Inconsistent language lateralisation - Testing the dissociable language laterality hypothesis using behaviour and lateralised cerebral blood flow.

BACKGROUND: Most people have strong left-brain lateralisation for language, with a minority showing right- or bilateral language representation. On some receptive language tasks, however, lateralisation appears to be reduced or absent. This contrasting pattern raises the question of whether and how language laterality may fractionate within individuals. Building on our prior work, we postulated (a) that there can be dissociations in lateralisation of different components of language, and (b) these would be more common in left-handers. A subsidiary hypothesis was that laterality indices will cluster according to two underlying factors corresponding to whether they involve generation of words or sentences, versus receptive language. METHODS: We tested these predictions in two stages: At Step 1 an online laterality battery (Dichotic listening, Rhyme Decision and Word Comprehension) was given to 621 individuals (56% left-handers); At Step 2, functional transcranial Doppler ultrasound (fTCD) was used with 230 of these individuals (51% left-handers). 108 left-handers and 101 right-handers gave useable data on a battery of three language generation and three receptive language tasks. RESULTS: Neither the online nor fTCD measures supported the notion of a single language laterality factor. In general, for both online and fTCD measures, tests of language generation were left-lateralised. In contrast, the receptive tasks were at best weakly left-lateralised or, in the case of Word Comprehension, slightly right-lateralised. The online measures were only weakly correlated, if at all, with fTCD measures. Most of the fTCD measures had split-half reliabilities of at least .7, and showed a distinctive pattern of intercorrelation, supporting a modified two-factor model in which Phonological Decision (generation) and Sentence Decision (reception) loaded on both factors. The same factor structure fitted data from left- and right-handers, but mean scores on the two factors were lower (less left-lateralised) in left-handers. CONCLUSIONS: There are at least two factors influencing language lateralization in individuals, but they do not correspond neatly to language generation and comprehension. Future fMRI studies could help clarify how far they reflect activity in specific brain regions.

How executive functions contribute to reading comprehension.

BACKGROUND: Executive functions have been proposed to account for individual variation in reading comprehension beyond the contributions of decoding skills and language skills. However, insight into the direct and indirect effects of multiple executive functions on fifth-grade reading comprehension, while accounting for decoding and language skills, is limited. AIM: The present study investigated the direct and indirect effects of fourth-grade executive functions (i.e., working memory, inhibition, and planning) on fifth-grade reading comprehension, after accounting for decoding and language skills. SAMPLE: The sample included 113 fourth-grade children (including 65 boys and 48 girls; Age M = 9.89; SD = .44 years). METHODS: The participants were tested on their executive functions (working memory, inhibition and planning), and their decoding skills, language skills (vocabulary and syntax knowledge) and reading comprehension, one year later. RESULTS: Using structural equation modelling, the results indicated direct effects of working memory and planning on reading comprehension, as well as indirect effects of working memory and inhibition via decoding (χ2  = 2.46). CONCLUSIONS: The results of the present study highlight the importance of executive functions for reading comprehension after taking variance in decoding and language skills into account: Both working memory and planning uniquely contributed to reading comprehension. In addition, working memory and inhibition also supported decoding. As a practical implication, educational professionals should not only consider the decoding and language skills children bring into the classroom, but their executive functions as well.

Online management of text production from pictures: a comparison between fifth graders and undergraduate students.

This study was designed to enhance our understanding of the online management of writing processes by two groups of writers with a different level of expertise, and to explore the impact of this online management on text quality. To this aim, fifth graders (mean age 10.5 years) and undergraduate students (mean age 22.6 years) were asked to compose a narrative from a visual source of images, while their handwriting activity and eye movements were recorded by means of Eye & Pen software and a digitizing tablet. Results showed that fifth graders and undergraduate students used different strategies to engage in high-level source-based text elaboration processes throughout their writing. The main differences concerned the density of source consultation during prewriting, on the one hand, and during pauses, on the other hand. Relationships between these characteristics of online management and text quality were minimal in fifth graders, while in undergraduate students they were more substantial as in the case of syntactic complexity. These findings suggest that with age, the online management of writing becomes more closely related to text quality. In line with a capacity view of writing, it is also concluded that the online management of writing processes of fifth graders is highly constrained by a lack of fluent text production skills which ultimately affects their text quality.

Enhanced semantic involvement during word recognition in children with dyslexia.

We investigated whether children with dyslexia show enhanced semantic involvement as compensation for deficient phonological processing during reading. Phonological and semantic processing during reading and moderating effects of word frequency and word length in children with and without dyslexia were examined using a picture-word priming paradigm. Participants were 61 children with dyslexia and 50 typical readers in Grade 6 of primary school. Primes were either semantically or phonologically (shared onset and rime) related or unrelated to their target word. Results showed that priming effects were stronger in children with dyslexia than in typical readers in the semantic condition but did not differ between groups in the phonological condition. Overall, word length and word frequency effects were stronger for children with dyslexia than for typical readers, but word length and word frequency did not affect priming effects differently for the two groups. In both groups, only semantic priming effects were stronger for low-frequency longer words. Finally, individual word and pseudoword reading efficiency correlated with priming effects only in the semantic condition and only in children with dyslexia. It can be concluded that children with dyslexia, compared with typical readers, rely more on semantic information in word reading but do not show deficient phonological activation during reading compared with typical readers.

Adult dyslexic readers benefit less from visual input during audiovisual speech processing: fMRI evidence.

The aim of the present fMRI study was to investigate whether typical and dyslexic adult readers differed in the neural correlates of audiovisual speech processing. We tested for Blood Oxygen-Level Dependent (BOLD) activity differences between these two groups in a 1-back task, as they processed written (word, illegal consonant strings) and spoken (auditory, visual and audiovisual) stimuli. When processing written stimuli, dyslexic readers showed reduced activity in the supramarginal gyrus, a region suggested to play an important role in phonological processing, but only when they processed strings of consonants, not when they read words. During the speech perception tasks, dyslexic readers were only slower than typical readers in their behavioral responses in the visual speech condition. Additionally, dyslexic readers presented reduced neural activation in the auditory, the visual, and the audiovisual speech conditions. The groups also differed in terms of superadditivity, with dyslexic readers showing decreased neural activation in the regions of interest. An additional analysis focusing on vision-related processing during the audiovisual condition showed diminished activation for the dyslexic readers in a fusiform gyrus cluster. Our results thus suggest that there are differences in audiovisual speech processing between dyslexic and normal readers. These differences might be explained by difficulties in processing the unisensory components of audiovisual speech, more specifically, dyslexic readers may benefit less from visual information during audiovisual speech processing than typical readers. Given that visual speech processing supports the development of phonological skills fundamental in reading, differences in processing of visual speech could contribute to differences in reading ability between typical and dyslexic readers.

Response to Intervention as a Predictor of Long-Term Reading Outcomes in Children with Dyslexia.

The goal of this study was to investigate how growth during a phonics-based intervention, as well as reading levels at baseline testing, predicted long-term reading outcomes of children with dyslexia. Eighty Dutch children with dyslexia who had completed a 50-week phonics-based intervention in grade 4 were tested in grade 5 on both word and pseudoword (following regular Dutch orthographic patterns) reading efficiency and compared to 93 typical readers. In grade 5 the children with dyslexia were still significantly slower in word and pseudoword reading than their typically developing peers. Results showed that long-term pseudoword reading in the group with dyslexia was predicted by pseudoword reading at pretest and growth in pseudoword reading during the intervention, which was itself predicted by pseudoword reading at pretest. This was not the case for word reading. We found that long-term word reading was directly predicted from pretest word reading, and indirectly via pretest pseudoword reading, via growth in pseudoword and word reading. It can be concluded that pseudoword reading is not only a good indicator of severity of reading difficulties in children with dyslexia, it is also an indicator of who will profit from intervention in the long-term. Copyright © 2017 John Wiley & Sons, Ltd.

Increased Response to Altered Auditory Feedback in Dyslexia: A Weaker Sensorimotor Magnet Implied in the Phonological Deficit.

Purpose: The purpose of this study was to examine whether developmental dyslexia (DD) is characterized by deficiencies in speech sensory and motor feedforward and feedback mechanisms, which are involved in the modulation of phonological representations. Method: A total of 42 adult native speakers of Dutch (22 adults with DD; 20 participants who were typically reading controls) were asked to produce /bep/ while the first formant (F1) of the /e/ was not altered (baseline), increased (ramp), held at maximal perturbation (hold), and not altered again (after-effect). The F1 of the produced utterance was measured for each trial and used for statistical analyses. The measured F1s produced during each phase were entered in a linear mixed-effects model. Results: Participants with DD adapted more strongly during the ramp phase and returned to baseline to a lesser extent when feedback was back to normal (after-effect phase) when compared with the typically reading group. In this study, a faster deviation from baseline during the ramp phase, a stronger adaptation response during the hold phase, and a slower return to baseline during the after-effect phase were associated with poorer reading and phonological abilities. Conclusion: The data of the current study are consistent with the notion that the phonological deficit in DD is associated with a weaker sensorimotor magnet for phonological representations.

How working memory relates to children's reading comprehension: the importance of domain-specificity in storage and processing.

Working memory is considered a well-established predictor of individual variation in reading comprehension in children and adults. However, how storage and processing capacities of working memory in both the phonological and semantic domain relate to reading comprehension is still unclear. In the current study, we investigated the contribution of phonological and semantic storage, and phonological and semantic processing to reading comprehension in 123 Dutch children in fifth grade. We conducted regression and mediation analyses to find out to what extent variation in reading comprehension could be explained by storage and processing capacities in both the phonological and the semantic domain, while controlling for children's decoding and vocabulary. The analyses included tasks that reflect storage only, and working memory tasks that assess processing in addition to storage. Regression analysis including only storage tasks as predictor measures, revealed semantic storage to be a better predictor of reading comprehension than phonological storage. Adding phonological and semantic working memory tasks as additional predictors to the model showed that semantic working memory explained individual variation in reading comprehension over and above all other memory measures. Additional mediation analysis made it clear that semantic storage contributed indirectly to reading comprehension via semantic working memory, indicating that semantic storage tapped by working memory, in addition to processing capacities, explains individual variation in reading comprehension. It can thus be concluded that semantic storage plays a more important role in children's reading comprehension than previously thought.

How executive functions predict development in syntactic complexity of narrative writing in the upper elementary grades.

The aim of this study was to examine the contribution of transcription skills, oral language skills, and executive functions to growth in narrative writing between fourth and sixth grade. While text length and story content of narratives did not increase with age, syntactic complexity of narratives showed a clear developmental progression. Results from path analyses revealed that later syntactic complexity of narrative writing was, in addition to initial syntactic complexity, predicted by oral grammar, inhibition, and planning. These results are discussed in light of the changes that characterize writing development in the upper elementary grades. More specifically, this study emphasizes the relevance of syntactic complexity as a developmental marker as well as the importance of executive functions for later writing development.

A General Audiovisual Temporal Processing Deficit in Adult Readers With Dyslexia.

Purpose: Because reading is an audiovisual process, reading impairment may reflect an audiovisual processing deficit. The aim of the present study was to test the existence and scope of such a deficit in adult readers with dyslexia. Method: We tested 39 typical readers and 51 adult readers with dyslexia on their sensitivity to the simultaneity of audiovisual speech and nonspeech stimuli, their time window of audiovisual integration for speech (using incongruent /aCa/ syllables), and their audiovisual perception of phonetic categories. Results: Adult readers with dyslexia showed less sensitivity to audiovisual simultaneity than typical readers for both speech and nonspeech events. We found no differences between readers with dyslexia and typical readers in the temporal window of integration for audiovisual speech or in the audiovisual perception of phonetic categories. Conclusions: The results suggest an audiovisual temporal deficit in dyslexia that is not specific to speech-related events. But the differences found for audiovisual temporal sensitivity did not translate into a deficit in audiovisual speech perception. Hence, there seems to be a hiatus between simultaneity judgment and perception, suggesting a multisensory system that uses different mechanisms across tasks. Alternatively, it is possible that the audiovisual deficit in dyslexia is only observable when explicit judgments about audiovisual simultaneity are required.

Children's use of evaluative devices in spoken and written narratives.

This study investigated the development of evaluation in narratives from middle to late childhood, within the context of differentiating between spoken and written modalities. Two parallel forms of a picture story were used to elicit spoken and written narratives from fourth- and sixth-graders. It was expected that, in addition to an increase of evaluative devices with age, written narratives would exhibit a higher frequency and diversity as a result of the intrinsic differences between the two modalities. From a developmental perspective, the results showed that only few categories exhibited the expected increase with age. Qualitative analyses provided a fruitful method to illustrate developmental changes. The results further indicated that modality had the expected impact on the diversity, and on the frequency, of most categories of evaluative language. Specifically, markers of decontextualized language and categories with a high degree of syntactic complexity were prone to modality differences.

Bidirectional Relations between Text Reading Prosody and Reading Comprehension in the Upper Primary School Grades: A Longitudinal Perspective.

The purpose of this study was to examine the directionality of the relationship between text reading prosody and reading comprehension in the upper grades of primary school. We compared three theoretical possibilities: Two unidirectional relations from text reading prosody to reading comprehension and from reading comprehension to text reading prosody and a bidirectional relation between text reading prosody and reading comprehension. Further, we controlled for autoregressive effects and included decoding efficiency as a measure of general reading skill. Participants were 99 Dutch children, followed longitudinally, from fourth- to sixth-grade. Structural equation modeling showed that the bidirectional relation provided the best fitting model. In fifth-grade, text reading prosody was related to prior decoding and reading comprehension, whereas in sixth-grade, reading comprehension was related to prior text reading prosody. As such, the results suggest that the relation between text reading prosody and reading comprehension is reciprocal, but dependent on grade level.

The Contribution of Segmental and Suprasegmental Phonology to Reading Comprehension.

The aim of the present study was to examine the relation between decoding and segmental and suprasegmental phonology, and their contribution to reading comprehension, in the upper primary grades. Following a longitudinal design, the performance of 99 Dutch primary school children on phonological awareness (segmental phonology) and text reading prosody (suprasegmental phonology) in fourth-grade and fifth-grade, and reading comprehension in sixth-grade were examined. In addition, decoding efficiency as a general assessment of reading was examined. Structural path modeling firstly showed that the relation between decoding efficiency and both measures of phonology from fourth- to fifth grade was unidirectional. Secondly, the relation between decoding in fourth- and fifth-grade and reading comprehension in sixth-grade became indirect when segmental and suprasegmental phonology were added to the model. Both factors independently exerted influence on later reading comprehension. This leads to the conclusion that not only segmental, but also suprasegmental phonology, contributes substantially to children's reading development.

The contribution of executive functions to narrative writing in fourth grade children.

The present study investigated the contribution of executive functions to narrative writing in fourth grade children, and evaluated to what extent executive functions contribute differentially to different levels of narrative composition. The written skills of 102 Dutch children in fourth grade were assessed using a narrative picture-elicitation task. In addition, a large test battery assessing transcription skills, language skills and executive functions, was administered. The results showed that executive functions contributed both directly and indirectly to narrative composition. More specifically, analyses revealed that inhibition and updating, but not planning, contributed directly to the text length of the narrative, and indirectly, through handwriting, to the text length, syntactic complexity, and story content. The findings underscore the need to assess a variety of executive functions and support the idea that in developing writers executive functions also play a role in more complex written composition tasks, such as narrative writing.

The role of speech prosody and text reading prosody in children's reading comprehension.

BACKGROUND: Text reading prosody has been associated with reading comprehension. However, text reading prosody is a reading-dependent measure that relies heavily on decoding skills. Investigation of the contribution of speech prosody - which is independent from reading skills - in addition to text reading prosody, to reading comprehension could provide more insight into the general role of prosody in reading comprehension. AIMS: The current study investigates how much variance in reading comprehension scores is explained by speech prosody and text reading prosody, after controlling for decoding, vocabulary, and syntactic awareness. SAMPLE: A battery of reading and language assessments was performed by 106 Dutch fourth-grade primary school children. METHODS: Speech prosody was assessed using a storytelling task and text reading prosody by oral text reading performance. Decoding skills, vocabulary, syntactic awareness, and reading comprehension were assessed using standardized tests. RESULTS: Hierarchical regression analyses showed that text reading prosody explained 6% of variance and that speech prosody explained 8% of variance in reading comprehension scores, after controlling for decoding, vocabulary, and syntactic awareness. Phrasing was the significant factor in both speech and text reading. When added in consecutive order, phrasing in speech added 5% variance to phrasing in reading. In contrast, phrasing in reading added only 3% variance to phrasing in speech. CONCLUSIONS: The variance that speech prosody explained in reading comprehension scores should not be neglected. Speech prosody seems to facilitate the construction of meaning in written language.

Associations between handedness and cerebral lateralisation for language: a comparison of three measures in children.

It has been known for many years that hand preference is associated with cerebral lateralisation for language, but the relationship is weak and indirect. It has been suggested that quantitative measures of differential hand skill or reaching preference may provide more valid measures than traditional inventories, but to date these have not been validated against direct measures of cerebral lateralisation. We investigated the associations of three different handedness assessments; 1) a hand preference inventory, 2) a measure of relative hand skill, and 3) performance on a reaching task; with cerebral lateralisation for language function as derived from functional transcranial Doppler ultrasound during a language production task, in a group of 57 typically developing children aged from 6 to 16 years. Significant correlations between cerebral lateralisation for language production and handedness were found for a short version of the inventory and for performance on the reaching task. However, confidence intervals for the correlations overlapped and no one measure emerged as clearly superior to the others. The best handedness measures accounted for only 8-16% of the variance in cerebral lateralisation. These findings indicate that researchers should not rely on handedness as an indicator of cerebral lateralisation for language. They also imply that lateralisation of language and motor functions in the human brain show considerable independence from one another.

Does cerebral lateralization develop? A study using functional transcranial Doppler ultrasound assessing lateralization for language production and visuospatial memory.

In the majority of people, language production is lateralized to the left cerebral hemisphere and visuospatial skills to the right. However, questions remain as to when, how, and why humans arrive at this division of labor. In this study, we assessed cerebral lateralization for language production and for visuospatial memory using functional transcranial Doppler ultrasound in a group of 60 typically developing children between the ages of six and 16 years. The typical pattern of left-lateralized activation for language production and right-lateralized activation for visuospatial memory was found in the majority of the children (58%). No age-related change in direction or strength of lateralization was found for language production. In contrast, the strength of lateralization (independent of direction) for visuospatial memory function continued to increase with age. In addition, boys showed a trend for stronger right-hemisphere lateralization for visuospatial memory than girls, but there was no gender effect on language laterality. We tested whether having language and visuospatial functions in the same hemisphere was associated with poor cognitive performance and found no evidence for this "functional crowding" hypothesis. We did, however, find that children with left-lateralized language production had higher vocabulary and nonword reading age-adjusted standard scores than other children, regardless of the laterality of visuospatial memory. Thus, a link between language function and left-hemisphere lateralization exists, and cannot be explained in terms of maturational change.

Where were those rabbits? A new paradigm to determine cerebral lateralisation of visuospatial memory function in children.

In the majority of people, functional differences are observed between the two cerebral hemispheres: language production is typically subserved by the left hemisphere and visuospatial skills by the right hemisphere. The development of this division of labour is not well understood and lateralisation of visuospatial function has received little attention in children. In this study we devised a child-friendly version of a paradigm to assess lateralisation of visuospatial memory using functional transcranial Doppler ultrasound (fTCD). In a group of 24 adults we found this child-friendly version gave similar results to the original version of the task. In addition, fourteen children aged 6-8 years successfully completed the child-friendly fTCD task, showing a negative lateralisation index, indicating right hemispheric specialisation at the group level. Additionally, we assessed effects of task accuracy and reaction time on the lateralisation index. No effects were found, at the group level or at the level of single trials, in either the adult or the child group. We conclude that this new task reliably assesses lateralisation of visuospatial memory function in children as young as 6 years of age, using fTCD. As such, it holds promise for investigating development of lateralisation of visuospatial function in typically and atypically developing children.

Reliability of a novel paradigm for determining hemispheric lateralization of visuospatial function.

In most individuals, language production and visuospatial skills are subserved predominantly by the left and right hemispheres, respectively. Functional Transcranial Doppler (fTCD) provides a noninvasive and relatively low-cost method for measuring functional lateralization. However, while the silent word generation task provides an accurate and reliable paradigm for investigating lateralization of language production, there is no comparable gold-standard method for measuring visuospatial skills. Thirty undergraduate students (19 females) completed a task of spatial memory while undergoing fTCD recording. Participants completed this task at two different time points, separated by between 26 to 155 days. The relative activation between hemispheres averaged across all participants was found to be consistent across testing sessions. This was observed at the individual level also, with a quantitative index of lateralization showing high reproducibility. These findings indicate that the use of the spatial memory task with fTCD is a robust methodology for examining laterality of visuospatial skills.