Monday, October 27, 2014

The Role of Singing in Language Recovery

In 1997, Jourdain wrote: “Basically the right brain bears areas similar to the language structures of the left. Yet the right brain is mute. Some call it ‘the silent hemisphere’” (p. 274). Much has transpired in neuroscience research since Jourdain wrote these words. Is the right brain really “the silent hemisphere”? What does current research tell us about the role of the right brain and music, specifically singing, in language recovery following an acquired brain injury?

According to Wan, Ruber, Hohmann, & Schlaug (2010), both singing and instrumental playing are multimodal activities involving integration of auditory and sensorimotor networks. It appears that music is processed by means of a bihemispheric network, including frontal, temporal and parietal lobes, as well as the premotor cortex. In addition, motions and emotions evoked through music listening and playing, experienced as pleasurable and rewarding activities, promote changes in the amygdala, ventral striatum, and other parts of the limbic system (Schlaug, Altenmuller, & Thaut, 2010).

Though singing ability may be enhanced by formal training, the ability to sing appears to be a natural proclivity, appearing first during infancy, and manifested in early years through singing of children’s songs. Researchers are now examining this natural ability to find out how the use of singing may help address speech/motor abnormalities associated with neurological conditions. For over 100 years it has been reported that persons diagnosed with nonfluent, Broca’s aphasia are capable of singing lyrics even though they are no longer able to speak. This observation has led to the development of the neurologically based music therapy technique of Melodic Intonation Therapy (MIT) (Schlaug, Norton, & Wan, 2010b). The success of MIT appears to be in part attributable to engagement of the right hemisphere through its melodic element (Schlaug, Marchina, & Norton, 2008).

The bihemispheric organization of music processing and production may help explain why persons with left hemispheric lesions can sing song lyrics even though they cannot articulate the words. Two possible routes to language production have been postulated, one through the language-based route of the left hemisphere, the other through a melodically intoned route processed either through the right or through both hemispheres (Ozdemir, Norton, & Schlaug, 2006). Though under normal physiological conditions there is greater left lateralization of speech, research using Transcranial Magnetic Stimulation (TMS) has found that when applied in an inhibitory mode to the left inferior frontal cortex of normal right-handed individuals, TMS causes speech interference. The same stimulation applied to the right, homologous region does not cause interference with either speech or singing (Epstein et al., 1999; Stewart et al., 2001, as cited in Ozdemir et al., 2006).

While the majority of sensorimotor processes for singing and speech are shared, singing appears to activate a larger network, according to research by Ozdemir et al., involving regions including the superior temporal gyrus, particularly in the right hemisphere, the inferior central operculum and inferior frontal gyrus. The greater bihemispheric utilization of singing may explain why speaking is more affected by unilateral left frontal lesions than singing. When more global processing than local is required (melodic contour, musical phrasing, and/or meter), there is greater activation of right hemispheric regions than of left; persons with right hemisphere lesions experience greater difficulty with global processing requirements of melody and contour (Schlaug et al. 2008).

For persons diagnosed with nonfluent aphasia, there are two possible routes to recovery. Those with smaller lesions tend to have greater activation of peri-lesional cortex regions of the left-hemisphere, with variable activation of the right-hemisphere. Those with larger left- hemisphere lesions tend to have greater activation of homologous language-capable regions in the right-hemisphere (2008). Research has shown music making to be a stimulant for neuroplastic changes, in the brains of adults as well as of children, involving both white and gray matter (Schlaug, Altenmuller & Thaut, 2010a). Therefore engaging in music making, in particular singing, may help to facilitate the establishment of alternative pathways and connections in the brain that circumvent dysfunctional regions affected by focal lesions (Wan et al, 2010). The arcuate fasciculus (AF), a fiber tract connecting auditory and motor regions, is one structure that appears to undergo neuroplastic change following intensive MIT therapy. Diffusion Tensor Imaging (DTI) has revealed both an increase in fiber volume and length following 75 sessions of MIT. Clients with neuroplastic changes demonstrated concomitant improvements in speech outcome measures, while also showing an ability to engage in spontaneous conversation (Schlaug et al., 2010b).

How is it that MIT is able to effect such notable changes beyond the limitations of natural recovery, or rehabilitation through non-intonation based speech therapies? The two unique components of MIT are melodic intonation and left-hand tapping. The right hemisphere, in particular the right temporal lobe, is engaged through the melodic element, in contrast to therapies that do not use pitch or melody. While left-hemispheric speech production occurs at faster rates, the emphasis of melody and prosodic features of MIT leads to a reduction of vocalization rate, with lengthening of syllables and chunking of longer units (Schlaug et al. 2009). Continuous voicing, decreased production rate, and increased emphasis on and awareness of individual phonemes is facilitated through the right hemisphere, ameliorating speech-motor difficulties, and reducing reliance on the left-hemisphere through a more modulated, time- defined stimulus (Wan et al., 2010). Concurrent left hand tapping helps prime the right hemispheric sensorimotor network for articulation, and acts as a pacemaker for auditory-motor coupling (Schlaug et al., 2009). As it engages both melodic and rhythmic elements of music, MIT has the potential to not only engage right auditory-motor regions, but also nonlesional regions situated in the left-hemisphere.

I first became aware of the potential of singing in facilitating language recovery when making music with a family member who had suffered a stroke. This family member could recall and sing lyrics to songs, yet was unable to speak. Due to the presence of comorbid conditions, the family member could not benefit from MIT, yet introducing singing activities contributed greatly towards enhancing quality of life, with music time a highlight of each day. I have since encountered a number of patients, in particular those with various kinds of dementia, who have retained the ability to sing while unable to articulate words. Clearly the homologous language regions in the right hemisphere have been unaffected by these neurodegenerative diseases; engaging in singing brings joy into their lives, provides means for communication, and improves quality of life. Yet for patients who fit the profile of candidates for MIT - those having good auditory comprehension, ability to self-correct, limited verbal output, functional attention span, and emotional stability - (Helm-Estabrrooks and Albert, as cited in Thaut M., Thaut C., and McIntosh 2014), MIT holds considerable promise as a means for facilitating restoration of functional language ability beyond music making. The story of Alison Wojiwada’s recovery from an aneurysm (Ireton, 2014), resulting in dysfunctional vocal output, through MIT facilitated by music therapist Cheryl Jones is testament to the effectiveness of this melodic based intervention, when administered by a skilled therapist to a client who is clearly able to benefit. The full potential of singing as a therapeutic tool in language recovery for persons with nonfluent aphasia is only beginning to be realized.

Ireton, J. (2014, Sep 24). Music unlocks teacher’s voice in brain aneurysm recovery. CBC News. Retrieved from voice-in-brain-aneurysm-recovery-1.2774330
Jourdain, R. (1997). Music, the brain, and ecstasy. New York, NY: William Morrow and Co, Inc. Ozdemir, E., Norton, A. & Schlaug, G. (2006). Shared and distinct neural correlates of singing
and speaking. Neuroimage, 33, 628-635.
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.
Schlaug, G., Marchina, S., & Norton, A. (2009). Evidence for plasticity in white matter tracts of chronic aphasic patients undergoing intense intonation-based speech therapy. Annals of New York Academy of Science, 1169, 385-394.
Schlaug, G., Altenmuller, E., & Thaut, M. (2010a). Music listening and music making in the treatment of neurological disorders and impairments. Music Perception, 27(4), 249-250.
Schlaug, G., Norton, A., & Wan, C.(2010b). From singing to speaking: facilitatin recovery from nonfluent aphasia.Future Neurology, 5(5), 657-685.
Thaut, M., Thaut, C., & McIntosh, K. (2014). Melodic Intonation Therapy (MIT). In Thaut, M. & Hoemberg, V. (Eds.), Handbook of neurologic music therapy (pp. 140-145). Oxford, UK: Oxford University Press.
Wan, C. Y., Ruber, T., Hohmann, A., & Schlaug, G. (2010). The therapeutic effects of singing in neurological disorders. Music Perception, 27(4), 287-295. 

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