» Archive for December, 2008

Music and the brain (2)

Saturday, December 20th, 2008 by Martin Hester

Oliver Sacks
Musicophilia – Tales of music and the brain.
Published by Knopf in English, and by Companhia das Letras in Portuguese.

 

Nearly a year ago I commented on some of the topics in this book by Dr. Sacks, who is a doctor specialising in neurology and psychiatry, and now also a best-selling author. The first realisation is that people have very different perceptions of music – what comes through to me is not the same as what comes through to you, even if we are hearing the same thing. In my brain, the amount allocated to processing auditory perception may be different from yours, past listening experiences may have built up different standards in my consciousness, and my hearing may be linked with my other senses and emotions in a different way. Dr. Sacks has brought together stories of patients from his own clinical practice, plus reports of colleagues, plus quotes from the literature, all to illustrate how people may react to music, how music may be present in the mind, and how it may influence behaviour. Unfortunately, this is done almost entirely as a narrative, without a summary or the drawing of conclusions. Nevertheless, some nuggets of interpretation are in there, and I have tried to draw them out.

This is probably unacceptable from the point of view of the science of medicine. Unlike the physical sciences, where you can experiment until you are confident you have an explanation for the way things work, in this area you have to rely on studying unfortunate cases of persons who through accident or illness have lost part of their normal brain functions. So the basis of experience is small, and all sorts of other factors about the person – previous training, age, environment – may influence what happens. For every tentative conclusion, some other researcher may come up with a contrary experience, or new research may shed light on it. So with due qualification, here are some interesting insights about music and the brain.

Musical hallucinations
Some people, usually those advanced in years and whose normal hearing is failing, may suddenly begin to hear music very clearly, as if someone has turned on a radio nearby. But investigation proves there is no source nearby, and nobody else can hear it! The “music” may be loud, repetitive, and often goes right back to songs heard long ago… the person may be able to control the “playing” partially, or else simply has to put up with it. There is a possible explanation for this in the understanding that the transmission of sound between the ear and the brain is in fact two-way! In normal hearing, the vibrations of the eardrum are transmitted to the cochlea – which has inside it some 3500 hair cells which turn vibrations into electrical impulses which interact with the brain. The mapping of these hair cells to the brain cortex is not fixed – it can be altered by training and use (professional musicians have a larger part of the cortex used for this function). Sound is thus transmitted to the brain, and this is the process which usually dominates. However, a part of the flow between brain and cochlea is in the reverse direction – the brain sends signals to the cochlea. Some of the hair cells are thus used for filtering the sound, and selecting what we perceive. This is why we can pick up someone speaking softly when there is a lot of background noise (particularly useful in Carioca restaurants!) and block out things like traffic noise or the hum of a refrigerator.

In the case of musical hallucinations, it seems that as deafness lessens the flow of impulses to the brain, the reverse flow becomes predominant, and starts sending stored musical memories back to the eardrum, where they play like an external source. There are some distinguished sufferers from such hallucinations – Schumann, Shostakovic and Ravel, for instance, towards the end of their lives.
 
Where is our musical experience stored?
If we regard hearing music as a complex appreciation of pitch and rhythm, then the two are processed and stored in different parts of the brain: the sense of pitch (which includes the tone scale, melody, timbre, harmony) is processed in the right hemisphere of the cortex which deals with perceptions – like sight and touch and so on. Rhythm, though, appears to be dealt with in the left hemisphere and in many other parts of the brain too, including some which control very basic body processes. The left hemisphere deals with logical thinking and language, and tends to become dominant over the right. (These are generalisations which work for the majority of people).

There are some interesting cases when the left hemisphere is damaged or doesn’t develop normally in childhood. Such people, seriously deficient in “normal” abilities, may develop a prodigious capacity to perceive and remember music – qualities of a savant. A musical environment is essential to this development, otherwise the interruption of the learning and dominance of the left hemisphere just stays as a deficiency.

There is evidence too for the re-allocation of functions of the right hemisphere when one of the senses is inhibited in childhood – the case of blind musicians. Blind children may have the third of the cortex normally used for vision re-mapped to other senses, such as audition and touch. Viz Stevie Wonder, Ray Charles…..

Rhythm and Coordination
It seems that human beings are unique among species in having an intimate link in the brain between the hearing and motor systems. We can beat in time to something with a pulse – but other animals can’t follow someone else’s rhythm. (Apparently coyotes and bottlenose dolphins, no less, have the beginnings of this ability). But for us, it’s very important. Every culture has a form of music with a regular rhythm, a pulse, which permits coordination between participants and evokes a feeling of belonging to a group. We can absorb rhythmic patterns and establish internal norms with great precision and stability. (Interestingly enough, what rhythms we are exposed to when young seems to set our preferences and even abilities for life). Music can join people in a social activity forged by their common reaction to rhythm, and common emotions may follow. This may favour cooperation and a sense of group identity….. pop concert anyone? And watch out for Obama’s use of rhythmic speech patterns!
 
Musical therapies
Music becomes so deep-seated in our mind that it may provide a lasting link to normality even when disease impedes the functioning of some parts of the brain. Sufferers from Alzheimer’s disease progressively lose memory, speech, and the ability to manage themselves. However, the response to music is preserved, even in advanced cases…. the person may be able to perform music, reproducing the past, while the act of listening to music re-awakens the perceptions, in an effect which may last for some hours. For such people music is not a luxury, as we so often treat it – to those lost in dementia it can bring them back to themselves and to others, at least for a time.

So….. be aware of what music can do to you and for you  – and Good Listening!