Considering Dysarthria: A Speech Disorder On the Margins :: Biology Essays Research Papers

Considering Dysarthria: A Speech Disorder 'On the Margins' The goal of this paper is to portray dysarthria, a language impairment, as a disorder that is "on the margins" of the category of speech disorders. The argumentation will be that since dysarthria shares common underlying neurological causes with motor diseases rather than with other language impairments, it is set apart from other language impairments and evidence for the overlap of the motor modality with the language modality. Language is arguably one if not the most complex functions produced by the human brain, and one that is all but transparent as to the underlying neurological structures and processes in that so much is going on at the same time that it is hard to tell what is what. What we do know is that there are different areas of representation for different aspects of language. An area in the left hemisphere above the perisylvian fissure in the frontal lobe anterior to the motor cortex roughly controls production and fluency of speech; another area, in the temporal lobe of the same hemisphere roughly controls comprehension and word retrieval. Other regions next to and between these areas carry related functions, and lesioning to them results in variations of the symptoms caused by lesioning one of the central regions described above(1).. These areas are known to us as the "language areas." However, they can be completely intact in a person that is suffering from severe language impairment. Are there other "language areas" then? Strictly speaking, no, loosely speaking, yes. Language is more than a mental function where structures are established, words are retrieved and sound associations are made. The final execution of language is purely a question of complex motor control. Disruption of this complex interaction of motor signals towards the formation of speech is known as dysarthria (2). It is sometimes confused with impairment resulting from injury to the "language areas" (1), illustrating the point that the process of producing language is multi-layered, and that it is often hard to tell what is what. The symptoms of dysarthria may be slurred speech, nasality of sound, or quiet and slow speech (3).. These different impairments reflect the sub-sections in the 'motor symphony' that produces speech: The lips, tongue, teeth and jaw shape specific sounds; the soft palate channels air into either the nasal or oral cavity, producing different sound qualities; the larynx (voice box) makes the air vibrate through the vocal folds to create voice; and finally, the respiratory system powers this process (3).