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26-09-2011 | Physical rehabilitation | Article

Rhythm, not singing per se, key to aphasia recovery after stroke


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MedWire News: Use of rhythmic phrases, whether or not they are sung, may help stroke patients to recover from non-fluent aphasia, suggest study findings.

"The question of whether singing may be helpful for stroke patients with non-fluent aphasia has been debated for many years," say Benjamin Stahl (Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany) and colleagues.

Previous research suggested that singing might stimulate the right hemisphere of the brain, which would then compensate for the damaged areas of the left hemisphere associated with speech.

Recent evidence has shown right hemisphere activation in these patients after repeated singing of phrases such as "How are you?" However, "this alone is not sufficient evidence that singing is an effective treatment for aphasics," said Stahl.

"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," he said.

Also, "changes in the right brain hemisphere are not necessarily the cause of improvement in a patient's articulation," he added.

To assess whether singing alone or individual elements such as melody and rhythm may be responsible for the observed improvements in speech, Stahl and co-workers recruited 17 German, non-fluent aphasic patients aged 56 years on average to take part in their study.

Melodic intoning, rhythmic speech, and spoken arrhythmic control phrases were spoken or sung by the participants after hearing a prerecorded voice and to a 4/4 percussion beat. The arrhythmic phrases were accompanied by a 3/4 beat that was shifted by an eighth note. The texts were linguistically similar, but differed in familiarity and in how formulaic they were.

The results showed that, contrary to previous suggestions, speaking or singing rhythmically rather than singing per se may help improve speech fluency in patients with non-fluent aphasia following stroke. By contrast, melodic intoning did not significantly influence speech fluency.

"The key element in our patients was, in fact, not the melody but the rhythm," said Stahl.

The improvement in speech seen when patients repeated rhythmic phrases was particularly noticeable in those with basal ganglia lesions (n=14), notes the team, and more than 50% of the variation in response to rhythmicity could be accounted for by the presence or absence of basal ganglia lesions.

Writing in the journal Brain, Stahl and co-investigators comment: "Our findings therefore suggest that benefits typically attributed to melodic intoning in the past could actually have their roots in rhythm."

The degree of familiarity with the phrase also influenced how easy the patients found it to say, with more formulaic phrases being reproduced more easily by patients, say the researchers.

"Our data indicate that lyric production in non-fluent aphasics may be strongly mediated by long-term memory and motor automaticity, irrespective of whether lyrics are sung or spoken," they conclude.

By Helen Albert

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