ABSTRACT
Acquired and developmental apraxia of speech (AOS and DAS) are defined as disorders
of the transition from an abstract phonological code into motor commands. However,
the natural course of these disorders differs substantially because of the fundamental
difference in the developmental stage at which the apraxia expresses itself. In normal
and pathological development alike, development of language and speech is an interactive
process, involving speech motor control, perception, and psycholinguistic processes.
Infant speech develops from random babbling and sensomotoric learning, followed by
more abstract phonological acquisition. Supposing that the core deficit of DAS comprises
a reduced sensomotoric learning capacity explains a large part of the symptomatology
of DAS in the psycholinguistic domain because of the impact on phonological, perceptual,
and higher-level processes. This contrasts with adults with AOS, who already have
acquired stable top-down processes. Implications for clinical management are discussed.
KEYWORDS
Speech motor disorders - speech development - psycholinguistics - child neuropsychology
