Children with reading difficulties show differences in brain regions associated with orthographic processing during spoken language processing.

We explored the neural basis of spoken language deficits in children with reading difficulty, specifically focusing on the role of orthography during spoken language processing. We used functional magnetic resonance imaging (fMRI) to examine differences in brain activation between children with reading difficulties (aged 9-to-15 years) and age-matched children with typical achievement during an auditory rhyming task. Both groups showed activation in bilateral superior temporal gyri (BA 42 and 22), a region associated with phonological processing, with no significant between-group differences. Interestingly, typically achieving children, but not children with reading difficulties, showed activation of left fusiform cortex (BA 37), a region implicated in orthographic processing. Furthermore, this activation was significantly greater for typically achieving children compared to those with reading difficulties. These findings suggest that typical children automatically activate orthographic representations during spoken language processing, while those with reading difficulties do not. Follow-up analyses revealed that the intensity of the activation in the fusiform gyrus was associated with significantly stronger behavioral conflict effects in typically achieving children only (i.e., longer latencies to rhyming pairs with orthographically dissimilar endings than to those with identical orthographic endings; jazz-has vs. cat-hat). Finally, for reading disabled children, a positive correlation between left fusiform activation and nonword reading was observed, such that greater access to orthography was related to decoding ability. Taken together, the results suggest that the integration of orthographic and phonological processing is directly related to reading ability.

Developmental changes in brain regions involved in phonological and orthographic processing during spoken language processing.

Developmental differences in brain activation of 9- to 15-year-old children were examined during an auditory rhyme decision task to spoken words using functional magnetic resonance imaging (fMRI). As a group, children showed activation in the left superior/middle temporal gyri (BA 22, 21), right middle temporal gyrus (BA 21), dorsal (BA 45, pars opercularis) and ventral (BA 46, pars triangularis) aspects of the left inferior frontal gyrus, and left fusiform gyrus (BA 37). There was a developmental increase in activation in the left middle temporal gyrus (BA 22) across all lexical conditions, suggesting that automatic semantic processing increases with age regardless of task demands. Activation in the left dorsal inferior frontal gyrus also showed developmental increases for the conflicting (e.g. PINT-MINT) compared to the non-conflicting (e.g. PRESS-LIST) non-rhyming conditions, indicating that this area becomes increasingly involved in strategic phonological processing in the face of conflicting orthographic and phonological representations. Left inferior temporal/fusiform gyrus (BA 37) activation was also greater for the conflicting (e.g. PINT-MINT) condition, and a developmental increase was found in the positive relationship between individuals' reaction time and activation in the left lingual/fusiform gyrus (BA 18) in this condition, indicating an age-related increase in the association between longer reaction times and greater visual-orthographic processing in this conflicting condition. These results suggest that orthographic processing is automatically engaged by children in a task that does not require access to orthographic information for correct performance, especially when orthographic and phonological representations conflict, and especially for longer response latencies in older children.

Neural correlates of orthographic and phonological consistency effects in children.

The objective of this study was to examine the neural correlates of phonological inconsistency (relationship of spelling to sound) and orthographic inconsistency (relationship of sound to spelling) in visual word processing using functional magnetic resonance imaging (fMRI). Children (9- to 15-year-old) performed a rhyming and spelling task in which two words were presented sequentially in the visual modality. Consistent with previous studies in adults, higher phonological inconsistency was associated with greater activation in several regions including left inferior frontal gyrus and medial frontal gyrus/anterior cingulate cortex. We additionally demonstrated an effect of orthographic inconsistency in these same areas, suggesting that these regions are involved in the integration of orthographic and phonological information and, with respect to the medial frontal/anterior cingulate, greater demands on executive function. Higher phonological and orthographic consistency was associated with greater activation in precuneus/posterior cingulate cortex, the putative steady state system active during resting, suggesting lower demands on cognitive resources for consistent items. Both consistency effects were larger for the rhyming compared with the spelling task suggesting greater demands of integrating spelling and sound in the former task. Finally, accuracy on the rhyming task was negatively correlated with the consistency effect in left fusiform gyrus. In particular, this region showed insensitivity to consistency in low performers, sensitivity to inconsistency (higher activity) in moderate performers, and sensitivity to inconsistency (high activation) and to consistency (deactivation). In general, these results show that the influence of spelling-sound (and sound-spelling) correspondences on processing in fusiform gyrus develops as a function of skill.

The interaction between orthographic and phonological information in children: an fMRI study.

We examined the neural representations of orthographic and phonological processing in children, while manipulating the consistency between orthographic and phonological information. Participants, aged 9-15, were scanned while performing rhyming and spelling judgments on pairs of visually presented words. The orthographic and phonological similarity between words in the pair was independently manipulated, resulting in four conditions. In the nonconflicting conditions, both orthography and phonology of the words were either (1) similar (lime-dime) or (2) different (staff-gain); in conflicting conditions, words had (3) similar phonology and different orthography (jazz-has) or (4) different phonology and similar orthography (pint-mint). The comparison between tasks resulted in greater activation for the rhyming task in bilateral inferior frontal gyri (BA 45/47), and greater activation for the spelling task in bilateral inferior/superior parietal lobules (BA 40/7), suggesting greater involvement of phonological and semantic processing in the rhyming task, and nonlinguistic spatial processing in the spelling task. Conflicting conditions were more difficult in both tasks and resulted in greater activation in the above regions. The results suggest that when children encounter inconsistency between orthographic and phonological information they show greater engagement of both orthographic and phonological processing.

Weaker top-down modulation from the left inferior frontal gyrus in children.

Previous studies have shown that developmental changes in the structure and function of prefrontal regions can continue throughout childhood and adolescence. Our recent results suggested a role for the left inferior frontal cortex in modulating task-dependent shifts in effective connectivity when adults focus on orthographic versus phonological aspects of presented words. Specifically, the top-down influence of the inferior frontal cortex determined whether incoming word-form information from the fusiform gyrus would have a greater impact on the parietal areas involved in orthographic processing or temporal areas involved in phonological processing (Bitan, T., Booth, J.R., Choy, J., Burman, D.D., Gitelman, D.R. and Mesulam, M.-M., 2005. Shifts of Effective Connectivity within a Language Network during Rhyming and Spelling. J. Neurosci. 25, 5397-5403.). In the current study, we find that children displayed an identical pattern of task-dependent functional activations within this network. In comparison to adults, however, children had significantly weaker top-down modulatory influences emanating from the inferior frontal area. Adult language processing may thus involve greater top-down cognitive control compared to children, resulting in less interference from task-irrelevant information.

Developmental and skill effects on the neural correlates of semantic processing to visually presented words.

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments to visual words in a group of 9- to 15-year-old children. Subjects were asked to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral inferior frontal gyri (Brodmann area [BA] 47, 45) and left middle temporal gyrus (BA 21). Words with strong semantic association elicited significantly greater activation in bilateral inferior parietal lobules (BA 40), suggesting stronger integration of highly related semantic features. By contrast, words with weak semantic association elicited greater activation in left inferior frontal gyrus (BA 45) and middle temporal gyrus (BA 21), suggesting more difficult feature search and more extensive access to semantic representations. We also examined whether age and skill explained unique variance in the patterns of activation. Increasing age was correlated with greater activation in left middle temporal gyrus (BA 21) and inferior parietal lobule (BA 40), suggesting that older children have more elaborated semantic representations and more complete semantic integration processes, respectively. Decreasing age was correlated with activation in right superior temporal gyrus (BA 22) and decreasing accuracy was correlated with activation in right middle temporal gyrus (BA 21), suggesting the engagement of ancillary systems in the right hemisphere for younger and lower-skill children.

Developmental changes in the neural correlates of semantic processing.

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments in the auditory modality in a group of 9- to 15-year-old children. Subjects were required to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral superior temporal gyri (BA 22) for recognizing spoken words as well as activations in bilateral inferior frontal gyri (BAs 47, 45) and left middle temporal gyrus (BA 21) for semantic processing. The neural substrates of semantic association and age differences were also investigated. Words with strong semantic association elicited significantly greater activation in the left inferior parietal lobule (BA 40), whereas words with weak semantic association elicited activation in left inferior frontal gyrus (BAs 47/45). Correlations with age were observed in the left middle temporal gyrus (BA 21) and the right inferior frontal gyrus (BA 47). The pattern of results for semantic association implies that the left inferior parietal lobule effectively integrates highly related semantic features and the left inferior frontal gyrus becomes more active for words that require a greater search for semantic associations. The developmental results suggest that older children recruit the right inferior frontal gyrus as they conduct a broader semantic search and the left middle temporal gyrus to provide more efficient access to semantic representations.