Gesa Schaadt

Genetic dyslexia risk variant is related to neural connectivity patterns underlying phonological awareness in children

Phonological awareness is the best-validated predictor of reading and spelling skill and therefore highly relevant for developmental dyslexia. Prior imaging genetics studies link several dyslexia risk genes to either brain-functional or brain-structural factors of phonological deficits. However, coherent evidence for genetic associations with both functional and structural neural phenotypes underlying variation in phonological awareness has not yet been provided. Here we demonstrate that rs11100040, a reported modifier of SLC2A3, is related to the functional connectivity of left fronto-temporal phonological processing areas at resting state in a sample of 9- to 12-year-old children. Furthermore, we provide evidence that rs11100040 is related to the fractional anisotropy of the arcuate fasciculus, which forms the structural connection between these areas. This structural connectivity phenotype is associated with phonological awareness, which is in turn associated with the individual retrospective risk scores in an early dyslexia screening as well as to spelling. These results suggest a link between a dyslexia risk genotype and a functional as well as a structural neural phenotype, which is associated with a phonological awareness phenotype. The present study goes beyond previous work by integrating genetic, brain-functional and brain-structural aspects of phonological awareness within a single approach. These combined findings might be another step towards a multimodal biomarker for developmental dyslexia.

Sex hormones in early infancy seem to predict aspects of later language development

Sex differences in the development of cognitive behavior such as language have long been of great research interest. Lately, researchers have started to associate language function and brain differences with diverse sex hormones (e.g., testosterone/estradiol). However, results concerning the impact of early postnatal sex hormone concentration on the childs later language development are rare. Here, we analyze the impact of testosterone and estradiol in girls and boys as well as their neurophysiological phonemic discrimination at age 5months on language development at age 4years. Interestingly, we found strong positive estradiol and negative testosterone impact on later language performance at age 4years, which was true for both girls and boys. These results demonstrate that postnatal sex hormone surge might be viewed as one factor determining later language development, independent of gender.

Impact of phonological processing skills on written language acquisition in illiterate adults

Illiteracy remains a world-wide problem not only for children but also for adults. Phonological processing has been defined as a crucial factor for the acquisition of written language, which usually occurs in childhood. However, it is unclear to what extent phonological processing is necessary in order for adults to acquire written language skills. We tested 47 illiterate adults before and after a one-year alphabetization course in several cognitive domains relevant to phonological processing and compared their results to 41 matched controls who did not take part in the alphabetization course. Phonological awareness in the narrower sense (e.g., phoneme association) was a stronger predictor of alphabetization outcome than demographic variables such as years of education. In addition, despite improvement of illiterate individuals in phonological awareness, short-term memory, and visual attention from before to after the alphabetization course, they did not reach the phonological processing level of literate controls. Our results confirm that the alphabetization of adults requires and enhances phonological processes similar to those of children. Nevertheless, specific aspects, such as improvements in short-term memory or visual attention, need to be considered in order to improve and optimize alphabetization programs for adults.

Present and past: Can writing abilities in school children be associated with their auditory discrimination capacities in infancy?

Literacy acquisition is highly associated with auditory processing abilities, such as auditory discrimination. The event-related potential Mismatch Response (MMR) is an indicator for cortical auditory discrimination abilities and it has been found to be reduced in individuals with reading and writing impairments and also in infants at risk for these impairments. The goal of the present study was to analyze the relationship between auditory speech discrimination in infancy and writing abilities at school age within subjects, and to determine when auditory speech discrimination differences, relevant for later writing abilities, start to develop. We analyzed the MMR registered in response to natural syllables in German children with and without writing problems at two points during development, that is, at school age and at infancy, namely at age 1 month and 5 months. We observed MMR related auditory discrimination differences between infants with and without later writing problems, starting to develop at age 5 months-an age when infants begin to establish language-specific phoneme representations. At school age, these children with and without writing problems also showed auditory discrimination differences, reflected in the MMR, confirming a relationship between writing and auditory speech processing skills. Thus, writing problems at school age are, at least, partly grounded in auditory discrimination problems developing already during the first months of life.

Predicting early signs of dyslexia at a preliterate age by combining behavioral assessment with structural MRI.

BACKGROUND Recent studies suggest that neurobiological anomalies are already detectable in pre-school children with a family history of developmental dyslexia (DD). However, there is a lack of longitudinal studies showing a direct link between those differences at a preliterate age and the subsequent literacy difficulties seen in school. It is also not clear whether the prediction of DD in pre-school children can be significantly improved when considering neurobiological predictors, compared to models based on behavioral literacy precursors only. METHODS We recruited 53 pre-reading children either with (N=25) or without a family risk of DD (N=28). Quantitative T1 MNI data and literacy precursor abilities were assessed at kindergarten age. A subsample of 35 children was tested for literacy skills either one or two years later, that is, either in first or second grade. RESULTS The group comparison of quantitative T1 measures revealed significantly higher T1 intensities in the left anterior arcuate fascicle (AF), suggesting reduced myelin concentration in preliterate children at risk of DD. A logistic regression showed that DD can be predicted significantly better (p=.024) when neuroanatomical differences between groups are used as predictors (80%) compared to a model based on behavioral predictors only (63%). The Wald statistic confirmed that the T1 intensity of the left AF is a statistically significant predictor of DD (p<.05). CONCLUSIONS Our longitudinal results provide evidence for the hypothesis that neuroanatomical anomalies in children with a family risk of DD are related to subsequent problems in acquiring literacy. Particularly, solid white matter organization in the left anterior arcuate fascicle seems to play a pivotal role.

Cortical differences in preliterate children at familiar risk of dyslexia are similar to those observed in dyslexic readers.

Sir, We thank Indra Kraft and colleagues (2015) for their insightful letter commenting on our recent report in Brain . We agree with the authors in their assessment that, while longitudinal studies are invaluable for disentangling cause and effect in neurodevelopmental disorders, such studies are unfortunately rare because of many practical difficulties. And because of such difficulties, longitudinal studies such as ours often end up with final sample sizes that are relatively low compared to cross-sectional studies. As the authors correctly identified, one of the risks of studies with a smaller sample size is that there is an increased chance of type II errors. One way to ameliorate this is to examine effect sizes in conjunction with statistical significance. In our study, the effect sizes of pre-reading differences were remarkably large (effect sizes >2, calculated as Cohen’s d, reported in the …

Dyslexia risk gene relates to representation of sound in the auditory brainstem

Highlights • Previous studies associate poor reading with unstable speech-evoked brainstem responses.• DCDC2 and KIAA0319 risk alleles form a strong genetic link with developmental dyslexia.• Genetic burden with KIAA0319 risk is related to unstable speech-evoked brainstem responses.• Genetic burden with DCDC2 risk is related to intact speech-evoked brainstem responses.• Revealed brain-gene relationships may inform the multifactorial pathophysiology of dyslexia.

Facial speech gestures: The relation between visual speech processing, phonological awareness, and developmental dyslexia in 10-year-olds

Successful communication in everyday life crucially involves the processing of auditory and visual components of speech. Viewing our interlocutor and processing visual components of speech facilitates speech processing by triggering auditory processing. Auditory phoneme processing, analyzed by event-related brain potentials (ERP), has been shown to be associated with impairments in reading and spelling (i.e. developmental dyslexia), but visual aspects of phoneme processing have not been investigated in individuals with such deficits. The present study analyzed the passive visual Mismatch Response (vMMR) in school children with and without developmental dyslexia in response to video-recorded mouth movements pronouncing syllables silently. Our results reveal that both groups of children showed processing of visual speech stimuli, but with different scalp distribution. Children without developmental dyslexia showed a vMMR with typical posterior distribution. In contrast, children with developmental dyslexia showed a vMMR with anterior distribution, which was even more pronounced in children with severe phonological deficits and very low spelling abilities. As anterior scalp distributions are typically reported for auditory speech processing, the anterior vMMR of children with developmental dyslexia might suggest an attempt to anticipate potentially upcoming auditory speech information in order to support phonological processing, which has been shown to be deficient in children with developmental dyslexia.

Dissociating improvement of attention and intelligence during written language acquisition in adults

About one tenth of the world’s population cannot read and write sufficiently. Cognitive abilities, such as selective attention and crystallized as well as fluid intelligence, have been defined as crucial factors for the acquisition of written language skills. However, it is unclear whether these abilities are necessary also for the alphabetization of adults. Before and after a one-year alphabetization course, we compared the attention and intelligence of 47 illiterate individuals to 41 matched literate controls who did not take part in the alphabetization course. Illiterate individuals improved in selective attention and crystallized intelligence from before to after the alphabetization course; however, they did not reach the same level of functioning as literate controls. In addition, the fluid intelligence of illiterates did not improve. More importantly, when controlling for attention improvement, we found that improvement in crystallized intelligence was associated with alphabetization above and beyond the influence of attention. Our results suggest that alphabetization is closely related to improvements in attention and crystallized intelligence. Specifically, socio-cultural, knowledge- specific learning processes improve during the acquisition of written language skills and may not depend on only the enhancement of the ability to attend to relevant stimuli. Alphabetization programs may, therefore, benefit from distinct considerations of attentional, intellectual, and literacy related skill acquisitions.

Phonological abilities in literacy-impaired children: Brain potentials reveal deficient phoneme discrimination, but intact prosodic processing

Intact phonological processing is crucial for successful literacy acquisition. While individuals with difficulties in reading and spelling (i.e., developmental dyslexia) are known to experience deficient phoneme discrimination (i.e., segmental phonology), findings concerning their prosodic processing (i.e., suprasegmental phonology) are controversial. Because there are no behavior-independent studies on the underlying neural correlates of prosodic processing in dyslexia, these controversial findings might be explained by different task demands. To provide an objective behavior-independent picture of segmental and suprasegmental phonological processing in impaired literacy acquisition, we investigated event-related brain potentials during passive listening in typically and poor-spelling German school children. For segmental phonology, we analyzed the Mismatch Negativity (MMN) during vowel length discrimination, capturing automatic auditory deviancy detection in repetitive contexts. For suprasegmental phonology, we analyzed the Closure Positive Shift (CPS) that automatically occurs in response to prosodic boundaries. Our results revealed spelling group differences for the MMN, but not for the CPS, indicating deficient segmental, but intact suprasegmental phonological processing in poor spellers. The present findings point towards a differential role of segmental and suprasegmental phonology in literacy disorders and call for interventions that invigorate impaired literacy by utilizing intact prosody in addition to training deficient phonemic awareness.