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ume and lower fractional anisotrophy values in the left arcu- ate fasciculus relative to other (instrumental) musicians, sug- gesting that experience-dependent plasticity is at work in shaping both neural structure and function of singers, espe- cially in the auditory-motor networks of the brain. Singing affects a network that is robust above and beyond the effects of other types of musical training. This “singing-related” net- work, possibly resulting from the long-term engagement of the vocal apparatus, may also be tied to nonmusical vocal functions such as speech. (see Fig. 3)
Study of tone-deafness has implications for the rehabilitation of speech disorders
As presented above, the network of brain regions that is deficient in tone-deaf individuals and hyper-developed in singers includes the superior temporal lobe (superior tempo- ral gyrus and middle temporal gyrus) and the inferior frontal lobe (inferior frontal gyrus). This network is not only involved in pitch production, but also plays a crucial role in speech and language processing. Indeed, numerous studies have shown that there are overlapping responses to music and language stimuli in the brain. For example, fMRI studies have reported activation of Broca’s area during music percep- tion tasks (e.g., Koelsch et al., 2002; Tillmann et al., 2003), during active music tasks such as singing (e.g., Ozdemir et al., 2006), and even when participants imagined playing an instrument (e.g., Meister et al., 2004; Baumann et al., 2007). Moreover, a common network appears to support the sen- sori-motor components for both speaking and singing (e.g., Pulvermuller, 2005; Ozdemir et al., 2006; Kleber et al., 2009). Given the shared neural correlates between music and lan- guage, as well as our understanding of the mechanisms underlying the deficits of tone-deaf individuals, researchers have begun to evaluate the potential utility of music-based interventions in the treatment of neurological disorders. This field of research is motivated by a large body of research demonstrating that engaging in musical activities has dra- matic effects on plasticity in the developing brain as well as in
the mature brain (Fujioka et al., 2006; Lahav et al., 2007; Hyde et al., 2009). Music-based interventions have the poten- tial to facilitate this recovery process of the injured brain as well as the development of language in children with devel- opmental disorders. We provide below, two examples of such an application: one in stroke patients with aphasia, and another in nonverbal children with autism.
Music-based intervention in the treatment of aphasia
Aphasia is a common complication of stroke that results in the loss of ability to produce and/or comprehend language. The nature and severity of language dysfunction depends on the location and extent of the brain lesion. Patients who are non-fluent usually have a lesion in the left frontal lobe involving, among others, the left posterior inferior frontal region (Broca’s area). These non-fluent patients often have the ability to comprehend the speech of others, but they also have impairments in the production of words or proposi- tional speech. The consensus is that there are two routes to recovery from a stroke-induced aphasia. In patients with small lesions in the left hemisphere, there tends to be recruit- ment of both left-hemispheric, perilesional cortex with vari- able involvement of right-hemispheric homologous regions during the recovery process. In patients with large left-hemi- spheric lesions involving language-related regions of the fronto-temporal lobes, the only path to recovery may be through recruitment of homologous language and speech- motor regions in the right hemisphere (Schlaug et al., 2010). For patients with large lesions that cover the language-rele- vant regions on the left, therapies that specifically engage or stimulate the homologous right-hemispheric regions have the potential to facilitate the language recovery process beyond the limitations of natural recovery. Melodic Intonation Therapy (MIT) is one music-based intervention that might be predestined in that approach—it may improve speech production and brain changes in patients with large left hemisphere lesions that result in severe non-fluent apha- sia. MIT is an intensive intervention that involves practicing
Fig. 3. Tractography results from averaged groups of a) 10 singers and b) 10 control musicians, showing the arcuate fasciculus. Pink and olive green are tracts identified in the left hemisphere, whereas red and green are tracts identified in the right hemisphere.
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