Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia

The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9-12.2 years; 55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers.

Theta band power changes in normal and dyslexic children

OBJECTIVE

Tonic and phasic (event-related) theta band power changes were analyzed in a sample of 8 dyslexic and 8 control children. Previous research with healthy subjects suggests that electroencephalograph (EEG) theta activity reflects the encoding of new information into working memory. The aim of the present study was to investigate whether the processing deficits of dyslexics are related to a reduced phasic theta response during reading.

METHOD

The EEG was recorded while subjects were reading numbers, words and pseudowords and analyzed in a lower and upper theta band (4--8 Hz). A phasic response is measured in terms of an increase in event related band power during reading with respect to a reference interval. Tonic power is measured in terms of (log) band power during a reference interval.

RESULTS

Large group differences in tonic and phasic lower theta were found for occipital sites where dyslexics show a complete lack of pseudoword processing. For words, only controls show a highly selective left hemispheric processing advantage.

CONCLUSIONS

Dyslexics have a lack to encode pseudowords in visual working memory with a concomitant lack of frontal processing selectivity. The upper theta band shows a different pattern of results which can be best interpreted to reflect the effort during the encoding process.

Alpha and beta band power changes in normal and dyslexic children

OBJECTIVE

Previous research with healthy subjects suggests that the lower alpha band reflects attentional whereas the upper alpha band semantic processes. The aim of the present study was to investigate whether dyslexics show deficits in attentional control and/or semantic encoding.

METHOD

The EEG was recorded while subjects were reading numbers, words and pseudowords and analyzed in a lower and upper alpha and two beta bands (spanning a range of about 8--16 Hz). A phasic response is measured in terms of a decrease in event related band power during reading with respect to a reference interval. Tonic power is measured in terms of (log) band power during a reference interval.

RESULTS

In the lower alpha band dyslexics show an increased phasic response to words and pseudowords at right hemispheric sites but a lack to respond to words at O1. The upper alpha band exhibits a highly selective phasic response to words at left frontal sites but for controls only, whereas dyslexics show a general increase in tonic upper alpha power. Whereas the low frequency beta band (beta-1a) exhibits a rather diffuse pattern, a highly selective finding was obtained for the beta-1b band.

CONCLUSIONS

Dyslexics have a lack of attentional control during the encoding of words at left occipital sites and a lack of a selective topographic activation pattern during the semantic encoding of words. Because only in controls reading of words is associated with a strong beta-1b desynchronization at those recording sites which correspond to Broca's area (FC5) and the angular gyrus (CP5, P3), we may conclude that this frequency band reflects the graphemicphonetic encoding of words.

Pseudoname learning by German-speaking children with dyslexia: evidence for a phonological learning deficit

In 2 experiments, German-speaking dyslexic children (9-year-olds) showed impaired learning of new phonological forms (pseudonames) in a variety of visual-verbal learning tasks. The dyslexic deficit was also found when phonological retrieval cues were provided and when the to-be-learned pseudonames were presented in spoken as well as printed form. However, the dyslexic children showed no name-learning deficit when short, familiar words were used and they also had no difficulty with immediate repetition of the pseudowords. The dyslexic children's difficulty in learning new phonological forms was associated with pseudoword-repetition and naming-speed deficits assessed at the beginning of school, but not with phonological awareness and visual-motor impairments. We propose that the difficulty in learning new phonological forms may affect reading and spelling acquisition via impaired storage of new phonological forms, which serve as phonological underpinnings of the letter patterns of words or parts of words.

Reading and dual-task balancing: evidence against the automatization deficit explanation of developmental dyslexia

Nicolson and Fawcett (1990) demonstrated specifically impaired balancing performance of children with dyslexia when balancing had to be done simultaneously with a secondary task. This finding was taken as evidence for a general automatization deficit of children with dyslexia. We attempted to replicate this finding with German children with dyslexia, whose characteristic reading difficulty is a fluency problem quite in correspondence with the automatization deficit explanation. Because we were concerned about a potential confound between dyslexia and attention-deficit/hyperactivity disorder (ADHD), we also collected teacher ratings on ADHD symptoms. We found that poor dual-task balancing was limited to children with higher ADHD ratings and that children with dyslexia without higher ADHD ratings performed as well on dual-task balancing as age-matched control children. This finding supports the aforementioned confound. Together with other findings from our research group, it supports the position that, even in consistent orthographies, difficulties in learning to read are caused by a specific phonological deficit.

GRC5 and NMD3 function in translational control of gene expression and interact genetically

The yeast gene, GRC5 (growth control), is a member of the highly conserved QM gene family, the human member of which has been associated with the suppression of Wilms' tumor. GRC5 encodes ribosomal protein L10, which is thought to play a regulatory role in the translational control of gene expression. A revertant screen identified four spontaneous revertants of the mutant grc5-1ts allele. Genetic and phenotypic analysis showed that these represent one gene, NMD3, and that the interaction of NMD3 and GRC5 is gene-specific. NMD3 was previously identified as a component of the nonsense-mediated mRNA decay pathway. The point mutations within NMD3 reported here may define a domain important for the functional interaction of Grc5p and Nmd3p.

Towards a molecular level understanding of protein stabilization: the interaction between lysozyme and sorbitol

The paper is investigating the mechanism of stabilization of proteins by polyols at the molecular level. It is addressing the interactions of sorbitol, a polyol commonly used as a protein stabilizing agent, with hen egg white lysozyme, a well studied protein. Differential scanning calorimetry shows an increase in denaturation temperature of lysozyme upon addition of sorbitol at a concentration of 250 mM and above. Increasing sorbitol concentration also caused an increase in signal intensity of the CD spectrum of lysozyme in the wavelength region of 280-300 nm. Two-dimensional nuclear magnetic resonance spectroscopy was used to examine interactions between lysozyme and sorbitol. Most significant changes are manifest in the anomalous relaxation properties of Ala and Thr methyl groups indicating modifications of local motions and possibly compression of the entire structure. This is further corroborated by new intra-protein nuclear Overhauser effects in the presence of sorbitol. There is also evidence that water is displaced from the enzyme surface close to Ile-88 upon addition of sorbitol. In combination these results reveal a complex interplay of different interactions. Comparison to NMR-spectra of lysozyme with a bound inhibitor (tri-N-acetyl-glucosamine) shows that the interaction with sorbitol affects spatially disparate regions of the protein.

The impact of orthographic consistency on dyslexia: a German-English comparison

We examined reading and phonological processing abilities in English and German dyslexic children, each compared with two control groups matched for reading level (8 years) and age (10-12 years). We hypothesised that the same underlying phonological processing deficit would exist in both language groups, but that there would be differences in the severity of written language impairments, due to differences in orthographic consistency. We also hypothesized that systematic differences due to orthographic consistency should be found equally for normal and dyslexic readers. All cross-language comparisons were based on a set of stimuli matched for meaning, pronunciation and spelling. The results supported both hypotheses: On a task challenging phonological processing skills (spoonerisms) both English and German dyslexics were significantly impaired compared to their age and reading age controls. However, there were extremely large differences in reading performance when English and German dyslexic children were compared. The evidence for systematic differences in reading performance due to differences in orthographic consistency was similar for normal and for dyslexic children, with English showing marked adverse effect on acquisition of reading skills.

The nonword reading deficit in developmental dyslexia: evidence from children learning to read German

This study examined whether dyslexic children learning to read German show the same nonword reading deficit, which is characteristic of dyslexic children learning to read English (Rack, Olson, & Snowling, 1992), a deficit which is taken as evidence for a phonological impairment underlying dyslexia. Because the German writing system, in contrast to English, exhibits comparatively simple and straightforward grapheme-phoneme correspondences, the generality of the nonword reading deficit across different alphabetic systems seemed questionable. Actually, it was found that 10-year-old dyslexic children learning to read German exhibited rather high reading accuracy for nonwords when compared to that typically found among dyslexic children learning to read English. Nevertheless, the children learning German did exhibit a nonword reading deficit. Specifically, their speed for nonwords was impaired in relation to younger control (nondyslexic) children matched on reading speed for frequent words. This nonword reading deficit was observed for nonwords with little similarity to existing German words as well as for nonwords which were analogous to short, frequent content words. It is hypothesized that dyslexic children learning German do not differ from dyslexic children learning English in their underlying phonological impairment, but that they do differ with respect to the expression of this impairment.

Children's theory of mind: Fodor's heuristics examined

The study reported in this manuscript examined Fodor's (1992) argument that standard false belief tasks used in developmental research seriously underestimate young children's understanding of false belief. The problem of these tasks according to Fodor is that always a unique, actual state of affairs (e.g., chocolate is now in cupboard B) is contrasted with a believed state of affairs (e.g., chocolate is still in cupboard A). Fodor argued that this uniqueness feature may be critical because young children with limited computational resources have to trade reliability of behavioral prediction for computational simplicity and, therefore, may rely on simple heuristics such as "Predict that the agent will act in a way that will satisfy his desires". In the standard false belief task such a heuristic will result in a unique, but incorrect (reality-based) prediction. Fodor's expectation is that when young children are not misled into applying such heuristics by the possibility of unique, reality-based prediction, then their true competence for belief-based reasoning will become evident. The present study contrasted for two different belief tasks a traditional unique version with a non-unique version, but found no support for Fodor's expectation as both 3- and 4-year-old children did not improve in the non-unique version.

The influence of orthographic consistency on reading development: word recognition in English and German children

Groups of 7, 8, and 9-year-old children who were learning to read in English and German were given three different continuous reading tasks: a numeral reading task, a number word reading task, and a nonsense word reading task. The nonsense words could be read by analogy to the number words. Whereas reading time and error rates in numeral and number word reading were very similar across the two orthographies, the German children showed a big advantage in reading the nonsense words. This pattern of results is interpreted as evidence for the initial adoption of different strategies for word recognition in the two orthographies. German children appear to rely on assembling pronunciations via grapheme-phoneme conversion, and English children appear to rely more on some kind of direct recognition strategy. A model of reading development that takes account of orthographic consistency is proposed.

On the origins of denial negation

These are the principal questions of this study: are the early functions of negation, such as REJECTION, and the later emerging DENIAL no developmentally related? And when do children start to deny? So far, evidence for the questions at hand has been almost exclusively observational. We decided on a simple elicitation procedure instead, asking 48 children (ages between 1;1 and 2;7) easy yes/no-questions. The most likely age range for the appearance of denial no was 1;8-2;1. Its error-free acquisition supports the continuity theory of negation development, which holds that essentials of denial no carry over from the earlier functions of no. Finally an attempt is made to account for the beginnings of denial in terms of semantics and the representational theory of child cognition.

The relationship of phonemic awareness to reading acquisition: more consequence than precondition but still important

Three studies examined the presence of phonemic awareness among Austrian children before reading instruction and its relationship to concurrent and later reading. These children were about 6-7 years of age but in the majority of cases unable to read when they entered school. Testing phonemic awareness with a newly developed, rather simple and natural vowel substitution task revealed that many children showed not a single correct response or little success. In contrast, the few readers at the beginning of grade one exhibited high phonemic awareness and after a few months of reading instruction most of the children scored at least close to perfect in the vowel substitution task. Despite this apparent effect of reading on phonemic awareness there was a specific predictive relationship between initial phonemic awareness differences and success in learning to read and to spell. In agreement with other studies it was found that phonemic awareness differences before instruction predicted the accuracy of alphabetic reading and spelling at the end of grade one independent from IQ and initial differences in letter knowledge and reading. However, closer examination of the relationship between phonemic awareness before instruction and later success in learning to read revealed a specific pattern. Children with high phonemic awareness at the beginning of grade one showed uniformly high reading and spelling achievement at the end of grade one. Such good progress in learning to read and to spell was also evident in the majority of children who showed no phonemic awareness at the beginning of reading instruction, but some of the many children with low phonemic awareness before instruction experienced difficulties in learning to read and to spell. This specific pattern suggests that individual differences in the ease or difficulty with which phonemic awareness can be induced by preschool experiences or by reading instruction is the critical variable underlying the observed correlations between phonemic awareness measures before reading instruction and progress in learning to read.