Under the Microscope: Music has a biological basis in the brain, where several regions are involved in particular aspects of processing music, such as recognising a melody, or expressing emotional reactions, writes Prof William Reville
Learning music sculpts the brain's musical capacities and musicians display hyperdevelopment of some brain music-processing structures. The current state of research on music and the brain is nicely described by Norman Weinberger in Scientific American, November 2004.
Music is ubiquitous in human societies and is as old as culture itself. Bone flutes more than 30,000 years old have been found; indeed flutes made by our Neanderthal cousins, as old as 53,000 years, have been unearthed in France and Slovenia. Appreciation of music seems to be innate in humans. Two-month-old infants turn towards pleasant consonant sounds and away from unpleasant discordant sounds. Even in-utero it has been shown that two weeks before birth the baby in the womb can differentiate between two different melodies.
Nobody knows why music was selected by evolution to be so important for us. Some think it may have assisted human survival by assisting courtship. Others think it promoted social cohesion in groups grown too large for grooming. Or, it may simply be a happy accident.
Neuroscientists carry out most of the research on how the brain processes music. Cell chemistry is the basis for life and it is now possible to image chemical activity in the living brain and to see which parts are active when music is being processed. This work shows that there is no special centre for music in the brain. Music activates several different regions in the brain, including regions involved in other kinds of cognition.
We perceive sound through our ears (bet you didn't know that!) and the information then travels along a long nervous route, ending up in the auditory cortex of the brain. The sensory cells in the ear are called inner hair cells, of which the average ear has 3,500. Musical sounds are normally complex and the hair cells sort this complexity into its constituent fundamental frequencies. This information is then passed along separately tuned fibres in the auditory nerve, eventually reaching the auditory cortex in the temporal lobe of the brain.
Different cells in the cortex respond best to certain frequencies. This functional anatomy is plastic and can be retuned as Norman M. Weinberger and colleagues demonstrated. Guinea pigs were presented with tones and the responses of various cells in the auditory cortex were noted to see which tones produced the greatest responses. Then the animals were taught that a specific non-preferred tone was important by making it a signal for a mild shock to the foot. The animals quickly learned the association. Then the cells' responses in the auditory cortex were again measured to discover that the cells' tuning preferences had shifted from their original frequencies to that of the signal tone. This learned response proved very durable, lasting for many months without additional training.
The same type of tuning shifts were later shown in humans. This may explain our ability to quickly recognise a familiar tune in a noisy environment and why people suffering memory loss in Alzheimer's can still remember music.
Professional musicians play and listen to music for several hours each day. One would expect, given the malleable learning behaviour of the brain confronted with music, that the brains of musicians would show marked modifications when compared with brains of non-musicians - and this is the case. The prolonged learning of musicians produces brain responses to music different from those of non-musicians, and musicians also show hyperdevelopment of certain areas of the brain. For example, when musicians listen to music, about 25 per cent more of their left auditory hemisphere responds than in non-musicians.
Most people report they enjoy music because it elicits feelings and emotions. I find, if I am tense, a very effective way to relax is to listen to soothing 19th-century classical music. Physiological studies have monitored heart rate, blood pressure, respiration, and so on while music played designed to express happiness, or sadness, or fear, or tension. Each type of music produced a different but consistent pattern of physiological changes in subjects. Brain imaging studies have also shown that different regions are activated when the subject is listening to pleasant consonant sounds than when listening to unpleasant dissonant chords. Brain scans of musicians who reported feelings of euphoria when listening to music showed that the music activated some of the same reward areas in the brain that are stimulated by food, sex and addictive drugs.
Ancient as human music is, music probably existed in this world long before humans arrived. Whale and human music have much in common, even though our evolutionary paths have not crossed for 60 million years. The songs of the humpback whale have been analysed by Patricia Gray of the National Academy of Sciences in the US. Humpback whales use several of the same techniques as human songwriters. They use similar rhythms, confine musical phrases to a few seconds, and create themes out of several phrases before singing the next one.
Humpback whale songs include repeating rhyming refrains. Whale songs can also be catchy. When some whales from the Indian Ocean strayed into the Pacific, singing their songs, the whales they met there changed their tunes to the new Indian Ocean songs.
William Reville is associate professor of biochemistry and director of microscopy at UCC
