September 23, 2011
After a left-sided stroke, many individuals suffer from serious speech disorders but are often able to sing complete texts relatively fluently. Researchers have now demonstrated that it is not singing itself that is the key. Instead, rhythm may be crucial.
Researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, have now demonstrated that it is not singing itself that is the key. Instead, rhythm may be crucial. Moreover, highly familiar song lyrics and formulaic phrases were found to have a strong impact on articulation -- regardless of whether they were sung or spoken. The results may lead the way to new rehabilitative therapies for speech disorders.
When a stroke damages speech areas in the brain's left hemisphere, sufferers often have severe difficulties speaking -- a condition known as non-fluent aphasia. Sometimes the inability to speak spontaneously is permanent. However, there are frequent cases of aphasics who are able to sing song lyrics and formulaic phrases relatively fluently. Until now, this astonishing observation has been explained by the fact that the right brain hemisphere, which supports important functions of singing, remains intact. Singing was thought to stimulate areas in the right hemisphere, which would then assume the function for damaged left speech areas. A treatment method known as Melodic Intonation Therapy is based on this idea.
Recent research has shown that changes indeed occur in the right brain hemisphere of patients after singing formulaic phrases like 'How are you?' over a period of months. "But this alone is not sufficient evidence that singing is an effective treatment for aphasics," says Benjamin Stahl, researcher at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig. "The formulaic phrases could just as easily be the cause, as similar areas of the right brain hemisphere are activated when such texts are produced." Moreover, one should not jump to conclusions, Stahl says: "Changes in the right brain hemisphere are not necessarily the cause of improvement in a patient's articulation."