Functional correlates of children's responsiveness to intervention

Inter-subject correlation during long narratives reveals widespread neural correlates of reading ability

Recent work using fMRI inter-subject correlation analysis has provided new information about the brain's response to video and audio narratives, particularly in frontal regions not typically activated by single words. This approach is very well suited to the study of reading, where narrative is central to natural experience. But since past reading paradigms have primarily presented single words or phrases, the influence of narrative on semantic processing in the brain - and how that influence might change with reading ability - remains largely unexplored. In this study, we presented coherent stories to adolescents and young adults with a wide range of reading abilities. The stories were presented in alternating visual and auditory blocks. We used a dimensional inter-subject correlation analysis to identify regions in which better and worse readers had varying levels of consistency with other readers. This analysis identified a widespread set of brain regions in which activity timecourses were more similar among better readers than among worse readers. These differences were not detected with standard block activation analyses. Worse readers had higher correlation with better readers than with other worse readers, suggesting that the worse readers had "idiosyncratic" responses rather than using a single compensatory mechanism. Close inspection confirmed that these differences were not explained by differences in IQ or motion. These results suggest an expansion of the current view of where and how reading ability is reflected in the brain, and in doing so, they establish inter-subject correlation as a sensitive tool for future studies of reading disorders.

Researcher-practitioner partnerships and in-school laboratories facilitate translational research in reading

Educational neuroscience approaches have helped to elucidate the brain basis of Reading Disability (RD) and of reading intervention response; however, there is often limited translation of this knowledge to the broader scientific and educational communities. Moreover, this work is traditionally lab-based, and thus the underlying theories and research questions are siloed from classroom practices. With growing awareness of the neurobiological origins of RD and increasing popularity of putative "brain-based" approaches in clinics and classrooms, it is imperative that we create more direct and bidirectional communication between scientists and practitioners. Such direct collaborations can help dispel neuromyths, and lead to increased understanding of the promises and pitfalls of neuroscience approaches. Moreover, direct partnerships between researchers and practitioners can lead to greater ecological validity in study designs to improve upon the translational potential of findings. To this end, we have forged collaborative partnerships, and built cognitive neuroscience laboratories within independent reading disabilities schools. This approach affords frequent and ecologically valid neurobiological assessment as children's reading improves in response to intervention. It also permits the creation of dynamic models of leading and lagging relationships of students' learning, and identification of individual-level predictors of intervention response. The partnerships also provide in-depth knowledge of student characteristics and classroom practices, which, when combined with the data we acquire, may facilitate optimization of instructional approaches. In this commentary, we discuss the creation of our partnerships, the scientific problem we are addressing (variable response to reading intervention), and the epistemological significance of researcher-practitioner bi-directional learning.

Reading intervention and neuroplasticity: A systematic review and meta-analysis of brain changes associated with reading intervention

Behavioral research supports the efficacy of intervention for reading disability, but the brain mechanisms underlying improvement in reading are not well understood. Here, we review 39 neuroimaging studies of reading intervention to characterize links between reading improvement and changes in the brain. We report evidence of changes in activation, connectivity, and structure within the reading network, and right hemisphere, frontal and sub-cortical regions. Our meta-analysis of changes in brain activation from pre- to post- reading intervention in eight studies did not yield any significant effects. Methodological heterogeneity among studies may contribute to the lack of significant meta-analytic findings. Based on our qualitative synthesis, we propose that brain changes in response to intervention should be considered in terms of interactions among distributed cognitive, linguistic and sensory systems, rather than via a "normalized" vs. "compensatory" dichotomy. Further empirical research is needed to identify effects of moderating factors such as features of intervention programs, neuroimaging tasks, and individual differences among participants.

Socioeconomic Status and Reading Disability: Neuroanatomy and Plasticity in Response to Intervention

Although reading disability (RD) and socioeconomic status (SES) are independently associated with variation in reading ability and brain structure/function, the joint influence of SES and RD on neuroanatomy and/or response to intervention is unknown. In total, 65 children with RD (ages 6-9) with diverse SES were assigned to an intensive, 6-week summer reading intervention (n = 40) or to a waiting-list control group (n = 25). Before and after, all children completed standardized reading assessments and magnetic resonance imaging to measure cortical thickness. At baseline, higher SES correlated with greater vocabulary and greater cortical thickness in bilateral perisylvian and supramarginal regions-especially in left pars opercularis. Within the intervention group, lower SES was associated with both greater reading improvement and greater cortical thickening across broad, bilateral occipitotemporal and temporoparietal regions following the intervention. Additionally, treatment responders (n = 20), compared with treatment nonresponders (n = 19), exhibited significantly greater cortical thickening within similar regions. The waiting control and nonresponder groups exhibited developmentally typical, nonsignificant cortical thinning during this time period. These findings indicate that effective summer reading intervention is coupled with cortical growth, and is especially beneficial for children with RD who come from lower-SES home environments.

Brain activity in struggling readers before intervention relates to future reading gains

Neural markers for reading-related changes in response to intervention could inform intervention plans by serving as a potential index of the malleability of the reading network in struggling readers. Of particular interest is the role of brain activation outside the reading network, especially in executive control networks important for reading comprehension. However, it is unclear whether any intervention-related executive control changes in the brain are specific to reading tasks or reflect more domain general changes. Brain changes associated with reading gains over time were compared for a sentence comprehension task as well as for a non-lexical executive control task (a behavioral inhibition task) in upper-elementary struggling readers, and in grade-matched non-struggling readers. Functional MRI scans were conducted before and after 16 weeks of reading intervention. Participants were grouped as improvers and non-improvers based on the consistency and size of post-intervention gains across multiple post-test measures. Engagement of the right fusiform during the reading task, both before and after intervention, was related to gains from remediation. Additionally, pre-intervention activation in regions that are part of the default-mode network (precuneus) and the fronto-parietal network (right posterior middle temporal gyrus) separated improvers and non-improvers from non-struggling readers. None of these differences were observed during the non-lexical inhibitory control task, indicating that the brain changes seen related to intervention outcome in struggling readers were specific to the reading process.

Effect of reading intervention and task difficulty on orthographic and phonological reading systems in the brain

Children with poor reading skills have differences in brain function when compared to typically-developing readers, and there may also be changes in the brain following reading intervention. However, most functional imaging studies focus on phonological reading tasks with one level of task difficulty. The purpose of this study was to compare good and poor readers on functional magnetic resonance imaging (fMRI) tasks of orthography (spelling) and phonology (rhyming) before and after 3 months of school-based intervention. These tasks were also modulated by task difficulty based on printed word frequency. The results showed that primarily left hemisphere regions were activated for the spelling and rhyming tasks, and poor readers showed a pattern of increased activation in bilateral inferior frontal, bilateral insula, right parietal, and left cerebellum following intervention. Activity in left pars triangularis and right parietal regions were associated with gains in decoding skills. Intervention effects appeared across blocks of easy and difficult words, except for the right parietal cortex. In this region, poor readers had greater activity on the easy word blocks after intervention, which indicates that there was increased recruitment of the right parietal cortex for relatively easy words. These results indicate that effects of intervention may be more evident on phonological tasks in comparison to orthographic tasks, and some of these effects may be modulated by relative task difficulty.

Prefrontal mediation of the reading network predicts intervention response in dyslexia

A primary challenge facing the development of interventions for dyslexia is identifying effective predictors of intervention response. While behavioral literature has identified core cognitive characteristics of response, the distinction of reading versus executive cognitive contributions to response profiles remains unclear, due in part to the difficulty of segregating these constructs using behavioral outputs. In the current study we used functional neuroimaging to piece apart the mechanisms of how/whether executive and reading network relationships are predictive of intervention response. We found that readers who are responsive to intervention have more typical pre-intervention functional interactions between executive and reading systems compared to nonresponsive readers. These findings suggest that intervention response in dyslexia is influenced not only by domain-specific reading regions, but also by contributions from intervening domain-general networks. Our results make a significant gain in identifying predictive bio-markers of outcomes in dyslexia, and have important implications for the development of personalized clinical interventions.

Knockdown of Dyslexia-Gene Dcdc2 Interferes with Speech Sound Discrimination in Continuous Streams

Dyslexia is the most common developmental language disorder and is marked by deficits in reading and phonological awareness. One theory of dyslexia suggests that the phonological awareness deficit is due to abnormal auditory processing of speech sounds. Variants in DCDC2 and several other neural migration genes are associated with dyslexia and may contribute to auditory processing deficits. In the current study, we tested the hypothesis that RNAi suppression of Dcdc2 in rats causes abnormal cortical responses to sound and impaired speech sound discrimination. In the current study, rats were subjected in utero to RNA interference targeting of the gene Dcdc2 or a scrambled sequence. Primary auditory cortex (A1) responses were acquired from 11 rats (5 with Dcdc2 RNAi; DC-) before any behavioral training. A separate group of 8 rats (3 DC-) were trained on a variety of speech sound discrimination tasks, and auditory cortex responses were acquired following training. Dcdc2 RNAi nearly eliminated the ability of rats to identify specific speech sounds from a continuous train of speech sounds but did not impair performance during discrimination of isolated speech sounds. The neural responses to speech sounds in A1 were not degraded as a function of presentation rate before training. These results suggest that A1 is not directly involved in the impaired speech discrimination caused by Dcdc2 RNAi. This result contrasts earlier results using Kiaa0319 RNAi and suggests that different dyslexia genes may cause different deficits in the speech processing circuitry, which may explain differential responses to therapy.

SIGNIFICANCE STATEMENT

Although dyslexia is diagnosed through reading difficulty, there is a great deal of variation in the phenotypes of these individuals. The underlying neural and genetic mechanisms causing these differences are still widely debated. In the current study, we demonstrate that suppression of a candidate-dyslexia gene causes deficits on tasks of rapid stimulus processing. These animals also exhibited abnormal neural plasticity after training, which may be a mechanism for why some children with dyslexia do not respond to intervention. These results are in stark contrast to our previous work with a different candidate gene, which caused a different set of deficits. Our results shed some light on possible neural and genetic mechanisms causing heterogeneity in the dyslexic population.

Responsivity to dyslexia training indexed by the N170 amplitude of the brain potential elicited by word reading

The present study examined training effects in dyslexic children on reading fluency and the amplitude of N170, a negative brain-potential component elicited by letter and symbol strings. A group of 18 children with dyslexia in 3rd grade (9.05±0.46years old) was tested before and after following a letter-speech sound mapping training. A group of 20 third-grade typical readers (8.78±0.35years old) performed a single time on the same brain potential task. The training was differentially effective in speeding up reading fluency in the dyslexic children. In some children, training had a beneficial effect on reading fluency ('improvers') while a training effect was absent in others ('non-improvers'). Improvers at pre-training showed larger N170 amplitude to words compared to non-improvers. N170 amplitude decreased following training in improvers but not in non-improvers. But the N170 amplitude pattern in improvers continued to differ from the N170 amplitude pattern across hemispheres seen in typical readers. Finally, we observed a positive relation between the decrease in N170 amplitude and gains in reading fluency. Collectively, the results that emerged from the present study indicate the sensitivity of N170 amplitude to reading fluency and its potential as a predictor of reading fluency acquisition.

What does the brain of children with developmental dyslexia tell us about reading improvement? ERP evidence from an intervention study

Intervention is key to managing developmental dyslexia (DD), but not all children with DD benefit from treatment. Some children improve (improvers, IMP), whereas others do not improve (non-improvers, NIMP). Neurobiological differences between IMP and NIMP have been suggested, but studies comparing IMP and NIMP in childhood are missing. The present study examined whether ERP patterns change with treatment and differ between IMP and NIMP. We investigated the ERPs of 28 children with DD and 25 control children (CON) while performing a phonological lexical decision (PLD) task before and after a 6-month intervention. After intervention children with DD were divided into IMP (n = 11) and NIMP (n = 17). In the PLD–task children were visually presented with words, pseudohomophones, pseudowords, and false fonts and had to decide whether the presented stimulus sounded like an existing German word or not. Prior to intervention IMP showed higher N300 amplitudes over fronto-temporal electrodes compared to NIMP and CON and N400 amplitudes were attenuated in both IMP and NIMP compared to CON. After intervention N300 amplitudes of IMP were comparable to those of CON and NIMP. This suggests that the N300, which has been related to phonological access of orthographic stimuli and integration of orthographic and phonological representations, might index a compensatory mechanism or precursor that facilitates reading improvement. The N400, which is thought to reflect grapheme-phoneme conversion or the access to the orthographic lexicon increased in IMP from pre to post and was comparable to CON after intervention. Correlations between N300 amplitudes pre, growth in reading ability and N400 amplitudes post indicated that higher N300 amplitudes might be important for reading improvement and increase in N400 amplitudes. The results suggest that children with DD, showing the same cognitive profile might differ regarding their neuronal profile which could further influence reading improvement.

Neuroimaging of reading intervention: a systematic review and activation likelihood estimate meta-analysis

A growing number of studies examine instructional training and brain activity. The purpose of this paper is to review the literature regarding neuroimaging of reading intervention, with a particular focus on reading difficulties (RD). To locate relevant studies, searches of peer-reviewed literature were conducted using electronic databases to search for studies from the imaging modalities of fMRI and MEG (including MSI) that explored reading intervention. Of the 96 identified studies, 22 met the inclusion criteria for descriptive analysis. A subset of these (8 fMRI experiments with post-intervention data) was subjected to activation likelihood estimate (ALE) meta-analysis to investigate differences in functional activation following reading intervention. Findings from the literature review suggest differences in functional activation of numerous brain regions associated with reading intervention, including bilateral inferior frontal, superior temporal, middle temporal, middle frontal, superior frontal, and postcentral gyri, as well as bilateral occipital cortex, inferior parietal lobules, thalami, and insulae. Findings from the meta-analysis indicate change in functional activation following reading intervention in the left thalamus, right insula/inferior frontal, left inferior frontal, right posterior cingulate, and left middle occipital gyri. Though these findings should be interpreted with caution due to the small number of studies and the disparate methodologies used, this paper is an effort to synthesize across studies and to guide future exploration of neuroimaging and reading intervention.

Cortical signatures of dyslexia and remediation: an intrinsic functional connectivity approach

This observational, cross-sectional study investigates cortical signatures of developmental dyslexia, particularly from the perspective of behavioral remediation. We employed resting-state fMRI, and compared intrinsic functional connectivity (iFC) patterns of known reading regions (seeds) among three dyslexia groups characterized by (a) no remediation (current reading and spelling deficits), (b) partial remediation (only reading deficit remediated), and (c) full remediation (both reading and spelling deficits remediated), and a group of age- and IQ-matched typically developing children (TDC) (total N = 44, age range = 7-15 years). We observed significant group differences in iFC of two seeds located in the left posterior reading network - left intraparietal sulcus (L.IPS) and left fusiform gyrus (L.FFG). Specifically, iFC between L.IPS and left middle frontal gyrus was significantly weaker in all dyslexia groups, irrespective of remediation status/literacy competence, suggesting that persistent dysfunction in the fronto-parietal attention network characterizes dyslexia. Additionally, relative to both TDC and the no remediation group, the remediation groups exhibited stronger iFC between L.FFG and right middle occipital gyrus (R.MOG). The full remediation group also exhibited stronger negative iFC between the same L.FFG seed and right medial prefrontal cortex (R.MPFC), a core region of the default network These results suggest that behavioral remediation may be associated with compensatory changes anchored in L.FFG, which reflect atypically stronger coupling between posterior visual regions (L.FFG-R.MOG) and greater functional segregation between task-positive and task-negative regions (L.FFG-R.MPFC). These findings were bolstered by significant relationships between the strength of the identified functional connections and literacy scores. We conclude that examining iFC can reveal cortical signatures of dyslexia with particular promise for monitoring neural changes associated with behavioral remediation.

Adequate versus inadequate response to reading intervention: an event-related potentials assessment

Three visual event-related potential components to the second of two sequentially presented words that rhymed or not discriminated children who improved (AR) from those who failed following (IR) reading intervention. Right hemisphere P100 amplitudes discriminated Typically Developing (TD) children from AR children but IR from AR children over left hemisphere sites. N200 amplitudes across hemispheres discriminated TD from IR children and AR from IR children. P300 hemisphere differences differentiated TD from AR and IR children. P300 amplitudes discriminated rhyming from non-rhyming words across children. Results extend prior work asserting that normalization and compensatory mechanisms are active during successful interventions.

Engagement of temporal lobe regions predicts response to educational interventions in adolescent struggling readers

Brain activation profiles obtained using magnetoencephalography were compared between middle-school students experiencing reading difficulties and non-reading-impaired students during performance of a continuous printed word recognition task. Struggling readers underwent small-group remedial instruction, and students who showed significant gains in word reading efficiency at a one-year follow-up assessment were classified as Adequate Responders whereas those not demonstrating such gains as Inadequate Responders. At baseline, compared to Inadequate Responders, the activation profiles of Adequate Responders featured increased activity in the left middle, superior temporal, and ventral occipitotemporal regions, as well as in the right mesial temporal cortex. The degree of activity in these regions was a significant predictor of improvement in word reading efficiency beyond the prediction afforded by baseline reading accuracy or fluency measures. The engagement of brain areas that typically serve as key components of the brain circuit for reading may be an important factor in predicting response to intervention in older students who experience reading difficulties.

Influences of Neural Pathway Integrity on Children's Response to Reading Instruction

As the education field moves toward using responsiveness to intervention to identify students with disabilities, an important question is the degree to which this classification can be connected to a student's neurobiological characteristics. A few functional neuroimaging studies have reported a relationship between activation and response to instruction; however, whether a similar correlation exists with white matter (WM) is not clear. To investigate this issue, we acquired high angular resolution diffusion images from a group of first grade children who differed in their levels of responsiveness to a year-long reading intervention. Using probabilistic tractography, we calculated the strength of WM connections among nine cortical regions of interest and correlated these estimates with participants' scores on four standardized reading measures. We found eight significant correlations, four of which were connections between the insular cortex and angular gyrus. In each of the correlations, a relationship with children's response to intervention was evident.