[Speech sound distortion of neuromotor speech disorders: a comparison between cerebral dysarthria and verbal apraxia]

Speech sound distortion is considered to be a salient feature of neuromotor speech disorders such as cerebellar dysarthria and apraxia of speech. The aim of this study was to compare the temporal and spatial aspects of speech of two persons with acquired cerebellar dysarthria and of one person with acquired apraxia of speech. Voice onset time of [d], duration of articulatory closure of [d], duration of [s] and [l], formants of [l] and the range of acoustic energy of [s] were analysed spectrographically in a number of utterances with various sound structures. The results indicated that spatial and temporal distortion of articulatory movements occurred in all three subjects. However, differences in the nature and degree of speech sound distortion in the two different disorders were observed. The theoretical implications of these differences are discussed with reference to a model of normal speech production.