lLove is blind, it is well known. Blind to the reality of the loved one, of course. We would almost apologize for providing such a clarification. However, a study published Wednesday, August 28 in the journal Nature invites us to consider expression in a completely different way. In an experiment with fruit flies, a team from the University of Birmingham has just shown that during courtship, males become insensitive to visual signals of the presence of a predator.
It must be said that among animals, staying alive and reproducing, two of the very purposes of their existence, are often contradictory. From hamsters forced to leave their burrows to find a mate to birds bursting with bright colours to seduce their boyfriend, at the risk of being discovered by their predator in both cases, the balance between threat and gain is essential for many species. Including humans. “But how does the brain evaluate danger and reward to make the best possible decision? We know little about this.”“This study is based on a study of the genetics of the brain, which is a key element in the development of the brain,” said Carolina Rezaval, a neurogeneticist at the University of Birmingham and coordinator of the study.
To address this general question, British researchers looked at Drosophila, or the fruit fly, a laboratory favourite for decades. In fact, every corner of its genome has been explored. Males also offer the advantage of practising a particularly stereotypical seduction ritual: the courtier first turns towards the object of his desire, chases him, touches his abdomen to detect pheromones, then starts a serenade by vibrating his wings. Finally, as the last step before acting, he flexes his abdomen. Could this sequence mark the perception of danger among the young Don Juan?
Action of dopamine
So the Birmingham team designed an artificial threat, a kind of predator made of light and shadow. “Normally fruit flies react by fleeing or immobilizing”describes Carolina Rezaval. In the brain, One of the main messengers is serotonin. Sometimes called the “happiness hormone” in humans, in flies it controls specific neurons associated with stress and fear. This could be verified and detailed thanks to optogenetics, a technique that allows a neuron to be activated or inhibited by a flash of light.
It was still necessary to be able to follow the phenomenon throughout the courtship. By opening a small window in the skull of the males, the scientists were able to observe in real time, under a microscope, the reaction of the neurons to the presentation of the threatening shadow. With a spectacular result: during the first stages, the male remains receptive to danger. But, once he bends his abdomen, nothing else matters. “Their brain is so focused on reproduction that it takes over the survival instinct, Carolina Rezaval insists. We were very surprised by how strongly dopamine blocks the perception of danger. »
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