From Singing to Speaking: Why Singing May Lead to Recovery of Expressive Language Function in Patients with Broca's Aphasia

Abstract

It has been reported that patients with severely nonfluent aphasia are better at singing lyrics than speaking the same words. This observation inspired the development of Melodic Intonation Therapy (MIT), a treatment whose effects have been shown, but whose efficacy is unproven and neural correlates remain unidentified. Because of its potential to engage/unmask language-capable regions in the unaffected right hemisphere, MIT is particularly well suited for patients with large left-hemisphere lesions. Using two patients with similar impairments and stroke size/location, we show the effects of MIT and a control intervention. Both interventions' post-treatment outcomes revealed significant improvement in propositional speech that generalized to unpracticed words and phrases; however, the MIT-treated patient's gains surpassed those of the control-treated patient. Treatment-associated imaging changes indicate that MIT's unique engagement of the right hemisphere, both through singing and tapping with the left hand to prime the sensorimotor and premotor cortices for articulation, accounts for its effect over nonintoned speech therapy.

FIGURE 1

Spoken phrases (prosodic patterns) transposed into melodic intonation patterns. Pitches are determined by the natural prosody of speech—accented syllables are presented on the higher of the two pitches.

FIGURE 2

High-resolution, T1-weighted images show the chronic, left-hemisphere lesion location and extent of Patients #1 and #2, encompassing both Broca's region and the anterior part of the superior temporal lobe.

FIGURE 3

fMRI activation maps (superimposed onto the surface projections of a spatially standardized normal brain) of the contrast “Overt Speaking vs. Silence (control condition)” (p < 0.05 FWE) for Patients #1 and #2 at baseline and after 40 therapy sessions. The color coding reflects different magnitudes of activation: the color yellow reflects a stronger activation than the color red. Patient #2 also shows the “Overt Speaking vs. Silence (control condition)” contrast after an additional 40 sessions of MIT that followed the SRT sessions. Slight differences can be seen in the regional magnitude of activation with a greater magnitude of activation in the right premotor/motor and temporal lobes (yellow level of activation) and the slightly lower magnitude of activation in the left posterior perisylvian region (more red than yellow) comparing the images after MIT with the images after SRT treatment for Patient #2.