Evidence has been well accumulated for more than two centuries that a patient with non-fluent, or Broca’s, aphasia secondary to a left hemisphere stroke is able to sing songs and words (e.g., Marina, Pasqualetti, & Carlomagno, 2007; Mills, 1904, Gerstmann, 1964, Stahl, Kotz, Henseler, Turner, & Geyer, 2011). The rationale behind this evidence relies on neuroplasticity that a patient’s intact right hemisphere, known to play an important role in processing steady-state spectral information and slowly changing aspects of the auditory-signal (e.g., prosodic contours and sustained vowels), may stimulate the damaged left hemisphere responsible for integrating auditory information across shorter intervals of time (Naeser & Helm-Estabrooks, 1985; Sparks & Deck, 1994; Zatorre & Belin, 2001; Zipse, Worek, Guarino, & Shattuck-Hufnagel, 2014).

This clinical observation has led to a variety of singing-based therapeutic techniques such as Melodic Intonation Therapy (MIT; Albert, Sparks, & Helm, 1973; Helm-Estabrooks, Nicholas, & Morgan, 1989; Sparks, Helm, & Albert, 1974; Wan, Ruber, Hohmann, & Schlaug, 2010). Techniques of MIT include sequentially training a patient to sing simple and familiar words and phrases with melody attached. While singing, a therapist rhythmically taps the patient’s left hand. In other words, MIT consists of three key elements: (1) melody, (2) rhythmic tapping, and (3) formulaic, or simple and familiar (e.g., “How are you?”) words or phrases.

Although the efficacy of MIT on the improvement of verbalization for patients with Broca’s aphasia has been substantially documented (e.g., Conklyn, Novak, Boissy, Bethoux, & Chemali, 2012; Hurkmans et al., 2012; Schlaug, Marchina, & Norton, 2009), there is an ongoing debate as to which element of the three is the driving force of the efficacy of MIT or singing-based therapeutic approaches (e.g., Boucher, Garcia, Fleurant, & Paradis, 2001; Zipse et al., 2014). The original authors of MIT considered the melody as the key component for stimulating the use of intact right hemisphere (Albert et al., 1973) or supporting the right hemisphere to activate residual left-hemisphere’s function (Sparks et al., 1974). Two case observations of MIT or modified MIT attempted to highlight the crucial role of melody controlling for rhythmic left-hand tapping. Hough (2010) reported that one participant with chronic Broca’s aphasia, who exhibited little progress with MIT due to difficulty with the tapping element of MIT, significantly increased production of short phrases using MIT without rhythmic tapping. Wilson, Parsons, and Reutens (2006) concluded that melody might account for the effect of MIT in a neurologically stable amateur male musician with severe expressive aphasia using a controlled pre- and post-treatment design. Consequently, these results appear to be somewhat confounded with the study participants’ unique characteristics (i.e., difficulty in the tapping element and musical training prior to stroke).

The most common finding in both cross-sectional speech facilitation studies and longitudinal treatment studies that attempt to test melody-only, rhythm-only, and combined conditions is that rhythmic condition may be an essential component of the efficacy of MIT (Boucher et al., 2001; Stahl, Henseler, Turner, Geyer, & Kotz, 2013; Stahl et al., 2011). Boucher et al. (2001) suggested that the experimental condition emphasizing rhythm resulted in significant improvements in two participants’ repetition of target utterances, compared to no or little gain following the treatment condition emphasizing melody. Stahl et al. (2011) concluded that the facilitating effect of MIT has its root in rhythm rather than melody. A relatively large number of participants (n=17) and rigorous study design (e.g., controlling for lip-reading, memory, and motor automaticity) allow the finding to be more credible than other case studies. Findings from a longitudinal experiment including 15 participants also confirmed that melody may not benefit speech recovery over and above rhythmic speech (Stahl et al., 2013).

In terms of formulaic speech, it is presumed that the production of common and familiar utterances (e.g., “Happy birthday to you”) is automatized at the motor level. Preserved automaticity in formulaic phrases for MIT revealed that memory and motor automaticity mediate speech production in patients with Broca’s aphasia (Stahl et al., 2011). In other words, individuals with non-fluent aphasia can repeat or produce formulaic utterances easier than propositional (i.e., non-formulaic, creative) speech, utilizing long-term memory and automaticity. Van Lancker Sidtis (2004) and Stahl et al. (2013) proposed that propositional and formulaic speech rely on different neural pathways. The researchers suggested that a patient with non-fluent aphasia should improve propositional speech, reactivating left hemisphere, and formulaic speech, stimulating intact right hemisphere, respectively.

In summary, researchers attempted to better understand the contribution of individual MIT components to its therapeutic effect. It is suggested that production of formulaic utterances for patients with non-fluent aphasia should be trained rhythmically. Until now the effect of melody on speech production in patients with Broca’s aphasia has been somewhat ambiguous, possibly due to lack of the rigor of prior studies. The current case study was designed to demonstrate differential effects of melody-only and rhythm and left-hand tapping-only conditions on accuracy of repetitions in a patient with severe Broca’s aphasia. Formulaic utterances were used in both conditions given the participant’s severe deficit in propositional speech. Considering the nature of case observational study, it is not possible to eliminate extraneous variables or biases. However, the authors hope to demonstrate the functional relationship between individual MIT elements and its therapeutic effect, carefully controlling for the melody-only and rhythm and left-hand tapping-only conditions.

Data are plotted in Figure 1 and summarized in Table 5. In the figure, numbers represent the percent of the participant’s accurate repetitions. Different phases are demarcated by vertical dotted lines. First, visual inspection of the data was conducted as suggested by Kromrey and Foster-Johnson (1996). The participant, in general, demonstrated fluctuating and variable performances of accurate repetitions across sessions. During baseline phrase, the participant consistently demonstrated difficulty repeating targets accurately, ranging from 20 to 33% accuracy of trials. During treatment phase one, the participant distinctively demonstrated a high level of accurate repetitions in session four under melody-only condition. The participant’s accurate repetitions in sessions four and five under melody-only condition were significantly superior to the rest of performances during treatment phase one. Treatment phase two exhibited more stable and consistent repetition patterns than treatment phase one. The participant’s performances under melody-only condition were significantly better than his performances under rhythm and left-hand tapping-only condition in four sessions among five. In session five, the participant accurately repeated targets in equal numbers under both conditions.

Next, to measure the differential effect of melody-only and rhythm and left-hand tapping-only conditions, the percentage of nonoverlapping data (PND) was calculated by dividing the number of treatment sessions exceeding the highest data point during baseline sessions and dividing by the total number of treatment sessions (Parker, Hagan-Burke, & Vannest, 2007; Manolov & Solanas, 2009; Scruggs & Mastropieri, 2013; Scruggs, Mastropieri, & Casto, 1987). PND statistics higher than 90% are interpreted as highly effective intervention, 70% to 90% as fairly effective treatment, 50% to 70% as questionable effectiveness, and less than 50% as unreliable treatment. The participant’s highest data point during baseline sessions is represented as a horizontal dotted line in Figure 1. PND statistic for melody-only condition is 7/10=70%, which is fairly effective. PDN statistic for rhythm and left-hand tapping-only condition is 3/10=30%, that is, unreliable treatment. Both follow-up sessions’ data were slightly higher than the participant’s highest data point during baseline sessions.

The purpose of the current case study was to explore differential effects of melody-only and rhythm and left-hand tapping-only conditions on the accuracy of repetitions in a patient with severe Broca’s aphasia. Formulaic utterances were used in both conditions given the participant’s severe deficit in propositional speech. The study’s preliminary findings have possibly added to the literature on MIT by examining a functional relationship between individual MIT elements and their effects on the accuracy of repetitions in a patient with severe Broca’s aphasia. By carefully controlling for the melody-only and rhythm and left-hand tapping-only conditions with an alternating treatment design and controls of bias (e.g., counterbalancing strategy of the two conditions, random selection of targets, and two treatment phases), these findings have possibly aimed to advance our understanding of the importance of clinical observational research for the contribution of individual MIT elements.

A major finding from the current observational study was that both visual inspection of data and PND calculation indicated an immediate effect of melody-only condition on the participant’s accuracy of repetitions. The positive effect of rhythm and left-hand tapping-only condition was not observed. During the treatment sessions, the participant exhibited a considerable amount of impulsivity. The participant’s speech was halting overall, but it was frequently observed that he rushed to complete repetition as quickly as possible. This impulsivity was accelerated during the rhythm and left-hand tapping-only condition. This condition caused the participant to move ahead of the examiner’s speed, whereas this behavior did not occur during the melody-only condition. The authors’ observation regarding the participant’s difficulty following the tapping was consistent with rhythm-processing deficits that at least some patients with Broca’s aphasia exhibit. For example, Hough (2010) reported a positive effect of MIT when the tapping element was deleted. Tapping was not presented in this study because the participant found the tapping distracting. The researcher speculated that the patient may have had impaired speech as well as impaired tapping, therefore, tapping interrupted attempts at speech production rather than facilitated them. Zipse et al. (2014) supported Hough’s hypothesis that some patients with aphasia have a particular difficulty processing rhythm as opposed to pitch information. It is suggested that therapists should consider modifying MIT with the tapping omitted when (1) patients with aphasia demonstrate little success with MIT, and (2) rhythm-processing deficit is suspected.

Motivation and mood effect of singing in unison can also be considered when examining the positive effect of melody-only condition on the accuracy of repetitions in the participant. Singing is a natural, pleasing, and stress-free way for patients with non-fluent aphasia to verbalize, and thus it possibly motivates the patients to continue to focus on verbal repetition activities (Merrett, Peretz, & Wilson, 2014; Racette, Bard, & Peretz, 2006). A positive relationship between music therapy and patients’ motivation and mood has been substantially observed in the fields of physical rehabilitation and mental health, indicating that singing may be intrinsically motivating (Merrett et al., 2014). Considering that low mood and lack of motivation are commonly observed in individuals with aphasia (Robinson, 2003), the positive influence of singing on the participant’s motivation and mood might have resulted in the improvement of accuracy of repetitions.

Limitations of the current study should be addressed. First, the results of the study were preliminary because of the selection of the participant. The participant’s fatigue, distraction, and overall weakness resulted in fluctuating and variable performances across phases. These extraneous variables negatively influenced the study’s validity given that only one participant was examined. Another limitation was that each treatment phase only included five sessions, and these were not intensive enough to examine the lasting effect of melody-only condition during the follow-up phase. Due to the university clinic’s summer schedule, the entire study including the testing, baseline, treatment, and maintenance phases had to be completed in six weeks. Although the follow-up data did not indicate the lasting effect of melody-only condition, the participant’s wife and authors anecdotally reported noticeable differences in the participant’s initiation of rehearsed speech at home and the clinic. For example, the participant’s greeting was changed from a head nod and the phrase “okay okay” during the baseline phase, to the phrase “I am good,” in later treatment sessions.

Exploring the differential effect of melody-only and rhythm and left-hand tapping-only conditions should not be viewed as a reductionist approach because clinical observations of individual conditions of MIT enrich our understanding of how MIT works for patients with Broca’s aphasia. Given that some evidence for the positive effect of melody-only condition versus rhythm and left-hand tapping-only condition has been reported, attempts to find a simple and single framework explaining the effects of MIT do not appear to be worthwhile. It is possible that pre-morbid factors (e.g., musicianship), lesion factors (e.g., time since onset and location), and comorbidity factors (e.g., aphasia only and aphasia with apraxia of speech) are intertwined to determine the progress of verbalization when MIT is implemented (Merrett et al., 2014). The current case study possibly attempted to extend the literature on the functional relationship between the participant’s pre-morbid, lesion, and comorbidity factors and the positive effect of individual MIT elements on the accuracy of verbal repetitions.