Authors: Bolger, D. J., Minas, J., Burman, D. D., & Booth, J. R..
Publication: Neuropsychologia (Elsevier). 46(14), 3210–3224 2008 | DOI: 10.1016/j.neuropsychologia.2008.07.024
One of the central challenges in mastering English is becoming sensitive to consistency from spelling to sound (i.e. phonological consistency) and from sound to spelling (i.e. orthographic consistency). Using functional magnetic resonance imaging (fMRI), we examined the neural correlates of consistency in 9–15-year-old Normal and Impaired Readers during a rhyming task in the visual modality. In line with our previous study [Bolger, D. J., Hornickel, J., Cone, N. E., Burman, D. D., & Booth, J. R. (in press). Neural correlates of orthographic and phonological consistency effects in children. Human Brain Mapping], for Normal Readers, lower phonological and orthographic consistency were associated with greater activation in several regions including bilateral inferior/middle frontal gyri, bilateral anterior cingulate cortex as well as left fusiform gyrus. Impaired Readers activated only bilateral anterior cingulate cortex in response to decreasing consistency. Group comparisons revealed that, relative to Impaired Readers, Normal Readers exhibited a larger response in this network for lower phonological consistency whereas orthographic consistency differences were limited. Lastly, brain–behavior correlations revealed a significant relationship between skill (i.e. Phonological Awareness and non-word decoding) and cortical consistency effects for Impaired Readers in left inferior/middle frontal gyri and left fusiform gyrus. Impaired Readers with higher skill showed greater activation for higher consistency. This relationship was reliably different from that of Normal Readers in which higher skill was associated with greater activation for lower consistency. According to single-route or connectionist models, these results suggest that Impaired Readers with higher skill devote neural resources to representing the mapping between orthography and phonology for higher consistency words, and therefore do not robustly activate this network for lower consistency words.
[L]ower phonological consistency … occurs when the same spelling has different pronunciations (e.g. seat versus sweat)….
Our previous study, with the same groups of participants on the same task, but that did not examine consistency effects, found that both normal and Impaired Readers activated medial frontal gyrus/anterior cingulate and that there was no difference between groups in activation in this region (Cao et al., in press). This suggests that Impaired Readers can robustly activate medial frontal gyrus/anterior cingulate, but that it is not as responsive to the conflict between orthographic and phonological representations as compared to Normal Readers. This lack of responsiveness is likely due to deficits in other brain regions that are responsible integrating orthographic and phonological representations.
[O]ur results suggests that a central deficit in reading disability is the lack of integration of orthographic and phonological information….That is, Impaired Readers may have an established lexical representation for the words ‘pint’ and ‘mint’, however, these readers may fail to decompose these items into sub-lexical orthographic constituents (e.g. p/m+int) and associate them with varying phonological constituents (e.g./AYnt/ versus /int/).
In our study, there was a (non-significant) trend for Normal Readers with higher Phonological Awareness to show greater activation for lower phonological consistency in left inferior and middle frontal gyri. In contrast, higher Phonological Awareness in Impaired Readers was reliably associated with greater activation for higher phonological consistency in these same regions.
In our study, there was a significant decrease in slope values for Impaired Readers as a function of decoding skill in left fusiform gyrus, indicating greater activation for higher orthographic consistency. In contrast, Normal Readers showed a reliably increase in slope values as decoding scores increased as illustrated in Fig. 4, indicating greater activation for lower orthographic consistency in this same region.
Impaired Readers with higher Phonological Awareness and decoding skills showed greater activation in left inferior/middle frontal gyri and left fusiform gyrus for higher consistency words, suggesting that they more effectively engage the reading network for processing words with consistent spelling-to-sound correspondences.
Bolger, D. J., Minas, J., Burman, D. D., & Booth, J. R. (2008). Differential effects of orthographic and phonological consistency in cortex for children with and without reading impairment. Neuropsychologia, 46(14), 3210–3224. doi:10.1016/j.neuropsychologia.2008.07.024