Neural specialization of phonological and semantic processing in young children

Abstract

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.

Neural bases of phonological and semantic processing in early childhood

“…Thus, our findings suggest that IFG sub-regions are specialized in early childhood for phonological processing but not for semantic categorization. We did not find specialization of temporal sub-regions as observed by Weiss et al (2018), which might be attributed to the modality of stimuli, visual-only stimuli (this study) versus audio-only stimuli (Weiss et al 2018).…”

“…However, our study does not show evidence for temporal specialization for the phonological processing and fronto-temporal specialization for the semantic processing. On the contrary, using an auditory rhyme and semantic judgment tasks, Weiss et al (2018) reported the specialization for the phonological processing in the left STG and SMG, and the specialization for the semantic processing in the left MTG by the age of 5-6-years. Some differences between our findings and results from Weiss et al (2018) could be attributed to modality of stimuli.…”

“…Our study provides evidence of bilateral parietal involvement for semantic decision making even in young children (5-7 years of age). On the contrary, Weiss et al (2018) did not find parietal specialization for semantic categorization task using auditory stimuli for young children (5-6 years of age) and instead they argued that parietal areas might specialize for semantic processing only later in development. We predict that perhaps visual stimuli implemented in this study require high imageability for semantic decision making and thus bilateral parietal areas are recruited for visual semantic categorization task in young children.…”

“…In adults, the grapho-phonological processing relies on opercularis part of left IFG and left STG, while the lexico-semantic processing relies on orbitalis part of left IFG and left MTG (Poldrack et al 1999;Devlin et al 2003;McDermott et al 2003;Price and Mechelli 2005;Friederici 2011;Price 2012;Binder 2016). There is only one recent study that directly compared the early specialization of brain regions for phonological and semantic processing of spoken language during early childhood (5-6 years) using an auditory rhyme and semantic judgment tasks, respectively (Weiss et al 2018). They reported overlap in activity in the bilateral frontotemporal cortex for the two tasks.…”

Early Phonological Neural Specialization Predicts Later Growth in Word Reading Skills

“…Recently, Weiss et al (2018) conducted one of the first investigations to date exploring whether language-related neural specialization is observable in young children. Specifically, the authors examined whether 5.5-to-6.5 year old children showed evidence of distinct brain regions uniquely supporting phonological over semantic processing (or alternatively semantic over phonological processing).…”