Smell is the fastest warning system in humans. Bad smells associated with unpleasant sensations or fear are in fact processed before the 'good' ones to physically remove us from the possible threat. This is indicated by the research published in the journal of the United States Academy of Sciences (PNAS) by the Swedish institute Karolinska.
Smell helps humans, like other mammals, recognize potential threats to survival. The researchers studied what happens in the brain when a smell associated with a possible danger is perceived.
"The human behavior of avoiding unpleasant odors associated with danger has long been seen as a conscious cognitive process. Our study instead demonstrates for the first time that it is unconscious and occurs very quickly", explains Behzad Iravani, first author. research. The olfactory signals reach the brain within 100-150 thousandths of a second after being inhaled by the brain. For a long time, however, it remained a mystery which neural mechanisms are involved in converting an unpleasant odor into human avoidance behavior.The Swedish researchers have succeeded in developing a method that for the first time allows to measure the signals of the human olfactory bulb (structure at the base of the brain) that processes odors and transmits signals to the areas of the brain that control the movement and behavior of avoid.
In three experiments they asked the volunteers to score 6 different odors, some positive, others negative, while the electrophysiological activity of their olfactory bulb was measured.
"The bulb reacts specifically and quickly to bad odors and sends a direct signal to the motor cerebral cortex in about 300 millisemes of a second. The signal instinctively drives the person away from the source of the smell," adds Johan Lundstrom, one of the researchers.
Smell is important, he concludes, "for our ability to detect nearby hazards, and much of this ability is more unconscious than our sight and hearing mediated response to hazards".
