Visual Explanation for Identification of the Brain Bases for Developmental Dyslexia on fMRI Data

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Visual illusions: An interesting tool to investigate developmental dyslexia and autism spectrum disorder

A visual illusion refers to a percept that is different in some aspect from the physical stimulus. Illusions are a powerful non-invasive tool for understanding the neurobiology of vision, telling us, indirectly, how the brain processes visual stimuli. There are some neurodevelopmental disorders characterized by visual deficits. Surprisingly, just a few studies investigated illusory perception in clinical populations. Our aim is to review the literature supporting a possible role for visual illusions in helping us understand the visual deficits in developmental dyslexia and autism spectrum disorder. Future studies could develop new tools – based on visual illusions – to identify an early risk for neurodevelopmental disorders

Brain bases of morphological processing in Chineseâ English bilingual children

Can bilingual exposure impact children’s neural circuitry for learning to read? To answer this question, we investigated the brain bases of morphological awareness, one of the key spoken language abilities for learning to read in English and Chinese. Bilingual Chineseâ English and monolingual English children (N = 22, ages 7â 12) completed morphological tasks that best characterize each of their languages: compound morphology in Chinese (e.g. basket + ball = basketball) and derivational morphology in English (e.g. re + do = redo). In contrast to monolinguals, bilinguals showed greater activation in the left middle temporal region, suggesting that bilingual exposure to Chinese impacts the functionality of brain regions supporting semantic abilities. Similar to monolinguals, bilinguals showed greater activation in the left inferior frontal region [BA 45] in English than Chinese, suggesting that young bilinguals form languageâ specific neural representations. The findings offer new insights to inform bilingual and crossâ linguistic models of language and literacy acquisition.The study investigated the impact of bilingual exposure on children’s language and reading abilities. During auditory morphological awareness tasks, young Chineseâ English bilinguals showed monolingualâ like competence as well as languageâ specific patterns of brain activation in left inferior frontal gyrus (IFG). This activation was greater for English than for Chinese in left IFG BA 45, but similar across languages in left IFG BA 47. Relative to English monolinguals, the bilinguals showed greater activation in left MTG region and this activation was significantly correlated with bilingualsâ English literacy. The findings suggest that bilingual exposure to a language with rich lexical morphology, such as Chinese, impacts the functionality of bilingualsâ left temporal regions typically associated with lexicoâ semantic processing and the ability to link word meanings to their orthographic forms.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138272/1/desc12449_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138272/2/desc12449.pd

Neural correlates of oral word reading, silent reading comprehension, and cognitive subcomponents

The ability to read is essential for cognitive development. To deepen our understanding of reading acquisition, we explored the neuroanatomical correlates (cortical thickness; CT) of word-reading fluency and sentence comprehension efficiency in Chinese with a group of typically developing children ( N = 21; 12 females and 9 males; age range 10.7–12.3 years). Then, we investigated the relationship between the CT of reading-defined regions and the cognitive subcomponents of reading to determine whether our study lends support to the multi-component model. The results demonstrated that children’s performance on oral word reading was positively correlated with CT in the left superior temporal gyrus (LSTG), left inferior temporal gyrus (LITG), left supramarginal gyrus (LSMG) and right superior temporal gyrus (RSTG). Moreover, CT in the LSTG, LSMG and LITG uniquely predicted children’s phonetic representation, phonological awareness, and orthography–phonology mapping skills, respectively. By contrast, children’s performance on sentence-reading comprehension was positively correlated with CT in the left parahippocampus (LPHP) and right calcarine fissure (RV1). As for the subcomponents of reading, CT in the LPHP was exclusively correlated with morphological awareness, whereas CT in the RV1 was correlated with orthography–semantic mapping. Taken together, these findings indicate that the reading network of typically developing children consists of multiple sub-divisions, thus providing neuroanatomical evidence in support of the multi-componential view of reading.</jats:p

Neural Correlates of Early-Stage Visual Processing Differences in Developmental Dyslexia

Reading requires the successful recruitment and coordination of brain networks to translate visual symbols into phonemes, which are then sequenced to match speech sounds and matched onto semantic representations. Although phonemic awareness is understood to be a core deficit associated with reading disability, neuroimaging has demonstrated an association between poor reading and disruption to various interrelated areas in the brain. This includes one of the major visual pathways, the magnocellular pathway, which contributes to the dorsal pathway in the brain and the processing of motion. For at least two decades, researchers have observed differences in motion processing, supported by the magnocellular pathway, between individuals with and without dyslexia (Eden et al., 1996; Gori et al., 2016; Livingstone et al., 1991; Wilmer, 2004). Further, psychometric studies report an association between reading ability and dorsal stream sensitivity in adults and in children before and after learning to read (Boets et al., 2011; Kevan & Pammer, 2009). Studies of the development of the major visual pathways have suggested that the magnocellular pathway follows a protracted course of development, which raises the possibility that it is vulnerable to pathological change during development and also has the potential for greater plasticity (Armstrong et al., 2002; Stevens & Neville, 2006). To explore the potential differences in early-stage visual processing, this dissertation study investigated whether neurophysiological measures, as indexed by event-related potentials (ERP), may differ between adults with and without dyslexia to stimuli tailored to evoke a response from each of two major visual pathways: magnocellular and parvocellular. The P1 component was elicited in response to motion stimuli designed to probe magnocellular pathways, and the N1 component was elicited in response to color stimuli designed for parvocellular processing. Group comparisons revealed statistically significant group differences in P1 amplitude for the motion/magnocellular condition, but no differences were found for N1 ERP measures for the parvocellular/color condition. Moderate to strong correlations between P1 measures in response to the magnocellular/motion condition were observed in relation to specific behavioral assessments: nonverbal reasoning and memory, orthographic choice, the word identification subtest from the Woodcock Reading Mastery Test (3rd edition: WRMT-III, Woodcock, 2011), and the sight word efficiency subtest from the Test of Word Reading Efficiency (2nd edition: TOWRE-2, Wagner, Torgesen, & Rashotte, 2011). These results are indicative of an early-stage visual processing disruption in individuals with dyslexia observable at the level of the brain. Due to the compounding impact of even small disruptions of sensory and cognitive processing on learning, refining our knowledge of the underlying neural mechanisms of reading may permit earlier identification and potentially more focused interventions that could yield better outcomes for struggling readers. Additionally, the association of those differences with measures of word decoding will inform further research into the underlying neural mechanisms that may contribute to dyslexia and skilled reading

Identifying brain and behavioral predictors of language and reading development in typically developing and at-risk children

Learning to read is essential, yet many children do not receive a diagnosis of developmental dyslexia (DD) until second or third grade. The aim of this dissertation is to identify brain and behavioral predictors of DD so that diagnosis and intervention can begin sooner. Experiment 1 examines infants with familial risk of DD longitudinally. Infants completed non-sedated diffusion-weighted imaging (DWI) between 4- and 18-months of age and cognitive-linguistic assessment at four years. Infants at- risk of DD displayed reduced fractional anisotropy (FA) and increased radial diffusivity (RD) in the left arcuate fasciculus (AF) and reduced FA and axial diffusivity (AD) of the splenium of the corpus callosum (CC) compared to peers without a familial risk. Both the left AF and CC are implicated in reading and reading-related tasks, and atypicalities have been observed in children and adults with DD. RD may reflect myelination and AD is thought to indicate pathway complexity suggesting infants at-risk of DD exhibit reduced myelination of the left AF and reduced pathway complexity of the CC at or shortly after birth. The left AF assessed in infancy predicted four-year-old vocabulary skills while the CC predicted four-year-old print knowledge. Experiment 2 explores the association between white matter microstructure of the left AF and CC and neural activity during phonological processing assessed via functional magnetic resonance imaging (fMRI). Preschoolers with and without a familial risk of DD completed DWI and an fMRI alliteration task where children indicated via button-press whether two words started with the same initial sound. Positive correlations were observed between FA of the left AF and CC and neural activity in the left medial temporal gyrus and the left lingual gyrus, two regions implicated in phonological processing. Experiment 3 examines whether white matter microstructure of the CC assessed in preschool is associated with school-age reading fluency in children with and without a familial risk of DD. Similar to children and adults with DD, preschoolers with a familial risk of DD displayed greater FA and AD of the CC compared to controls. Furthermore, AD of the CC predicted school-age reading fluency.2018-12-03T00:00:00