Remember. During the COVID-19 epidemic, one of the most spectacular symptoms experienced by some patients infected with the coronavirus was the more or less temporary loss of the precious sense of smell. The virus has highlighted the great usefulness of one of our five senses, too often underestimated, but which, once inoperative, can radically change the daily lives of people suffering from anosmia. Because being deprived of smell is not simply being treated to bland and flavorless meals, it is also the inability to smell the scent of our loved ones and the surrounding nature, which can go so far as to isolate us in a deep depression.
To fully understand the complex mechanisms of smell and its multiple impacts on our lives, you must read Smell. How smells affect our brainthe new book full of erudition by the specialist Hirac Gurden. The internationally renowned neurobiologist of Turkish origin deciphers the plethora of invisible olfactory phenomena that act in our brain mass. Because when it comes to senses, everything is originally a question of biology. “Everything that is alive has an odor, and generally this living being uses it to communicate. That is to say that odorous molecules are communication mediums used by plants and animals,” reminds us the author, also research director at the National Center for Scientific Research.
These hundreds of odorous molecules, weightless in the air, infiltrate the nostrils and travel to the nasal cavities, the ends of which are made up of odor receptors. The latter, located in the mucous membranes at the back of the nose, are themselves made up of millions of olfactory neurons. Stimulated by the odors we smell, they send a signal to our brain. The initial process, even if it is now known, has long remained mysterious. It should be noted that it was only in 2004 that scientists discovered the genes that code for olfactory receptors.
What follows is an incredible chemical and sensory process that the specialist decodes with solid pedagogy. He lists the crucial role of sorting the olfactory bulb into different areas: the cortex for sensory perceptions, the amygdala complex for pleasant or unpleasant emotions, and the hippocampus for memory and memories.
But the highlight of the show is located in the heart of the orbitofrontal cortex, known as the perfumer’s fetish organ. It is in this precise place that we consciously perceive a smell that can attract us if it is pleasant, but make us run away immediately if it is perceived as fetid or dangerous.
Beyond this impressive mechanism, Hirac Gurden tells us about the vital role of smell in a host of human interactions. And it starts in the first days with pheromones released by the mother’s breast indicating to the baby, who has poor vision, where the source of breast milk is. Recent studies indicate that between birth and the age of 10, the most powerful and memorable memories are olfactory in nature. A memory that guides us throughout our existence.