Music and Brain
What is it that makes a sound music? Scientists are piecing together a picture of what happens in the brains of listeners and musicians.
Our fondness for music has some deep roots. We have been making music since the dawn of culture. More than 30,000 years ago, early humans were already playing bone flutes, and other musical instruments, and all known societies throughout the world have had music. Indeed, our appreciation appears to be innate. Therein lays the biological mystery why we love music so much even though it is just a mixture of different sounds.
Neuroscientists don’t yet have the ultimate answers to that question. But in recent years we have begun to gain a firmer understanding of where and how music is processed in the brain, which should lay a foundation for answering evolutionary questions. Studies of patients with brain injuries and imaging of healthy individuals have unexpectedly uncovered no specialized brain center for music. It has been found that music engages many areas distributed throughout the brain, including those that are normally involved in other kinds of cognition. The active areas vary with the person’s individual experiences and musical training. The ear has the fewest sensory cells of any sensory organ of about 3,500 inner hair cells occupy the ear versus 100 million photoreceptors in the eye. Yet the auditory system is crucial and necessary for communication and to give an emotional response whenever necessary.
Incoming sounds, in other words, air-pressure waves, are converted by the external and middle ear into fluid waves in the inner ear. A tiny bone called the stapes pushes into the cochlea creating varying pressure on the fluid inside. Vibrations in the basilar membrane of the cochlea in turn cause inner hair cells, the sensory receptors, to generate electrical signals to the auditory nerve, which ultimately transmits them to the brain. Individual hair cells are tuned to different vibration frequencies.
Researchers have found that the brain processes music both hierarchically and in a distributed manner. Within the overall auditory cortex, the primary auditory cortex, which receives inputs from the ear and lower auditory system via the thalamus, is involved in early stages of music perception, such as pitch (a tone’s frequency) and contour (the pattern of changes in pitch), which is the basis for melody. The primary auditory cortex is “retuned” by experience so that more cells become maximally responsive to important sounds and musical tones. This learning induced retuning affects further cortical processing in areas such as secondary auditory cortical field and related called auditory association regions, which are thought to process more complex music patterns of harmony, melody and rhythm, the different cues of music. Thereby making a sound a music.
