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Neural specialization of linguistic processes
The neural specialization of phonological and semantic processing during auditory word processing in 7 and 9-year-old children
Findings:
- Using univariate analysis, we compared brain activation during a phonological awareness task with that during a semantic association task to assess neural specialization. We found that the left superior temporal gyrus (STG) and dorsal inferior frontal gyrus (dIFG) showed greater activation for the phonological than the semantic task, whereas the left middle temporal gyrus (MTG) and ventral inferior frontal gyrus (vIFG) exhibited greater activation for the semantic than the phonological task. This double dissociation, observed in both 7- and 9-year-old children, supports the presence of functional specialization within the language network. Compared with 5-year-old children, who showed temporal specialization only in a prior study (Weiss et al., 2018), the additional frontal specialization observed in our study suggests that by age 7, children are already efficiently engaging higher-level linguistic control for auditory word processing, similar to adults.
- Beyond specialization, we examined neural sensitivity by comparing harder versus easier conditions within each task. In 7-year-old children, the dorsal IFG emerged as a shared region showing greater activation for harder than easier conditions across both language tasks. In contrast, by age 9, only linguistically specialized regions showed increased activation for harder conditions. This developmental shift—from reliance on domain-general to domain-specific brain regions for challenging language tasks—suggests continued fine-tuning of neural specialization for phonological and semantic processing through approximately ages 9–10.
Educational or Practical Implications
- Around age 7, teachers and parents should shift from primarily providing high-quality spoken word exposure, which engages the temporal lobe, to incorporating more analytical activities on spoken words that engage the frontal lobe. This approach can leverage the emerging frontal specialization for auditory words and support continued refinement of phonological and semantic processing through age 10. Around age 7, teachers and parents should shift from primarily providing high-quality spoken word exposure, which engages the temporal lobe, to incorporating more analytical activities on spoken words that engage the frontal lobe. This approach can leverage the emerging frontal specialization for auditory words and support continued refinement of phonological and semantic processing through age 10.
The neural specialization of semantic and syntactic specialization during auditory sentence processing in 5, 7, and 9-year-old children
Citations: Wang et al., 2020 in JCN (see original paper); Wang et al., 2021 in Cortex (see original paper); Wang et al., 2024 in Scientific Reports (see original paper).
Findings:
- Using multi-voxel pattern analysis (MVPA), we compared brain activation patterns during a semantic plausibility task and a grammaticality judgment task to examine neural specialization for semantic and syntactic processing in auditory sentence comprehension. In 5-year-old children, the left superior temporal gyrus (STG) was sensitive to both semantic and syntactic information, with distinct activation patterns representing each type of information within the same region. Strong semantic specialization was observed in the left middle temporal gyrus (MTG), which showed no sensitivity to syntactic information. By age 7, strong semantic specialization began to emerge in the left ventral inferior frontal gyrus (vIFG), while the left MTG showed reduced specialization as its sensitivity to syntactic information increased. In 9-year-old children, syntactic specialization started to appear in the left dorsal inferior frontal gyrus (dIFG), whereas other language regions—including the STG, MTG, and vIFG—remained sensitive to both semantic and syntactic information, showing distinct activation patterns without exclusive specialization for either component. These findings support the existence and developmental progression of neural specialization for auditory sentence processing. Notably, unlike auditory word processing, which gradually recruits distinct brain regions for phonological and semantic information, children appear to utilize overlapping language areas for sentences, differentiating semantic and syntactic information primarily through distinct activation patterns as specialization develops.
Educational or Practical Implications
- Between ages 5 and 7, teachers and parents should focus on supporting vocabulary and meaning acquisition in auditory sentences to promote sentence comprehension. Around age 7, instruction should transition from primarily increasing vocabulary exposure to fostering analytical skills with vocabulary, leveraging the emerging frontal lobe specialization. By approximately age 9, emphasis should shift to developing analytical skills for grammar in auditory sentences, aligning with the emergence of syntactic neural specialization.
Lateralization of activation within the superior temporal gyrus during speech perception in sleeping infants is associated with subsequent language skills in kindergarten: A passive listening task-fMRI study
Citations: Wang et al., 2024 in Brain and Language (see original paper).
Findings:
- Using a passive-listening task-fMRI design during natural sleep, we analyzed brain activity in the superior temporal gyrus (STG) of 25 infants (aged 2–13 months) listening to forward and backward speech, and longitudinally reassessed their language abilities 4 to 5 years later in preschool/kindergarten (aged 55–69 months).
- Infants showed a group-level right-lateration of brain activation for the forward versus backward speech contrast within STG. This pattern is different from the widely observed left-lateralization of speech perception in adults, suggesting that infants are still developing their brain specialization.However, analyses focusing on individual differences showed that stronger left-lateralization for the forward versus backward speech contrast in the infant STG was significantly associated with higher subsequent oral expressive, phonetic coding (phonological skills), and receptive picture vocabulary skills in kindergarten age.Hierarchical regression analyses further demonstrated that this longitudinal predictive effect remained even after controlling for baseline infant language scores.
- Neither infant behavioral language scores nor infant anatomical lateralization of the STG (measured by surface area, cortical thickness, and gray matter volume) was significantly related to subsequent language outcomes. These null findings suggest that early functional, rather than structural, brain measures may be uniquely sensitive to future language development.
Educational or Practical Implications
- Functional brain activation for speech perception in the infant STG may be a more sensitive index for predicting long-term language skill development than behavioral observations in infancy or infant structural brains . Although we are far from using infant brains to diagnose future language delays, this early emergence of skill-related neural markers in infancy indicates that preventive language-rich environmental supports should be dynamically considered from birth as brain differences already start to appear.
