Music in my head
Before modern methods of neuroimaging were developed, researchers studied the musical abilities of the brain, observing patients (including famous composers) with various disorders of its activity due to trauma or stroke. So, in 1933, the French composer Maurice Ravel had symptoms of local cerebral degeneration – a disease accompanied by atrophy of certain parts of the brain tissue. The composer’s mental abilities were not affected: he remembered his old works and played scales well. But he could not compose music. Speaking about his alleged opera Joan of Arc, Ravel admitted: “The opera is in my head, I hear it, but I never write. It’s over. I’m not able to compose music anymore.” He died four years after a failed neurosurgical operation. The history of his illness gave rise among scientists the idea that the brain is deprived of a specialized music center.
The hypothesis was confirmed by the case of another famous musician. After a stroke suffered in 1953, the Russian composer Vissarion Shebalin was paralyzed and ceased to understand speech, but until his death, which followed 10 years later, he retained the ability to compose. Thus, the assumption of independent processing of musical and speech information turned out to be true. However, more recent studies have made corrections related to two common features of music and language: both mental functions are a means of communication and have a syntax – a set of rules that determine the proper combination of elements (notes and words, respectively). According to Aniruddh Patel of the Institute of Neurobiology in San Diego, studies using neuroimaging techniques indicate that the frontal (frontal) cortex provides the correct construction of linguistic and musical syntaxes, and other parts of the brain are responsible for processing related components of language and music.
We also got a complete picture of how the brain responds to music. The auditory system, like all other sensory systems of the body, has a hierarchical organization. It consists of a chain of centers that process nerve signals sent from the ear to the higher section of the auditory analyzer – the auditory cortex. Processing of sounds (for example, musical tones) begins in the inner ear (cochlea), sorting complex sounds (made, for example, by a violin) into component elementary frequencies. Then, through the fibers of the auditory nerve, tuned to a different frequency, the cochlea sends information in the form of a sequence of neural discharges (pulses) to the brain. As a result, they reach the auditory cortex in the temporal lobes of the brain, where each cell responds to sounds of a certain frequency. The frequency tuning curves of neighboring cells overlap, i.e. there are no gaps between them, and a frequency map of sounds is formed on the surface of the auditory cortex.
The brain’s response to music is much more complicated. Music consists of a sequence of notes, and its perception depends on the brain’s ability to capture the relationship between sounds. Many of its areas are involved in the processing of various components of music. Take, for example, a tone that includes both frequency components and sound volume. At one time, researchers believed that cells tuned to a specific frequency, “hearing” it, always react the same way.
But in the late 1980s. Thomas M. McKenna and the author of this article questioned this view. In those years, we studied the reactions of the brain to sound circuits – complexes of sounds of increasing or decreasing pitch, which form the basis of any melody. We constructed melodies consisting of different contours using five identical tones, and then recorded the reactions of single neurons of the auditory cortex of a cat. It was found that the reactions of the cells (the number of discharges) depended on the position of the given tone in the melody: neurons could discharge more intensively if the tone was preceded by other tones than when it was the first in the melody. In addition, the cells reacted differently to the same tone, depending on whether it was part of an upward contour (in which the pitch of the sounds increased) or downward. This indicates the great importance of the pattern of the melody: the processing of information in the auditory system is significantly different from the simple relay of sounds in the phone or stereo.
Brain responses to music also depend on the listener’s experience and preparedness. They can change even under the influence of short-term training. So, for example, even 10 years ago, scientists believed that each cell of the auditory cortex was once and for all tuned to certain characteristics of sound. However, it turned out that the tuning of the cells can change: some neurons become hypersensitive to sounds that attract the attention of animals and are stored in their memory.