Abnormality in Coordination between Articulators and Vocal Organ in the Realization of Japanese Word Accent by Patient with Apraxia of Speech

Abstract

The possibility of disturbance of temporal coordination between articulators and vocal organ was examined in apraxic speech. Speech samples consisted of Japanese words beginning with [ai] or [amV] (V=a, e, or i) and having a low-high type accent pattern, uttered by a patient with pure apraxia of speech and normal controls. For words beginning with [ai], the accent command and articulatory command for the second vowel [i] were estimated from fundamental and formant frequencies, respectively, based on the functional model for realization of Japanese word accent and articulation. The results showed that delay of onset of the accent command relative to that of the articulatory command was markedly larger in apraxic speech than that in normal speech at a slow speaking rate. For words beginning with [amV], the delay of onset of the accent command relative to lip closure for [m] was larger in apraxic speech than that in normal speech.
Several previous studies have reported on abnormalities of temporal coordination among different articulators in apraxic speech. However, our results in the present study suggest that abnormalities of temporal coordination exist between articulators and vocal organ as well.