Melodic intonation therapy
Melodic Intonation Therapy (MIT) is a therapeutic process used by music therapists and speech-language pathologists to help patients with communication disorders caused by damage to the left hemisphere of the brain. This method uses a style of singing that is supposed to stimulate the intact right hemisphere to facilitate speech and language recovery in the damaged portion of the left hemisphere. However, according to recent research, it may not be singing that is the crucial element in MIT, but rhythmic pacing and the intensive use of conversational speech formulas.
Neurological researchers Sparks, Helm, and Albert developed Melodic Intonation Therapy in 1973 while working with adults in the Aphasia Research Unit at the Boston VA Hospital (Marshal & Holtzapple 1976). MIT is based on the hypothesis of these researchers that “increased use of the right hemisphere dominance for the melodic aspect of speech increases the role of that hemisphere in inter-hemispheric control of language, possibly diminishing the language dominance of the damaged left hemisphere” (Marshal & Holtzapple, 1976). In order to do this, common words and phrases are turned into melodic phrases emulating typical speech intonation and rhythmic patterns (Davis et al., 1999; Marshal & Holtzapple, 1976).
One study using positron emission tomography (PET) scans found that areas controlling speech in the left hemisphere were "reactivated" by the end of Melodic Intonation Therapy (Belin et al., 1996), in 7 patients. Further work suggests that MIT can result in significant changes in brain structure through the brain's own neuroplasticity. Right-hemisphere axon connections in 6 patients were found to be increased in volume after MIT. At least theoretically, this could allow for language processing in right homologous areas, suggesting that the right hemisphere may compensate for an impaired left hemisphere by taking up language processing responsibilities (Schlaug et al., 2009). Some evidence suggests that the positive effects of MIT can be enhanced with non-invasive brain stimulation (Vines et al., 2011). During MIT training sessions, the researchers applied anodal transcranial direct current stimulation (tDCS) over the equivalent of Broca's area in the right hemisphere of 6 stroke patients with non-fluent aphasia. Compared to sham stimulation, the anodal stimulation led to a significant improvement in fluency.
However, a recent experiment with 17 patients suggests that it may not be singing itself that aids speech production in patients with non-fluent aphasia, but rhythm and lyric type (Stahl et al., 2011). The rates of correct syllable production were found to be similar when patients were singing and speaking rhythmically. In other words, the experiment did not reveal an effect of singing over and above rhythmic speech. Furthermore, the results indicate that speech production in patients with left-sided basal ganglia lesions may critically depend on external rhythmic pacemakers, such as a metronome. Patients with larger basal ganglia lesions produced more syllables correctly when they were singing or speaking with rhythmic accompaniment. Finally, the results also confirmed that common, formulaic phrases (e.g., “How are you?”) may have a strong impact on speech production in non-fluent aphasic patients. Formulaic phrases yielded higher rates of correct syllable production than non-formulaic utterances, whether they were sung or rhythmically spoken.
The critical role of rhythmic pacing and formulaic language in MIT was confirmed in a subsequent therapy study with 15 non-fluent aphasic patients (Stahl et al., 2013). The results of the study suggest that singing and rhythmic speech may be similarly effective in the treatment of non-fluent aphasia. This finding challenges the view that singing causes a transfer of language function from the left to the right hemisphere. Instead, patients made good progress in the production of formulaic phrases — known to be supported by areas of the right hemisphere. Thus, the particular sensitivity of the right hemisphere to MIT could actually arise from the extensive use of formulaic phrases. The results of the 2013 study recommend the combined use of standard speech-language therapy and the training of conversational speech formulas, whether they are sung or rhythmically spoken. “Standard speech-language therapy may engage, in particular, left perilesional brain regions, while training of formulaic phrases may open new ways of tapping into right-hemisphere language resources — even without singing,” the authors of the study conclude.
Who Benefits from Melodic Intonation Therapy
The majority of research in Melodic Intonation Therapy has been conducted with aphasia patients. Aphasia is a deficit in language abilities resulting from damage to the brain. There are different types of aphasia depending on the location of the damage. Patients that would benefit from MIT typically suffer from non-fluent aphasia or Broca’s aphasia. Some individuals with apraxia of speech have also benefited from MIT. As the name suggests, the damage to the brain in this category is mostly in the Broca’s area and thus speech production is affected. Sparks and associates found that adult patients meeting the following criteria achieved positive results with MIT (Marshal and Holtzapple, 1976, p. 115):
1. Good auditory comprehension
2. Facility for self correction
3. Markedly limited verbal output
4. Reasonably good attention span
5. Good emotional stability
Later researchers have also noted that for MIT to be effective the patient must not exhibit any “bi-lateral brain damage” (Roper, 2003). Melodic Intonation Therapy is not appropriate for patients suffering from receptive aphasia or brain damage affecting the patient’s ability to read and comprehend language. The main goal is to help the patient speak in a comprehendible manner. MIT may also be an effective treatment for speech impairments caused by other disorders such as Down syndrome, but research on this topic is even more limited than general research in MIT (Carroll, 1996).
How Melodic Intonation Therapy Works
The traditional Melodic Intonation Therapy process is divided into four progressive stages. However, modifications are often made to meet the specific needs of the patient. This is one reason why it is difficult to obtain definitive research results in MIT. In the early stages, MIT was used solely for adult patients, but eventually therapists began to use MIT with children. Therapists found that the traditional procedure did not work well with children, so a new three level structure was developed by Helfrich-Miller (Roper, 2003). The following sections will describe both the adult and child models of Melodic Intonation Therapy.
As stated above, this is a four level process. As the patient progresses through the stages the role of the therapist decreases. In the first stage the therapist hums “intoned phrases” and the patient taps the “rhythm and stress of each pattern” with his/her hands or feet (Roper, 2003). In the beginning of the second stage the patient joins the therapist in humming while continuing to beat the rhythms. As the patient progresses, the therapist begins to sing “intoned phrases” and the patient repeats them (Carroll, 1996; Roper, 2003). The third stage is the same as the final level of stage two except that now the patient is required to wait for a designated period of time before repeating the phrase or sentence. This helps to increase the patients ability to “retrieve” words (Carroll, 1996). In the fourth and final stage the sentence length is increased and “sprechgesang” is used to facilitate the transition to normal speech. “This technique involves keeping the same melodic line as the intoned sentence of the proceeding step, except that the constant pitch of the intoned words is replaced by the variable pitch of speech” (Roper, 2003). The ultimate goal is to remove the musical elements entirely so the patient presents normal speech.
Roper (2003) provides an in depth description of MIT with children. She notes that this model was created by researchers working with children suffering from apraxia of speech, due to similarities between children with this disorder and adults with aphasia. This model is divided into three stages each with five or six progressive levels. Stage one is the same as that in the adult model, but instead of tapping the patient signs, using Signed English. The therapist also signs while singing the intoned phrases. This is step one of the process, by step six the patient will respond to an “intoned question” by singing and signing the “last words” of the question. The second stage is similar to the third stage of the adult model. In this stage the patient is required to wait roughly “six seconds” before repeating the intoned question. As this stage progresses the role of the therapist decreases. The final stage is the same as that of the adult model. As the patient moves through the steps of this stage “signing is faded out and the last two stages involve questioning, using normal speech” (Roper, 2003).
Today, Melodic Intonation Therapy is commonly used with patients suffering from non-fluent aphasia and apraxia of speech. The Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology labeled MIT as "promising"; however, there have not been many studies published that can truly support the effectiveness of MIT. There are two main reasons for this lack of evidence. First, it is difficult to find homogeneous groups of patients with regard to lesion site and symptom variability. Second, MIT consists of various therapeutic elements, including singing, rhythmic speech, training of common phrases, and rhythmic hand-tapping. Unfortunately, it is unclear whether or not these elements contribute to the overall efficacy of MIT. Researchers are working to resolve this issue. For example, a recent therapy study compared the clinical efficacy of singing and rhythmic speech in a relatively homogeneous sample of 15 patients with non-fluent aphasia and apraxia of speech (Stahl et al., 2013). The results of the study did not suggest an effect of singing over rhythmic speech. Moreover, the results highlight the importance of standard speech-language therapy in combination with the training of conversational speech formulas, whether they are sung or rhythmically spoken.
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Carroll, Debbie. 1996. A study of the effectiveness of an adaptation of Melodic Intonation Therapy in increasing the communicative speech of young children with Down syndrome. McGill University.
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Schlaug, G., Marchina, S., Norton, A. (2009). Evidence for plasticity in white-matter tracts of patients with chronic broca’s aphasia undergoing intense intonation-based speech therapy. Annals of the New York academy of sciences, 1169(1), 385.
Stahl, B., Henseler, I., Turner, R., Geyer, S, & Kotz, S. A. (2013). How to engage the right brain hemisphere in aphasics without even singing: Evidence for two paths of speech recovery. Frontiers in Human Neuroscience, 7(35), 1–12.