Please don't stop the music: Song completion in patients with aphasia

摘要

Aphasia, an acquired language disorder resulting from brain damage, affects over one million individuals in the United States alone. Many persons with aphasia (PWA), particularly those with non-fluent aphasia, have been observed to be able to sing the lyrics of songs more easily than they can speak the same words. Remarkably, even humming a melody can facilitate speech output in PWA, and this has been capitalized on in therapies such as Melodic Intonation Therapy. The current study examined PWA's ability to complete phrases from songs by either singing, speaking, or intoning them in an experimental stem-completion format. Twenty PWA of varying severity, all but one of whom had aphasia as a result of stroke, and 20 age-matched healthy controls participated in the task. The task consisted of three conditions (sung, spoken, and melodic) each consisting of 20 well-known songs. Participants heard the first half of a phrase that was either sung in its original format (sung condition), spoken (spoken condition), or intoned on the syllable "bum," (melodic condition) and were asked to complete the phrase according to the format in which the stimulus was presented. PWA achieved the highest accuracy in the sung condition, followed by the spoken and then melodic conditions, while controls scored comparably in the sung and spoken condition and much lower in the melodic condition. PWA and controls were better able to access and produce both the melody and lyrics of songs in the sung condition (when both components were presented together), compared to when the melody and lyrics of songs were presented in isolation. Here, melody confers an advantage for word retrieval for PWA, as lyric production is better in a sung context, and these results substantiate the theoretical framework of MIT. Additionally, the present results may be attributed to the integration hypothesis, which postulates that the text and tune of a song are integrated in memory. Interestingly, a subset of the most severe PWA scored higher in the melodic condition relative to the spoken condition, while this pattern was not found for less severe PWA and for controls. Taken together, our results suggest that singing appears to influence PWA when trying to access the lyrics of songs; access to melody is preserved in PWA even while they exhibit profound and diverse language impairments. Findings may have implications for using music as a more widely implemented tool in speech therapy for PWA.