Sunday, October 16, 2011

From singing to speaking: facilitating recovery from nonfluent aphasia.


Reference:

Schlaug, Gottfried, Andrea Norton, Sarah Marchina, Lauryn Zipse, and Catherine Y Wan. "From singing to speaking: facilitating recovery from nonfluent aphasia." Future Neurology Sep. 2010; 5(5): 657-665.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2982746/?tool=pubmed


Summary:

Aphasia is an impairment of language ability that ranges from having difficulty remembering words to being completely unable to speak, read, or write. This disorder usually develops quickly as a result of head injury or stroke, but can develop slowly from a brain tumor, infection, or dementia. Of the estimated 750,000–800,000 new stroke cases occurring in the USA each year, approximately 25–50% present with some form of aphasia. Nonfluent aphasia is caused by damage to or developmental issues in anterior regions of the brain, including the left posterior inferior frontal gyrus known as Broca’s area.


Recovery from aphasia can happen in two ways using a recruitment process, which is an increase in the response to a stimulus owing to the activation of additional receptors, resulting from the continuous application of the stimulus with the same intensity. The first type of recovery consists of the recruitment of perilesional brain regions in the affected hemisphere, with variable recruitment of right-hemispheric regions if the lesion is small. The second type of recovery consists of the recruitment of homologous language and speech-motor regions in the unaffected hemisphere if the lesion of the affected hemisphere is extensive. Patients with large left-hemispheric lesions that result in severe nonfluent aphasia typically do not show a good natural recovery nor do they appear to be as responsive to traditional speech therapy methods as patients with smaller lesions or other types of aphasia.


Melodic intonation therapy (MIT) is an intonation-based treatment method for nonfluent or dysfluent aphasic patients that was developed in response to the observation that severely aphasic patients can often produce well-articulated, linguistically accurate words while singing, but not during speech. The intonation works by translating prosodic speech patterns (spoken phrases) into melodically intoned patterns using just two pitches. The higher pitch represents the syllables that would naturally be stressed (accented) during speech. Compared with nonintonation-based speech therapies, MIT contains two unique components: the melodic intonation (singing), with its inherent continuous voicing, and the rhythmic tapping of each syllable (using the patient’s left hand) while phrases are intoned and repeated.


In one of their previous studies, the authors compared two patients with similar speech output impairments and similar lesion sizes. One was subjected to MIT and the other to a control intervention termed ‘speech repetition therapy’. Both interventions yielded significant improvements in propositional speech that generalized to nonpracticed words and phrases, but the MIT-treated patient gains surpassed those of the control-treated patients. Since MIT incorporates both the melodic and rhythmic aspects of music, it may be unique in its potential for engaging not only auditory–motor regions on the right but also nonlesional regions in the affected left hemisphere. The following image shows diffusion tensor imaging scans of a patient before and after an intense course of melodic intonation therapy.


There is a visible increase in the size (number of fibers and volume of tract) of the right arcuate fasciculus after therapy (B).


Research has shown that both components of MIT are capable of engaging fronto–temporal regions in the right hemisphere, thereby making it particularly well suited for patients with large left hemisphere lesions who also suffer from nonfluent aphasia. Treatment-associated neural changes in patients undergoing MIT indicate that the unique engagement of right-hemispheric structures (e.g., the superior temporal lobe, primary sensorimotor, premotor and inferior frontal gyrus regions) and changes in the connections across these brain regions may be responsible for its therapeutic effect. However, despite several small case series, the efficacy of MIT has not been substantiated and its neural correlates remain largely unexplored. Research


Reflections:

The research conducted by Gottfried Schlaug & al. explores new approaches to traditional therapy for patients with nonfluent aphasia. It is encouraging to discover that melodic intonation therapy engages the right fronto–temporal network through two unique components: melodic intonation and left-hand tapping. This leads to improvement in spontaneous language skills, therefore increasing the recovery rate of patients. Although approximately 1,000,000 people in the USA suffer from aphasia, reliable and standard treatment methods have not been established for this disorder. More case studies have to be conducted on the efficacy of MIT, as well as understanding the specific differences within the brain between singing and speaking, in order to implement this therapy as a standard treatment process.


As a voice performer, I always find that it is much easier and faster to learn the poetry of a song by singing it and taping the rhythm at the same time. I often tap the rhythm by clapping the hands, using conducting gestures, or even dance if it is a dance rhythm. It seems that the more body parts you have working in synchronism, the faster the brain memorizes the musical patterns. When reading this article, I was not surprise to learn that MIT was proven to be a more effective therapy for patients with nonfluent aphasia, as opposed to simple speech therapy. If a patient has a lesion in the speech area of the brain, it will be difficult to stimulate that area with speech, since it is this specific area of the brain that has been affected. By contrast, singing stimulates more areas of the brain, therefore implicating regions of the brain that do not have lesions. This seems to be the reason why the recovery process is more effective when singing for patients with nonfluent aphasia.

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