What is the secret of the mesmerizing power of music?
Music surrounds us everywhere. At the sounds of a powerful orchestral crescendo, tears come to my eyes and goose bumps run down my back. Musical accompaniment enhances the artistic expression of films and performances. Rock musicians make us jump to our feet and dance, and our parents lull babies with quiet lullabies.
The love of music has deep roots: people compose and listen to it since the inception of culture. More than 30 thousand years ago, our ancestors already played stone flutes and bone harps. It seems that this hobby has an innate nature. Babies turn to the source of pleasant sounds (consonances) and turn away from unpleasant (dissonances). And when we feel awe with the final sounds of the symphony, the same centers of pleasure are activated in the brain as during a delicious meal, having sex or taking drugs.
Why is music so significant for a person and has such power over him? Neurobiologists have no final answers yet. However, in recent years, some data began to appear on where and how the processing of musical information occurs. The study of patients with traumatic brain injuries and the study of healthy people with modern methods of neuroimaging led scientists to an unexpected conclusion: there is no specialized music center in the human brain. Its processing involves numerous areas dispersed throughout the brain, including those that are usually involved in other forms of cognitive activity. The sizes of the active zones vary depending on the individual experience and musical preparation of the person. Our ear has the smallest number of sensory cells in comparison with other sensory organs: in the inner ear there are only 3.5 thousand hair cells, and in the eye – 100 million photoreceptors. But our mental reactions to music are incredibly flexible, because even short-term training can change the nature of brain processing of “musical inputs.”
In the 1990s Jon S. Bakin, Jean-Marc Edeline, and I conducted an experiment in which I tried to find out if the animal’s basic organization of the auditory cortex changes when it begins to realize that there is a certain tone for important to him. Initially, we offered guinea pigs a wide variety of tones and recorded the responses of neurons to determine which of them caused the maximum cell responses. Then we trained the animals to perceive a certain tone as a signal preceding the painful irritation of the paws with a weak electric current. A conditioned reflex was developed in guinea pigs after a few minutes. After that, we again determined the strength of neural responses immediately after training and some time (up to two months) later. It was found that the tuning of neurons changed, shifting to the frequency range of the signal tone. Thus, we found that learning causes a brain reconfiguration, which results in an increase in the number of neurons that respond with maximum responses to behaviorally significant sounds. The process covers the entire auditory cortex, changing the frequency map so that more extensive sections of it are involved in processing information about significant sounds. In order to determine which sound frequencies are of particular importance to an animal, it is enough to study the frequency organization of its auditory cortex.
In 1988, Ray Dolan of London University College conducted a similar study with people: they were trained to give special significance to one of the presented tones. It was found that this causes the subjects the exact same shift in the frequency tuning of neurons as in animals. The long-term effects of learning through neural reconfiguration help, for example, to explain why we recognize a familiar melody in a noisy room so quickly and why people suffering from memory loss due to Alzheimer’s disease and other neurodegenerative diseases are able to recall the music they remembered in the distant past.