Heikki Lyytinen

Orthographic Depth and Its Impact on Universal Predictors of Reading A Cross-Language Investigation

Alphabetic orthographies differ in the transparency of their letter-sound mappings, with English orthography being less transparent than other alphabetic scripts. The outlier status of English has led scientists to question the generality of findings based on English-language studies. We investigated the role of phonological awareness, memory, vocabulary, rapid naming, and nonverbal intelligence in reading performance across five languages lying at differing positions along a transparency continuum (Finnish, Hungarian, Dutch, Portuguese, and French). Results from a sample of 1,265 children in Grade 2 showed that phonological awareness was the main factor associated with reading performance in each language. However, its impact was modulated by the transparency of the orthography, being stronger in less transparent orthographies. The influence of rapid naming was rather weak and limited to reading and decoding speed. Most predictors of reading performance were relatively universal across these alphabetic languages, although their precise weight varied systematically as a function of script transparency.

Corpus Callosum Morphology in Attention Deficit-Hyperactivity Disorder: Morphometric Analysis of MRI:

Although behavioral evidence provides support for the notion that attention deficit-hyperactivity disorder (ADHD) is related to central nervous system dysfunction, there is little direct evidence to reveal which neurometabolic systems or brain structures are involved. Recent magnetic resonance imaging (MRI) studies suggest that, compared to nondisabled controls, ADHD children may have a smaller right frontal region. Morphometric analysis of MRI scans was used in this exploratory study to determine whether correlated regional variation might exist in the corpus callosum of children with ADHD. While all MRI scans were judged to be clinically normal, morphometric analysis revealed that, compared to nondisabled controls, ADHD children had a smaller corpus callosum, particularly in the region of the genu and splenium, and in the area just anterior to the splenium. Interhemispheric fibers in these regions interconnect the left and right frontal, occipital, parietal, and posterior temporal regions. These results suggest that subtle differences may exist in the brains of children with ADHD and that deviations in normal corticogenesis may underlie the behavioral manifestations of this disorder.

A candidate gene for developmental dyslexia encodes a nuclear tetratricopeptide repeat domain protein dynamically regulated in brain

Approximately 3–10% of people have specific difficulties in reading, despite adequate intelligence, education, and social environment. We report here the characterization of a gene, DYX1C1 near the DYX1 locus in chromosome 15q21, that is disrupted by a translocation t(2;15)(q11;q21) segregating coincidentally with dyslexia. Two sequence changes in DYX1C1, one involving the translation initiation sequence and an Elk-1 transcription factor binding site (–3G → A) and a codon (1249G → T), introducing a premature stop codon and truncating the predicted protein by 4 aa, associate alone and in combination with dyslexia. DYX1C1 encodes a 420-aa protein with three tetratricopeptide repeat (TPR) domains, thought to be protein interaction modules, but otherwise with no homology to known proteins. The mouse Dyx2016 protein is 78% identical to the human protein, and the nonhuman primates differ at 0.5–1.4% of residues. DYX1C1 is expressed in several tissues, including the brain, and the protein resides in the nucleus. In human brain, DYX1C1 protein localizes to a fraction of cortical neurons and white matter glial cells. We conclude that DYX1C1 should be regarded as a candidate gene for developmental dyslexia. Detailed study of its function may open a path to understanding a complex process of development and maturation of the human brain.

Neural systems predicting long-term outcome in dyslexia

Individuals with developmental dyslexia vary in their ability to improve reading skills, but the brain basis for improvement remains largely unknown. We performed a prospective, longitudinal study over 2.5 y in children with dyslexia (n = 25) or without dyslexia (n = 20) to discover whether initial behavioral or brain measures, including functional MRI (fMRI) and diffusion tensor imaging (DTI), can predict future long-term reading gains in dyslexia. No behavioral measure, including widely used and standardized reading and language tests, reliably predicted future reading gains in dyslexia. Greater right prefrontal activation during a reading task that demanded phonological awareness and right superior longitudinal fasciculus (including arcuate fasciculus) white-matter organization significantly predicted future reading gains in dyslexia. Multivariate pattern analysis (MVPA) of these two brain measures, using linear support vector machine (SVM) and cross-validation, predicted significantly above chance (72% accuracy) which particular child would or would not improve reading skills (behavioral measures were at chance). MVPA of whole-brain activation pattern during phonological processing predicted which children with dyslexia would improve reading skills 2.5 y later with >90% accuracy. These findings identify right prefrontal brain mechanisms that may be critical for reading improvement in dyslexia and that may differ from typical reading development. Brain measures that predict future behavioral outcomes (neuroprognosis) may be more accurate, in some cases, than available behavioral measures.

Brain sensitivity to print emerges when children learn letter-speech sound correspondences

The acquisition of reading skills is a major landmark process in a humans cognitive development. On the neural level, a new functional network develops during this time, as children typically learn to associate the well-known sounds of their spoken language with unfamiliar characters in alphabetic languages and finally access the meaning of written words, allowing for later reading. A critical component of the mature reading network located in the left occipito-temporal cortex, termed the “visual word-form system” (VWFS), exhibits print-sensitive activation in readers. When and how the sensitivity of the VWFS to print comes about remains an open question. In this study, we demonstrate the initiation of occipito-temporal cortex sensitivity to print using functional MRI (fMRI) (n = 16) and event-related potentials (ERP) (n = 32) in a controlled, longitudinal training study. Print sensitivity of fast (<250 ms) processes in posterior occipito-temporal brain regions accompanied basic associative learning of letter–speech sound correspondences in young (mean age 6.4 ± 0.08 y) nonreading kindergarten children, as shown by concordant ERP and fMRI results. The occipito-temporal print sensitivity thus is established during the earliest phase of reading acquisition in childhood, suggesting that a crucial part of the later reading network first adopts a role in mapping print and sound.

Cortical responses of infants with and without a genetic risk for dyslexia: II. Group effects.

Infants born to families with a background of developmental dyslexia have an increased risk of becoming dyslexic. In our previous study no major group or stimulus effects in the event-related potentials (ERPs) of at-risk and control infants were found until the age of 6 months. However, in the current study, when we made the stimulus presentation rate slower, the ERPs to the short deviant /ka/ were different from those to the long standard /kaa/ stimulus already in newborns. In addition, clear group differences in the ERPs were found. The results demonstrate that infants born with a high familial risk for dyslexia process speech/auditory stimulus durations differently from control infants at birth.

Predicting Delay in Reading Achievement in a Highly Transparent Language

A random sample of 91 preschool children was assessed prior to receiving formal reading instruction. Verbal and nonverbal measures were used as predictors for the time of instruction required to accurately decode pseudowords in the highly orthographically regular Finnish language. After 2 years, participants were divided into four groups depending on the duration of instruction they had required to reach 90 % accuracy in their reading of pseudowords. Participants were classified as precocious decoders (PD), who could read at school entry; early decoders (ED), who learned to read within the first 4 months of Grade 1; ordinary decoders (OD), who learned to read within 9 months; and late decoders (LD), who failed to reach the criterion after 18 months of reading instruction at Grade 2. Phonological awareness played a significant role only in differentiating PD from ED and OD. However, phonological awareness failed to predict the delayed learning process of LD. LD differed from all other groups in visual analogical reasoning in an analysis not containing phonological awareness measures. Letter knowledge and visual analogical reasoning explained above 90% of the PD-LD difference. Preschool composite (objects, colors, and digits) naming speed measures best predicted reading fluency at the end of Grade 2. The supportive role of orthographic knowledge in phonological awareness, the role of visual analogical reasoning, and the inability of phonological measures to discriminate late decoders are discussed.

Heterogeneity in adult dyslexic readers: Relating processing skills to the speed and accuracy of oral text reading ∗

Subgroups of Finnish dyslexic adults (N = 84)displaying, relative to each other, a distinctivecombination of accuracy and speed of oral text readingwere compared in phonological and orthographicprocessing, verbal short-term memory and readinghabits. Inaccurate phonological decoding appeared todetermine the number of errors made in text reading,while inability to utilize effectively rapid lexicalaccess of words manifested as slow text reading speed.Phonological and orthographic word recognitionprocesses were less tightly integrated among dyslexicthan normal readers. Our results indicate thatadvanced orthographic processing skills might help anumber of the dyslexic readers to compensate for theirserious phonological deficits. The subgroups alsodiffered from each other in reading habits. Arelatively fast reading speed, even with numerouserrors, appears to be more rewarding in everydayreading than a slower but more accurate readingstyle.

Brain Event-Related Potentials (ERPs) Measured at Birth Predict Later Language Development in Children with and Without Familial Risk for Dyslexia

We report associations between brain event-related potentials (ERPs) measured from newborns with and without familial risk for dyslexia and these same childrens later language and verbal memory skills at 2.5, 3.5, and 5 years of age. ERPs to synthetic consonant-vowel syllables (/ba/, /da/, /ga/; presented equiprobably with 3,910-7,285 msec interstimulus intervals) were recorded from 26 newborns at risk for familial dyslexia and 23 control infants participating in the Jyväskylä Longitudinal Study of Dyslexia. The correlation and regression analyses showed that the at-risk type of response pattern at birth (a slower shift in polarity from positivity to negativity in responses to /ga/ at 540-630 msec) in the right hemisphere was related to significantly poorer receptive language skills across both groups at the age of 2.5 years. The similar ERP pattern in the left hemisphere was associated with poorer verbal memory skills at the age of 5 years. These results demonstrate that ERPs of newborns may be valid predictors of later language and neurocognitive outcomes.

Brain Responses to Changes in Speech Sound Durations Differ Between Infants With and Without Familial Risk for Dyslexia

A specific learning disability, developmental dyslexia, is a language-based disorder that is shown to be strongly familial. Therefore, infants born to families with a history of the disorder are at an elevated risk for the disorder. However, little is known of the potential early markers of dyslexia. Here we report differences between 6-month-old infants with and without high risk of familial dyslexia in brain electrical activation generated by changes in the temporal structure of speech sounds, a critical cueing feature in speech. We measured event-related brain responses to consonant duration changes embedded in ata pseudowords applying an oddball paradigm, in which pseudoword tokens with varying /t/ duration were presented as frequent standard (80%) or as rare deviant stimuli (each 10%) with an interval of 610 msec between the stimuli. The infants at risk differ from control infants in both their initial responsiveness to sounds per se and in their change-detection responses dependent on the stimulus context. These results show that infants at risk due to a familial background of reading problems process auditory temporal cues of speech sounds differently from infants without such a risk even before they learn to speak.