Acoustic patterns of apraxia of speech

Apraxia of speech (or verbal apraxia) is a controversial disorder, considered by some to be an impairment of the motor programming of speech. Because the disorder is characterized by "higher order" errors such as metathesis and segment addition as well as by errors of apparent dyscoordination of articulation, it seems to reflect a relatively high level of damage to the nervous system. This report presents acoustic descriptions of the speech of seven persons diagnosed as having apraxia of speech but without severe aphasic impairment, especially agrammatism. The acoustic results indicate a variety of segmental and prosodic abnormalities, including slow speaking rate with prolongations of transitions, steady states, and intersyllable pauses; reduced intensity variation across syllables; slow and inaccurate movements of the articulators; incoordination of voicing with other articulations; initiation difficulties; and errors of selection or sequencing of segments. These error patterns are discussed with respect to a theory of motor control based on spatial-temporal schemata. In addition, consideration is given to the controversy about phonologic versus motor programming impairment in apraxia of speech.