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| The Sound of Science |
| Tuesday, 04 October 2005 | |
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Owain Vaughan and Neta Spiro explore the biological and cultural phenomenon that is music Music. Emotional, ineffable; an enigmatic and ethereal art form. Such descriptions are commonplace, and whilst there have been some attempts in the past to uncover the scientific basis of music, these have been limited and in some cases led only to exasperation and resignation. Take, for example, Claude Lévi-Strauss, who tried to describe the influence of music on human nature, including how we perceive musical time and its effects on the internal organs. Eventually he gave in, concluding that “music will remain the supreme mystery of human sciences”. But the mystery is slowly being unravelled as science meets music head on.
Humans have the ability to perceive effortlessly the patterns of acoustic energy that we know as sound. After travelling through the outer and middle ear, sounds arrive at the inner ear (the cochlea) where they are sorted into their constituent elementary frequencies.This information is then transmitted from the cochlea as a string of neural discharges along individual fibres of the auditory nerve, finally arriving at the auditory cortex in the temporal lobe of the brain. But this is only half the story. When it comes to listening to music, not only do numerous regions of the brain become involved in processing its various perceptual elements (such as melody, rhythm and harmony), but the very construction of the ear has an important influence on the details of this procedure. Researchers in the field of psychoacoustics, for example, have demonstrated that the physiology of the ear has a direct effect on our perception of sounds as either pleasant or unpleasant (consonant or dissonant). Situated in the cochlea of the inner ear is the basilar membrane. This membrane has groups of sensory receptors, composed of hair cells running along its length, that become activated in response to sounds of specific frequencies. If the positions of excitation on the basilar membrane are too close, interference occurs, resulting in an unpleasant sensation for the listener. When it comes to deciphering the role of the brain, our understanding has recently begun to flourish with the use of brain-imaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Blood flow increases to those regions of the brain activated by particular cognitive tasks, and PET and fMRI techniques are able to pinpoint these activated regions by measuring certain properties of the blood. Imaging studies of healthy individuals, together with evidence taken from patients with brain damage, have shown that there is no specialized ‘music centre’ in the brain. Instead, many areas distributed throughout the brain contribute to the processing of music, including those functioning in other kinds of cognition. Scientists are gradually mapping these areas in greater detail. For example, the right temporal lobe of the auditory cortex is involved in perceiving aspects of melody, harmony and timbre. Different regions within the auditory cortex also process various features of rhythm. A more precise understanding of certain brain structures has also been attained. Recent work at the John Hopkins University in Baltimore, Maryland, has revealed the existence of pitch-sensitive neurons. The pitch of a sound depends on its fundamental frequency, even when this frequency is physically missing from a complex sound. Individual cells have been found in the auditory cortex of marmoset monkeys that consistently responded in a similar way to various sounds that, although having no common frequency, shared the same fundamental frequency. For example, a neuron that responds to 200 Hertz also responds to the mixture of 800, 1000 and 1,200 Hertz because all have the same fundamental frequency. The location of these pitch-sensitive cells is consistent with the location of pitch-selective areas identified in human brain scans. The response of the brain, however, is variable and depends on factors such as personal experience or musical training. Studies have shown, for example, that the volume of the auditory cortex in musicians is 130 percent larger than that in non-musicians. Music is, of course, more than a catalogue of auditory aspects.The emotional response that music evokes is key to the listening experience, and the areas of the brain responsible are partially segregated from those that deal with the auditory processing of music. Though research into this area is still in its infancy, PET imaging studies carried out on volunteers listening to consonant or dissonant patterns of notes have revealed that at least two systems, each dealing with a separate type of emotion, are involved. Furthermore, it has been shown that when music induced a pleasurable response it activated the same brain structures as those stirred by food, sex, and drugs. A comprehensive explanation of our musical experiences cannot, however, be achieved through studies of the ear and brain alone. To venture towards a more complete understanding, the science of sound is being placed in a broader context, both theoretically and experimentally. Research by Dr Ian Cross and other members of the Cambridge CMS emphasizes music as a biological and cultural phenomenon, studying such issues as the origins of music, the abilities that predispose humans to music, and the reasons for its existence. Consider, for example, the following three aspects of music, hitherto largely neglected. The first is that music is an embodied action, inextricably bound to the movement of our bodies. The notion of sitting in a concert hall and simply listening to music is unique to Western classical music: most music involves some kind of movement or dance. Indeed many cultures do not distinguish between music and movement and have the same word for both. The Igbo of Nigeria, for example, use the word nkwa to denote “singing, playing instruments and dancing”. Secondly, the fact that music is embodied may provide the basis and explanation for music’s capacity for entrainment, the process that allows us to act together in time. This is reflected in our ability, rare in the animal kingdom, to tap along to a beat.Thirdly, that music is embedded in social actions, playing an integral part in occasions like weddings, funerals, and parties.This provides yet another way in which music can be imbued with meaning, although the meaning may vary from person to person. Combined with the idea of entrainment, this social aspect of music allows it to create feelings of togetherness and of shared experience that most forms of language are unable to achieve. A comprehensive explanation of our musical experiences cannot, however, be achieved through studies of the ear and brain alone. To venture towards a more complete understanding, the science of sound is being placed in a broader context, both theoretically and experimentally. Research by Dr Ian Cross and other members of the Cambridge CMS emphasizes music as a biological and cultural phenomenon, studying such issues as the origins of music, the abilities that predispose humans to music, and the reasons for its existence. Consider, for example, the following three aspects of music, hitherto largely neglected. The first is that music is an embodied action, inextricably bound to the movement of our bodies. The notion of sitting in a concert hall and simply listening to music is unique to Western classical music: most music involves some kind of movement or dance. Indeed many cultures do not distinguish between music and movement and have the same word for both. The Igbo of Nigeria, for example, use the word These ideas contribute to the intriguing suggestion that music - with the capabilities it requires, the positive effects it has on social cohesion, and the power it holds over our emotions - may have played a key role in the evolution of the human mind. These fresh angles, and the questions that they evoke, are thus encouraging new ways to investigate the subject. Music and science started out using physics, psychophysics, psychology, artificial intelligence, and neuroscience. But things move quickly. Recognition of the wide-ranging impact of music, and our experience of it has led to additional fields such as biology, archaeology and sociology entering the score.The overture has ended; the opera is about to begin. Owain Vaughan is a PhD student in the Department of Chemistry; Neta Spiro is a PhD student at the Institute for Logic, Language and Computation, University of Amsterdam and the Centre for Music and Science, Faculty of Music, University of Cambridge. |
The field of science and music draws on aspects of both disciplines, including music analysis, experimental psychology and neuroscience, in a quest that leads from decoding the ways in which we process music to fundamental questions about its origins and purpose. One of the few centres specialising in this amalgamation is the Centre for Music and Science (CMS), directed by Dr Ian Cross, here in Cambridge. News Archives
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