From singing to speaking: facilitating recovery from nonfluent aphasia

Abstract

It has been reported for more than 100 years that patients with severe nonfluent aphasia are better at singing lyrics than they are at speaking the same words. This observation led to the development of melodic intonation therapy (MIT). However, the efficacy of this therapy has yet to be substantiated in a randomized controlled trial. Furthermore, its underlying neural mechanisms remain unclear. The two unique components of MIT are the intonation of words and simple phrases using a melodic contour that follows the prosody of speech and the rhythmic tapping of the left hand that accompanies the production of each syllable and serves as a catalyst for fluency. Research has shown that both components are capable of engaging fronto-temporal regions in the right hemisphere, thereby making MIT particularly well suited for patients with large left hemisphere lesions who also suffer from nonfluent aphasia. Recovery from aphasia can happen in two ways: either through the recruitment of perilesional brain regions in the affected hemisphere, with variable recruitment of right-hemispheric regions if the lesion is small, or through the recruitment of homologous language and speech-motor regions in the unaffected hemisphere if the lesion of the affected hemisphere is extensive. Treatment-associated neural changes in patients undergoing MIT indicate that the unique engagement of right-hemispheric structures (e.g., the superior temporal lobe, primary sensorimotor, premotor and inferior frontal gyrus regions) and changes in the connections across these brain regions may be responsible for its therapeutic effect.

Figure 1. Functional MRI activation maps (superimposed onto the surface projections of a spatially-standardized normal brain) of a patient treated with melodic intonation therapy

Presents the contrast ‘overt speaking versus silence (control condition)’ in the top row and ‘overt speaking versus vowel production’ in the bottom row (p < 0.05 family-wise error) (A) before therapy and (B) after therapy, as well as (C) a voxel-by-voxel comparison of the two time-points. The color codes represent different magnitudes of activation: the color yellow indicates stronger activation than the color red. All comparisons are thresholded at p < 0.05 (family-wise error corrected). For more details on the functional MRI tasks and functional MRI data analysis, see [46]. Phon: Phonation of vowels; Sil: Silence; Speak: Speaking; TP1: Before therapy; TP3: After therapy; TP3 > TP1: Voxel-by-voxel comparison of the two functional MRI acquisitions.

Figure 2. Diffusion tensor imaging scans of a patient before and after an intense course of melodic intonation therapy

There is a visible increase in the size (number of fibers and volume of tract) and length of fibers of the right arcuate fasciculus when the acquisition before therapy (A) is compared with the acquisition after therapy (B).