Speech Motor Development in Childhood Apraxia of Speech: Generating Testable Hypotheses by Neurocomputational Modeling

H. Terband, B. Maassen
2010 Folia Phoniatrica et Logopaedica  
years to acquire the pragmatic, linguistic, and perceptual-motor knowledge and skills required for the production and perception of speech. In the development of speech, 2 main stages can be distinguished. The first is a perceptual-motor stage, during which the infant acquires control over the articulo-motoric system by establishing an internal model [1, 2] , i.e. a systemic mapping between the movements and their auditory and somatosensory consequences. This stage is usually characterized as
more » ... e babbling stage [3, 4] . The second, phonological stage comprises the acquisition of the phonological system of the language, for perception as well as production. In this stage, the perceptual-motor skills acquired thus far are further shaped and exploited to produce the first meaningful utterances, resulting in a set of phonemic mappings between articulatory movements and specific goals (which could be either auditory [5] or gestural [6] in nature). A common example of phonemic shaping is the acquisition of the /r/ versus /l/ distinction for English, and the loss of this phonemic distinction after babbled production of both sounds in the Japanese phonemic system. All children struggle with the acquisition of systemic and phonemic mappings at a certain point, but most children come through successfully. Children with childhood apraxia of speech (CAS), however, keep struggling with the planning and execution of motor commands at the stage where they want to produce the phonemes of meaningful speech. As a clinical entity, CAS is highly controversial both with respect to clinical signs and with Abstract Childhood apraxia of speech (CAS) is a highly controversial clinical entity, with respect to both clinical signs and underlying neuromotor deficit. In the current paper, we advocate a modeling approach in which a computational neural model of speech acquisition and production is utilized in order to find the neuromotor deficits that underlie the diversity of phonological and speech-motor symptoms of CAS. Based on existing approaches and behavioral data, we first generated specific hypotheses about the underlying deficits. These hypotheses were then tested in a series of computer simulations, and the resulting speech patterns were compared to the available behavioral data. Finally, the model was used to derive further predictions that can be tested empirically in behavioral experiments and possible new angles for clinical intervention.
doi:10.1159/000287212 pmid:20424469 fatcat:63wh5xfvuzekxn7doebbh5vjdy