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Abstract

This study explores the nature of sign production in individuals with neurogenic movement disorders. The research goals are to broadly define the phenomenon of dysarthria in signed language; to determine whether anything other than the set of articulators involved differentiates it from dysarthria in spoken language; and to delineate the differences between sign dysarthria and apraxia, and between sign dysarthria and disruption of simple limb movements. In the same way that hearing people may exhibit speech dysarthria in the absence of oral apraxia, deaf signers may, in some cases, exhibit sign dysarthria in the absence of higher level ideomotor impairments. Conversely, just as many movement disorders are more apparent in speech than in simple limb movements, sign dysarthria may also arise in the absence of severe impairment of simple movements, such as reaching or pointing. An ancillary question that this research addresses is the establishment of articulatory measures of sign dysarthria, and of normal signing.

Findings from this study indicate that dysarthria, as distinct from apraxia, aphasia, and loss of simple movement, does manifest itself in sign language, which suggests that speech motor control research should eschew models of dysarthria framed around specific articulators, in favour of those that emphasize patterns of movement. However, just as dysarthria is not articulator-specific, it is also not fundamentally linguistic in nature. The reason that dysarthria can occur in either a vocal or a manual language modality is because both use very rapid, complex, co-ordinated movements. The movement speed and complexity facilitate the rapid information transfer that is necessary for any linguistic system, but that does not make disruptions to it inherently linguistic. One would predict that subjects with dysarthria would also be impaired at any task with similar motor demands, but since few normal activities require such a high level of movement precision, deficits manifest themselves primarily in speech or sign.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > RZ Other systems of medicine
Departments:	School of Health & Psychological Sciences > Language & Communication Science School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses Doctoral Theses

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