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Efficient localization of the cortical language network and its functional neuroanatomy in dyslexia
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Abstract:
The functional neuroanatomy of language localization in dyslexia has primarily been studied in the context of reading. However, dyslexia is sometimes referred to as a “language-based learning disability,” yet the functional signature of the core language comprehension network in dyslexia is far less understood. This thesis presents a series of studies designed to compare the functionality of the brain regions supporting linguistic processing between typical and impaired readers in order to characterize the cortical language network in dyslexia. First, we investigate the extent to which the efficiency (or quality of data vs. amount of scan time) of a functional language localizer based on passive spoken language comprehension can be maximized in Chapter 2. By demarcating the language network based on smaller amounts of data and testing stability and reliability within this framework, we found that scan time can be substantially reduced without sacrificing functional specialization for language. In Chapter 3, we apply the spoken language localizer to determine differences in functional organization of language in dyslexia and provide evidence that the core spoken language comprehension network is not markedly different between typical readers and those with dyslexia. We compared the individual activations from whole-brain analysis and functional profiles in the canonical language-selective regions and found that the functional response of localized language regions in individuals with dyslexia was as selective as in typically reading adults. Chapter 4 follows up on the functional evidence reported in Chapter 3 to examine the structural connectivity within the same functional language network and additionally found essentially no differences between controls and dyslexia, further supporting the observations made in Chapter 3 that core linguistic processing is intact in dyslexia. All together, these findings converge on the suggestion that individuals with dyslexia do not rely on a separate cognitive architecture for language, potentially revealing important new insight into the dissociation of language specialization abilities and reading difficulty in dyslexia.
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Keyword:
Cognition; DWI; fMRI; Language; Neuroimaging; Speech; Test-retest reliability
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URL: https://hdl.handle.net/2144/43724
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