Scientists are beginning to elucidate differences in activation patterns in children with SLIs using neuroimaging techniques to capture brain activity while performing different cognitive tasks. fMRI studies have shown that children with SLI have a significantly smaller left hemispheric pars triangularis (Broca's area) and asymmetry of dominance of language structures, as opposed to the more typical left hemisphere dominance. A larger body of research exists around neuroscientific studies with children diagnosed with a specific language impairment (SLI). ĭue to the vague nature of the diagnosis of expressive language disorder, there is little specific scientific research that we can currently locate. This volume reduction showed a high correlation between reduced volume and tests of oral praxis, supporting the idea that odd development of the caudate nucleus is related to the problems in motor control observed in the KE family. However, more subtle and sophisticated techniques, such as voxel-based morphometry studies have allowed researchers to identify bilateral abnormalities in neural volume in areas of the brain associated with motor functions, such as the caudate nucleus, in the affected members of the KE family when compared to the unaffected family members. Neuroimaging techniques, such as structural and functional MRI, found no significant differences between individuals with SLI and normal controls. Main article: Specific language impairment Mutant alleles of the normal FOXP2 gene have been found to be the cause of severe speech impairments. These studies have allowed scientists to begin to investigate how changes to one gene can alter human communication.įOXP2 is the first gene that has been identified that is specifically linked to speech and language production. Further analysis traced this inheritance pattern back to mutations in the FOXP2 genes. In 1990, it was reported that the several generations of the KE family had developmental verbal dyspraxia and orofacial praxis that were inherited in a typical autosomal dominant pattern. Modern neuroscientific research has verified this, though language may be lateralizaed to the right hemisphere in some right-handed individuals. Paul Broca was the first to note that the left hemisphere of the brain appeared to be localized for language function, particularly for right handed patients. Lesions in these parts of the brain impair language comprehension and language production, respectively. Some of the earliest neuroscientific discoveries were related to the discovery that damage to certain areas of the brain related to impairments in language, such as the discovery of Wernicke's area and Broca's area. Scientific studies of speech and language The procedural memory system is associated with basal-ganglia circuits in the frontal lobe and further investigation of this particular hypothesis could aid in the development of a clinical neurological picture of what the underlying causes of SLI are. The Procedural Deficit Hypothesis opines that we can explain language impairments due to abnormal development of brain structures that are involved in procedural memory, our memories that remember how to perform different cognitive and motor tasks. However, an alternative hypothesis to the cause of SLIs has been posited, called the Procedural Deficit Hypothesis. There is also a lot of debate about whether specific language impairments, such as expressive language disorder, are caused by deficits in grammar or by a deficit in processing language information. Words are produced after the concept waiting to be produced is conceptualized, related words are selected, encoded and the sound waves of speech are produced. Willem Levelt outlined the currently accepted theory of speech production.
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