Articulatory disorders in primary progressive aphasia: an acoustic and kinematic analysis

Articulatory performance was investigated in a patient suffering from nonfluent primary progressive aphasia (PPA) characterized, among other factors, by apraxia of speech. Normal speakers and three subjects with spastic dysarthria due to pseudobulbar palsy served as controls. In addition to the acoustic signal, lower lip trajectories were recorded by means of an optoelectronic system during production of test sentences comprising either the sequence /pa:p/ (long vowel) or /pap/(short vowel). Normal speakers and pseudobulbar patients produced a clear-cut durational distinction between short and long vocalic targets at the acoustic and perceptual level. As compared to the short vowels, the long cognates were characterized by lengthened lower lip opening and closing gestures. In contrast, the PPA patient showed an impaired durational contrast of the vowels /a/ and /a:/. Furthermore, this subject produced, unexpectedly, a similar temporal distinction of the opening, gesture, as did the controls, but not of the closing movement. Prevailing concepts on apraxia of speech suggest impaired temporal coordination of independent articulators, whereas single gestures are considered to be largely unimpaired. Contrary to these assumptions, the present study revealed that the durational adjustment of specific orofacial movements during speech might also be disrupted.