconds for the signal to reach the motor cortex. If the smell is not dangerous, the signal may take longer to arrive.

Johan Lundström, a biologist in the Karolinska Institute's Department of Clinical Neuroscience, said : 'It is clear that the brain responds particularly quickly to dangerous odors and sends signals directly to the motor cortex for about 300 milliseconds'.

Our sense of smell plays an important role in detecting dangers around us.

The visual and auditory reaction time study measured the entire process from detection to action. Specifically about 150 milliseconds for audio response and less than 200 milliseconds for vision.

It can take us longer to identify odors and stay away, possibly even significantly longer if our sense of smell cannot distinguish the cues.

Lundström said: 'The results suggest that our sense of smell plays an important role in detecting dangers around us and is largely unconscious, different from our response to dangers through our eyes. and hearing'.

Which means we can all breathe a sigh of relief and confidently say that our nose knows us best.

The study was recently published in the journal PNAS.