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Definitely, research on our cerebral organ is raining in at the moment! Between the brain mapping designed by Harvard and Google, this study concerning the effects of mobile games on it or the one revealing certain memorization mechanisms, we are served. This time, it is a study published on May 28 in the journal PLOS Biology, carried out by an international team of researchers, led by Andrew Chang of New York University, which ;is focused on another theme.
That of the brain's ability to immediately distinguish music from words. A complex process, finally deciphered, which could be a game-changer for improving therapies for people with language disorders such as aphasia (partial or complete loss of the ability to express themselves).
L’amplitude and frequency: fundamental markers
The distinction between music and speech lies in very basic acoustic parameters. As Andrew Chang explains: “ Although music and speech differ in many ways, ranging from pitch to sound texture, our results show that the auditory system uses remarkably simple acoustic parameters to distinguish music and speech “.
Indeed, the musical compositions present a relatively stable amplitude modulation oscillating between 1 and 2 Hz, while speech fluctuates at higher frequencies, between 4 and 5 Hz. For example, the rhythm of the song Superstition by Stevie Wonder is around 1.6 Hz, when Roller Girl by Anna Karina peaks at 2 Hz.
In order to deepen their understanding of this phenomenon, Chang and his colleagues conducted four experiments involving more than 300 participants. During the latter, the subjects were presented with synthetic sound segments imitating music or speech, but modified so as to vary the speed and regularity of the amplitude modulation. Subsequently, they were asked to identify whether the sounds heard were music or words.
Results revealed that slower, regular segments (<2 Hz) were perceived as music, while faster, irregular segments (~4 Hz) were perceived as speech. The researchers concluded that our brains automatically use these acoustic cues to classify sounds. A phenomenon that scientists have compared to the one that makes us “ see faces in the clouds ”, known as pareidolia . It is actually a tendency of the human brain to perceive familiar shapes, often human faces, in random or unstructured visual stimuli.
Therapeutic applications for language disorders
Understanding the mechanisms by which our brain distinguishes between music and speech is an important advance for the treatment of language disorders. As the authors note, this knowledge may help improve rehabilitation programs for aphasic patients, using, for example, melodic intonation therapy (MIT).
This method is based on the idea that music and singing can activate different parts of the brain involved in communication and language (Broca's area, Wernicke, auditory cortex or motor cortex among others). By singing phrases or words to simple melodies, people can learn to bypass damaged areas of the brain and use alternative pathways to relearn how to communicate. Therefore, knowing what makes speech and music similar or distinct in the brain could help design more effective rehabilitation programs.
The findings from this study, supported by The National Institute on Deafness and Other Communication Disorders as well as the Leon Levy neuroscience grants, opens new perspectives for therapists and researchers. By identifying more precisely the acoustic parameters used by our brain, they are now able to develop specific exercises aimed at taking advantage of musical detection capabilities patients to improve their verbal communication.
- A new study investigated the mechanisms at work in the brain which help it to distinguish music from speech.
- This distinction is made possible thanks to the differentiation of amplitudes and sound frequencies.
- A discovery that will facilitate the design of therapies for people with communication disorders.
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