The Effect of Prosodic Timing Structure on Unison Production in People With Aphasia.

PURPOSE: Unison production is a common aphasia treatment technique in which the clinician and the person with aphasia (PWA) produce phrases aloud together. It can be implemented using a typical "conversational," syntax-influenced prosodic timing structure, or with a "metrical," beat-based timing structure, but to date no study has directly compared these two approaches. This study compared the effects of metrical versus conversational prosodic timing during unison production on the (a) accuracy of participants' spoken output and (b) timing alignment of participants' productions with the stimuli.

METHOD: PWAs and controls listened to conversationally timed and metrically timed sentences and repeated them in unison with audio recordings. Productions were transcribed and scored in two ways: (a) Accuracy was calculated as the percentage of correctly produced syllables, and (b) timing alignment was determined by extracting the voice onset moment of identical target syllables in the unison stimuli and participant productions in both conditions and comparing the corresponding time points.

RESULTS: Metrical timing yielded a greater number of accurate syllables in both groups, with larger effect in PWAs than in controls. Both groups exhibited more anticipatory, less variable timing when speaking along with metrical stimuli, though evidence of such prediction was also present in the conversational condition.

CONCLUSIONS: Results suggest that unison production works via entrainment-a process that utilizes prediction to guide synchronous production of spoken output. Metrically regular stimuli may facilitate this process as they are more rhythmically predictable. Future work will examine key behavioral variables that predict benefit from unison production and metrical timing.