Impaired Statistical Learning in Developmental Dyslexia

Two groups of pupils from special tract learning schools were randomly selected for this study. The first group (55 pupils) fulfilled the World Federation of Neurology (WFN) definition of developmental dyslexia (DD). The second group (retarded readers, RR) included 20 pupils with IQs between 80 and 90. A group of normal readers was randomly selected from the 5 school grades as a control group. This study showed that the performance IQ of the DD group was not only higher than the verbal IQ, but the DD group also had superior performance IQ compared to normal readers. In the arithmetic achievement test, both DD and RR groups had nearly similar total scores, which were significantly lower than that of the control group. None of the arithmetic subtests could differentiate between DD and RR groups. In linguistic achievement tests, only spontaneous writing and oral spelling could differentiate subjects with DD from the RR group.

The human brain extracts statistical regularities from the surrounding environment in a process called statistical learning. Behavioural evidence suggests that developmental dyslexia affects statistical learning. However, surprisingly few studies have assessed how developmental dyslexia affects the neural processing underlying this type of learning. We used electroencephalography to explore the neural correlates of an important aspect of statistical learning – sensitivity to transitional probabilities – in individuals with developmental dyslexia. Adults diagnosed with developmental dyslexia (n = 17) and controls (n = 19) were exposed to a continuous stream of sound triplets. Every so often, a triplet ending had a low transitional probability given the triplet’s first two sounds (“statistical deviants”). Furthermore, every so often a triplet ending was presented from a deviant location (“acoustic deviants”). We examined mismatch negativity elicited by statistical deviants (sMMN), and MMN elicited by location deviants (i.e., acoustic changes). Acoustic deviants elicited a MMN which was larger in the control group than in the developmental dyslexia group. Statistical deviants elicited a small, yet significant, sMMN in the control group, but not in the developmental dyslexia group. However, the difference between the groups was not significant. Our findings indicate that the neural mechanisms underlying pre-attentive acoustic change detection and implicit statistical auditory learning are both affected in developmental dyslexia.

Excessive crowding in the visual periphery has been demonstrated in children with developmental dyslexia (DD). However, less is known about crowding in the fovea, even though foveal crowding is at least equally important, as reading is mostly accomplished through foveal vision. Here we used a special set of digitstimuli (Pelli fonts) to measure foveal crowding in DD and DD + ADHD children, and compared it to that in TD (typically developing) and ADHD children. We also used the Chinese reading acuity charts (C-READ) to assess the maximum reading speed and reading acuity, along with tests to evaluate cognitive attributes including phonological awareness, rapid automatized naming, morphological awareness, and orthographic knowledge. The results indicate significantly stronger foveal crowding in the DD and DD + ADHD groups, as well as in the ADHD group, than in the TD group. Furthermore, the DD and DD + ADHD groups exhibited poorer maximum reading speed and reading acuity compared to the ADHD and TD groups.Within the two DD groups, theslower maximum reading speed and higher reading acuitycan be predicted bystronger foveal crowding. In addition, the DD and DD + ADHD groups performed the worst in four cognitive skills, with the DD group showing negative correlations between foveal crowding and performances across all these skills. Our findings thus move beyond previously well-documented peripheral crowding in dyslexia, and the easy administration of the Pelli-font-based crowding test may be useful for early diagnosis of developmental dyslexia in young children.

This study aims to compare the word decoding skills, phonological awareness (PA), rapid automatized naming (RAN) skills, and letter knowledge of first graders with developmental dyslexia (DD) and those who were typically developing (TD). Eighteen children with DD and eighteen TD children, matched by nonverbal intelligence and discourse ability, participated in the study. Word decoding of Korean language-based reading assessment(<xref ref-type="bibr" rid="B27">Pae <italic>et al.,</italic> 2015</xref>) was conducted. Phoneme-grapheme correspondent words were analyzed according to whether the word has meaning, whether the syllable has a final consonant, and the position of the grapheme in the syllable. Letter knowledge asked about the names and sounds of 12 consonants and 6 vowels. The children’s PA of word, syllable, body-coda, and phoneme blending was tested. Object and letter RAN was measured in seconds. The decoding difficulty of non-words was more noticeable in the DD group than in the TD one. The TD children read the syllable initial and syllable final position with 99% correctness. Children with DD read with 80% and 82% correctness, respectively. In addition, the DD group had more difficulty in decoding words with two patchims when compared with the TD one. The DD group read only 57% of words with two patchims correctly, while the TD one read 91% correctly. There were significant differences in body-coda PA, phoneme level PA, letter RAN, object RAN, and letter-sound knowledge between the two groups. This study confirms the existence of Korean developmental dyslexics, and the urgent need for the inclusion of a Korean-specific phonics approach in the education system.

Altered effective connectivity on rapid automatized naming deficits in Chinese children with developmental dyslexia: An rs-fMRI study with Ganger causality analysis

Impaired print tuning in dyslexia has been shown in alphabetic languages; whether we can observe the same in a nonalphabetic language such as Chinese is still questionable. The present study investigated the N170 component in response to Chinese words versus nonword pseudo-words in 10-year-old children with developmental dyslexia (DD) when they were asked to performed a lexical decision task. The N170 was enhanced for DD group than control group, regardless of Chinese words or pseudo-words. The group effect of N170 amplitudes was more robust for Chinese words over pseudo-words. Although the N170 did not show the word advantage in the control group, larger N170 for Chinese words versus pseudo-words was found in the DD group. These findings suggest that there was a dysfunction/inefficient processing in the early stage of processing Chinese words in patients with DD.

ABSTRACTRecent work exploring syntax in developmental dyslexia (DD) has identified morphosyntactic deficits, striking parallelisms between children with DD and specific language impairment (SLI). The question remains open if the underlying causes for such deficits are related to difficulties in phonology, which is affected in DD, or to working memory, as has been previously reported for SLI. We focus on the production of third person accusative clitic pronouns (ACC3) and of homophonous definite determiners in French-speaking children with DD and SLI as well as typically developing (TD) controls. If syntactic complexity modulates performance of DD children, as has already been shown for SLI, we predict children with DD to perform significantly worse on ACC3 compared to definite determiners, which are homophonous but syntactically simpler. In addition, if impairment in ACC3 stems from phonology or working memory difficulties, we expect ACC3 performance in both clinical groups to relate to performance on non-word repetition or forward/backward digit spans. We studied 2 groups of 21 children and adolescents, with DD and SLI (7–15 years) and age-matched TD controls. Results reveal significant weaknesses with ACC3 in DD and SLI groups compared to TD controls, but no difficulty for homophonous definite determiners, confirming a deficit relating specifically to syntactic complexity. As for links to phonology and working memory, a single correlation emerged between ACC3 and the backward digit span in SLI, but not in DD, suggesting different underlying sources for syntactic deficits in these populations. Clinical implications of these results are discussed.

ABSTRACTA recent theoretical account posits that, during the acquisition of word recognition in childhood, the pressure to couple visual and language representations in the left hemisphere (LH) results in competition with the LH representation of faces, which consequently become largely, albeit not exclusively, lateralized to the right hemisphere (RH). We explore predictions from this hypothesis using a hemifield behavioural paradigm with words and faces as stimuli, with concurrent event-related potential (ERP) measurement, in a group of adults with developmental dyslexia (DD) or with congenital prosopagnosia (CP) and matched control participants. Behaviourally, the DD group exhibited clear deficits in both word and face processing relative to controls, while the CP group showed a specific deficit in face processing only. This pattern was mirrored in the ERP data too. The DD group evinced neither the normal ERP pattern of RH dominance for faces nor the LH dominance for words. In contrast, the CP group showed the typical ERP superiority for words in the LH but did not show the typical RH superiority for faces. These findings are consistent with the hypothesis that the typical hemispheric organization for words can develop in the absence of typical hemispheric organization for faces but not vice versa, supporting the account of interactive perceptual development.

ABSTRACTVerbal fluency tasks, in which participants generate words during a set time, have been used in research and assessments of neurobiological disorders and impairments. Research on verbal fluency in dyslexia has shown impaired performance in semantic and letter fluency. However, studies report inconsistent results, and action fluency has not been examined in dyslexia. Current research has mainly examined verbal fluency in relation to executive functions, vocabulary, and phonological processing. The present study examined performance on letter, semantic, and action fluency in relation to reading ability in 42 students in higher education, of which 16 had developmental dyslexia and 26 had typical reading development. It was examined if verbal fluency can predict variance in reading ability when group, phonological awareness, and rapid automatized naming are controlled for. Results showed impaired verbal fluency in the developmental dyslexia group. Action fluency and group were significant predictors of reading ability, together explaining 73% of the variance, in a backward elimination regression analysis. The results point to a possible, unique connection between action fluency and reading ability; this connection is discussed based on their neurocognitive underpinnings.

Failure of resting-state frontal–occipital connectivity in linking visual perception with reading fluency in Chinese children with developmental dyslexia

Reading is vital to every aspect of modern life, exacerbated by reliance of the internet, email, and social media on the written medium. Developmental dyslexia (DD) characterizes a disorder in which the core deficit involves reading. Traditionally, DD is thought to be associated with a phonological impairment. However, recent evidence has begun to suggest that the reading impairment in some individuals is provoked by a visual processing deficit. In this paper, we present WISC‐IV data from more than 300 Italian children with a diagnosis of DD to investigate the manifestation of phonological and visual subtypes. Our results indicate the existence of two clusters of children with DD. In one cluster, the deficit was more pronounced in the phonological component, while both clusters were impaired in visual processing. These data indicate that DD may be an umbrella term that encompasses different profiles. From a theoretical perspective, our results demonstrate that dyslexia cannot be explained in terms of an isolated phonological deficit alone; visual impairment plays a crucial role. Moreover, general rather than specific accounts of DD are discussed.

Sensory auditory interval perception errors in developmental dyslexia

ABSTRACTIn the light of the literature describing oral language difficulties in developmental dyslexia (DD), event-related potentials were used in order to compare morphosyntactic processing in 16 adults with DD (aged 20–28 years) and unimpaired controls. Sentences including subject–verb agreement violations were presented auditorily, with grammaticality and subject number as main factors. Electrophysiological data revealed differences between groups concerning both the latency of the P600 component and the additional presence in the DD group of a negativity broadly diffused all over the scalp. Moreover, these electrophysiological anomalies increased when plural sentences were processed. On the whole, the results support the hypothesis of a linguistic deficit and of different language processing modalities in DD participants.

ABSTRACTPrevious studies found a relationship between performance on statistical learning (SL) tasks and reading ability and developmental dyslexia. Thus, it has been suggested that the ability to implicitly learn patterns may be important for reading acquisition. Causal mechanisms behind this relationship are unclear: Although orthographic sensitivity to letter bigrams may emerge through SL and facilitate reading, there is no empirical support for this link. We test 84 adults on two SL tasks, reading tests, and a bigram sensitivity task. We test for correlations using Bayes factors. This serves to test the prediction that SL and reading ability are correlated and to explore sensitivity to bigram legality as a potential mediator. We find no correlations between SL tasks and reading ability, SL and bigram sensitivity, or between the SL tasks. We conclude that correlating SL with reading ability may not yield replicable results, partly due to low correlations between SL tasks.

Several studies have signaled grammatical difficulties in individuals with developmental dyslexia. These difficulties may stem from a phonological deficit, but may alternatively be explained through a domain-general deficit in statistical learning. This study investigates grammar in children with and without dyslexia, and whether phonological memory and/or statistical learning ability contribute to individual differences in grammatical performance. We administered the CELF “word structure” and “recalling sentences” subtests and measures of phonological memory (digit span, nonword repetition) and statistical learning (serial reaction time, nonadjacent dependency learning) among 8- to 11-year-old children with and without dyslexia (N= 50 per group). Consistent with previous findings, our results show subtle difficulties in grammar, as children with dyslexia achieved lower scores on the CELF (word structure:p= .0027, recalling sentences:p= .053). While the two phonological memory measures were found to contribute to individual differences in grammatical performance, no evidence for a relationship with statistical learning was found. An error analysis revealed errors in irregular morphology (e.g., plural and past tense), suggesting problems with lexical retrieval. These findings are discussed in light of theoretical accounts of the underlying deficit in dyslexia.