14 DAY TRIAL // According to a new scientific study, it may be that as much as ten percent of the total world population is entirely tone-deaf, as in it cannot sing a single song in tune. Experts believe that this is happening because nerve fibers that usually link perception and motor regions of the brain are disconnected in this category, which leads to their inability. Details of the study, which identifies the missing brain circuit accurately, were published in the August 19th issue of The Journal of Neuroscience.
“The anomaly suggests that tone-deafness may be a previously undetected neurological syndrome similar to other speech and language disorders, in which connections between perceptual and motor regions are impaired,” Harvard Medical School expert Psyche Loui, PhD, who also holds an appointment at the Beth Israel Deaconess Medical Center, explains. Loui is one of the authors of the new study.
The expert and his colleagues used a type of Magnetic Resonance Imaging (MRI) called diffusion tensor imaging (DTI), in order to analyze how connections between the frontal and temporal lobes in tone-deaf people looked like. The scientists noticed that the arcuate fasciculus, a neural pathway known to play an important role in linking music and language perception to vocal production, was a lot smaller in the participants who had been previously identified as tone-deaf through listening tests. DTI was applied to the brains of about 20 participants, ten tone-deaf, and ten in a control study.
The fasciculus appeared to be a lot smaller in tone-deaf individuals than in healthy participants, and it also exhibited a lower neural count. In addition, the team reveals, the superior branch of the pathway in the right hemisphere could not be detected through either MRI or DTI, which can only mean two things – either it is terribly deformed and small, so that even the most advanced imaging techniques cannot detect it, or it is missing entirely, which seems like a more plausible explanation.
“The findings are clear. They show that the arcuate fasciculus, a structure long-known to join perceptual and motor areas, has reduced connectivity in individuals with tone deafness. Beyond improving our understanding of the anatomical underpinnings of tone-deafness, this study provides new insight into a person's ability to detect pitch,” Northwestern University scientist Nina Kraus, PhD, who has not been involved in the new research, shares.