Search

As reading is inherently a multisensory, audiovisual (AV) process where visual symbols (i.e., letters) are connected to speech sounds, the question has been raised whether individuals with reading difficulties, like children with developmental dyslexia (DD), have broader impairments in multisensory processing. This question has been posed before, yet it remains unanswered due to (a) the complexity and contentious etiology of DD along with (b) lack of consensus on developmentally appropriate AV processing tasks. We created an ecologically valid task for measuring multisensory AV processing by leveraging the natural phenomenon that speech perception improves when listeners are provided visual information from mouth movements (particularly when the auditory signal is degraded). We designed this AV processing task with low cognitive and linguistic demands such that children with and without DD would have equal unimodal (auditory and visual) performance. We then collected data in a group of 135 children (age 6.5-15) with an AV speech perception task to answer the following questions: (1) How do AV speech perception benefits manifest in children, with and without DD? (2) Do children all use the same perceptual weights to create AV speech perception benefits, and (3) what is the role of phonological processing in AV speech perception? We show that children with and without DD have equal AV speech perception benefits on this task, but that children with DD rely less on auditory processing in more difficult listening situations to create these benefits and weigh both incoming information streams differently. Lastly, any reported differences in speech perception in children with DD might be better explained by differences in phonological processing than differences in reading skills.

Purpose: It is generally accepted that adults use visual cues to improve speech intelligibility in noisy environments, but findings regarding visual speech benefit in children are mixed. We explored factors that contribute to audiovisual (AV) gain in young children's speech understanding. We examined whether there is an AV benefit to speech-in-noise recognition in children in first grade and if visual salience of phonemes influences their AV benefit. We explored if individual differences in AV speech enhancement could be explained by vocabulary knowledge, phonological awareness, or general psychophysical testing performance. Method: Thirty-seven first graders completed online psychophysical experiments. We used an online single-interval, four-alternative forced-choice picture-pointing task with age-appropriate consonant-vowel-consonant words to measure auditory-only, visual-only, and AV word recognition in noise at -2 and -8 dB SNR. We obtained standard measures of vocabulary and phonological awareness and included a general psychophysical test to examine correlations with AV benefits. Results: We observed a significant overall AV gain among children in first grade. This effect was mainly attributed to the benefit at -8 dB SNR, for visually distinct targets. Individual differences were not explained by any of the child variables. Boys showed lower auditory-only performances, leading to significantly larger AV gains. Conclusions: This study shows AV benefit, of distinctive visual cues, to word recognition in challenging noisy conditions in first graders. The cognitive and linguistic constraints of the task may have minimized the impact of individual differences of vocabulary and phonological awareness on AV benefit. The gender difference should be studied on a larger sample and age range.

Competing theories of dyslexia posit that reading difficulties arise from impaired visual, auditory, phonological, or statistical learning mechanisms. Importantly, many theories posit that dyslexia reflects a cascade of impairments emanating from a single "core deficit". Here we report two studies evaluating core deficit and multifactorial models. In Study 1, we use publicly available data from the Healthy Brain Network to test the accuracy of phonological processing measures for predicting dyslexia diagnosis and find that over 30% of cases are misclassified (sensitivity = 66.7%; specificity = 68.2%). In Study 2, we collect a battery of psychophysical measures of visual motion processing and standardized measures of phonological processing in 106 school-aged children to investigate whether dyslexia is best conceptualized under a core-deficit model, or as a disorder with heterogenous origins. Specifically, by capitalizing on the drift diffusion model to analyze performance on a visual motion discrimination experiment, we show that deficits in visual motion processing, perceptual decision-making, and phonological processing manifest largely independently. Based on statistical models of how variance in reading skill is parceled across measures of visual processing, phonological processing, and decision-making, our results challenge the notion that a unifying deficit characterizes dyslexia. Instead, these findings indicate a model where reading skill is explained by several distinct, additive predictors, or risk factors, of reading (dis)ability.

Circuitry in ventral occipital-temporal cortex is essential for seeing words. We analyze the circuitry within a specific ventral-occipital region, the visual word form area (VWFA). The VWFA is immediately adjacent to the retinotopically organized VO-1 and VO-2 visual field maps and lies medial and inferior to visual field maps within motion selective human cortex. Three distinct white matter fascicles pass within close proximity to the VWFA: (1) the inferior longitudinal fasciculus, (2) the inferior frontal occipital fasciculus, and (3) the vertical occipital fasciculus. The vertical occipital fasciculus terminates in or adjacent to the functionally defined VWFA voxels in every individual. The vertical occipital fasciculus projects dorsally to language and reading related cortex. The combination of functional responses from cortex and anatomical measures in the white matter provides an overview of how the written word is encoded and communicated along the ventral occipital-temporal circuitry for seeing words. (Contains 6 figures.)

Children born preterm are at risk for deficits in language and reading. They are also at risk for injury to the white matter of the brain. The goal of this study was to determine whether performance in language and reading skills would be associated with white matter properties in children born preterm and full-term. Children born before 36 weeks gestation (n = 23, mean plus or minus SD age 12.5 plus or minus 2.0 years, gestational age 28.7 plus or minus 2.5 weeks, birth weight 1184 plus or minus 431 g) and controls born after 37 weeks gestation (n = 19, 13.1 plus or minus 2.1 years, 39.3 plus or minus 1.0 weeks, 3178 plus or minus 413 g) underwent a battery of language and reading tests. Diffusion Tensor Imaging (DTI) scans were processed using Tract-Based Spatial Statistics to generate a core white matter skeleton that was anatomically comparable across participants. Fractional anisotropy (FA) was the diffusion property used in analyses. In the full-term group, no regions of the whole FA-skeleton were associated with language and reading. In the preterm group, regions of the FA-skeleton were significantly associated with verbal IQ, linguistic processing speed, syntactic comprehension, and decoding. Combined, the regions formed a composite map of 22 clusters on 15 tracts in both hemispheres and in the ventral and dorsal streams. ROI analyses in the preterm group found that several of these regions also showed positive associations with receptive vocabulary, verbal memory, and reading comprehension. Some of the same regions showed weak negative correlations within the full-term group. Exploratory multiple regression in the preterm group found that specific white matter pathways were related to different aspects of language processing and reading, accounting for 27-44% of the variance. The findings suggest that higher performance in language and reading in a group of preterm but not full-term children is associated with higher fractional anisotropy of a bilateral and distributed white matter network. (Contains 2 tables and 7 figures.)

For more than a century, neurologists have hypothesized that the arcuate fasciculus carries signals that are essential for language function; however, the relevance of the pathway for particular behaviors is highly controversial. The primary objective of this study was to use diffusion tensor imaging to examine the relationship between individual variation in the microstructural properties of arcuate fibers and behavioral measures of language and reading skills. A second objective was to use novel fiber-tracking methods to reassess estimates of arcuate lateralization. In a sample of 55 children, we found that measurements of diffusivity in the left arcuate correlate with phonological awareness skills and arcuate volume lateralization correlates with phonological memory and reading skills. Contrary to previous investigations that report the absence of the right arcuate in some subjects, we demonstrate that new techniques can identify the pathway in every individual. Our results provide empirical support for the role of the arcuate fasciculus in the development of reading skills.

Although studies of long-term outcomes of children born preterm consistently show low intelligence quotient (IQ) and visual-motor impairment, studies of their performance in language and reading have found inconsistent results. In this study, we examined which specific language and reading skills were associated with prematurity independent of the effects of gender, socioeconomic status (SES), and IQ. Participants from two study sites (N = 100) included 9-16-year old children born before 36 weeks gestation and weighing less than 2500 grams (preterm group, n = 65) compared to children born at 37 weeks gestation or more (full-term group, n = 35). Children born preterm had significantly lower scores than full-term controls on Performance IQ, Verbal IQ, receptive and expressive language skills, syntactic comprehension, linguistic processing speed, verbal memory, decoding, and reading comprehension but not on receptive vocabulary. Using MANCOVA, we found that SES, IQ, and prematurity all contributed to the variance in scores on a set of six non-overlapping measures of language and reading. Simple regression analyses found that after controlling for SES and Performance IQ, the degree of prematurity as measured by gestational age group was a significant predictor of linguistic processing speed, beta = -0.27, p less than 0.05, R[superscript 2] = 0.07, verbal memory, beta = 0.31, p less than 0.05, R[superscript 2] = 0.09, and reading comprehension, beta = 0.28, p less than 0.05, R[superscript 2] = 0.08, but not of receptive vocabulary, syntactic comprehension, or decoding. The language and reading domains where prematurity had a direct effect can be classified as fluid as opposed to crystallized functions and should be monitored in school-aged children and adolescents born preterm.

The purpose of this study was to explore changes in activation of the cortical network that serves auditory sentence comprehension in children in response to increasing demands of complex sentences. A further goal is to study how individual differences in children's receptive language abilities are associated with such changes in cortical responses. Fourteen children, 10-16 years old, participated in an event-related functional magnetic resonance imaging experiment using a cross modal sentence-picture verification paradigm. We manipulated sentence difficulty and length in a 2 x 2 factorial design. Task-related activation covered large regions of the left and right superior temporal cortex, inferior parietal lobe, precuneous, cingulate, middle frontal gyrus and precentral gyrus. Sentence difficulty, independent of length, led to increased activation in the left temporal-parietal junction and right superior temporal gyrus. Changes in activation in frontal regions positively correlated with age-standardized receptive vocabulary scores and negatively correlated with reaction time on a receptive grammar test outside the scanner. Thus, individual differences in language skills were associated with changes in the network in response to changing task demands. These preliminary findings in a small sample of typically developing children suggest that the investigation of individual differences may prove useful in elucidating the underlying neural mechanisms of language disorders in children. (Contains 4 tables and 2 figures.)

Aim: We used diffusion tensor imaging to investigate the association between white-matter integrity and reading ability in a cohort of 28 children. Nineteen preterm children (14 males, five females; mean age 11y 11mo [SD 1y 10mo], mean gestational age 30.5wks (SD 3.2), mean birthweight was 1455g [SD 625]); and nine term children (five males, four females; mean age 12y 8mo [SD 2y 5mo], mean gestational age 39.6wks (SD 1.2), and mean birthweight 3877g [SD 473]). Method: We tested whether fractional anisotropy in a left hemisphere temporoparietal region and in the corpus callosum correlates with birthweight and scores on the following three subtests of the Woodcock-Johnson III Tests of Achievement: word identification, word attack, and passage comprehension. Results: Preterm children had lower reading scores than a comparison group for all reading subtests (p less than 0.05). We found significant correlations between birthweight and fractional anisotropy in the whole corpus callosum (p = 0.001), and between fractional anisotropy and reading skill in the genu (p = 0.001) and body (p = 0.001) of the corpus callosum. The correlation between reading skill and fractional anisotropy in a left temporoparietal region previously associated with reading disability was not significant (p = 0.095). Interpretation: We conclude that perinatal white-matter injury of the central corpus callosum may have long-term developmental implications for reading performance. (Contains 2 tables and 3 figures.)