Cross-modal integration in the brain is related to phonological awareness only in typical readers, not in those with reading difficulty

Control energy detects discrepancies in good vs. poor readers' structural-functional coupling during a rhyming task

Neuroimaging studies have identified functional and structural brain circuits that support reading. However, much less is known about how reading-related functional dynamics are constrained by white matter structure. Network control theory proposes that cortical brain dynamics are linearly determined by the white matter connectome, using control energy to evaluate the difficulty of the transition from one cognitive state to another. Here we apply this approach to linking brain dynamics with reading ability and disability in school-age children. A total of 51 children ages 8.25 -14.6 years performed an in-scanner rhyming task in visual and auditory modalities, with orthographic (spelling) and phonological (rhyming) similarity manipulated across trials. White matter structure and fMRI activation were used conjointly to compute the control energy of the reading network in each condition relative to a null fixation state. We then tested differences in control energy across trial types, finding higher control energy during non-word trials than word trials, and during incongruent trials than congruent trials. ROI analyses further showed a dissociation between control energy of the left fusiform and superior temporal gyrus depending on stimulus modality, with higher control energy for visual modalities in fusiform and higher control energy for auditory modalities in STG. Together, this study highlights that control theory can explain variations on cognitive demands in higher-level abilities such as reading, beyond what can be inferred from either functional or structural MRI measures alone.

Audiovisual multisensory integration in individuals with reading and language impairments: A systematic review and meta-analysis

Differences in sensory function have been documented for a number of neurodevelopmental conditions, including reading and language impairments. Prior studies have measured audiovisual multisensory integration (i.e., the ability to combine inputs from the auditory and visual modalities) in these populations. The present study sought to systematically review and quantitatively synthesize the extant literature on audiovisual multisensory integration in individuals with reading and language impairments. A comprehensive search strategy yielded 56 reports, of which 38 were used to extract 109 group difference and 68 correlational effect sizes. There was an overall difference between individuals with reading and language impairments and comparisons on audiovisual integration. There was a nonsignificant trend towards moderation according to sample type (i.e., reading versus language) and publication/small study bias for this model. Overall, there was a small but non-significant correlation between metrics of audiovisual integration and reading or language ability; this model was not moderated by sample or study characteristics, nor was there evidence of publication/small study bias. Limitations and future directions for primary and meta-analytic research are discussed.

Neurodevelopmental trajectories of letter and speech sound processing from preschool to the end of elementary school

Learning to read alphabetic languages starts with learning letter-speech-sound associations. How this process changes brain function during development is still largely unknown. We followed 102 children with varying reading skills in a mixed-longitudinal/cross-sectional design from the prereading stage to the end of elementary school over five time points (n = 46 with two and more time points, of which n = 16 fully-longitudinal) to investigate the neural trajectories of letter and speech sound processing using fMRI. Children were presented with letters and speech sounds visually, auditorily, and audiovisually in kindergarten (6.7yo), at the middle (7.3yo) and end of first grade (7.6yo), and in second (8.4yo) and fifth grades (11.5yo). Activation of the ventral occipitotemporal cortex for visual and audiovisual processing followed a complex trajectory, with two peaks in first and fifth grades. The superior temporal gyrus (STG) showed an inverted U-shaped trajectory for audiovisual letter processing, a development that in poor readers was attenuated in middle STG and absent in posterior STG. Finally, the trajectories for letter-speech-sound integration were modulated by reading skills and showed differing directionality in the congruency effect depending on the time point. This unprecedented study captures the development of letter processing across elementary school and its neural trajectories in children with varying reading skills.

Differences in brain functional networks for audiovisual integration during reading between children and adults

Building robust letter-to-sound correspondences is a prerequisite for developing reading capacity. However, the neural mechanisms underlying the development of audiovisual integration for reading are largely unknown. This study used functional magnetic resonance imaging in a lexical decision task to investigate functional brain networks that support audiovisual integration during reading in developing child readers (10-12 years old) and skilled adult readers (20-28 years old). The results revealed enhanced connectivity in a prefrontal-superior temporal network (including the right medial frontal gyrus, right superior frontal gyrus, and left superior temporal gyrus) in adults relative to children, reflecting the development of attentional modulation of audiovisual integration involved in reading processing. Furthermore, the connectivity strength of this brain network was correlated with reading accuracy. Collectively, this study, for the first time, elucidates the differences in brain networks of audiovisual integration for reading between children and adults, promoting the understanding of the neurodevelopment of multisensory integration in high-level human cognition.

Intersecting distributed networks support convergent linguistic functioning across different languages in bilinguals

How bilingual brains accomplish the processing of more than one language has been widely investigated by neuroimaging studies. The assimilation-accommodation hypothesis holds that both the same brain neural networks supporting the native language and additional new neural networks are utilized to implement second language processing. However, whether and how this hypothesis applies at the finer-grained levels of both brain anatomical organization and linguistic functions remains unknown. To address this issue, we scanned Chinese-English bilinguals during an implicit reading task involving Chinese words, English words and Chinese pinyin. We observed broad brain cortical regions wherein interdigitated distributed neural populations supported the same cognitive components of different languages. Although spatially separate, regions including the opercular and triangular parts of the inferior frontal gyrus, temporal pole, superior and middle temporal gyrus, precentral gyrus and supplementary motor areas were found to perform the same linguistic functions across languages, indicating regional-level functional assimilation supported by voxel-wise anatomical accommodation. Taken together, the findings not only verify the functional independence of neural representations of different languages, but show co-representation organization of both languages in most language regions, revealing linguistic-feature specific accommodation and assimilation between first and second languages.

Longitudinal changes in cortical responses to letter-speech sound stimuli in 8-11 year-old children

While children are able to name letters fairly quickly, the automatisation of letter-speech sound mappings continues over the first years of reading development. In the current longitudinal fMRI study, we explored developmental changes in cortical responses to letters and speech sounds across 3 yearly measurements in a sample of 18 8-11 year old children. We employed a text-based recalibration paradigm in which combined exposure to text and ambiguous speech sounds shifts participants' later perception of the ambiguous sounds towards the text. Our results showed that activity of the left superior temporal and lateral inferior precentral gyri followed a non-linear developmental pattern across the measurement sessions. This pattern is reminiscent of previously reported inverted-u-shape developmental trajectories in children's visual cortical responses to text. Our findings suggest that the processing of letters and speech sounds involves non-linear changes in the brain's spoken language network possibly related to progressive automatisation of reading skills.

How Learning to Read Changes the Listening Brain

Reading acquisition reorganizes existing brain networks for speech and visual processing to form novel audio-visual language representations. This requires substantial cortical plasticity that is reflected in changes in brain activation and functional as well as structural connectivity between brain areas. The extent to which a child's brain can accommodate these changes may underlie the high variability in reading outcome in both typical and dyslexic readers. In this review, we focus on reading-induced functional changes of the dorsal speech network in particular and discuss how its reciprocal interactions with the ventral reading network contributes to reading outcome. We discuss how the dynamic and intertwined development of both reading networks may be best captured by approaching reading from a skill learning perspective, using audio-visual learning paradigms and longitudinal designs to follow neuro-behavioral changes while children's reading skills unfold.

The Connectivity Fingerprints of Highly-Skilled and Disordered Reading Persist Across Cognitive Domains

The capacity to produce and understand written language is a uniquely human skill that exists on a continuum, and foundational to other facets of human cognition. Multivariate classifiers based on support vector machines (SVM) have provided much insight into the networks underlying reading skill beyond what traditional univariate methods can tell us. Shallow models like SVM require large amounts of data, and this problem is compounded when functional connections, which increase exponentially with network size, are predictors of interest. Data reduction using independent component analyses (ICA) mitigates this problem, but conventionally assumes linear relationships. Multilayer feedforward networks, in contrast, readily find optimal low-dimensional encodings of complex patterns that include complex nonlinear or conditional relationships. Samples of poor and highly-skilled young readers were selected from two open access data sets using rhyming and mental multiplication tasks, respectively. Functional connectivity was computed for the rhyming task within a functionally-defined reading network and used to train multilayer feedforward classifier models to simultaneously associate functional connectivity patterns with lexicality (word vs. pseudoword) and reading skill (poor vs. highly-skilled). Classifiers identified validation set lexicality with significantly better than chance accuracy, and reading skill with near-ceiling accuracy. Critically, a series of replications used pre-trained rhyming-task models to classify reading skill from mental multiplication task participants' connectivity with near-ceiling accuracy. The novel deep learning approach presented here provides the clearest demonstration to date that reading-skill dependent functional connectivity within the reading network influences brain processing dynamics across cognitive domains.

Letter fluency in 7-8-year-old children is related to the anterior, but not posterior, ventral occipito-temporal cortex during an auditory phonological task

Previous studies have shown that reading skill in 3- to 6-year-old children is related to the automatic activation of the posterior left ventral occipitotemporal cortex (vOT) during spoken language processing, whereas 8- to 15-year-old children and adult readers activate the anterior vOT. However, it is unknown how children who are between these two age groups automatically activate orthographic representations in vOT for spoken language. In the current study, we recruited 153 7- to 8-year-old children to fill the age gap from previous studies. Using functional magnetic resonance imaging (fMRI), we measured children's reading-related skills and brain activity during an auditory phonological task with both a small (i.e. onset) and a large (i.e. rhyme) grain size condition. We found that letter fluency, but not reading accuracy, was correlated with activation in the anterior vOT for the rhyme condition. There were no reading-related skill correlations for the posterior vOT or for activation during the onset condition in this age group. Our findings reveal that automatic activation in the anterior vOT during spoken language processing already occurs in higher skilled 7- to 8-year-old children. In addition, increases in naming automaticity is the primary determinant of the engagement of vOT during phonological awareness tasks.

Neural representations of phonology in temporal cortex scaffold longitudinal reading gains in 5- to 7-year-old children

The objective of this study was to investigate whether phonological processes measured through brain activation are crucial for the development of reading skill (i.e. scaffolding hypothesis) and/or whether learning to read words fine-tunes phonology in the brain (i.e. refinement hypothesis). We specifically looked at how different grain sizes in two brain regions implicated in phonological processing played a role in this bidirectional relation. According to the dual-stream model of speech processing and previous empirical studies, the posterior superior temporal gyrus (STG) appears to be a perceptual region associated with phonological representations, whereas the dorsal inferior frontal gyrus (IFG) appears to be an articulatory region that accesses phonological representations in STG during more difficult tasks. 36 children completed a reading test outside the scanner and an auditory phonological task which included both small (i.e. onset) and large (i.e. rhyme) grain size conditions inside the scanner when they were 5.5-6.5 years old (Time 1) and once again approximately 1.5 years later (Time 2). To study the scaffolding hypothesis, a regression analysis was carried out by entering brain activation in either STG or IFG for either small (onset > perceptual) or large (rhyme > perceptual) grain size phonological processing at T1 as the predictors and reading skill at T2 as the dependent measure, with several covariates of no interest included. To study the refinement hypothesis, the regression analysis included reading skill at T1 as the predictor and brain activation in either STG or IFG for either small or large grain size phonological processing at T2 as the dependent measures, with several covariates of no interest included. We found that only posterior STG, regardless of grain size, was predictive of reading gains. Parallel models with only behavioral accuracy were not significant. Taken together, our results suggest that the representational quality of phonology in temporal cortex is crucial for reading development. Moreover, our study provides neural evidence supporting the scaffolding hypothesis, suggesting that brain measures of phonology could be helpful in early identification of reading difficulties.

Neural Processing and Production of Gesture in Children and Adolescents With Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) demonstrate impairments in non-verbal communication, including gesturing and imitation deficits. Reduced sensitivity to biological motion (BM) in ASD may impair processing of dynamic social cues like gestures, which in turn may impede encoding and subsequent performance of these actions. Using both an fMRI task involving observation of action gestures and a charade style paradigm assessing gesture performance, this study examined the brain-behavior relationships between neural activity during gesture processing, gesturing abilities and social symptomology in a group of children and adolescents with and without ASD. Compared to typically developing (TD) controls, participants with ASD showed atypical sensitivity to movement in right posterior superior temporal sulcus (pSTS), a region implicated in action processing, and had poorer overall gesture performance with specific deficits in hand posture. The TD group showed associations between neural activity, gesture performance and social skills, that were weak or non-significant in the ASD group. These findings suggest that those with ASD demonstrate abnormalities in both processing and production of gestures and may reflect dysfunction in the mechanism underlying perception-action coupling resulting in atypical development of social and communicative skills.

A longitudinal neuroimaging dataset on multisensory lexical processing in school-aged children

Here we describe the open access dataset entitled “Longitudinal Brain Correlates of Multisensory Lexical Processing in Children” hosted on OpenNeuro.org. This dataset examines reading development through a longitudinal multimodal neuroimaging and behavioral approach, including diffusion-weighted and T1-weighted structural magnetic resonance imaging (MRI), task based functional MRI, and a battery of psycho-educational assessments and parental questionnaires. Neuroimaging, psycho-educational testing, and functional task behavioral data were collected from 188 typically developing children when they were approximately 10.5 years old (session T1). Seventy children returned approximately 2.5 years later (session T2), of which all completed longitudinal follow-ups of psycho-educational testing, and 49 completed neuroimaging and functional tasks. At session T1 participants completed auditory, visual, and audio-visual word and pseudo-word rhyming judgment tasks in the scanner. At session T2 participants completed visual word and pseudo-word rhyming judgement tasks in the scanner.

Measurement(s)	reading and spelling ability • intelligence • brain • brain physiology trait
Technology Type(s)	psychoeducational test administration • magnetic resonance imaging • functional magnetic resonance imaging • Diffusion Weighted Imaging
Factor Type(s)	age • reading disability • type of task • parental educational level
Sample Characteristic - Organism	Homo sapiens

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11298188

Children With Reading Difficulty Rely on Unimodal Neural Processing for Phonemic Awareness

Phonological awareness skills in children with reading difficulty (RD) may reflect impaired automatic integration of orthographic and phonological representations. However, little is known about the underlying neural mechanisms involved in phonological awareness for children with RD. Eighteen children with RD, ages 9–13, participated in a functional magnetic resonance imaging (fMRI) study designed to assess the relationship of two constructs of phonological awareness, phoneme synthesis, and phoneme analysis, with crossmodal rhyme judgment. Participants completed a rhyme judgment task presented in two modality conditions; unimodal auditory only and crossmodal audiovisual. Measures of phonological awareness were correlated with unimodal, but not crossmodal, lexical processing. Moreover, these relationships were found only in unisensory brain regions, and not in multisensory brain areas. The results of this study suggest that children with RD rely on unimodal representations and unisensory brain areas, and provide insight into the role of phonemic awareness in mapping between auditory and visual modalities during literacy acquisition.

An fMRI-adaptation study of phonological and orthographic selectivity to written words in adults with poor reading skills

Typical readers rely on two brain pathways for word processing in the left hemisphere: temporo-parietal cortex (TPC) and inferior frontal cortex (IFC), thought to subserve phonological decoding, and occipito-temporal cortex (OTC), including the "visual word form area" (VWFA), thought to subserve orthographic processing. How these regions are affected in developmental dyslexia has been a topic of intense research. We employed fMRI rapid adaptation (fMRI-RA) in adults with low reading skills to examine in independently-defined functional regions of interest (ROIs) phonological selectivity to written words in left TPC and IFC, and to orthographic selectivity to written words in OTC. Consistent with the phonological deficit hypothesis of dyslexia, we found responsivity but not selectivity to phonology, as accessed by written words, in the posterior superior temporal gyrus (pSTG) of the TPC. On the other hand, we found orthographic selectivity in the VWFA of the OTC. We also found selectivity to orthographic and not phonological processing in the IFG, a finding previously reported for typical readers. Together our results demonstrate that in adults with poor reading skills, selectivity to phonology is compromised in pSTG, while selectivity to orthography in the VWFA remains unaffected at this level of processing.

Dyslexia on a continuum: A complex network approach

We investigated the efficacy of graph-theoretic metrics of task-related functional brain connectivity in predicting reading difficulty and explored the hypothesis that task conditions emphasizing audiovisual integration would be especially diagnostic of reading difficulty. An fMRI study was conducted in which 24 children (8 to 14 years old) who were previously diagnosed with dyslexia completed a rhyming judgment task under three presentation modality conditions. Regression analyses found that characteristic connectivity metrics of the reading network showed a presentation modality dependent relationship with reading difficulty: Children with more segregated reading networks and those that used fewer of the available connections were those with the least severe reading difficulty. These results are consistent with the hypothesis that a lack of coordinated processing between the neural regions involved in phonological and orthographic processing contributes towards reading difficulty.

Longitudinal Task-Related Functional Connectivity Changes Predict Reading Development

Longitudinal studies suggest developmentally dependent changes in lexical processing during reading development, implying a change in inter-regional functional connectivity over this period. The current study used functional magnetic resonance imaging (fMRI) to explore developmental changes in functional connectivity across multiple runs of a rhyming judgment task in young readers (8–14 years) over an average 2.5-year span. Changes in functional segregation are correlated with and predict changes in the skill with which typically developing children learn to apply the alphabetic principle, as measured by pseudoword decoding. This indicates a developmental shift in the proportion of specialized functional clusters is associated with changes in reading skill and suggests a dependency of reading development on changes of particular neural pathways, specifically decreases in transitivity is indicative of greater network integration. This work provides evidence that characteristics of these pathways, quantified using graph-theoretic metrics, can be used to predict individual differences in reading development.

A Selective Deficit in Phonetic Recalibration by Text in Developmental Dyslexia

Upon hearing an ambiguous speech sound, listeners may adjust their perceptual interpretation of the speech input in accordance with contextual information, like accompanying text or lipread speech (i.e., phonetic recalibration; Bertelson et al., 2003). As developmental dyslexia (DD) has been associated with reduced integration of text and speech sounds, we investigated whether this deficit becomes manifest when text is used to induce this type of audiovisual learning. Adults with DD and normal readers were exposed to ambiguous consonants halfway between /aba/ and /ada/ together with text or lipread speech. After this audiovisual exposure phase, they categorized auditory-only ambiguous test sounds. Results showed that individuals with DD, unlike normal readers, did not use text to recalibrate their phoneme categories, whereas their recalibration by lipread speech was spared. Individuals with DD demonstrated similar deficits when ambiguous vowels (halfway between /wIt/ and /wet/) were recalibrated by text. These findings indicate that DD is related to a specific letter-speech sound association deficit that extends over phoneme classes (vowels and consonants), but – as lipreading was spared – does not extend to a more general audio–visual integration deficit. In particular, these results highlight diminished reading-related audiovisual learning in addition to the commonly reported phonological problems in developmental dyslexia.

Elaborative feedback: Engaging reward and task-relevant brain regions promotes learning in pseudoword reading aloud

Although much is known about the cognitive and neural basis of establishing letter-sound mappings in learning word forms, relatively little is known about what makes for the most effective feedback during this process. We sought to determine the neural basis by which elaborative feedback (EF), which contains both reward-related and content-specific information, may be more helpful than feedback containing only one kind of information (simple positive feedback, PF) or the other (content feedback, CF) in learning orthography-phonology (spelling-sound) mappings for novel letter strings. Compared to CF, EF activated the ventromedial prefrontal cortex, implicated in reward processing. Compared to PF, EF activated the posterior middle temporal, superior temporal, and supramarginal gyri-regions implicated in orthography-phonology conversion. In the same comparison, EF also activated the left fusiform gyrus/visual word form area-implicated in orthographic processing. Also EF, but not CF or PF, modulated activity in the caudate nucleus. In a postscan questionnaire, EF and PF were rated as more pleasant than CF, suggesting that modulation of the caudate for EF may be due to the coupling of reward and skill content. These findings suggest the enhanced effectiveness of EF may be due to concurrent activation of reward-related and task-relevant brain regions.

Print-Speech Convergence Predicts Future Reading Outcomes in Early Readers

Becoming a skilled reader requires building a functional neurocircuitry for printed-language processing that integrates with spoken-language-processing networks. In this longitudinal study, functional MRI (fMRI) was used to examine convergent activation for printed and spoken language (print-speech coactivation) in selected regions implicated in printed-language processing (the reading network). We found that print-speech coactivation across the left-hemisphere reading network in beginning readers predicted reading achievement 2 years later beyond the effects of brain activity for either modality alone; moreover, coactivation effects accounted for variance in later reading after controlling for initial reading performance. Within the reading network, effects of coactivation were significant in bilateral inferior frontal gyrus (IFG) and left inferior parietal cortex and fusiform gyrus. The contribution of left and right IFG differed, with more coactivation in left IFG predicting better achievement but more coactivation in right IFG predicting poorer achievement. Findings point to the centrality of print-speech convergence in building an efficient reading circuitry in children.

Functional neuroimaging of visuospatial working memory tasks enables accurate detection of attention deficit and hyperactivity disorder

Finding neurobiological markers for neurodevelopmental disorders, such as attention deficit and hyperactivity disorder (ADHD), is a major objective of clinicians and neuroscientists. We examined if functional Magnetic Resonance Imaging (fMRI) data from a few distinct visuospatial working memory (VSWM) tasks enables accurately detecting cases with ADHD. We tested 20 boys with ADHD combined type and 20 typically developed (TD) boys in four VSWM tasks that differed in feedback availability (feedback, no-feedback) and reward size (large, small). We used a multimodal analysis based on brain activity in 16 regions of interest, significantly activated or deactivated in the four VSWM tasks (based on the entire participants' sample). Dimensionality of the data was reduced into 10 principal components that were used as the input variables to a logistic regression classifier. fMRI data from the four VSWM tasks enabled a classification accuracy of 92.5%, with high predicted ADHD probability values for most clinical cases, and low predicted ADHD probabilities for most TDs. This accuracy level was higher than those achieved by using the fMRI data of any single task, or the respective behavioral data. This indicates that task-based fMRI data acquired while participants perform a few distinct VSWM tasks enables improved detection of clinical cases.

Crossmodal deficit in dyslexic children: practice affects the neural timing of letter-speech sound integration

A failure to build solid letter-speech sound associations may contribute to reading impairments in developmental dyslexia. Whether this reduced neural integration of letters and speech sounds changes over time within individual children and how this relates to behavioral gains in reading skills remains unknown. In this research, we examined changes in event-related potential (ERP) measures of letter-speech sound integration over a 6-month period during which 9-year-old dyslexic readers (n = 17) followed a training in letter-speech sound coupling next to their regular reading curriculum. We presented the Dutch spoken vowels /a/ and /o/ as standard and deviant stimuli in one auditory and two audiovisual oddball conditions. In one audiovisual condition (AV0), the letter “a” was presented simultaneously with the vowels, while in the other (AV200) it was preceding vowel onset for 200 ms. Prior to the training (T1), dyslexic readers showed the expected pattern of typical auditory mismatch responses, together with the absence of letter-speech sound effects in a late negativity (LN) window. After the training (T2), our results showed earlier (and enhanced) crossmodal effects in the LN window. Most interestingly, earlier LN latency at T2 was significantly related to higher behavioral accuracy in letter-speech sound coupling. On a more general level, the timing of the earlier mismatch negativity (MMN) in the simultaneous condition (AV0) measured at T1, significantly related to reading fluency at both T1 and T2 as well as with reading gains. Our findings suggest that the reduced neural integration of letters and speech sounds in dyslexic children may show moderate improvement with reading instruction and training and that behavioral improvements relate especially to individual differences in the timing of this neural integration.

Skill dependent audiovisual integration in the fusiform induces repetition suppression

Learning to read entails mapping existing phonological representations to novel orthographic representations and is thus an ideal context for investigating experience driven audiovisual integration. Because two dominant brain-based theories of reading development hinge on the sensitivity of the visual-object processing stream to phonological information, we were interested in how reading skill relates to audiovisual integration in this area. Thirty-two children between 8 and 13 years of age spanning a range of reading skill participated in a functional magnetic resonance imaging experiment. Participants completed a rhyme judgment task to word pairs presented unimodally (auditory- or visual-only) and cross-modally (auditory followed by visual). Skill-dependent sub-additive audiovisual modulation was found in left fusiform gyrus, extending into the putative visual word form area, and was correlated with behavioral orthographic priming. These results suggest learning to read promotes facilitatory audiovisual integration in the ventral visual-object processing stream and may optimize this region for orthographic processing.

Reduced neural integration of letters and speech sounds in dyslexic children scales with individual differences in reading fluency

The acquisition of letter-speech sound associations is one of the basic requirements for fluent reading acquisition and its failure may contribute to reading difficulties in developmental dyslexia. Here we investigated event-related potential (ERP) measures of letter-speech sound integration in 9-year-old typical and dyslexic readers and specifically test their relation to individual differences in reading fluency. We employed an audiovisual oddball paradigm in typical readers (n = 20), dysfluent (n = 18) and severely dysfluent (n = 18) dyslexic children. In one auditory and two audiovisual conditions the Dutch spoken vowels/a/and/o/were presented as standard and deviant stimuli. In audiovisual blocks, the letter ‘a’ was presented either simultaneously (AV0), or 200 ms before (AV200) vowel sound onset. Across the three children groups, vowel deviancy in auditory blocks elicited comparable mismatch negativity (MMN) and late negativity (LN) responses. In typical readers, both audiovisual conditions (AV0 and AV200) led to enhanced MMN and LN amplitudes. In both dyslexic groups, the audiovisual LN effects were mildly reduced. Most interestingly, individual differences in reading fluency were correlated with MMN latency in the AV0 condition. A further analysis revealed that this effect was driven by a short-lived MMN effect encompassing only the N1 window in severely dysfluent dyslexics versus a longer MMN effect encompassing both the N1 and P2 windows in the other two groups. Our results confirm and extend previous findings in dyslexic children by demonstrating a deficient pattern of letter-speech sound integration depending on the level of reading dysfluency. These findings underscore the importance of considering individual differences across the entire spectrum of reading skills in addition to group differences between typical and dyslexic readers.