Nadine Gaab - Academia.edu (original) (raw)

Papers by Nadine Gaab

BackgroundPrenatal alcohol exposure (PAE) has been linked to atypical brain development and a wid... more BackgroundPrenatal alcohol exposure (PAE) has been linked to atypical brain development and a wide range of cognitive and behavioral impairments, including poor reading performance in childhood and adolescence. However, little is known about how structural and/or functional teratogenesis in the brain mediate reading impairment in fetal alcohol spectrum disorders (FASD) and whether neural correlates of reading and phonological processing differ between FASD subtypes with different clinical presentations in facial morphology.MethodsThe current study utilized functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to characterize functional and structural mechanisms mediating reading deficits in 26 syndromal adolescents with PAE-related facial dysmorphology (i.e., fetal alcohol syndrome (FAS) or partial FAS (PFAS)) and 30 heavily exposed (HE) without this dysmorphology, in comparison with 19 typically developing controls. Importantly, the levels of PAE and readi...

Reading fluency – the speed and accuracy of reading connected text – is foundational to education... more Reading fluency – the speed and accuracy of reading connected text – is foundational to educational success. The current longitudinal study investigates the neural correlates of fluency development using a connected-text paradigm with an individualized presentation rate. Twenty-six children completed a functional MRI task in 1st/2nd grade (time 1) and again 1-2 years later (time 2). There was a longitudinal increase in activation in the ventral occipito-temporal (vOT) cortex from time 1 to time 2. This increase was also associated with improvements in reading fluency skills and modulated by individual speed demands. These findings highlight the reciprocal relationship of the vOT region with reading proficiency and its importance for supporting the developmental transition to fluent reading. These results have implications for developing effective interventions to target increased automaticity in reading.

According to several influential theoretical frameworks, phonological deficits in dyslexia result... more According to several influential theoretical frameworks, phonological deficits in dyslexia result from reduced sensitivity to acoustic cues that are essential for the development of robust phonemic representations. Some accounts suggest that these deficits arise from impairments in rapid auditory adaptation processes that are either speech-specific or domain-general. Here, we examined the specificity of auditory adaptation deficits in dyslexia using a non-linguistic tone anchoring (adaptation) task and a linguistic selective adaptation task in children and adults with and without dyslexia. Children and adults with dyslexia had elevated tone-frequency discrimination thresholds, but both groups benefitted from anchoring to repeated stimuli to the same extent as typical readers. Additionally, although both dyslexia groups had overall reduced accuracy for speech sound identification, only the child group had reduced categorical perception for speech. Across both age groups, individuals ...

Rapid and widespread changes in brain anatomy and physiology in the first five years of life pres... more Rapid and widespread changes in brain anatomy and physiology in the first five years of life present substantial challenges for developmental MRI studies. One persistent challenge is that methods best suited to earlier developmental stages are suboptimal for later stages, which engenders a trade-off between using different, but age-appropriate, methods for different developmental stages or identical methods across stages. Both options have potential benefits, but also biases, as pipelines for each developmental stage can be matched on either whether methods are age-appropriate or the employed methods themselves, but not both. This review describes the data acquisition, processing, and analysis challenges that introduce these potential biases and attempts to elucidate decisions and recommendations that would optimize developmental comparisons.

Developmental dyslexia is a learning disability characterized by difficulties in word reading. Wh... more Developmental dyslexia is a learning disability characterized by difficulties in word reading. While the prevalence in the general public is around 10-12%, an increased prevalence of 40-60% has been reported for children with a familial risk. Neural atypicalities in the reading network have been observed in children with (FHD+) compared to without (FHD-) a family history of dyslexia, even before reading onset. Despite the hereditary risk, about half of FHD+ children develop typical reading abilities (FHD+Typical) but the underlying neural characteristics and the developmental trajectories of these favorable reading outcomes remain unknown. Utilizing a retrospective, longitudinal approach, this is the first study to examine whether potential protective neural mechanisms are present before reading onset in FHD+Typical. Functional and structural brain characteristics were examined in 69 pre-readers who subsequently developed typical reading abilities (35 FHD+Typical/34 FHD-Typical) usi...

Recent efforts have focused on screening methods to identify children at risk for dyslexia as ear... more Recent efforts have focused on screening methods to identify children at risk for dyslexia as early as preschool/kindergarten. Unfortunately, while low sensitivity leads to under-identification of at-risk children, low specificity can lead to over-identification, resulting in inaccurate allocation of limited educational resources. The present study focused on children identified as at-risk in kindergarten who do not subsequently develop dyslexia to specify factors associated with better reading outcomes among at-risk children. Early screening was conducted in kindergarten and a subset of children was tracked longitudinally until second grade. Potential protective factors were evaluated at cognitive-linguistic, environmental, and neural levels. Relative to at-risk kindergarteners who subsequently developed dyslexia, those who did not were characterized by significantly higher socioeconomic status (SES), speech production accuracy, and microstructure of the posterior right-hemispheric...

Developmental science, Jan 5, 2018

A functional region of left fusiform gyrus termed "the visual word form area" (VWFA) de... more A functional region of left fusiform gyrus termed "the visual word form area" (VWFA) develops during reading acquisition to respond more strongly to printed words than to other visual stimuli. Here, we examined responses to letters among 5- and 6-year-old early kindergarten children (N = 48) with little or no school-based reading instruction who varied in their reading ability. We used functional magnetic resonance imaging (fMRI) to measure responses to individual letters, false fonts, and faces in left and right fusiform gyri. We then evaluated whether signal change and size (spatial extent) of letter-sensitive cortex (greater activation for letters versus faces) and letter-specific cortex (greater activation for letters versus false fonts) in these regions related to (a) standardized measures of word-reading ability and (b) signal change and size of face-sensitive cortex (fusiform face area or FFA; greater activation for faces versus letters). Greater letter specificity,...

Human brain mapping, May 29, 2018

Numerous studies have shown that phonological skills are critical for successful reading acquisit... more Numerous studies have shown that phonological skills are critical for successful reading acquisition. However, how the brain network supporting phonological processing evolves and how it supports the initial course of learning to read is largely unknown. Here, for the first time, we characterized the emergence of the phonological network in 28 children over three stages (prereading, beginning reading, and emergent reading) longitudinally. Across these three time points, decreases in neural activation in the left inferior parietal cortex (LIPC) were observed during an audiovisual phonological processing task, suggesting a specialization process in response to reading instruction/experience. Furthermore, using the LIPC as the seed, a functional network consisting of the left inferior frontal, left posterior occipitotemporal, and right angular gyri was identified. The connection strength in this network co-developed with the growth of phonological skills. Moreover, children with above-...

Journal of Experimental Psychology: General, 2017

Developmental Science, 2016

Annals of Dyslexia, 2016

Examining the relationship between home literacy environment and neural correlates of phonologica... more Examining the relationship between home literacy environment and neural correlates of phonological processing in beginning readers with and without a familial risk for dyslexia: an fMRI study

Nature neuroscience, Sep 8, 2016

What determines the cortical location at which a given functionally specific region will arise in... more What determines the cortical location at which a given functionally specific region will arise in development? We tested the hypothesis that functionally specific regions develop in their characteristic locations because of pre-existing differences in the extrinsic connectivity of that region to the rest of the brain. We exploited the visual word form area (VWFA) as a test case, scanning children with diffusion and functional imaging at age 5, before they learned to read, and at age 8, after they learned to read. We found the VWFA developed functionally in this interval and that its location in a particular child at age 8 could be predicted from that child's connectivity fingerprints (but not functional responses) at age 5. These results suggest that early connectivity instructs the functional development of the VWFA, possibly reflecting a general mechanism of cortical development.

Current Opinion in Behavioral Sciences, 2016

Dyslexia is a heritable reading disorder with an estimated prevalence of 5-17%. A multiple defici... more Dyslexia is a heritable reading disorder with an estimated prevalence of 5-17%. A multiple deficit model has been proposed that illustrates dyslexia as an outcome of multiple risks and protective factors interacting at the genetic, neural, cognitive, and environmental levels. Here we review the evidence on each of these levels and discuss possible underlying mechanisms and their reciprocal interactions along a developmental timeline. Current and potential implications of neuroscientific findings for contemporary challenges in the field of dyslexia, as well as for reading development and education in general, are then discussed. 'Children are wired for sound, but print is an optional accessory that must be painstakingly bolted on' [Pinker in [1], p. ix-x]. Developmental dyslexia is a heritable neurobiological condition that is characterized by an unexpected failure to develop accurate or fluent reading and affects approximately 5-17% of children [2]. Individuals with dyslexia have shown structural and functional brain atypicalities in the complex reading network which consists of (1) left inferior frontal regions, (2) dorsal temporo-parietal regions, and (3) ventral occipital-temporal regions [3,4]. The etiological basis of dyslexia is not well understood due to the complex interactions among multiple genetic risk variants and environmental factors, which collectively affect typical and atypical reading development. This paper aims to disambiguate the genetic, environmental, cognitive, and neurobiological components that are involved in predisposing a child to developing dyslexia. In particular, it

Wiley Interdisciplinary Reviews: Cognitive Science, 2016

Developmental dyslexia is an unexplained inability to acquire accurate or fluent reading that aff... more Developmental dyslexia is an unexplained inability to acquire accurate or fluent reading that affects approximately 5-17% of children. Dyslexia is associated with structural and functional alterations in various brain regions that support reading. Neuroimaging studies in infants and prereading children suggest that these alterations predate reading instruction and reading failure, supporting the hypothesis that variant function in dyslexia susceptibility genes lead to atypical neural migration and/or axonal growth during early, most likely in utero, brain development. Yet, dyslexia is typically not diagnosed until a child has failed to learn to read as expected (usually in second grade or later). There is emerging evidence that neuroimaging measures, when combined with key behavioral measures, can enhance the accuracy of identification of dyslexia risk in prereading children but its sensitivity, specificity, and cost-efficiency is still unclear. Early identification of dyslexia risk carries important implications for dyslexia remediation and the amelioration of the psychosocial consequences commonly associated with reading failure.

Cerebral cortex (New York, N.Y. : 1991), Feb 7, 2015

Developmental dyslexia (DD) is a heritable condition characterized by persistent difficulties in ... more Developmental dyslexia (DD) is a heritable condition characterized by persistent difficulties in learning to read. White matter alterations in left-lateralized language areas, particularly in the arcuate fasciculus (AF), have been observed in DD, and diffusion properties within the AF correlate with (pre-)reading skills as early as kindergarten. However, it is unclear how early these alterations can be observed. We investigated white matter structure in 14 infants with (FHD+; ages 6.6-17.6 months) and 18 without (FHD-; ages 5.1-17.6 months) familial risk for DD. Diffusion scans were acquired during natural sleep, and early language skills were assessed. Tractography for bilateral AF was reconstructed using manual and automated methods, allowing for independent validation of results. Fractional anisotropy (FA) was calculated at multiple nodes along the tracts for more precise localization of group differences. The analyses revealed significantly lower FA in the left AF for FHD+ compa...

Dauvermann, M. R., Raschle, N. M., Sliva, D., Becker, Ozranov-Palchik, O., Peysakhovich, B., Smit... more Dauvermann, M. R., Raschle, N. M., Sliva, D., Becker, Ozranov-Palchik, O., Peysakhovich, B., Smith, Sara, Figgucio, M., Zuk, J. & Gaab, N., Poster presented at the 21st Annual Cognitive Neuroscience Society, Boston, USA. April 5-8, 2014.

Raschle, N. M., Becker, B., Smith, Sara & Gaab, N., Poster presented at the 21st Annual Cogni... more Raschle, N. M., Becker, B., Smith, Sara & Gaab, N., Poster presented at the 21st Annual Cognitive Neuroscience Society, Boston, USA. April 5-8, 2014.

Bilingualism: Language and Cognition, 2015

Auditory phonological processing skills are critical for successful reading development in Englis... more Auditory phonological processing skills are critical for successful reading development in English not only in native (L1) speakers but also in second language (L2) learners. However, the neural deficits of auditory phonological processing remain unknown in English-as-the-second-language (ESL) learners with reading difficulties. Here we investigated neural responses during spoken word rhyme judgments in typical and impaired ESL readers in China. The impaired readers showed comparable activation in the left superior temporal gyrus (LSTG), but reduced activation in the left inferior frontal gyrus (LIFG) and left fusiform and reduced connectivity between the LSTG and left fusiform when compared to typical readers. These findings suggest that impaired ESL readers have relative intact representations but impaired manipulation of phonology and reduced or absent automatic access to orthographic representations. This is consistent with previous findings in native English speakers and sugges...

Journal of Neuroscience, 2013

Developmental dyslexia, an unexplained difficulty in learning to read, has been associated with a... more Developmental dyslexia, an unexplained difficulty in learning to read, has been associated with alterations in white matter organization as measured by diffusion-weighted imaging. It is unknown, however, whether these differences in structural connectivity are related to the cause of dyslexia or if they are consequences of reading difficulty (e.g., less reading experience or compensatory brain organization). Here, in 40 kindergartners who had received little or no reading instruction, we examined the relation between behavioral predictors of dyslexia and white matter organization in left arcuate fasciculus, inferior longitudinal fasciculus, and the parietal portion of the superior longitudinal fasciculus using probabilistic tractography. Higher composite phonological awareness scores were significantly and positively correlated with the volume of the arcuate fasciculus, but not with other tracts. Two other behavioral predictors of dyslexia, rapid naming and letter knowledge, did not correlate with volumes or diffusion values in these tracts. The volume and fractional anisotropy of the left arcuate showed a particularly strong positive correlation with a phoneme blending test. Whole-brain regressions of behavioral scores with diffusion measures confirmed the unique relation between phonological awareness and the left arcuate. These findings indicate that the left arcuate fasciculus, which connects anterior and posterior language regions of the human brain and which has been previously associated with reading ability in older individuals, is already smaller and has less integrity in kindergartners who are at risk for dyslexia because of poor phonological awareness. These findings suggest a structural basis of behavioral risk for dyslexia that predates reading instruction.