Why do some people sing so out of tune? Two teams of French researchers have finally found the answer. The origin of the amusia is cerebral and abnormalities of the cortex would be involved.
Singing out of tune, difficulty hearing a wrong note, or downright aversion to music … these are evils that sometimes make you smile. However, these disorders characterize in certain cases congenital amusia, a disease which would concern between 2 and 4% of the population. Those affected say that they experience music as a foreign language or as a simple noise. The most famous person affected by this handicap would be the Cuban revolutionary Che Guevara, who according to testimonies suffered greatly from his inability to sing a few bloody but catchy tunes. However, theamuse is not due to any hearing or psychological problem.
So, in an attempt to answer the questions linked to this disease, two French teams from the Lyon Neuroscience Research Center (CNRS / Inserm) recently took an interest in the encoding of musical information and the short-term memorization of music. notes, with unpublished results published in the May 2013 edition of the journal Brain.
Based on the already known observation that amusing people have a very particular difficulty perceiving the pitch of notes (low or high) and also struggle to memorize them, the researchers tried to determine the brain regions affected by these memorization difficulties. They thus made, on a group of funny people performing a musical task, a recording of magnetoencephalography (a technique which makes it possible to measure, on the surface of the head, very weak magnetic fields resulting from the functioning of neurons) . The task consisted of listening to two melodies separated by a silence of two seconds. The volunteers had to determine if the melodies were the same or different from each other.
Scientists then observed that, while perceiving and memorizing notes, amusing people exhibited altered processing of sound in two brain regions: the auditory cortex and the frontal cortex, mainly in the right hemisphere. Compared to non-fun people, their brain activity was delayed and decreased in these specific areas when encoding musical notes. These anomalies occurred as early as 100 milliseconds after the start of a note.
These conclusions, the researchers then confirmed them thanks to MRI images. As a result, in amusing people, we find in the lower frontal cortex, an excess of gray matter accompanied by a deficit in white matter, one of the essential constituents of which is myelin. This surrounds and protects the axons of neurons, allowing the nerve signal to propagate rapidly. The researchers also observed anatomical abnormalities in the auditory cortex. These data support the hypothesis according to which the amusia is due to a dysfunction of the communication between the auditory cortex and the frontal cortex. And this work ultimately offers hope for the entertainers, because “they now allow us to consider a program to rehabilitate these musical difficulties, by targeting the early stages of the brain’s processing of sounds and their memorization,” the authors conclude. scientific. A hope for the entertainers but also can be the end of an ordeal for the absolute ears, theability, which some people would have, to recognize and determine without prior reference, the name of one or more notes corresponding to the sound they hear. The Bach where the Mozart may soon finally be able to rest in peace …
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