This study aimed to examine early specialization of brain regions for phonological and semantic processing of spoken language in young children. Thirty-five typically developing children from 5- to 6-years of age performed auditory phonological (same sound judgment) and semantic (related meaning judgment) word-level tasks. Using functional Magnetic Resonance Imaging, we examined specialization within the language network, by conducting three levels of analysis. First, we directly compared activation between tasks and found a greater sound judgment as compared to meaning judgment activation in left superior temporal gyrus (STG) and supramarginal gyrus. In contrast, greater meaning judgment as compared to sound judgment task activation was found in left middle temporal gyrus (MTG). Second, we examined the brain-behavior correlations and found that phonological skill was correlated with the task difference in activation in left superior temporal sulcus, whereas semantic skill was correlated with the task difference in activation in left MTG. Third, we compared between two experimental conditions within each task and found a parametric effect in left STG for the sound judgment task, and a parametric effect in left MTG for the meaning judgment task. The results of this study indicate that, by the age of 5-6 years, typically developing children already show some specialization of temporo-parietal brain regions for phonological and semantic processes. However, there were no task differences in the left inferior frontal gyrus, suggesting that the frontal cortex may not yet be specialized in this age range, which is consistent with the delayed maturation of the frontal cortex.

A previous functional magnetic resonance imaging (fMRI) study by Weiss et al.

The comparison of words and pseudowords has been extensively used in adult neuroimaging studies to inform neurocognitive models of reading but has rarely been used to inform models of reading acquisition. Using a rhyming judgment task, the current study examined age-related differences in the spelling to sound mapping mechanisms involved in word and pseudoword reading. We hypothesized a developmental increase in specialization of the brain mechanisms engaged for word and pseudoword processing. Consistent with adult studies, children in the current study demonstrated a greater activation for words as compared to pseudowords in the anterior left ventral occipito-temporal cortex (vOT). Inconsistent with adult studies, children also showed greater activation for words as compared to pseudowords in the mid-posterior left vOT, indicating a robust semantic influence on orthographic processing in young readers. Furthermore, our results did not indicate a lexicality by age interaction for 8- to 13-year-old children, suggesting that the adult-like specialization in the left vOT only appears later in development.

The current study examined the effects of transparency and familiarity on word recognition in adult Hebrew dyslexic readers with a phonological processing deficit as compared to typical readers. We measured oral reading response time and accuracy of single nouns in several conditions: diacritics that provide transparent but less familiar information and vowel letters that increase orthographic transparency without compromise familiarity. In line with former studies with adult dyslexics, Hebrew-speaking adults with dyslexia were significantly slower than controls. However, both dyslexic and typical readers read unpointed words faster when vowel letters were present, indicating that they may benefit from increase in orthographic transparency, when the graphemic representations are familiar. Only dyslexics read pointed words slower than unpointed words and were more sensitive to word frequency. In unpointed words, only typical readers benefitted from the reduced competition of orthographic neighbors of longer words. Results indicate that both orthographic transparency and familiarity play an important role in word recognition. Dyslexics are impaired in decoding of smaller units and are more sensitive to reduction in the familiarity of words.

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