Reading skill correlates in frontal cortex during semantic and phonological processing

Abstract

Previous studies have generally shown that reading skill is related to a left hemisphere network involving temporal, parietal, or frontal components. A limitation of many of these studies, however, is the neuroimaging of a single reading task, so we know less about how skill modulates the engagement of reading network during various reading tasks. Within the connectionist model, reading engages both phonological and semantic processing regardless of whether it is for pronunciation or meaning. Both target [i.e., ortho-phonological (OP) or ortho-semantic (OS) ] and non-target [i.e., ortho-phono-semantic (OPS) or ortho-sem-phonological (OSP)] paths are likely simultaneously involved in reading. However, readers may vary in their division of labor across target and non-target paths as a function of task and reading skill. Therefore, the goal of the current study was to examine how skill modulates the neural mechanism of reading depending on the task. Children (aged 8 to 15) were given two reading tasks, namely, a rhyming judgment task tapping into orthographic-to-phonological mapping and a meaning judgment task tapping into orthographic-to-semantic mapping. Brain activation during these two reading tasks was then correlated with reading skill. Consistent with previous research showing functional separation of the dorsal versus ventral left inferior frontal gyrus (IFG), we found that better readers showed greater engagement of the opercularis for the rhyming task, whereas they showed a trend for greater engagement of the triangularis for the meaning task. A novel component of the study was to determine whether these skill related regions identified during the reading tasks were also correlated with activation during parallel rhyming and meaning tasks in the auditory modality. We found that better readers only reliably showed greater engagement of opercularis during auditory phonological processing, but there were trends for overall greater engagement of frontal regions with increasing skill. We did not find evidence for compensatory mechanisms for lower skill readers, either in the left or right hemisphere. Taken together, our study suggests some specificity of the frontal cortex for phonological versus semantic processing during reading, but that more effective access to posterior representations by the frontal cortex seems to be a general characteristic of better readers

Neural pathways of phonological and semantic processing and its relations to children’s reading skills

“…In 7-year-old children, stronger functional connectivity from dorsal IFG to STG during phonological processing has been shown to predict better word reading skills later in development ( Wang et al, 2021a ). A recent study using the same word rhyming and meaning tasks as the current study found that better readers showed greater engagement of the dorsal IFG (pars opercularis) during phonological processing and greater engagement of the ventral IFG (pars triangularis) during semantic processing ( Brozdowski and Booth, 2021 , preprint ). However, this study focused on single word reading and did not examine connectivity.…”

“…In a recent study using a word rhyming and a word meaning task, better readers showed greater engagement of the dorsal IFG (pars opercularis) during phonological processing ( r = 0.40) and a trend for greater engagement of the ventral IFG (pars triangularis) during semantic processing ( r = 0.30; Brozdowski and Booth, 2021 , preprint ). However, reading skill was only assessed at the single-word level.…”

Adaptive plasticity in the healthy reading network investigated through combined neurostimulation and neuroimaging

“…Nevertheless, we found TMS-induced changes in fine-grained multi-voxel activity patterns in the left IFC between effective and sham TMS, selectively for pseudoword (but not for word) reading. In terms of the functional role of the left IFC for reading, theories hold that it is crucial for phonological output resolution and rhyming during reading (Taylor et al, 2013; Brozdowski & Booth, 2021), as well as attention and working memory (Corbetta et al, 2002; Tops & Boksem, 2011). With pseudowords having a higher decoding demand and thus requiring more effort, specifically after inhibition of the left TPC, it is likely that differences in response patterns of the left IFC at least partially stem from higher demands on attention, executive functions, and cognitive control.…”