How to engage the right brain hemisphere in aphasics without even singing: evidence for two paths of speech recovery

Abstract

There is an ongoing debate as to whether singing helps left-hemispheric stroke patients recover from non-fluent aphasia through stimulation of the right hemisphere. According to recent work, it may not be singing itself that aids speech production in non-fluent aphasic patients, but rhythm and lyric type. However, the long-term effects of melody and rhythm on speech recovery are largely unknown. In the current experiment, we tested 15 patients with chronic non-fluent aphasia who underwent either singing therapy, rhythmic therapy, or standard speech therapy. The experiment controlled for phonatory quality, vocal frequency variability, pitch accuracy, syllable duration, phonetic complexity and other influences, such as the acoustic setting and learning effects induced by the testing itself. The results provide the first evidence that singing and rhythmic speech may be similarly effective in the treatment of non-fluent aphasia. This finding may challenge the view that singing causes a transfer of language function from the left to the right hemisphere. Instead, both singing and rhythmic therapy patients made good progress in the production of common, formulaic phrases—known to be supported by right corticostriatal brain areas. This progress occurred at an early stage of both therapies and was stable over time. Conversely, patients receiving standard therapy made less progress in the production of formulaic phrases. They did, however, improve their production of non-formulaic speech, in contrast to singing and rhythmic therapy patients, who did not. In light of these results, it may be worth considering the combined use of standard therapy and the training of formulaic phrases, whether sung or rhythmically spoken. Standard 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 Efficacy and Timing of Melodic Intonation Therapy in Subacute Aphasia

“…This would require partner questionnaires, which are not very reliable. Anecdotic reports from partners suggest that patients did benefit from the improvement on trained utterances in daily life; this is in line with the results of Stahl et al 20 Remarkably, the present study also showed that a small difference in the timing of MIT had considerable consequences for its effect. A delay of merely 6 weeks was related to less improvement.…”

“…Several therapeutic elements of MIT may be responsible for its effects on language production: melody, rhythm, hand tapping, or reduction of speed in singing versus speaking. 20,21,38,39 A recent study comparing the effect of melody and rhythm on language production in nonfluent aphasia showed that melody had no additional effect over rhythm. 20 In the present study, it was impossible to unravel the impact of the MIT components, since we used the original MIT technique.…”

The effectiveness of Speech–Music Therapy for Aphasia (SMTA) in five speakers with Apraxia of Speech and aphasia

“…They compared melodic therapy with rhythmic therapy and spoken therapy in a cross-over design in three individuals with chronic Broca's aphasia. Their results showed, in contrast to Stahl et al (2013), that only the melodic therapy, which consisted of both pitch and rhythm, significantly improved speech production. The above-mentioned controlled studies have demonstrated the importance of using musical elements in the efficacy of MIT, including various modifications on MIT, without leading to an understanding of which therapeutic elements, melody or rhythm, contribute to its success.…”

“…In individuals with AoS, these aspects can be disturbed in speech production (Ziegler, 2008). As mentioned earlier, MIT uses two musical elements: rhythm and melody of which both underlying mechanisms are still unclear (Stahl et al, 2013;Zumbansen et al, 2014b). However, MIT structures are restricted to two notes and two durations.…”

“…Recent findings suggest that singing may not be decisive but, instead, rhythm may be crucial (Stahl, Kotz, Henseler, Turner, & Geyer, 2011). Stahl, Henseler, Turner, Geyer, and Kotz (2013) found that both singing and rhythmic therapies were effective in the production of formulaic speech in 15 individuals with global or Broca's aphasia. They, therefore, concluded that singing may not benefit speech recovery over and above rhythmic speech.…”