You are here
The brain knows the score
Whether it is in public transport, while working, or while cooking, music accompanies our everyday lives. Pop, rap, classical, jazz, rock, electro, metal, techno… The styles are different, but all involve two elements: rhythm and melody.
However, hidden behind the pleasure of listening to a song lies an astonishing brain activity, namely that of predicting what it will hear next. Thanks to rhythms and repetition, our auditory system permanently anticipates what is coming next in music, a mechanism that plays a central role in musical pleasure.
Sound travels
Originally, sound is a variation in air pressure. When we push the “Play” button, it travels through the air to our ears, then through a series of structures, before ultimately being interpreted by the brain. It travels through the ear canal to the eardrum, and then to the ossicles, which amplify vibrations. It completes its path in the cochlea, an organ resembling a snail shell, from where it is transmitted to the basilar membrane. The mechanical movement of this membrane’s cilia is transformed into an electrical signal that travels along the auditory nerve all the way to the brain.
“This system is remarkable for its speed. Variations in air pressure are conveyed in the auditory nerve in less than 2 milliseconds,” emphasises Boris Gourévitch, a research professor at the Hearing Institute (IdA) in Paris1 and member of the Plasticity of Central Auditory Circuits team.
Music (de)coded by the brain
The perception of melodies and rhythms is very well organised in the brain. Sound is first decomposed when it travels through the cochlea. Depending on their frequency, deep or low sounds activate a certain area of the cochlea, while higher ones stimulate a different part. This organisation, known as “tonotopic”, stretches all the way to the auditory cortex.
The rhythm of music is also coded directly in the auditory nerve. “All frequency and temporal variations are reproduced in the auditory nerve, a little like a spectrogram,” Gourévitch explains.
Musical information is coded individually by a neuron, or within a group of neurons. They can, for instance, code the harmonics that make up sound in order to bring forth its specific tone. “When a violin and a piano play the same note, they can be distinguished by their tone. With the piano, some harmonics will be stronger than those of the violin, and others less so,” Gourévitch points out.
The brain is on the beat…
For the brain, repetitive musical rhythms and structures play a special role. “When something is repeated, reorganisation and neuroplasticity mechanisms are set in motion, and become extremely powerful for the auditory brain,” stresses Daniel Pressnitzer, a CNRS research professor at the LSP perceptual systems laboratory2.
This neuroplasticity is partly based on the auditory cortex. In the presence of a rhythm, the brain will use those that have already been memorised in order to anticipate the content of the next measure, thereby stabilising and lending meaning to its sound environment. Such anticipatory mechanisms are crucial for hearing in general. The musical sensation emerges from this faculty.
…but there is room for surprise
When a prediction proves correct, the auditory cortex enters a kind of resonance that activates the areas of the brain associated with pleasure and reward. The enjoyment of listening to music is based on a subtle balance between predictability and surprise.
“Musical elation seems to occur when the brain can anticipate changes to a piece of music, all while remaining slightly surprised. It is these small surprises that generate the sense of pleasure,” Pressnitzer explains.
The brain paced by electronic music
Some musical styles make extensive use of these prediction and surprise mechanisms. This is especially true of electronic music, whose repetitive structures offer a preferred playground for the brain. Composers engage listeners by repeating words or abstract sounds, all while modulating their rhythms.
“In the song ‘Dominas’3 by Carl Craig, a pioneer of techno music, the word ‘Dominas’ is repeated. With each measure, the repetition transforms this simple word into music.” This brings to mind an auditory illusion currently being studied by his team, known as “speech to song”4.
Electronic music also exploits the brain’s prediction mechanisms thanks to a “drop” phenomenon: the music gradually rises, creating an expectation, then briefly interrupts this movement before building up again.
Shared emotion
Anticipation is also a social aspect of listening to music. Whether it is at a concert or festival, a crowd hearing the same music shares the same rhythmical points of reference, and generally the same musical expectations. This common experience encourages synchronised movements and emotions, creating a strong sense of cohesion within the group. The word “trance” is often used…but that is another story.
From the first vibration captured by the ear to the emotions shared during a concert, behind each rhythm hides an ever-active brain busy predicting the next note.
See also
How the piano set the world in tune
- 1. CNRS / INSERM / Institut Pasteur.
- 2. CNRS / ENS-PSL.
- 3. https://www.youtube.com/watch?v=aHg0s6DtH74
- 4. https://deutsch.ucsd.edu/psychology/pages.php?i=212
Explore more
