Tuesday, October 21, 2014

From singing to speaking: Why singing may lead to recovery of expressive language function in patients with Broca’s aphasia

Schlaug, G., Marchina, S., & Norton, A. (2008). From singing to speaking: Why singing may lead to recovery of expressive language function in patients with Broca’s aphasia. Music Perception, 25 (4), 315-323.


The authors used two patients with similar impairments and stroke size/location to contrast the behavioural and neural treatment effects of Melodic Intonation Therapy (MIT) with a control intervention using Speech Repetition Therapy (SRT). Both patients had nonfluent aphasia, resulting from lesions in the frontal lobe, including Broca’s region in the left frontal lobe, and were randomly assigned to treatment type. Most patients with Broca’s aphasia are treated by speech therapists in the subacute and chronic phases, using interventions to help recover language and facilitate communication. Routes to recovery involve recruiting either undamaged portions of the left-hemisphere language network, homologous language-capable regions in the right hemisphere, or both. MIT is a structured intervention capable of engaging both hemispheres, with its use of intoned patterns that exaggerate normal melodic speech content at three levels of difficulty, while simultaneously tapping each syllable with the left hand to prime the sensorimotor and premotor cortices for articulation.

The between-treatments comparison of the two patients showed that the patient treated with MIT had greater improvement on all outcomes than the patient treated with SRT. The unique contribution of MIT therapy is through the sustained vocalization of melodic intonation as well as the tapping with the left hand. Facilitating effects of MIT may be due to reduction of speed, syllable lengthening, syllable chunking, and hand tapping. Perception of musical components, such as melodic contour and/or meter, require more global than local processing; greater right-hemispheric brain region activation has been shown in tasks involving global processing. (The patient treated with MIT had significant changes in a right-hemisphere network, as revealed through an fMRI, involving premotor, inferior frontal, and temporal lobes.) Furthermore, rhythmic tapping may engage a right-hemispheric sensorimotor network that coordinates hand as well as orofacial and articulatory movements. Left hand tapping may also facilitate production of speech through rhythmic entrainment, anticipation, and auditory-motor coupling.


I first became interested in the effects of music on the brain when observing a family member, diagnosed with dementia and stroke, recalling and singing lyrics to songs that hadn’t been sung in decades, even though the family member hadn’t been able to speak for some time. How was this possible, both from a memory and language production standpoint? I was mystified by this discovery, which I have since learned has been documented on numerous occasions. Apparently MIT was developed based on a similar observation. In this study, both patients were a year post stroke onset, yet significant changes in the brain were revealed through neuroimaging following MIT. It shows the potential of the brain for neurorehabilitation, even after a significant amount of time has lapsed. Some of the interventions, such as tapping each syllable on a person’s left hand, are so easy to administer, yet can have such far reaching consequences,  given links between sensorimotor network, articulatory movements, and linguistic expression. I realize there are strict patient selection criteria for the use of MIT - it is not a suitable protocol for every patient with aphasia; however, there is still significant potential for its use in facilitating language recovery in patients who fit the criteria, a potential which has yet to be realized in our medical system.

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