The ability to guess, detect, and react to any smell is one of the most potential pre-condition of mammal survival. It is known that the ability to smell has helped living beings in various aspects so far.
By using some techniques, researchers at Karolinska Institute were able to analyze what happens in the brain when the central nervous system interprets a smell as a threat using a unique technique.
Sense Of Smell Is Our Most Rapid Warning System
The human brain is the center of all of its activities. These activities are carried out with the help of neurons and various senses, as well as sensors that are spread all over the body.
Among all the senses, the neurons are more sensitive towards the sense of smell, and that is why the same is affected with a common disease also.
The sense of smell acts as a warning system to the brain that passes necessary signals to the rest of the body to stay away from such place of smell or leave it at the earliest.
Negative and unpleasant smells associated with discomfort or unease are processed earlier than good smells, according to the study, and prompt a bodily avoidance response.
The human avoidance response to unpleasant smells associated with danger has long been thought to be a conscious cognitive process. Still, our study shows for the first time that it is unconscious and extremely rapid,” says BehzadIravani, a researcher at Karolinska Institute’s Department of Clinical Neuroscience.
The olfactory organ, which occupies around 5% of the human brain, allows humans to distinguish between millions of different kinds of smells. Chemicals and rotten food are related to a high number of those kinds of smells that pose a threat to human health and life. After being inhaled through the nose, smells impulses reach the brain in 100 to 150 milliseconds.
Measuring the Olfactory response
All living species rely on their ability to avoid danger and seek rewards to survive. The olfactory sense appears to be especially crucial in humans for identifying and reacting to potentially hazardous stimuli.
The brain mechanisms involved in the conversion of an unpleasant smell into avoidance behavior in humans have long remained a mystery. This differs from person to person and how they react to any specific smell regardless of pleasant and unpleasant smells.
One reason for this is the lack of non-invasive methods for measuring signals from the olfactory bulb, the first part of the rhinencephalon (literally “nose brain”) with direct (monosynaptic) connections to important central nervous system parts that aid in the detection and memory of threatening and dangerous situations and substances.
Researchers at Karolinska Institute have discovered a method to detect signals from the human olfactory bulb, which processes smells and provides signals to areas of the brain that control movement and avoidance behavior for the first time.
The fastest warning system
Their findings are based on three tests in which individuals were asked to score their reactions to six distinct smells, some of which were good and some of which were negative, while the electrical activity of the olfactory bulb was monitored.
“It was obvious that the bulb reacts specifically and quickly to unfavorable smells, sending a direct signal to the motor cortex in roughly 300 milliseconds,” explains Johan Lundström, associate professor at Karolinska Institute’s Department of Clinical Neuroscience.
“The signal induces the person to lean back and away from the source of the odor involuntarily.” The findings show that our sense of smell is vital in detecting threats in our environment and that most of this ability is more unconscious than our reaction to danger mediated by our senses of sight and hearing.”