Music is a fantastic collection of soundwaves. When we hear it, the brain reacts spontaneously and interprets it. How does it work? Within this article, we describe the paths of soundwaves and their complex processing inside the human brain.
Music as a language of the soul
Music has accompanied people for centuries, both in moments of happiness and sadness. It might be even older than writing and reading, perhaps even fire-making! People turn to music for fun, relaxation, or inspiration. Music carries messages, and Charles Darwin even classified the music as a universal language .
The brain as a music processing unit
The brain’s processing of music is quite complex. Each melody has many dimensions – such as volume, frequency, and the type of sound produced by the instrument being played – all of which influence perception. To understand how the brain processes music, it first helps to understand how sound is perceived.
Sound recognition is crucial to communication and perception. The auditory pathway consists of two main components: the primary path and the non-lemniscal pathway. The former transmits the information to the primary auditory cortex, while the latter connects attention and emotional responses .
The outer ear, called the pinna, is responsible for the collection of soundwaves. There, these waves travel to the tympanic membrane and force it to vibrate. Generated soundwaves then travel across the air-filled middle ear cavity through tiny and delicate bones called auditory ossicles that strengthen soundwaves.
The auditory pathways, where sound travels from the outer ear to the auditory cortex. The cochlea converts vibrations into nerve impulses that travel to the brain via the cochlea nerve. The eustachian tube connects the middle ear with the upper throat.
Sounds are heard thanks to this hidden labyrinth of structures in the ear. The brain’s sound processing center is the auditory cortex  that identifies and analyzes music. The figure below shows the brain regions involved in hearing. The sensory cortex controls tactile feedback while hearing music or playing an instrument. Memories connected with the music, prior experience, and the surrounding context are processed by a curvy structure that looks like a seahorse called the hippocampus. Meanwhile, the nucleus accumbens and amygdala are responsible for an emotional reaction to music. Another brain region involved in processing music is the motor cortex, which is involved in movement processing, particularly during dancing and playing an instrument. The cerebellum is also involved in movement during dancing and playing instruments. The visual cortex is responsible for reading sheet music and observing dance moves. Finally, to process tempo or rhythm, the brain uses the lateral cerebellum and basal ganglia. In sum, a lot is happening between your ears when you play your favorite song!
Some of the many brain regions involved in music processing.
How music influences the body
Even short exposure to music causes the brain to release neurotransmitters, or chemical compounds responsible for transporting biological signals between neurons and other cells . For example, the neurotransmitter serotonin oversees mood regulation, whereas dopamine is associated with motivation and pleasure. The level of these neurotransmitters can be influenced by listening to music. For example, listening to classical music has been found to reduce stress  and help regulate heart rate and blood pressure .
Interestingly, the effects of music on our mood may depend on the volume and frequency of the sound we hear. Volume, or sound intensity, is measured in decibels (dB). A whisper ranges from about 20-40 dB, whereas a jet engine is about 100 dB. Absolute silence is irritating and not natural for our brain. The music that has a positive influence on our body is usually not louder than 75 dB. Sounds beyond 90 dB can affect hearing and can even lead to deafness. How high or low a pitch is, or the frequency of its sound wave, also matters: Music positively influences the brain when the frequency of sound is below 1,000 Hz. That said, everyone hears music differently  – for example, it becomes more difficult to hear high frequency sounds as we age.
Therapeutic applications of music
Listening to music is not only pleasurable, but it can provide benefits to learning and memory. Extended exposure to classical music can enhance learning, especially for spatial tasks , practical skills , language learning, and mathematics [10, 11]. Music can also benefit social relationships, reduce feelings of loneliness, and have other positive effects on human health. For example, music can be a handy tool in treating Parkinson’s disease by helping patients regain their motor and speech skills [12, 13]. Listening to music can also aid in pain reduction, such as chronic pain caused by cancer or surgery . Therefore, having patients listen to music while in the hospital after surgery could be a promising way to aid in their recovery, by relieving pain and boosting morale.
There are some frequencies called binaural beats that can be used therapeutically. Listening to beats that have the same frequencies as brain waves can help to synchronize the brain waves in varying ways. For example, beats at 0.5-4 Hz correspond to the deeper stage of sleep. Beats at 4–7 Hz improves creativity, meditation and corresponds to the REM sleep phase (dream phase), while 7–13 Hz may encourage relaxation. In contrast, the brain is more aroused when listening to beats at frequencies of around 13 Hz and above [7,15].
Music engages many areas of the brain simultaneously. Listening to the music not only improves mood and reduces stress, but it can also be an invaluable therapy. Music provides so much pleasure that it is difficult to imagine living in a world without it.
This article was the joint work of Zuzanna Kozłowska (Faculty of Chemistry, University of Warsaw), Agnieszka Pregowska (Institute of Fundamental Technological Research Polish Academy of Sciences), Magdalena Osial (Faculty of Chemistry, University of Warsaw) as a part of the Science Embassy project. Images by Magdalena Osial.
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