Publications

2023
Marks RA, Pollack C, Meisler SL, D'Mello AM, Centanni TM, Romeo RR, Wade K, Matejko AA, Ansari D, Gabrieli JDE, et al. Neurocognitive mechanisms of co-occurring math difficulties in dyslexia: Differences in executive function and visuospatial processing. Dev Sci. 2023 :e13443.Abstract
Children with dyslexia frequently also struggle with math. However, studies of reading disability (RD) rarely assess math skill, and the neurocognitive mechanisms underlying co-occurring reading and math disability (RD+MD) are not clear. The current study aimed to identify behavioral and neurocognitive factors associated with co-occurring MD among 86 children with RD. Within this sample, 43% had co-occurring RD+MD and 22% demonstrated a possible vulnerability in math, while 35% had no math difficulties (RD-Only). We investigated whether RD-Only and RD+MD students differed behaviorally in their phonological awareness, reading skills, or executive functions, as well as in the brain mechanisms underlying word reading and visuospatial working memory using functional magnetic resonance imaging (fMRI). The RD+MD group did not differ from RD-Only on behavioral or brain measures of phonological awareness related to speech or print. However, the RD+MD group demonstrated significantly worse working memory and processing speed performance than the RD-Only group. The RD+MD group also exhibited reduced brain activations for visuospatial working memory relative to RD-Only. Exploratory brain-behavior correlations along a broad spectrum of math ability revealed that stronger math skills were associated with greater activation in bilateral visual cortex. These converging neuro-behavioral findings suggest that poor executive functions in general, including differences in visuospatial working memory, are specifically associated with co-occurring MD in the context of RD. RESEARCH HIGHLIGHTS: Children with reading disabilities (RD) frequently have a co-occurring math disability (MD), but the mechanisms behind this high comorbidity are not well understood. We examined differences in phonological awareness, reading skills, and executive function between children with RD only versus co-occurring RD+MD using behavioral and fMRI measures. Children with RD only versus RD+MD did not differ in their phonological processing, either behaviorally or in the brain. RD+MD was associated with additional behavioral difficulties in working memory, and reduced visual cortex activation during a visuospatial working memory task.
Marks RA, Norton RT, Mesite L, Fox AB, Christodoulou JA. Risk and resilience correlates of reading among adolescents with language-based learning disabilities during COVID-19. Read Writ. 2023;36 (2) :401-428.Abstract
UNLABELLED: Students with language-based learning disabilities (LBLD) can face elevated socio-emotional well-being challenges in addition to literacy challenges. We examined the prevalence of risk and resilience factors among adolescents with LBLD (N = 93), ages 16-18, and the association with reading performance during the COVID-19 pandemic. Data were collected at the start and end of the first fully remote academic year of COVID-19 (2020-2021). Participants completed standardized word and text reading measures, as well as self-report surveys of executive functions (EF), and socio-emotional skills associated with resilience (grit, growth mindset, self-management, self-efficacy, and social awareness) or risk (anxiety, depression, COVID-19 related PTSD, and perceived COVID-19 impact). Survey data at the start of the school year (Time 1) captured three underlying factors associated with socioemotional risk, socioemotional resilience, and regulation (i.e., EF). Path analyses revealed that students' Time 2 oral reading scores were significantly and uniquely predicted by socioemotional resilience, even when controlling for word-level reading at Time 1. Socioemotional risk, EF, and perceived COVID-19 impact were not directly related to Time 2 oral reading scores; however, students' resilience mediated the associations between risk and reading outcomes. These results demonstrate that adolescents' mental health concerns, self-regulatory ability, and socioemotional resilience were all associated with their experiences of the COVID-19-related stress. However, despite the high-risk context of the pandemic, and socio-emotional challenges faced by students with LBLD, our findings indicate that resilience directly predicts end-of-year reading outcomes and mediates the impact of socioemotional risk on achievement. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11145-022-10361-8.
2022
Al Dahhan NZ, Halverson K, Peek CP, Wilmot D, D'Mello A, Romeo RR, Meegoda O, Imhof A, Wade K, Sridhar A, et al. Dissociating executive function and ADHD influences on reading ability in children with dyslexia. Cortex. 2022;153 :126-142.Abstract
Developmental dyslexia (DD) and attention-deficit/hyperactivity disorder (ADHD) are two of the most common neurodevelopmental disorders among school-age children. These disorders frequently co-occur, with up to 40-50% of children with one diagnosis meeting criteria for the other, and similar percentages of children with either DD or ADHD exhibiting impaired executive functions (EF). Although both ADHD and EF deficits are common in dyslexia, there is little evidence about how ADHD and EF deficits specifically influence the brain basis of reading difficulty in dyslexia, and whether the influences of ADHD and EF on dyslexia can be disentangled. The goal of the current study was to investigate, at both behavioral and brain levels, whether reading performance in individuals with dyslexia is more strongly associated with EF or with diagnostic status of comorbid ADHD. We examined reading abilities and EF in children (8-13 years old) with typical reading ability, DD only, or both DD + ADHD. Across both groups with dyslexia, impaired EF was associated with greater impairment on measures loading onto a reading fluency, but not a reading accuracy, factor. There were no significant differences between the DD and DD + ADHD groups on measures of reading fluency or reading accuracy. During functional magnetic resonance imaging (fMRI) while performing a rhyme-matching reading task requiring phonological awareness, typically developing readers showed greater left-hemisphere reading network activation than children with DD or DD + ADHD. Children with DD and DD + ADHD did not show differential activation, but DD children with unimpaired EF showed greater activation than those with impaired EF in reading-related areas. Thus, ADHD status alone had no measurable influence on reading performance or brain activation. Impaired EF in dyslexia, independent of ADHD status, was associated with greater deficits in reading fluency and greater reductions of activation in response to print in the typical left-hemisphere reading network.
Jones M, Harris WB, Perry SM, Behrmann M, Christodoulou J, Fallah A, Kolb B, Musiek F, Paul LK, Puka K, et al. Knowledge gaps for functional outcomes after multilobar resective and disconnective pediatric epilepsy surgery: Conference Proceedings of the Patient-Centered Stakeholder Meeting 2019. Epileptic Disord. 2022;24 (1) :50-66.Abstract
For children with medication-resistant epilepsy who undergo multilobar or hemispheric surgery, the goal of achieving seizure freedom is met with a variety of potential functional consequences, both favorable and unfavorable. However, there is a paucity of literature that comprehensively addresses the cognitive, medical, behavioral, orthopedic, and sensory outcomes across the lifespan following large epilepsy surgeries in childhood, leaving all stakeholders underinformed with regard to counseling and expectations. Through collaboration between clinicians, researchers, and patient/caregiver stakeholders, the "Functional Impacts of Large Resective or Disconnective Pediatric Epilepsy Surgery: Identifying Gaps and Setting PCOR Priorities" meeting was convened on July 18, 2019, to identify gaps in knowledge and inform various patient-centered research initiatives. Clinicians and researchers with content expertise presented the best available data in each functional domain which is summarized here. As a result of the meeting, the top three consensus priorities included research focused on postoperative: (1) hydrocephalus; (2) mental health issues; and (3) literacy and other educational outcomes. The proceedings of this meeting mark the first time research on functional outcomes after resective and disconnective pediatric epilepsy surgery has been codified and shared among multidisciplinary stakeholders. This joint initiative promotes continued collaboration in the field and ensures that advancements align with actual patient and family needs and experiences. Collaboration around common objectives will lead to better informed counseling around postoperative expectations and management for children undergoing epilepsy surgery.
Radville KM, Larrivee EC, Baron LS, Kelley-Nazzaro P, Christodoulou JA. Online Training Modules for Teaching Assessment Skills to Graduate Student Clinicians. Lang Speech Hear Serv Sch. 2022;53 (2) :417-430.Abstract
PURPOSE: Assessment is a crucial skill for speech-language pathologists, who rely on standardized tests to identify characteristics of speech, language, hearing, literacy, and related skill sets. Training in assessment administration is an integral part of graduate education that lays the foundation for appropriate use of these tools. Teaching students to administer standardized assessments is time intensive, can vary depending on student learning pace, and involves both general and test-specific knowledge. The current pilot study investigated the effectiveness of researcher-developed and scalable online training modules for beginning and advanced graduate students for knowledge and self-efficacy outcomes. METHOD: Graduate students (n = 61) across four cohorts (two beginning and two advanced) were trained using online, asynchronous assessment training modules. The modules addressed the administration of standardized assessments using written tutorials, video demonstrations, and quizzes. Students completed pre- and posttests on knowledge and self-efficacy for administering and scoring the trained assessments before and after the online training modules. RESULTS: We found significant pretest to posttest gains in specific assessment-related knowledge for beginning and advanced groups. Following completion of the training modules, beginning graduate students demonstrated increased self-efficacy for general assessment principles, whereas advanced graduate students started and remained high in self-efficacy at posttest. CONCLUSIONS: Using researcher-developed online training modules, both beginning and advanced graduate students improved knowledge for assessment skills. These training modules can be used as a model for developing teaching materials across a range of assessments and related topics that are scalable in the context of remote teaching and learning.
Romeo RR, Perrachione TK, Olson HA, Halverson KK, Gabrieli JDE, Christodoulou JA. Socioeconomic dissociations in the neural and cognitive bases of reading disorders. Dev Cogn Neurosci. 2022;58 :101175.Abstract
Childhood socioeconomic status (SES) strongly predicts disparities in reading development, yet it is unknown whether early environments also moderate the cognitive and neurobiological bases of reading disorders (RD) such as dyslexia, the most prevalent learning disability. SES-diverse 6-9-year-old children (n = 155, half with RD) completed behavioral and functional magnetic resonance imaging (fMRI) tasks engaging phonological and orthographic processing, which revealed corresponding double-dissociations in neurocognitive deficits. At the higher end of the SES spectrum, RD was most strongly explained by differences in phonological skill and corresponding activation in left inferior frontal and temporoparietal regions during phonological processing-widely considered the "core deficit" of RD. However, at the lower end of the SES spectrum, RD was most strongly explained by differences in rapid naming skills and corresponding activation in left temporoparietal and fusiform regions during orthographic processing. Findings indicate that children's early environments systematically moderate the neurocognitive systems underlying RD, which has implications for assessment and treatment approaches to reduce SES disparities in RD outcomes. Further, results suggest that reliance on high-SES convenience samples may mask critical heterogeneity in the foundations of both typical and disordered reading development.
Romeo RR, Uchida L, Christodoulou JA. Socioeconomic status and reading outcomes: Neurobiological and behavioral correlates. New Dir Child Adolesc Dev. 2022;2022 (183-184) :57-70.Abstract
In this chapter, we examine reading outcomes and socioeconomic status (SES) using a developmental cognitive and educational neuroscience perspective. Our focus is on reading achievement and intervention outcomes for students from lower SES backgrounds who struggle with reading. Socioeconomic disadvantage is a specific type of vulnerability students experience, which is often narrowly defined based on parental income, education level, and/or occupational prestige. However, implications of socioeconomic status extend broadly to a suite of areas relevant for reading outcomes including a student's access to resources, experiences, language exposure, academic outcomes, and psychological correlates. Underlying this constellation of factors are brain systems supporting the processing of oral and written language as well as stress-related factors. We review the implications of SES and reading achievement, and their intersectionality, for the science and practice of reading instruction.
2021
Pollack C, Wilmot D, Centanni TM, Halverson K, Frosch I, D'Mello AM, Romeo RR, Imhof A, Capella J, Wade K, et al. Anxiety, Motivation, and Competence in Mathematics and Reading for Children With and Without Learning Difficulties. Front Psychol. 2021;12 :704821.Abstract
Knowledge of the relations among learners' socio-emotional characteristics and competencies as they engage in mathematics and reading is limited, especially for children with academic difficulties. This study examined the relations between anxiety, motivation, and competence in mathematics and reading, within and across domains, in an academically-diverse set of 8-13-year-old learners (n = 146). To measure anxiety and motivation across domains, we paired existing measures of math anxiety and reading motivation with researcher-developed analogs for reading anxiety and math motivation. Participants completed standardized assessments of mathematics and reading, anxiety and motivation surveys for math and reading, and a measure of nonverbal cognitive ability. Results showed high internal consistency for all anxiety and motivation scales (Cronbach's alpha = 0.76-0.91). Pearson correlations showed that within and across domains, participants with higher competence had lower anxiety and higher motivation. Higher anxiety was also associated with lower motivation. Regression analyses showed that for both math and reading, within-domain motivation was a stronger predictor of competence than anxiety. There was a unidirectional across-domain relation: socio-emotional characteristics for reading predicted math competence, after accounting for nonverbal cognitive ability, age, gender, and within-domain anxiety and motivation. Results contribute to knowledge of the socio-emotional characteristics of children with and without learning difficulties in association with reading and math activities. Implications of a unidirectional socio-emotional link between the two domains can advance research and theory of the relations among socio-emotional characteristics and competence for academically-diverse learners.
Christodoulou JA, Halverson K, Meegoda O, Beckius H, Moser S, Imhof A, Maguire A. Literacy-related skills among children after left or right hemispherectomy. Epilepsy Behav. 2021;121 (Pt A) :107995.Abstract
OBJECTIVE: Following hemispherectomy surgery, children's educational outcomes are of great importance but are understudied. The study goal was to investigate reading, language, and nonverbal cognitive skills in children obligatorily relying on a left versus right hemisphere using a cross-sectional design. METHODS: Participants (ages 6-18) who had undergone left hemispherectomy (LH; n = 10) or right hemispherectomy (RH; n = 14) completed standardized measures of reading, language, and nonverbal cognition. RESULTS: LH and RH groups were balanced for socioeconomic status, sex, and age. Both groups scored below the population mean across standardized measures (RH: -0.79 to -1.95 SDs; LH: -0.97 to -2.32 SDs). Compared to the LH group, the group retaining a functional left hemisphere (RH group) learned to read sooner (p = .011) despite no significant differences for surgery age, and scored higher on untimed real word and pseudoword reading measures (p < .05). Effect sizes were medium (r = 0.34-0.46) for the LH and RH comparison on measures of phonological awareness and both untimed and timed word and pseudoword reading. In examining the association between clinical variables and reading-related outcomes, younger age of post-hemispherectomy reading acquisition and shorter duration between seizure onset and hemispherectomy surgery were associated with higher standardized reading and language test scores (p < .05). SIGNIFICANCE: Investigations of psychoeducational skills in reading, language, and nonverbal cognition among children who have undergone hemispherectomy can offer important insights into compensatory potential for left and right hemispheres as well as inform educational programming for children following medical stabilization.
2020
D'Mello AM, Centanni TM, Gabrieli JDE, Christodoulou JA. Cerebellar contributions to rapid semantic processing in reading. Brain Lang. 2020;208 :104828.
2018
Romeo RR, Christodoulou JA, Halverson KK, Murtagh J, Cyr AB, Schimmel C, Chang P, Hook PE, Gabrieli JDE. Socioeconomic Status and Reading Disability: Neuroanatomy and Plasticity in Response to Intervention. Cereb Cortex. 2018;28 (7) :2297-2312.Abstract
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.
2017
Macdonald K, Germine L, Anderson A, Christodoulou J, McGrath LM. Dispelling the Myth: Training in Education or Neuroscience Decreases but Does Not Eliminate Beliefs in Neuromyths. Front Psychol. 2017;8 :1314.Abstract
Neuromyths are misconceptions about brain research and its application to education and learning. Previous research has shown that these myths may be quite pervasive among educators, but less is known about how these rates compare to the general public or to individuals who have more exposure to neuroscience. This study is the first to use a large sample from the United States to compare the prevalence and predictors of neuromyths among educators, the general public, and individuals with high neuroscience exposure. Neuromyth survey responses and demographics were gathered via an online survey hosted at TestMyBrain.org. We compared performance among the three groups of interest: educators (N = 598), high neuroscience exposure (N = 234), and the general public (N = 3,045) and analyzed predictors of individual differences in neuromyths performance. In an exploratory factor analysis, we found that a core group of 7 "classic" neuromyths factored together (items related to learning styles, dyslexia, the Mozart effect, the impact of sugar on attention, right-brain/left-brain learners, and using 10% of the brain). The general public endorsed the greatest number of neuromyths (M = 68%), with significantly fewer endorsed by educators (M = 56%), and still fewer endorsed by the high neuroscience exposure group (M = 46%). The two most commonly endorsed neuromyths across all groups were related to learning styles and dyslexia. More accurate performance on neuromyths was predicted by age (being younger), education (having a graduate degree), exposure to neuroscience courses, and exposure to peer-reviewed science. These findings suggest that training in education and neuroscience can help reduce but does not eliminate belief in neuromyths. We discuss the possible underlying roots of the most prevalent neuromyths and implications for classroom practice. These empirical results can be useful for developing comprehensive training modules for educators that target general misconceptions about the brain and learning.
Christodoulou JA, Cyr A, Murtagh J, Chang P, Lin J, Guarino AJ, Hook P, Gabrieli JDE. Impact of Intensive Summer Reading Intervention for Children With Reading Disabilities and Difficulties in Early Elementary School. J Learn Disabil. 2017;50 (2) :115-127.Abstract
Efficacy of an intensive reading intervention implemented during the nonacademic summer was evaluated in children with reading disabilities or difficulties (RD). Students (ages 6-9) were randomly assigned to receive Lindamood-Bell's Seeing Stars program ( n = 23) as an intervention or to a waiting-list control group ( n = 24). Analysis of pre- and posttesting revealed significant interactions in favor of the intervention group for untimed word and pseudoword reading, timed pseudoword reading, oral reading fluency, and symbol imagery. The interactions mostly reflected (a) significant declines in the nonintervention group from pre- to posttesting, and (2) no decline in the intervention group. The current study offers direct evidence for widening differences in reading abilities between students with RD who do and do not receive intensive summer reading instruction. Intervention implications for RD children are discussed, especially in relation to the relevance of summer intervention to prevent further decline in struggling early readers.
Christodoulou JA, Murtagh J, Cyr A, Perrachione TK, Chang P, Halverson K, Hook P, Yendiki A, Ghosh S, Gabrieli JDE. Relation of white-matter microstructure to reading ability and disability in beginning readers. Neuropsychology. 2017;31 (5) :508-515.Abstract
UNLABELLED: [Correction Notice: An Erratum for this article was reported in Vol 31(5) of Neuropsychology (see record 2017-22816-001). Errors in the dataset owing to two incorrect scores have skewed results. In the 2nd paragraph of the Results section, the 2nd sentence should read: "Within the typical reader group, FA in the left AF correlated negatively with pseudoword reading (WRMT-III Word Attack: rs = .37, p = .064), but not real-word reading (WRMT-III Word Identification: rs = .07, p = .75)." The 4th sentence of the 3rd paragraph should read: "The negative correlation between FA and Word Attack in the typical reader group was driven by Daxial (Dradial: rs = .19, p = .373, Daxial: rs = .38, p = .060)." The 2nd sentence of the 4th paragraph should read: "Results of this analysis replicated those of the larger reading disability group, with a statistically greater reduction of FA in this more severely affected group (p = .008) that was associated with a significant increase in Dradial (p = .008) and no difference in Daxial (p = .47)." In Table 1, for the typical reader group, the resulting values should read: age, 94.00 ± 7.66; KBIT-2-Matrices, 118.31 ± 15.24; WRMT-III-Word Identification, 119.00 ± 9.33; WRMT-III-Word Attack, 114.04 ± 9.31; and TOWRE-2-Sight Word Efficiency, 114.48 ± 8.07. For the reading disability group, the resulting values for age and TOWRE-2- Phonemic Decoding Efficiency should be 93.65 ± 7.81 and 81.76 ± 9.33, respectively. The p values for age and KBIT-2-Matrices should be .87 and .172, respectively. In Figure 3, the image for the typical reader group has been replaced. All versions of this article have been corrected.] Objective: We examined the white-matter microstructure of the left arcuate fasciculus, which has been associated with reading ability, in beginning readers with or without reading disability. METHOD: Groups were typically reading children (n = 26) or children with reading disability (n = 26), Ages 6-9, and equated on nonverbal cognitive abilities. Diffusion-weighted images were collected and TRACULA was used to extract fractional anisotropy measures from the left arcuate fasciculus. RESULTS: White-matter microstructure was altered in children with reading disability, who exhibited significantly reduced fractional anisotropy in the left arcuate fasciculus. Among typically reading children, lower fractional anisotropy of the left arcuate fasciculus was associated with superior pseudoword reading performance. Both the group differences and variation in reading scores among the children with reading disability were associated with radial diffusivity (but not axial diffusivity), whereas variation in reading scores among typically reading children was associated with axial diffusivity (but not radial diffusivity). CONCLUSIONS: The paradoxical findings that lower fractional anisotropy was associated both with reading disability and also with better phonological awareness in typical reading development suggest that there are different maturational trajectories of white-matter microstructure in typical readers and children with reading disability, and that this difference is unique to the beginning stages of reading acquisition. The finding that reading disability was associated with radial diffusivity, but that variation in ability among typically developing readers was associated with axial diffusivity, suggests that different neural mechanisms may be associated with reading development in children with or without reading disability. (PsycINFO Database Record
2016
Perrachione TK, Del Tufo SN, Winter R, Murtagh J, Cyr A, Chang P, Halverson K, Ghosh SS, Christodoulou JA, Gabrieli JDE. Dysfunction of Rapid Neural Adaptation in Dyslexia. Neuron. 2016;92 (6) :1383-1397.Abstract
Identification of specific neurophysiological dysfunctions resulting in selective reading difficulty (dyslexia) has remained elusive. In addition to impaired reading development, individuals with dyslexia frequently exhibit behavioral deficits in perceptual adaptation. Here, we assessed neurophysiological adaptation to stimulus repetition in adults and children with dyslexia for a wide variety of stimuli, spoken words, written words, visual objects, and faces. For every stimulus type, individuals with dyslexia exhibited significantly diminished neural adaptation compared to controls in stimulus-specific cortical areas. Better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation. These results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development. Reduced neurophysiological adaptation may relate to prior reports of reduced behavioral adaptation in dyslexia and may reveal a difference in brain functions that ultimately results in a specific reading impairment.
Katzir T, Christodoulou JA, de Bode S. When left-hemisphere reading is compromised: Comparing reading ability in participants after left cerebral hemispherectomy and participants with developmental dyslexia. Epilepsia. 2016;57 (10) :1602-1609.Abstract
OBJECTIVE: We investigated reading skills in individuals who have undergone left cerebral hemispherectomy and in readers with developmental dyslexia to understand diverse characteristics contributing to reading difficulty. Although dyslexia is a developmental disorder, left hemispherectomy requires that patients (re)establish the language process needed to perform the language-based tasks in the nondominant (right) hemisphere to become readers. METHODS: Participants with developmental dyslexia (DD; n = 11) and participants who had undergone left hemispherectomy (HEMI; n = 11) were matched on age and gender, and were compared on timed and untimed measures of single word and pseudo-word reading. The hemispherectomy group was subdivided into prenatal (in utero) and postnatal (>3 years) insult groups, indicating the timing of the primary lesion that ultimately required surgical intervention. RESULTS: On an untimed reading measure, the readers with DD were comparable to individuals who had undergone left hemispherectomy due to prenatal insult, but both scored higher than the postnatal hemispherectomy group. Timed word reading differed across groups. The hemispherectomy prenatal subgroup had low average scores on both timed and untimed tests. The group with dyslexia had average scores on untimed measures and below average scores on timed reading. The hemispherectomy postnatal group had the lowest scores among the groups by a significant margin, and the most pronounced reading difficulty. SIGNIFICANCE: Patients with prenatal lesions leading to an isolated right hemisphere (RH) have the potential to develop reading to a degree comparable to that in persons with dyslexia for single word reading. This potential sharply diminishes in individuals who undergo hemispherectomy due to postnatal insult. The higher scores of the prenatal hemispherectomy group on timed reading suggest that under these conditions, individuals with an isolated RH can compensate to a significant degree.
2015
Pollack C, Luk G, Christodoulou JA. A meta-analysis of functional reading systems in typically developing and struggling readers across different alphabetic languages. Front Psychol. 2015;6 :191.Abstract
Functional neuroimaging research has identified multiple brain regions supporting reading-related activity in typical and atypical readers across different alphabetic languages. Previous meta-analyses performed on these functional magnetic resonance imaging findings typically report significant between-group contrasts comparing typical readers and readers with reading difficulty or a clinical diagnosis of developmental dyslexia. In order to advance our understanding of cross-linguistic convergence of reading-related brain activations for these reader groups, analyses using activation likelihood estimation were carried out separately for typical and atypical readers who ranged from children to adults. Contrasts were analyzed for tasks involving rhyming or reading of letter or word stimuli presented visually in English, Dutch, Italian, German, French, or Norwegian. Typical readers showed reliable activation in only left lateralized regions, including the inferior frontal area, precentral area and middle temporal gyrus. Atypical readers also showed activation in the left inferior frontal area and precentral region, in addition to significant activations in the right hemisphere, including the superior, medial and inferior frontal regions, lingual gyrus and the inferior occipital area. These results distinguish between typical and atypical reader group activations, showing common and distinct regions of activation when engaged in reading-related activities, extending previous meta-analyses on identifying brain regions relevant to reading to include cross-linguistic analyses for alphabetic scripts. Results support the universality of a signature pattern of brain activation in developmental dyslexia across alphabetic languages.
Shafi MM, Vernet M, Klooster D, Chu CJ, Boric K, Barnard ME, Romatoski K, Westover BM, Christodoulou JA, Gabrieli JDE, et al. Physiological consequences of abnormal connectivity in a developmental epilepsy. Ann Neurol. 2015;77 (3) :487-503.Abstract
OBJECTIVE: Many forms of epilepsy are associated with aberrant neuronal connections, but the relationship between such pathological connectivity and the underlying physiological predisposition to seizures is unclear. We sought to characterize the cortical excitability profile of a developmental form of epilepsy known to have structural and functional connectivity abnormalities. METHODS: We employed transcranial magnetic stimulation (TMS) with simultaneous electroencephalographic (EEG) recording in 8 patients with epilepsy from periventricular nodular heterotopia and matched healthy controls. We used connectivity imaging findings to guide TMS targeting and compared the evoked responses to single-pulse stimulation from different cortical regions. RESULTS: Heterotopia patients with active epilepsy demonstrated a relatively augmented late cortical response that was greater than that of matched controls. This abnormality was specific to cortical regions with connectivity to subcortical heterotopic gray matter. Topographic mapping of the late response differences showed distributed cortical networks that were not limited to the stimulation site, and source analysis in 1 subject revealed that the generator of abnormal TMS-evoked activity overlapped with the spike and seizure onset zone. INTERPRETATION: Our findings indicate that patients with epilepsy from gray matter heterotopia have altered cortical physiology consistent with hyperexcitability, and that this abnormality is specifically linked to the presence of aberrant connectivity. These results support the idea that TMS-EEG could be a useful biomarker in epilepsy in gray matter heterotopia, expand our understanding of circuit mechanisms of epileptogenesis, and have potential implications for therapeutic neuromodulation in similar epileptic conditions associated with deep lesions.
2014
Geiser E, Kjelgaard M, Christodoulou JA, Cyr A, Gabrieli JDE. Auditory temporal structure processing in dyslexia: processing of prosodic phrase boundaries is not impaired in children with dyslexia. Ann Dyslexia. 2014;64 (1) :77-90.Abstract
Reading disability in children with dyslexia has been proposed to reflect impairment in auditory timing perception. We investigated one aspect of timing perception--temporal grouping--as present in prosodic phrase boundaries of natural speech, in age-matched groups of children, ages 6-8 years, with and without dyslexia. Prosodic phrase boundaries are characterized by temporal grouping of functionally related speech elements and can facilitate syntactic processing of speech. For example, temporary syntactic ambiguities, such as early-closure structures, are processed faster when prosodic phrase boundaries are present. We examined children's prosodic facilitation by measuring their efficiency of sentence processing for temporary syntactic ambiguities spoken with (facilitating) versus without (neutral) prosodic phrase boundaries. Both groups of children benefited similarly from prosodic facilitation, displaying faster reaction times in facilitating compared to neutral prosody. These findings indicate that the use of prosodic phrase boundaries for speech processing is not impaired in children with dyslexia.
Christodoulou JA, Del Tufo SN, Lymberis J, Saxler PK, Ghosh SS, Triantafyllou C, Whitfield-Gabrieli S, Gabrieli JDE. Brain bases of reading fluency in typical reading and impaired fluency in dyslexia. PLoS One. 2014;9 (7) :e100552.Abstract
Although the neural systems supporting single word reading are well studied, there are limited direct comparisons between typical and dyslexic readers of the neural correlates of reading fluency. Reading fluency deficits are a persistent behavioral marker of dyslexia into adulthood. The current study identified the neural correlates of fluent reading in typical and dyslexic adult readers, using sentences presented in a word-by-word format in which single words were presented sequentially at fixed rates. Sentences were presented at slow, medium, and fast rates, and participants were asked to decide whether each sentence did or did not make sense semantically. As presentation rates increased, participants became less accurate and slower at making judgments, with comprehension accuracy decreasing disproportionately for dyslexic readers. In-scanner performance on the sentence task correlated significantly with standardized clinical measures of both reading fluency and phonological awareness. Both typical readers and readers with dyslexia exhibited widespread, bilateral increases in activation that corresponded to increases in presentation rate. Typical readers exhibited significantly larger gains in activation as a function of faster presentation rates than readers with dyslexia in several areas, including left prefrontal and left superior temporal regions associated with semantic retrieval and semantic and phonological representations. Group differences were more extensive when behavioral differences between conditions were equated across groups. These findings suggest a brain basis for impaired reading fluency in dyslexia, specifically a failure of brain regions involved in semantic retrieval and semantic and phonological representations to become fully engaged for comprehension at rapid reading rates.

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