Cortical Thickness and Local Gyrification in Children with Developmental Dyslexia

Localized alterations in cortical thickness and sulcal depth of the cingulo-opercular network in relation to lower reading fluency skills in children with dyslexia

The traditional models of reading development describe how language processing and word decoding contribute to reading comprehension and how impairments in word decoding, a defining feature of dyslexia, affect reading comprehension outcomes. However, these models do not include word and sentence reading (contextual reading) fluency, both of which engage executive functions, with notably decreased performance in children with dyslexia. In the current study, we compared cortical thickness and sulcal depth (CT/SD) in the cingulo-opercular (CO) executive functions brain network in children with dyslexia and typical readers and examined associations with word vs. contextual reading fluency. Overall, CT was lower in insular regions and higher in parietal and caudal anterior cingulate cortex regions in children with dyslexia. Children with dyslexia showed positive correlations between word reading fluency and CT/SD in insular regions, whereas no significant correlations were observed in typical readers. For sentence reading fluency, negative correlations with CT/SD were found in insular regions in children with dyslexia, while positive correlations with SD were found in insular regions in typical readers. These results demonstrate the differential relations between word and sentence reading fluency and anatomical circuitry supporting executive functions in children with dyslexia vs. typical readers. It also suggests that word and sentence reading fluency, relate to morphology of executive function-related regions in children with dyslexia, whereas in typical readers, only sentence reading fluency relates to morphology of executive function regions. The results also highlight the role of the insula within the CO network in reading fluency. Here we suggest that word and sentence reading fluency are distinct components of reading that should each be included in the Simple View of Reading traditional model.

Cortical Structure in Pre-Readers at Cognitive Risk for Dyslexia: Baseline Differences and Response to Intervention

Early childhood is a critical period for structural brain development as well as an important window for the identification and remediation of reading difficulties. Recent research supports the implementation of interventions in at-risk populations as early as kindergarten or first grade, yet the neurocognitive mechanisms following such interventions remain understudied. To address this, we investigated cortical structure by means of anatomical MRI before and after a 12-week tablet-based intervention in: (1) at-risk children receiving phonics-based training (n = 29; n = 16 complete pre-post datasets), (2) at-risk children engaging with AC training (n = 24; n = 15 complete pre-post datasets) and (3) typically developing children (n = 25; n = 14 complete pre-post datasets) receiving no intervention. At baseline, we found higher surface area of the right supramarginal gyrus in at-risk children compared to typically developing peers, extending previous evidence that early anatomical differences exist in children who may later develop dyslexia. Our longitudinal analysis revealed significant post-intervention thickening of the left supramarginal gyrus, present exclusively in the intervention group but not the active control or typical control groups. Altogether, this study contributes new knowledge to our understanding of the brain morphology associated with cognitive risk for dyslexia and response to early intervention, which in turn raises new questions on how early anatomy and plasticity may shape the trajectories of long-term literacy development.

Neural Correlates of Trait Impulsivity among Adult Healthy Individuals

Objective

: Impulsivity can be observed in individuals with or without mental illness. The discovery of neural correlates responsible for trait impulsivity can therefore help to understand the severity of psychiatric symptoms, personality characteristics and social adjustment. In this study, we aimed to identify the gray matter substrates of trait impulsivity in healthy individuals.

Methods

: Seventy-five healthy individuals were enrolled. At baseline, trait impulsivity was assessed using the Barratt Impulsiveness Scale (BIS) and all participants underwent T1-weighted magnetic resonance imaging scan. Beck Anxiety Inventory (BAI), World Health Organization Quality of Life (WHOQOL-BREF) and Connor-Davidson Resilience Scale (CD-RISC) were also assessed. Mean cortical thickness (CT) and the local gyrification index (LGI) were calculated to perform whole-brain vertex-wise correlation analysis, which were performed to investigate the relationship between BIS scores and CT or LGI in each brain region. We also revealed the relationship between brain regions and psychological measurements.

Results

: Total BIS scores were significantly and negatively correlated with mean CT values in the left lateral occipital cortex (OC) and LGIs in the inferior frontal gyrus (IFG). Correlation analyses revealed that the lateral OC's mean CT values were negatively correlated with BAI scores and positively correlated with WHOQOL-BREF scores, while LGI in the IFG was positively correlated with CD-RISC scores.

Conclusion

: Our study showed that trait impulsivity might be associated with the lateral OC and IFG in healthy individuals. Understanding the neural correlates of trait impulsivity could provide ways to expect high impulsivity, anxiety, and poor resilience in healthy adults.

Exposure to organophosphate, pyrethroid, and neonicotinoid insecticides and dyslexia: Association with oxidative stress

Organophosphates (OPPs), pyrethroids (PYRs), and neonicotinoids (NNIs) are three major classes of insecticides used worldwide. They might compromise child neurodevelopment. However, few studies have explored the association between exposure to them and dyslexia. The present study aimed to investigate the association between dyslexia and exposure to the three classes of insecticides, as well as explore the potential role of oxidative stress in the association. A total of 355 dyslexic children and 390 controls were included in this study. The exposure biomarkers were determined by liquid chromatography-tandem mass spectrometry. Specifically, the exposure biomarkers included three typical metabolites of OPPs, three of PYRs, and nine of NNIs. Additionally, three typical oxidative stress biomarkers, namely, 8-hydroxy-2'-deoxyguanosine (8-OHdG) for DNA damage, 8-hydroxyguanosine (8-OHG) for RNA damage, and 4-hydroxy-2-nonenal-mercapturic acid (HNEMA) for lipid peroxidation were measured. The detection frequencies of the urinary biomarkers ranged from 83.9% to 100%. Among the target metabolites of the insecticides, a significant association was observed between urinary 3,5,6-trichloro-2-pyridinol (TCPy, the metabolite of chlorpyrifos, an OPP insecticide) and dyslexia. After adjusting for potential confounding variables, children in the highest quartile of TCPy levels had an increased odds of dyslexia (odds ratio [OR], 1.68; 95% confidence interval [CI]: 1.03, 2.75] in comparison to those in the lowest quartile. Among the three oxidative stress biomarkers, urinary HNEMA concentration showed a significant relationship with dyslexia. Children in the highest quartile of HNEMA levels demonstrated an increased dyslexic odds in comparison to those in the lowest quartile after multiple adjustments (OR, 1.64; 95% CI: 1.01, 2.65). Mediation analysis indicated a significant effect of HNEMA in the association between urinary TCPy and dyslexia, with an estimate of 17.2% (P < 0.01). In conclusion, this study suggested the association between urinary TCPy and dyslexia. The association could be attributed to lipid peroxidation partially.

Beyond the language network: Associations between reading, receptive vocabulary, and grey matter volume in 10-year-olds

Most research on the neurostructural basis of language abilities in children stems from small samples and surface-based measures. To complement and expand the existent knowledge, we investigated associations between grey matter volume and language performance in a large sample of 9-to-11-year-old children, using data from the Adolescent Brain Cognitive Development (ABCD) Study (N = 1865) and an alternative measure of grey matter morphology. We estimated whole-brain grey matter volume for one half of the sample (N = 939) and tested for correlations with scores on a picture vocabulary and a letter and word reading test, with and without factoring in general intelligence and total grey matter volume as additional covariates. The initial analyses yielded correlations between grey matter in the right occipital fusiform gyrus, the right lingual gyrus, and the cerebellum for both vocabulary and reading. Employing the significant clusters from the first analyses as regions of interest in the second half of the cohort (N = 926) in correlational and multiple regression analyses suggests the cluster in the right occipital fusiform and lingual gyri to be most robust. Overall, the amount of variance explained by grey matter volume is limited and factoring in additional covariates paints an inconsistent picture. The present findings reinforce existent doubt with respect to explaining individual differences in reading and vocabulary performance based on unique contributions of macrostructural brain features.

Cortical Thickness Is Related to Variability in Heritage Bilingual Language Proficiency

Research suggests that bilingual experience is associated with gray matter changes, such that initial language gains are associated with expansion and language expertise is associated with renormalization. Previous studies on language proficiency development primarily focused on between-subjects, quasiexperimental comparisons of monolinguals and bilinguals. This study proposes a new paradigm to examine language expertise and cortical thickness within heritage bilinguals (n = 215), as well as between bilinguals and monolinguals (n = 145), using data combined from eight previous magnetic resonance imaging studies. In general, results highlight variability within bilinguals, finding relationships between cortical thickness and English proficiency that are relatively consistent within monolinguals, but inconsistent within bilinguals. In all participants, higher levels of proficiency in English-monolinguals' only language and bilinguals' second but stronger language-were negatively related to cortical thickness. In bilinguals, higher proficiency in the weaker, albeit first learned, language was positively related to cortical thickness. Moreover, there was an interaction between language group and English proficiency in predicting cortical thickness, such that the relationship between proficiency and thickness was stronger in monolinguals than in bilinguals. Findings also demonstrate that the regions associated with language expertise differ between bilinguals and monolinguals. Future directions for cognitive-developmental neuroscience research in bilinguals are suggested, particularly the longitudinal examination of cortical changes in relation to bilingual experiences.

Elevated levels of mixed-hand preference in dyslexia: Meta-analyses of 68 studies

Since almost a hundred years, psychologists have investigated the link between hand preference and dyslexia. We present a meta-analysis to determine whether there is indeed an increase in atypical hand preference in dyslexia. We included studies used in two previous meta-analyses (Bishop, 1990; Eglinton & Annett, 1994) as well as studies identified through PubMed MEDLINE, PsycInfo, Google Scholar, and Web of Science up to August 2022. K = 68 studies (n = 4660 individuals with dyslexia; n = 40845 controls) were entered into three random effects meta-analyses using the odds ratio as the effect size (non-right-handers; left-handers; mixed-handers vs. total). Evidence of elevated levels of atypical hand preference in dyslexia emerged that were especially pronounced for mixed-hand preference (OR = 1.57), although this category was underdefined. Differences in (direction or degree) of hand skill or degree of hand preference could not be assessed as no pertinent studies were located. Our findings allow for robust conclusions only for a relationship of mixed-hand preference with dyslexia.

Anatomical and behavioral correlates of auditory perception in developmental dyslexia

Developmental dyslexia (DD) is typically associated with difficulties in manipulating speech sounds and, sometimes, in basic auditory processing. However, the neuroanatomical correlates of auditory difficulties in DD and their contribution to individual clinical phenotypes are still unknown. Recent intracranial electrocorticography (ECoG) findings associated processing of sound amplitude rises and speech sounds with posterior and middle superior temporal gyrus (STG), respectively. We hypothesize that regional STG anatomy will relate to specific auditory abilities in DD and that auditory processing abilities will relate to behavioral difficulties. One hundred and ten children (78 DD, 32 typically developing, age 7-15 years) completed amplitude rise time (ART) and speech in noise discrimination (SiN) tasks. They also underwent a battery of cognitive tests. Anatomical MRI scans were used to identify regions in which local cortical gyrification complexity correlated with auditory tasks in DD. Behaviorally, ART but not SiN performance was impaired in DD. Neurally, ART and SiN performance correlated with gyrification in posterior STG and middle STG, respectively. Furthermore, ART significantly contributed to reading impairments in DD, while SiN explained variance in phonological awareness only. Finally, ART and SiN performance was not correlated, and each task was correlated with distinct neuropsychological measures, such that distinct DD subgroups could be identified. Overall, we provide a direct link between the neurodevelopment of the left STG and individual variability in auditory processing abilities in DD. The dissociation between speech and non-speech deficits supports distinct DD phenotypes and implicates different approaches to interventions.

The Role of Neural and Genetic Processes in Learning to Read and Specific Reading Disabilities: Implications for Instruction

To learn to read, the brain must repurpose neural systems for oral language and visual processing to mediate written language. We begin with a description of computational models for how alphabetic written language is processed. Next, we explain the roles of a dorsal sublexical system in the brain that relates print and speech, a ventral lexical system that develops the visual expertise for rapid orthographic processing at the word level, and the role of cognitive control networks that regulate attentional processes as children read. We then use studies of children, adult illiterates learning to read, and studies of poor readers involved in intervention, to demonstrate the plasticity of these neural networks in development and in relation to instruction. We provide a brief overview of the rapid increase in the field's understanding and technology for assessing genetic influence on reading. Family studies of twins have shown that reading skills are heritable, and molecular genetic studies have identified numerous regions of the genome that may harbor candidate genes for the heritability of reading. In selected families, reading impairment has been associated with major genetic effects, despite individual gene contributions across the broader population that appear to be small. Neural and genetic studies do not prescribe how children should be taught to read, but these studies have underscored the critical role of early intervention and ongoing support. These studies also have highlighted how structured instruction that facilitates access to the sublexical components of words is a critical part of training the brain to read.

The relationship between reading abilities and the left occipitotemporal sulcus: A dual perspective study

Reading activates a region within the left lateral occipitotemporal sulcus (OTS) known as the 'visual word form area' (VWFA). While several studies have investigated the impact of reading on brain structure through neuroplastic mechanisms, it has been recently suggested that individual differences in the pattern of the posterior OTS may predict reading skills in adults. In the present study, we first examined whether the structure and morphology and the anatomical connectivity of the left OTS are associated to reading ability. Second, we explored whether reading skills are predicted by the pattern of the left OTS. We found that reading skills were positively associated with increased connectivity between the left OTS and a network of reading-related regions in the left hemisphere. On the other hand, we did not observe an association between the pattern of the left OTS and reading skills. Finally, we found evidence that the morphology and the connectivity of the left OTS are correlated to its sulcal pattern.

Associations between digital media use and brain surface structural measures in preschool-aged children

The American Academy of Pediatrics recommends limits on digital media use ("screen time"), citing cognitive-behavioral risks. Media use in early childhood is ubiquitous, though few imaging-based studies have been conducted to quantify impacts on brain development. Cortical morphology changes dynamically from infancy through adulthood and is associated with cognitive-behavioral abilities. The current study involved 52 children who completed MRI and cognitive testing at a single visit. The MRI protocol included a high-resolution T1-weighted anatomical scan. The child's parent completed the ScreenQ composite measure of media use. MRI measures included cortical thickness (CT) and sulcal depth (SD) across the cerebrum. ScreenQ was applied as a predictor of CT and SD first in whole-brain regression analyses and then for regions of interest (ROIs) identified in a prior study of screen time involving adolescents, controlling for sex, age and maternal education. Higher ScreenQ scores were correlated with lower CT in right-lateralized occipital, parietal, temporal and fusiform areas, and also lower SD in right-lateralized inferior temporal/fusiform areas, with substantially greater statistical significance in ROI-based analyses. These areas support primary visual and higher-order processing and align with prior findings in adolescents. While differences in visual areas likely reflect maturation, those in higher-order areas may suggest under-development, though further studies are needed.

Structural gray matter features and behavioral preliterate skills predict future literacy – A machine learning approach

When children learn to read, their neural system undergoes major changes to become responsive to print. There seem to be nuanced interindividual differences in the neurostructural anatomy of regions that later become integral parts of the reading network. These differences might affect literacy acquisition and, in some cases, might result in developmental disorders like dyslexia. Consequently, the main objective of this longitudinal study was to investigate those interindividual differences in gray matter morphology that might facilitate or hamper future reading acquisition. We used a machine learning approach to examine to what extent gray matter macrostructural features and cognitive-linguistic skills measured before formal literacy teaching could predict literacy 2 years later. Forty-two native German-speaking children underwent T1-weighted magnetic resonance imaging and psychometric testing at the end of kindergarten. They were tested again 2 years later to assess their literacy skills. A leave-one-out cross-validated machine-learning regression approach was applied to identify the best predictors of future literacy based on cognitive-linguistic preliterate behavioral skills and cortical measures in a priori selected areas of the future reading network. With surprisingly high accuracy, future literacy was predicted, predominantly based on gray matter volume in the left occipito-temporal cortex and local gyrification in the left insular, inferior frontal, and supramarginal gyri. Furthermore, phonological awareness significantly predicted future literacy. In sum, the results indicate that the brain morphology of the large-scale reading network at a preliterate age can predict how well children learn to read.

Atypical cortical thickness and folding of language regions in Chinese nonsyndromic cleft lip and palate children after speech rehabilitation

Objective

Even after palatoplasty and speech rehabilitation, patients with cleft lip and palate (CLP) remain to produce pronunciation errors. We hypothesized that nonsyndromic CLP (NSCLP) after speech rehabilitation had structural abnormalities in language-related brain regions. This study investigates structural patterns in NSCLP children after speech rehabilitation using surface-based morphometry (SBM) analysis.

Methods

Forty-two children with NSCLP and 42 age- and gender-matched healthy controls were scanned for 3D T1-weighted images on a 3T MRI scanner. After reconstructing each brain surface, we computed SBM parameters and assessed between-group differences using two-sample t-tests and permutation tests (5,000 times). Then, we assessed the relationship between the SBM parameters and the Chinese language clear degree scale (CLCDS) using Pearson's correlation analysis.

Result

The speech-rehabilitated children with NSCLP showed lower cortical thickness and higher gyrification index mainly involving left language-related brain regions (permutation tests, p < 0.05). Furthermore, the lower cortical thickness of the left parahippocampal gyrus was positively correlated with CLCDS scores (r = 0.370, p = 0.017) in patients with NSCLP.

Conclusion

The SBM analysis showed that the structural abnormalities of speech-rehabilitated children with NSCLP mainly involved language-related brain regions, especially the dominant cerebral hemisphere. The structural abnormalities of the cortical thickness and folding in the language-related brain regions might be the neural mechanisms of speech errors in NSCLP children after speech rehabilitation. The cortical thickness of the parahippocampal gyrus may be a biomarker to evaluate pronunciation function.

Association of Elevated Maternal Psychological Distress, Altered Fetal Brain, and Offspring Cognitive and Social-Emotional Outcomes at 18 Months

IMPORTANCE

Prenatal maternal psychological distress is associated with disturbances in fetal brain development. However, the association between altered fetal brain development, prenatal maternal psychological distress, and long-term neurodevelopmental outcomes is unknown.

OBJECTIVE

To determine the association of fetal brain development using 3-dimensional magnetic resonance imaging (MRI) volumes, cortical folding, and metabolites in the setting of maternal psychological distress with infant 18-month neurodevelopment.

DESIGN, SETTING, AND PARTICIPANTS

Healthy mother-infant dyads were prospectively recruited into a longitudinal observational cohort study from January 2016 to October 2020 at Children's National Hospital in Washington, DC. Data analysis was performed from January 2016 to July 2021.

EXPOSURES

Prenatal maternal stress, anxiety, and depression.

MAIN OUTCOMES AND MEASURES

Prenatal maternal stress, anxiety, and depression were measured using validated self-report questionnaires. Fetal brain volumes and cortical folding were measured from 3-dimensional, reconstructed T2-weighted MRI scans. Fetal brain creatine and choline were quantified using proton magnetic resonance spectroscopy. Infant neurodevelopment at 18 months was measured using Bayley Scales of Infant and Toddler Development III and Infant-Toddler Social and Emotional Assessment. The parenting stress in the parent-child dyad was measured using the Parenting Stress Index-Short Form at 18-month testing.

RESULTS

The cohort consisted of 97 mother-infant dyads (mean [SD] maternal age, 34.79 [5.64] years) who underwent 184 fetal MRI visits (87 participants with 2 fetal studies each) with maternal psychological distress measures between 24 and 40 gestational weeks and completed follow-up infant neurodevelopmental testing. Prenatal maternal stress was negatively associated with infant cognitive performance (β = -0.51; 95% CI, -0.92 to -0.09; P = .01), and this association was mediated by fetal left hippocampal volume. In addition, prenatal maternal anxiety, stress, and depression were positively associated with all parenting stress measures at 18-month testing. Finally, fetal cortical local gyrification index and sulcal depth were negatively associated with infant social-emotional performance (local gyrification index: β = -54.62; 95% CI, -85.05 to -24.19; P < .001; sulcal depth: β = -14.22; 95% CI, -23.59 to -4.85; P = .002) and competence scores (local gyrification index: β = -24.01; 95% CI, -40.34 to -7.69; P = .003; sulcal depth: β = -7.53; 95% CI, -11.73 to -3.32; P < .001).

CONCLUSIONS AND RELEVANCE

In this cohort study of 97 mother-infant dyads, fetal cortical local gyrification index and sulcal depth were associated with infant 18-month social-emotional and competence outcomes, and fetal left hippocampal volume mediated the association between prenatal maternal stress and infant cognitive outcome. These findings suggest that altered prenatal brain development in the setting of elevated maternal distress has adverse infant sociocognitive outcomes, and identifying early biomarkers associated with long-term neurodevelopment may assist in early targeted interventions.

Mother-child similarity in brain morphology: A comparison of structural characteristics of the brain's reading network

BACKGROUND

Substantial evidence acknowledges the complex gene-environment interplay impacting brain development and learning. Intergenerational neuroimaging allows the assessment of familial transfer effects on brain structure, function and behavior by investigating neural similarity in caregiver-child dyads.

METHODS

Neural similarity in the human reading network was assessed through well-used measures of brain structure (i.e., surface area (SA), gyrification (lG), sulcal morphology, gray matter volume (GMV) and cortical thickness (CT)) in 69 mother-child dyads (children's age~11 y). Regions of interest for the reading network included left-hemispheric inferior frontal gyrus, inferior parietal lobe and fusiform gyrus. Mother-child similarity was quantified by correlation coefficients and familial specificity was tested by comparison to random adult-child dyads. Sulcal morphology analyses focused on occipitotemporal sulcus interruptions and similarity was assessed by chi-square goodness of fit.

RESULTS

Significant structural brain similarity was observed for mother-child dyads in the reading network for lG, SA and GMV (r = 0.349/0.534/0.542, respectively), but not CT. Sulcal morphology associations were non-significant. Structural brain similarity in lG, SA and GMV were specific to mother-child pairs. Furthermore, structural brain similarity for SA and GMV was higher compared to CT.

CONCLUSION

Intergenerational neuroimaging techniques promise to enhance our knowledge of familial transfer effects on brain development and disorders.

Decreased Cortical Thickness and Local Gyrification in Individuals with Subjective Cognitive Impairment

Objective

Subjective cognitive impairment (SCI) is associated with future cognitive decline. This study aimed to compare cortical thickness and local gyrification index (LGI) between individuals with SCI and normal control (NC) subjects.

Methods

Forty-seven participants (27 SCI and 20 NC) were recruited. All participants underwent brain magnetic resonance imaging scanning and were clinically assessed using the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery of tests. We compared cortical thickness and LGI between the two groups and analyzed correlations between cortical thickness/LGI and scores on CERAD protocol subtests in the SCI group for region of interests with significant between-group differences.

Results

Cortical thickness reduction in the left entorhinal, superior temporal, insular, rostral middle frontal, precentral, superior frontal, and supramarginal regions, and right supramarginal, precentral, insular, postcentral, and posterior cingulate regions was observed in the SCI compared to the NC group. Cortical thickness in these regions correlated with scores of constructional praxis, word list memory, word list recall, constructional recall, trail making test A, and verbal fluency under the CERAD protocol. Significantly decreased gyrification was observed in the left lingual gyrus of the SCI group. In addition, gyrification of this region was positively associated with scores of constructional praxis.

Conclusion

Our results may provide an additional reference to the notion that SCI may be associated with future cognitive impairment. This study may help clinicians to assess individuals with SCI who may progress to mild cognitive impairment and Alzheimer’s dementia.

Functional and morphological correlates of developmental dyslexia: A multimodal investigation of the ventral occipitotemporal cortex

BACKGROUND AND PURPOSE

The ventral occipitotemporal cortex (vOT) is a region crucial for reading acquisition through selective tuning to printed words. Developmental dyslexia is a disorder of reading with underlying neurobiological bases often associated with atypical neural responses to printed words. Previous studies have discovered anomalous structural development and function of the vOT in individuals with dyslexia. However, it remains unclear if or how structural abnormalities relate to functional alterations.

METHODS

In this study, we acquired structural, functional (words and faces processing), and diffusion MRI data from 26 children with dyslexia (average age = 10.4 ± 2.0 years) and 14 age-matched typically developing readers (average age = 10.4 ± 1.6 years). Morphological indices of local gyrification, neurite density (i.e., dendritic arborization structure), and orientation dispersion (i.e., dendritic arborization orientation) were analyzed within the vOT region that showed preferential activation in typically developing readers for words (as compared to face stimuli).

RESULTS

The two cohorts diverged significantly in both functional and structural measures. Compared to typically developing controls, children with dyslexia did not show selectivity for words in the left vOT (contrast: words > false fonts). This lack of tuning to printed words was associated with greater neurite dispersion heterogeneity in the dyslexia cohort, but similar neurite density. These group differences were not present in the homologous contralateral area, the right vOT.

CONCLUSIONS

Our findings provide new insight into the neurobiology of the lack of vOT word tuning in dyslexia by linking behavior, alterations in functional activation, and neurite organization.

Neuro-Behavioral Correlates of Executive Dysfunctions in Dyslexia Over Development From Childhood to Adulthood

Dyslexia is a neurobiological learning disability in the reading domain that has symptoms in early childhood and persists throughout life. Individuals with dyslexia experience difficulties in academia and cognitive and emotional challenges that can affect wellbeing. Early intervention is critical to minimize the long-term difficulties of these individuals. However, the behavioral and neural correlates which predict dyslexia are challenging to depict before reading is acquired. One of the precursors for language and reading acquisition is executive functions (EF). The present review aims to highlight the current atypicality found in individuals with dyslexia in the domain of EF using behavioral measures, brain mapping, functional connectivity, and diffusion tensor imaging along development. Individuals with dyslexia show EF abnormalities in both behavioral and neurobiological domains, starting in early childhood that persist into adulthood. EF impairment precedes reading disability, therefore adding an EF assessment to the neuropsychological testing is recommended for early intervention. EF training should also be considered for the most comprehensive outcomes.

Development of an Eco-Biodevelopmental Model of Emergent Literacy Before Kindergarten: A Review

IMPORTANCE

Literacy has been described as an important social determinant of health. Its components emerge in infancy and are dependent on genetic, medical, and environmental factors. The American Academy of Pediatrics advocates a substantial role for pediatricians in literacy promotion, developmental surveillance, and school readiness to promote cognitive, relational, and brain development. Many children, especially those from minority and underserved households, enter kindergarten unprepared to learn to read and subsequently have difficulty in school.

OBSERVATIONS

Emergent literacy is a developmental process beginning in infancy. Component skills are supported by brain regions that must be adequately stimulated and integrated to form a functional reading network. Trajectories are associated with genetic, medical, and environmental factors, notably the home literacy environment, which is defined as resources, motivation, and stimulation that encourage the literacy development process. Eco-biodevelopmental models are advocated by the American Academy of Pediatrics, and these models offer insights into the neurobiological processes associated with environmental factors and the ways in which these processes may be addressed to improve outcomes. Emergent literacy is well suited for such a model, particularly because the mechanisms underlying component skills are elucidated. In addition to cognitive-behavioral benefits, the association of home literacy environment with the developing brain before kindergarten has recently been described via neuroimaging. Rather than a passive approach, which may subject the child to stress and engender negative attitudes, early literacy screening and interventions that are administered by pediatric practitioners can help identify potential reading difficulties, address risk factors during a period when neural plasticity is high, and improve outcomes.

CONCLUSIONS AND RELEVANCE

Neuroimaging and behavioral evidence inform an eco-biodevelopmental model of emergent literacy that is associated with genetic, medical, and home literacy environmental factors before kindergarten, a time of rapid brain development. This framework is consistent with recommendations from the American Academy of Pediatrics and provides insights to help identify risk factors and signs of potential reading difficulties, tailor guidance, and provide direction for future research.

Morphological and Age-Related Changes in the Narcolepsy Brain

Morphological changes in the cortex of narcolepsy patients were investigated by surface-based morphometry analysis in this study. Fifty-one type 1 narcolepsy patients and 60 demographically group-matched healthy controls provided resting-state functional and high-resolution 3T anatomical magnetic resonance imaging scans. Vertex-level cortical thickness (CT), gyrification, and voxel-wise functional connectivity were calculated. Adolescent narcolepsy patients showed decreased CT in bilateral frontal cortex and left precuneus. Adolescent narcolepsy demonstrated increased gyrification in left occipital lobe, left precuneus, and right fusiform but decreased gyrification in left postcentral gyrus, whereas adult narcolepsy exhibited increased gyrification in left temporal lobe and right frontal cortex. Furthermore, sleepiness severity was associated with altered CT and gyrification. Increased gyrification was associated with reduced long-range functional connectivity. In adolescent patients, those with more severe sleepiness showed increased right postcentral gyrification. Decreased frontal and occipital gyrification was found in cases with hallucination. In adult patients, a wide range of regions showed reduced gyrification in those with adolescence-onset compared adult-onset narcolepsy patients. Particularly the frontal lobes showed altered brain morphology, being a thinner cortex and more gyri. The impact of narcolepsy on age-related brain morphological changes may remain from adolescence to young adulthood, and it was especially exacerbated in adolescence.

Structural neural correlates of individual differences in categorical perception

Listeners perceive speech sounds categorically. While group-level differences in categorical perception have been observed in children or individuals with reading disorders, recent findings suggest that typical adults vary in how categorically they perceive sounds. The current study investigated neural sources of individual variability in categorical perception of speech. Fifty-seven participants rated phonetic tokens on a visual analogue scale; categoricity and response consistency were measured and related to measures of brain structure from MRI. Increased surface area of the right middle frontal gyrus predicted more categorical perception of a fricative continuum. This finding supports the idea that frontal regions are sensitive to phonetic category-level information and extends it to make behavioral predictions at the individual level. Additionally, more gyrification in bilateral transverse temporal gyri predicted less consistent responses on the task, perhaps reflecting subtle variation in language ability across the population.

Neuroimaging genetic associations between SEMA6D, brain structure, and reading skills

Specific reading disability (SRD) is defined by genetic and neural risk factors that are not fully understood. The current study used imaging genetics methodology to investigate relationships between SEMA6D, brain structure, and reading. SEMA6D, located on SRD risk locus DYX1, is involved in axon guidance, synapse formation, and dendrite development. SEMA6D's associations with brain structure in reading-related regions of interest (ROIs) were investigated in a sample of children with a range of reading performance, from sites in Connecticut, CT (n = 67, 6-13 years, mean age = 9.07) and San Francisco, SF (n = 28, 5-8 years, mean age = 6.5). Multiple regression analyses revealed significant associations between SEMA6D's rs16959669 and cortical thickness in the fusiform gyrus and rs4270119 and gyrification in the supramarginal gyrus in the CT sample, but this was not replicated in the SF sample. Significant clusters were not associated with reading. For white matter volume, combined analyses across both samples revealed associations between reading and the left transverse temporal gyrus, left pars triangularis, left cerebellum, and right cerebellum. White matter volume in the left transverse temporal gyrus was nominally related to rs1817178, rs12050859, and rs1898110 in SEMA6D, and rs1817178 was significantly related to reading. Haplotype analyses revealed significant associations between the whole gene and brain phenotypes. Results suggest SEMA6D likely has an impact on multiple reading-related neural structures, but only white matter volume in the transverse temporal gyrus was significantly related to reading in the current sample. As the sample was young, the transverse temporal gyrus, involved in auditory perception, may be more strongly involved in reading because phonological processing is still being learned. The relationship between SEMA6D and reading may change as different brain regions are involved during reading development. Future research should examine mediating effects, use additional brain measures, and use an older sample to better understand effects.

Validation of The Reading House and Association With Cortical Thickness

BACKGROUND AND OBJECTIVES

The American Academy of Pediatrics recommends literacy and school readiness promotion during well visits. The Reading House (TRH) is a children's book-based screener of emergent literacy skills in preschool-aged children. Vocabulary, rhyming, and rapid naming are core emergent skills, and reading abilities are associated with thicker cortex in the left hemisphere. Our objective was to expand validity of TRH relative to these skills and explore association with cortical thickness.

METHODS

Healthy preschool-aged children completed MRI including a T1-weighted anatomic scan. Before MRI, TRH and assessments of rapid naming (Comprehensive Test of Phonological Processing, Second Edition), rhyming (Pre-Reading Inventory of Phonological Awareness), vocabulary (Expressive Vocabulary Test, Second Edition), and emergent literacy (Get Ready to Read!) were administered. Analyses included Spearman-ρ correlations (r _ρ) accounting for age, sex, and socioeconomic status (SES). MRI analyses involved whole-brain measures of cortical thickness relative to TRH scores, accounting for covariates.

RESULTS

Seventy children completed assessments (36-63 months old; 36 female) and 52 completed MRI (37-63 months; 29 female). TRH scores were positively correlated with Comprehensive Test of Phonological Processing, Second Edition (r _ρ = 0.61), Expressive Vocabulary Test, Second Edition (r _ρ = 0.54), Get Ready to Read! (r _ρ = 0.87), and Pre-Reading Inventory of Phonological Awareness scores (r _ρ = 0.64; all P < .001). These correlations remained statistically significant across age, sex, and SES groups. TRH scores were correlated with greater thickness in left-sided language and visual cortex (P-family-wise error <.05), which were similar for higher SES yet more bilateral and frontal for low SES, reflecting a less mature pattern (P-family-wise error <.10).

CONCLUSIONS

These findings expand validation evidence for TRH as a screening tool for preschool-aged children, including associations with emergent skills and cortical thickness, and suggest important differences related to SES.

Brain structure and neural activity related to reading in boys with isolated oral clefts

Background: The purpose of this study was to evaluate brain structure and function in participants with iCL/P and unaffected controls. Effects of cleft presence and reading status (average vs impaired) were evaluated.Methods: Males, ages 8-11 years old, including 26 with iCL/P and 57 unaffected peers were recruited and coded for reading status (average vs impaired). All participants underwent a volumetric and task-based functional MRI. Volumes and significant regions of activation during the decoding task were obtained. Main effects of cleft and reading status, and their interaction were evaluated.Results: Participants with iCL/P had significantly increased frontal gray matter volume (associated with average reading) and occipital gray and white matter volume (associated with impaired reading). Impaired readers with iCL/P had a distinctive activation pattern in visual association and motor regions relative to other groups.Conclusions: Findings suggest that increases in frontal gray matter volume may be associated with effective compensation during reading, while posterior increases in occipital volume may be associated with ineffective compensation for participants with iCL/P. These patterns were different from idiopathic dyslexia. Further work in a larger sample is needed to determine if these differences are associated with cleft type and with sex.Abbreviations: iCL/P (isolated cleft lip and/or palate); iCL (isolated cleft lip only); iCLP (isolated cleft lip and palate); iCP (isolated cleft palate only); uAR (unaffected average reader); uIR (unaffected impaired reader); cAR (average reader with iCL/P); cIR (impaired reader with iCL/P).

A preliminary study of cortical morphology changes in acute brainstem ischemic stroke patients

The study aimed to explore the cortical thickness and gyrification abnormalities in acute brainstem ischemic patients in both the ipsilateral and contralateral hemisphere compared with healthy controls. Structural magnetic resonance imaging data were prospectively acquired in 48 acute brainstem ischemic patients, 21 patients with left lesion and 27 with right lesion, respectively. Thirty healthy controls were recruited. Cortical morphometry based on surface-based data analysis driven by CAT12 toolbox implemented in SPM12 was used to compare changes in cortical thickness and gyrification. Significant decreases of cortical thickness loss were found in bilateral cerebral hemispheres of the brainstem ischemic patients compared to the healthy controls (P < .05, family-wise error (FWE)-corrected). We also found significant gyrification decreases in the insula, transverse temporal, supramarginal of the ipsilateral on hemisphere in the right brainstem ischemic patients compared to the healthy controls (P < .05, FWE-corrected). Brainstem ischemic patients have widely morphological changes in the early phase and may be helpful in designing individualized rehabilitative strategies for these patients.

Enhanced visceromotor emotional reactivity in dyslexia and its relation to salience network connectivity

Dyslexia is a neurodevelopmental disorder mainly defined by reading difficulties. During reading, individuals with dyslexia exhibit hypoactivity in left-lateralized language systems. Lower activity in one brain circuit can be accompanied by greater activity in another, and, here, we examined whether right-hemisphere-based emotional reactivity may be elevated in dyslexia. We measured emotional reactivity (i.e., facial behavior, physiological activity, and subjective experience) in 54 children ages 7-12 with (n = 32) and without (n = 22) dyslexia while they viewed emotion-inducing film clips. Participants also underwent task-free functional magnetic resonance imaging. Parents of children with dyslexia completed the Behavior Assessment System for Children, which assesses real-world behavior. During film viewing, children with dyslexia exhibited significantly greater reactivity in emotional facial behavior, skin conductance level, and respiration rate than those without dyslexia. Across the sample, greater emotional facial behavior correlated with stronger connectivity between right ventral anterior insula and right pregenual anterior cingulate cortex (pFWE<.05), key salience network hubs. In children with dyslexia, greater emotional facial behavior related to better real-world social skills and higher anxiety and depression. Our findings suggest there is heightened visceromotor emotional reactivity in dyslexia, which may lead to interpersonal strengths as well as affective vulnerabilities.

Shared Neural Substrates Underlying Reading and Visual Matching: A Longitudinal Investigation

The role of visual skills in reading acquisition has long been debated and whether there is shared neurobiological basis between visual skills and reading is not clear. This study investigated the relationship between Visual Matching and reading and their shared neuroanatomical basis. Two hundred and ninety-three typically developing Mandarin-speaking children were followed in a longitudinal study from ages 4 to 11 years old. A subsample of 79 children was further followed up at 14 years old when the MRI data were collected. Results showed that the development of Visual Matching from ages 6 to 8 predicted reading accuracy at age 11. In addition, both the development of Visual Matching and reading accuracy were associated with cortical surface area of a cluster located in fusiform gyrus. These findings suggested that the mapping from visual codes to phonological codes is important in learning to read and that left fusiform gyrus provided neural basis for such mapping. Implications of these findings in light of a new approach toward the neurocognitive mechanisms underlying reading development are discussed.

Gray Matter Structure Is Associated with Reading Skill in Typically Developing Young Readers

Research using functional and structural magnetic resonance imaging has identified areas of reduced brain activation and gray matter volume in children and adults with reading disability, but associations between cortical structure and individual differences in reading in typically developing children remain underexplored. Furthermore, the majority of research linking gray matter structure to reading ability quantifies gray matter in terms of volume, and cannot specify unique contributions of cortical surface area and thickness to these relationships. Here, we applied a continuous analytic approach to investigate associations between distinct surface-based properties of cortical structure and individual differences in reading-related skills in a sample of typically developing young children. Correlations between cortical structure and reading-related skills were conducted using a surface-based vertex-wise approach. Cortical thickness in the left superior temporal cortex was positively correlated with word and pseudoword reading performance. The observed positive correlation between cortical thickness in the left superior temporal cortex and reading may have implications for the patterns of brain activation that support reading.

Cortical Thickness in Crouzon-Pfeiffer Syndrome: Findings in Relation to Primary Cranial Vault Expansion

Background

Episodes of intracranial hypertension are associated with reductions in cerebral cortical thickness (CT) in syndromic craniosynostosis. Here we focus on Crouzon-Pfeiffer syndrome patients to measure CT and evaluate associations with type of primary cranial vault expansion and synostosis pattern.

Methods

Records from 34 Crouzon-Pfeiffer patients were reviewed along with MRI data on CT and intracranial volume to examine associations. Patients were grouped according to initial cranial vault expansion (frontal/occipital). Data were analyzed by multiple linear regression controlled for age and brain volume to determine an association between global/lobar CT and vault expansion type. Synostosis pattern effect sizes on global/lobar CT were calculated as secondary outcomes.

Results

Occipital expansion patients demonstrated 0.02 mm thicker cortex globally (P = 0.81) with regional findings, including: thicker cortex in frontal (0.02 mm, P = 0.77), parietal (0.06 mm, P = 0.44) and occipital (0.04 mm, P = 0.54) regions; and thinner cortex in temporal (-0.03 mm, P = 0.69), cingulate (-0.04 mm, P = 0.785), and, insula (-0.09 mm, P = 0.51) regions. Greatest effect sizes were observed between left lambdoid synostosis and the right cingulate (d = -1.00) and right lambdoid synostosis and the left cingulate (d = -1.23). Left and right coronal synostosis yielded effect sizes of d = -0.56 and d = -0.42 on respective frontal lobes.

Conclusions

Both frontal and occipital primary cranial vault expansions correlate to similar regional CT in Crouzon-Pfeiffer patients. Lambdoid synostosis appears to be associated with cortical thinning, particularly in the cingulate gyri.

Neuroanatomy of dyslexia: An allometric approach

Despite evidence for a difference in total brain volume between dyslexic and good readers, no previous neuroimaging study examined differences in allometric scaling (i.e. differences in the relationship between regional and total brain volumes) between dyslexic and good readers. The present study aims to fill this gap by testing differences in allometric scaling and regional brain volume differences in dyslexic and good readers. Object-based morphometry analysis was used to determine grey and white matter volumes of the four lobes, the cerebellum and limbic structures in 130 dyslexic and 106 good readers aged 8-14 years. Data were collected across three countries (France, Poland and Germany). Three methodological approaches were used as follows: principal component analysis (PCA), linear regression and multiple-group confirmatory factor analysis (MGCFA). Difference in total brain volume between good and dyslexic readers was Cohen's d = 0.39. We found no difference in allometric scaling, nor in regional brain volume between dyslexic and good readers. Results of our three methodological approaches (PCA, linear regression and MGCFA) were consistent. This study provides evidence for total brain volume differences between dyslexic and control children, but no evidence for differences in the volumes of the four lobes, the cerebellum or limbic structures, once allometry is taken into account. It also finds no evidence for a difference in allometric relationships between the groups. We highlight the methodological interest of the MGCFA approach to investigate such research issues.

The emergence of dyslexia in the developing brain

Developmental dyslexia, a severe deficit in literacy learning, is a neurodevelopmental learning disorder. Yet, it is not clear whether existing neurobiological accounts of dyslexia capture potential predispositions of the deficit or consequences of reduced reading experience. Here, we longitudinally followed 32 children from preliterate to school age using functional and structural magnetic resonance imaging techniques. Based on standardised and age-normed reading and spelling tests administered at school age, children were classified as 16 dyslexic participants and 16 controls. This longitudinal design allowed us to disentangle possible neurobiological predispositions for developing dyslexia from effects of individual differences in literacy experience. In our sample, the disorder can be predicted already before literacy learning from auditory cortex gyrification and aberrant downstream connectivity within the speech processing system. These results provide evidence for the notion that dyslexia may originate from an atypical maturation of the speech network that precedes literacy instruction.

Frontal volume as a potential source of the comorbidity between attention-deficit/hyperactivity disorder and reading disorders

Prefrontal volume reductions commonly are demonstrated in ADHD, but the literature examining prefrontal volume in reading disorders (RD) is scant despite their also having executive functioning (EF) deficits. Furthermore, only a few anatomical studies have examined the frontal lobes in comorbid RD/ADHD, though they have EF deficits similar to RD and ADHD. Hence, we examined frontal gyri volume in children with RD, ADHD, RD/ADHD and controls, as well as their relationship to EF for gyri found to differ between groups. We found right inferior frontal (RIF) volume was smaller in ADHD, and smaller volume was related to worse behavioral regulation. Left superior frontal (LSF) volume was larger in RD than ADHD, and its size was negatively related to basic reading ability. Left middle frontal (LMF) volume was largest in RD/ADHD overall. Further, its volume was not related to basic reading nor behavioral regulation but was related to worse attentional control, suggesting some specificity in its EF relationship. When examining hypotheses on the etiology of RD/ADHD, RD/ADHD was commensurate with ADHD in RIF volume and both RD and ADHD in LSF volume (being midway between the groups), consistent with the common etiology hypothesis. Nevertheless, they also had an additional gyrus affected: LMF, consistent with the cognitive subtype hypothesis in its specificity to RD/ADHD. The few other frontal aMRI studies on RD/ADHD supported both hypotheses as well. Given this, future research should continue to focus on frontal morphology in its endeavors to find neurobiological contributors to the comorbidity between RD and ADHD.

Atypical gray matter in children with dyslexia before the onset of reading instruction

Many studies have focused on neuroanatomical anomalies in dyslexia, yet primarily in school-aged children and adults. In the present study, we investigated gray matter surface area and cortical thickness at the pre-reading stage in a cohort of 54 children, 31 with a family risk for dyslexia and 23 without a family risk for dyslexia, of whom 16 children developed dyslexia. Surface-based analyses in the core regions of the reading network in the left hemisphere and in the corresponding right hemispheric regions were performed in FreeSurfer. Results revealed that pre-readers who develop dyslexia show reduced surface area in bilateral fusiform gyri. In addition, anomalies related to a family risk for dyslexia, irrespectively of later reading ability, were observed in the area of the bilateral inferior and middle temporal gyri. Differences were apparent in surface area, as opposed to cortical thickness. Results indicate that the neuroanatomical anomalies, since they are observed in the pre-reading phase, are not the consequence of impoverished reading experience.

Morphometric correlates of anomia in patients with small left temporopolar lesions

Visual object naming is a complex cognitive process that engages an interconnected network of cortical regions moving from occipitotemporal to anterior-inferior temporal cortices, and extending into the inferior frontal cortex. Naming can fail for diverse reasons, and different stages of the naming multi-step process appear to be reliant upon the integrity of different neuroanatomical locations. While the neural correlates of semantic errors have been extensively studied, the neural basis of omission errors remains relatively unspecified. Although a strong line of evidence supports an association between anterior temporal lobe damage and semantic errors, there are some studies suggesting that the anterior temporal lobe could be also associated with omissions. However, support for this hypothesis comes from studies with patients in whom damage affected extensive brain regions, sometimes bilaterally. Here, we availed of a group of 12 patients with epilepsy associated with a small lesion at the tip of the left temporal pole. Using an unbiased surface-based morphometry methodology, we correlated two morphological features with errors observed during visual naming. Analyses revealed a correlation between omission errors and reduced local gyrification index in three cortical clusters: one in the left anteromedial temporal lobe region (AMTL) and two in the left anterior cingulate cortex (ACC). Our findings support the view that regions in ACC and AMTL are critical structures within a network engaged in word selection from semantics.

Comorbidity of reading disabilities and ADHD: Structural and functional brain characteristics

Reading disabilities (RD) and attention-deficit/hyperactivity disorder (ADHD) are two of the most common developmental disorders. RD and ADHD frequently co-occur, which raises questions about how the disorders interact and to what extent they can be differentiated. To date, the underlying neural mechanisms leading to RD-ADHD comorbidity (COM) are not understood. In this study, structural and functional magnetic resonance imaging (fMRI) were combined with comprehensive behavioral testing in order to characterize the behavior, brain structure, and neural correlates of executive function, phonological processing and reading fluency in 60 children with clinical diagnoses of RD, ADHD, or COM, and controls. Whole-brain analyses of variance were performed on cortical thickness values and on the data of the three fMRI tasks to investigate overall group differences. To validate these findings, a region of interest analysis was performed in regions that have previously been shown to exhibit group differences in children with RD or ADHD using the same paradigms. The neuroimaging results demonstrated structural and functional atypicalities for COM in regions that are frequently associated with deficits in children with isolated ADHD or RD. A combination of shared and distinctive brain alterations between the clinical groups was identified, supporting the multiple deficit model for ADHD, RD, and its comorbidity.

Neural Correlates of Oral Word Reading, Silent Reading Comprehension, and Cognitive Subcomponents

The ability to read is essential for cognitive development. To deepen our understanding of reading acquisition, we explored the neuroanatomical correlates (cortical thickness (CT)) of word reading fluency and sentence comprehension efficiency in Chinese with a group of typically developing children (N = 21; 12 females and 9 males; age range 10.7-12.3 years). Then, we investigated the relationship between the CT of reading-defined regions and the cognitive subcomponents of reading to determine whether our study lends support to the multi-component model. The results demonstrated that children's performance on oral word reading was positively correlated with CT in the left superior temporal gyrus (LSTG), inferior temporal gyrus (LITG), supramarginal gyrus (LSMG) and right superior temporal gyrus (RSTG). Moreover, CT in the LSTG, LSMG and LITG uniquely predicted children's phonetic representation, phonological awareness, and orthography-phonology mapping skills, respectively. By contrast, children's performance on sentence reading comprehension was positively correlated with CT in the left parahippocampus (LPHP) and right calcarine fissure (RV1). As for the subcomponents of reading, CT in the LPHP was exclusively correlated with morphological awareness, whereas CT in the RV1 was correlated with orthography-semantic mapping. Taken together, these findings indicate that the reading network of typically developing children consists of multiple subdivisions, thus providing neuroanatomical evidence in support of the multi-componential view of reading.

Altered brain morphometry in 7-year old HIV-infected children on early ART

Even with the increased roll out of combination antiretroviral therapy (cART), paediatric HIV infection is associated with neurodevelopmental delays and neurocognitive deficits that may be accompanied by alterations in brain structure. Few neuroimaging studies have been done in children initiating ART before 2 years of age, and even fewer in children within the critical stage of brain development between 5 and 11 years. We hypothesized that early ART would limit HIV-related brain morphometric deficits at age 7. Study participants were 7-year old HIV-infected (HIV+) children from the Children with HIV Early Antiretroviral Therapy (CHER) trial whose viral loads were supressed at a young age, and age-matched uninfected controls. We used structural magnetic resonance imaging (MRI) and FreeSurfer ( http://www.freesurfer.net/ ) software to investigate effects of HIV and age at ART initiation on cortical thickness, gyrification and regional brain volumes. HIV+ children showed reduced gyrification compared to controls in bilateral medial parietal regions, as well as reduced volumes of the right putamen, left hippocampus, and global white and gray matter and thicker cortex in small lateral occipital region. Earlier ART initiation was associated with lower gyrification and thicker cortex in medial frontal regions. Although early ART appears to preserve cortical thickness and volumes of certain brain structures, HIV infection is nevertheless associated with reduced gyrification in the parietal cortex, and lower putamen and hippocampus volumes. Our results indicate that in early childhood gyrification is more sensitive than cortical thickness to timing of ART initiation. Future work will clarify the implications of these morphometric effects for neuropsychological function.

Abnormal age-related cortical folding and neurite morphology in children with developmental dyslexia

There is increasing recognition of a relationship between regional variability in cerebral gyrification and neurodevelopment. Recent work in morphometric MRI has shown that the local gyrification index (lGI), a measure of regional brain folding, may be altered in certain neurodevelopmental disorders. Other studies report that the lGI generally decreases with age in adolescence and young adulthood; however, little is known about how these age-dependent differences in brain maturation occur in atypical neurodevelopment and mechanisms underlying gyrification, such as synaptic pruning. Organization and optimization of dendrites and axons connections across the brain might be driving gyrification and folding processes. In this study, we first assessed lGI differences in the left hemisphere in a cohort of 39 children with developmental dyslexia (DD) between the ages of 7 and 15 years in comparison to 56 typically developing controls (TDC). To better understand the microstructural basis of these changes, we next explored the relationship between lGI differences and cortical thickness and neurite morphology by applying neurite orientation dispersion and density imaging (NODDI). We identified significant differences in lGI between children with DD and TDC in left lateral temporal and middle frontal regions. Further, DD failed to show the expected age-related decreases in lGI in the same regions. Age-related differences in lGI in DD were not explained by differences in cortical thickness, but did correlate with NODDI neurite density and orientation dispersion index. Our findings suggest that gyrification changes in DD are related to abnormal neurite morphology, and are possibly an expression of differences in synaptic pruning.

The Importance of the Left Occipitotemporal Cortex in Developmental Dyslexia

Purpose of Review

Developmental dyslexia is characterized by an impaired acquisition of fluent and skilled reading ability. Numerous studies have explored the neural correlates of this neurodevelopmental disorder, with most classic accounts strongly focussing on left temporoparietal regions. We will review recent findings from structural and functional MRI studies that suggest a more important role of occipitotemporal cortex abnormalities in dyslexia.

Recent Findings

Recent findings highlight the role of the occipitotemporal cortex which exhibits functional as well as structural abnormalities in dyslexic readers and in children at risk for dyslexia and suggest a more central role for the occipitotemporal cortex in the pathophysiology of dyslexia.

Summary

We demonstrate the importance of the occipitotemporal cortex in for understanding impaired reading acquisition and point out how future research might enhance our understanding of functional and structural impairments in the reading network via large-scale data analysis approaches.

Neurobiological Bases of Reading Disorder Part II: The Importance of Developmental Considerations in Typical and Atypical Reading

Decoding-based reading disorder (RD; aka developmental dyslexia) is one of the most common neurodevelopmental disorders, affecting approximately 5-10% of school-aged children across languages. Even though neuroimaging studies suggest an impairment of the left reading network in RD, the onset of this deficit and its developmental course, which may include constancy and change, is largely unknown. There is now growing evidence that the recruitment of brain networks underlying perceptual, cognitive and linguistic processes relevant to reading acquisition varies with age. These age-dependent changes may in turn impact the neurocognitive characteristics of RD observed at specific developmental stages. Here we synthesize findings from functional and structural magnetic resonance imaging (MRI) studies to increase our understanding of the developmental time course of the neural bases underlying (a)typical reading. We first provide an overview of the brain bases of typical and atypical (impaired) reading. Next we describe how the understanding of RD can be deepened through scientific attention to age effects, for example, by integrating findings from cross-sectional studies of RD at various ages. Finally, we accent findings from extant longitudinal studies that directly examine developmental reading trajectories beginning in the preliterate stage at both group and individual levels. Although science is at the very early stage of understanding developmental aspects of neural deficits in RD, evidence to date characterizes RD by atypical brain maturation. We know that reading impairment may adversely impact multiple life domains such as academic achievement and social relationships, and unfortunately, that these negative outcomes can persist and compound into adulthood. We contend that exploring the developmental trajectories of RD will contribute to a greater understanding of how neural systems support reading acquisition. Further, we propose and cite evidence that the etiology of RD can be better investigated by distinguishing primary deficits from secondary impairments unfolding along development. These exciting and modern investigatory efforts can also indirectly contribute to a centered practice of early and accurate identification and optimal intervention to support the development of foundational pre-literacy skills and fluent reading. In sum, integrating a developmental understanding into the science and practice of reading acquisition and intervention is both possible and necessary.