On the importance of anchoring and the consequences of its impairment in dyslexia

Impaired neural discrimination of regular words from pseudowords in dyslexic adults as revealed by fast periodic visual stimulation

We used Fast Periodic Visual Stimulation with EEG recordings to assess the sensitivity of adults with dyslexia to fine-grained psycholinguistic variations of letter strings: lexicality and orthographic regularity. Dyslexic and non-dyslexic university students watched 60-s streams of stimuli presented at 10 Hz with deviant items (words) inserted periodically (1/8, at 1.25 Hz). While there was no overall difference in neural response between groups at the base stimulation frequency (10 Hz), individuals with dyslexia showed significantly reduced 1.25 Hz discrimination response for regular and irregular words among pseudowords (lexicality) over the left occipito-temporal cortex. Interestingly, while dyslexic individuals had significant weaker responses for irregular words than normal readers, they did not show any discrimination response for regular words within streams of pseudowords. However, they displayed responses to regularity changes within streams of words, that were not significantly below typical readers'. Overall, these observations suggest that lexical processes are not automatically triggered in dyslexia when a decoding strategy is enhanced by context (i.e., pseudowords) but may be at work when the overall activation of the lexicon is high (i.e., words). The results also show the diagnostic value of the FPVS-EEG approach to determine and characterize reading impairments rapidly, objectively and implicitly.

Perceptual anchoring: Children with dyslexia benefit less than controls from contextual repetitions in speech processing

OBJECTIVES

Individuals with dyslexia perceive and utilize statistical features in the auditory input deficiently. The present study investigates whether affected children also benefit less from repeating context tones as perceptual anchors for subsequent speech processing.

METHODS

In an event-related potential study, eleven-year-old children with dyslexia (n = 21) and without dyslexia (n = 20) heard syllable pairs, with the first syllable either receiving a constant pitch (anchor) or variable pitch (no-anchor), while second syllables were identical across conditions.

RESULTS

Children with and without dyslexia showed smaller auditory P2 responses to constant-pitch versus variable-pitch first syllables, while only control children additionally showed smaller N1 and faster P1 responses. This suggests less automatic processing of anchor repetitions in dyslexia. For the second syllables, both groups showed faster P2 responses following anchor than no-anchor first syllables, but only controls additionally showed smaller P2 responses.

CONCLUSIONS

Children with and without dyslexia show differences in anchor effects. While both groups seem to allocate less attention to speech stimuli after contextual repetitions, children with dyslexia display less facilitation in speech processing from acoustic anchors.

SIGNIFICANCE

Altered anchoring in the linguistic domain may contribute to the difficulties of individuals with dyslexia in establishing long-term representations of speech.

The ReadFree tool for the identification of poor readers: a validation study based on a machine learning approach in monolingual and minority-language children

In this study, we validated the "ReadFree tool", a computerised battery of 12 visual and auditory tasks developed to identify poor readers also in minority-language children (MLC). We tested the task-specific discriminant power on 142 Italian-monolingual participants (8-13 years old) divided into monolingual poor readers (N = 37) and good readers (N = 105) according to standardised Italian reading tests. The performances at the discriminant tasks of the "ReadFree tool" were entered into a classification and regression tree (CART) model to identify monolingual poor and good readers. The set of classification rules extracted from the CART model were applied to the MLC's performance and the ensuing classification was compared to the one based on standardised Italian reading tests. According to the CART model, auditory go-no/go (regular), RAN and Entrainment100bpm were the most discriminant tasks. When compared with the clinical classification, the CART model accuracy was 86% for the monolinguals and 76% for the MLC. Executive functions and timing skills turned out to have a relevant role in reading. Results of the CART model on MLC support the idea that ad hoc standardised tasks that go beyond reading are needed.

The Role of Visual Factors in Dyslexia

What are the causes of dyslexia? Decades of research reflect a determined search for a single cause where a common assumption is that dyslexia is a consequence of problems with converting phonological information into lexical codes. But reading is a highly complex activity requiring many well-functioning mechanisms, and several different visual problems have been documented in dyslexic readers. We critically review evidence from various sources for the role of visual factors in dyslexia, from magnocellular dysfunction through accounts based on abnormal eye movements and attentional processing, to recent proposals that problems with high-level vision contribute to dyslexia. We believe that the role of visual problems in dyslexia has been underestimated in the literature, to the detriment of the understanding and treatment of the disorder. We propose that rather than focusing on a single core cause, the role of visual factors in dyslexia fits well with risk and resilience models that assume that several variables interact throughout prenatal and postnatal development to either promote or hinder efficient reading.

Omit needless words: Sentence length perception

Short sentences improve readability. Short sentences also promote social justice through accessibility and inclusiveness. Despite this, much remains unknown about sentence length perception-an important factor in producing readable writing. Accordingly, we conducted a psychophysical study using procedures from Signal Detection Theory to examine sentence length perception in naive adults. Participants viewed real-world full-page text samples and judged whether a bolded target sentence contained more or fewer than 17 words. The experiment yielded four findings. First, naïve adults perceived sentence length in real-world text samples quickly (median = 300-400 ms) and precisely (median = ~90% correct). Second, flipping real-world text samples upside-down generated no reaction-time cost and nearly no loss in the precision of sentence length perception. This differs from the large inversion effects that characterize other highly practiced, real-world perceptual tasks involving canonically oriented stimuli, most notably face perception and reading. Third, participants significantly underestimated the length of mirror-reversed sentences-but not upside-down, nor standard sentences. This finding parallels participants' familiarity with commonly occurring left-justified right-ragged text, and suggests a novel demonstration of left-lateralized anchoring in scene syntax. Fourth, error patterns demonstrated that participants achieved their high speed, high precision sentence-length judgments by heuristically counting text lines, not by explicitly counting words. This suggests practical advice for writing instructors to offer students. When copy editing, students can quickly and precisely identify their long sentences via a line-counting heuristic, e.g., "a 17-word sentence spans about 1.5 text lines". Students can subsequently improve a long sentence's readability and inclusiveness by omitting needless words.

Repeated series learning revisited with a novel prediction on the reduced effect of item frequency in dyslexia

Developmental dyslexia, a difficulty with acquiring fluent reading, has also been characterized by reduced short-term memory (STM) capacity, which is often operationalized with span tasks. The low performance of individuals with dyslexia (IDDs) in such tasks is commonly attributed to poor phonological memory. However, we suggest an alternative explanation based on the observation that many times the items that are used in spans tasks are high-frequency items (e.g., digit words). We suggest that IDDs do not enjoy the benefit of item frequency to the same extent as controls, and thus their performance in span tasks is especially hampered. On the contrary, learning of repeated sequences was shown to be largely independent of item frequency, and therefore this type of learning may be unimpaired in dyslexia. To test both predictions, we used the Hebb-learning paradigm. We found that IDDs’ performance is especially poor compared to controls’ when high-frequency items are used, and that their repeated series learning does not differ from that of controls. Taken together with existing literature, our findings suggest that impaired learning of repeated series is not a core characteristic of dyslexia, and that the reports on reduced STM in dyslexia may to a large extent be explained by reduced benefit of item frequency.

Orthographic depth and developmental dyslexia: a meta-analytic study

Cross-cultural studies have suggested that reading deficits in developmental dyslexia (DD) can be moderated by orthographic depth. To further explore this issue and assess the moderating role of orthographic depth in the developmental cognitive trajectories of dyslexic and typical readers, we systematically reviewed 113 studies on DD that were published from 2013 to 2018 and selected 79 in which participants received an official DD diagnosis. Each study was classified according to orthographic depth (deep vs. shallow) and participant age (children vs. adults). We assessed the difference between DD and control groups' performance in reading tasks and in a wide range of cognitive domains associated with reading (phonological awareness (PA), rapid automatized naming (RAN), short-term working memory (WM), and nonverbal reasoning), including age and orthographies as moderators. We found an age-by-orthography interaction effect in word reading accuracy and a significant effect of age in pseudoword reading accuracy, but we found no effect of age and orthographic depth on the fluency parameters. These results suggest that reading speed is a reliable index for discriminating between DD and control groups across European orthographies from childhood to adulthood. A similar pattern of results emerged for PA, RAN, and short-term/WM. Our findings are discussed in relation to their impact on clinical practice while considering the orthographic depth and developmental level.

Chasing the Anchor: A Systematic Review and Meta-Analysis of Perceptual Anchoring Deficits in Developmental Dyslexia

Purpose We report the results of a systematic review and meta-analysis investigating the relationship between perceptual anchoring and dyslexia. Our goal was to assess the direction and degree of the effect between perceptual anchoring and reading ability in typical and atypical (i.e., dyslexic) readers. Method We performed a literature search of experiments explicitly assessing perceptual anchoring and reading ability using PsycInfo (Ovid, 1860-2020), MEDLINE (Ovid, 1860-2019), EMBASE (Ovid, 1883-2019), and PubMed for all available years up to June (2020). Our eligibility criteria consisted of English language articles, and, at minimum, one experimental group identified as dyslexic-either by reading assessment at the time or by previous diagnosis. We assessed for risk of bias using an adapted version of the Newcastle-Ottawa Scale. Eight studies were included in this review and meta-analysis (n = 422 participants). Results The overall effect was negative, moderate, and statistically significant; g = -0.70, 95% confidence interval [-1.10, -0.29]: a negative effect size indicating less perceptual anchoring in dyslexic versus nondyslexic groups. Visual assessment of funnel plot and Egger's test suggest minimal bias but with significant heterogeneity; Q (7) = 17.03, prediction interval [-1.79, 0.40]. Conclusions Of the included studies, we find evidence for a moderate perceptual anchoring deficit in individuals with dyslexia. The primary limitation of the current review is the small number of included studies. The variability of effect sizes appears consistent with the inherent variability within subtypes of dyslexia.

Neurophysiological tracking of speech-structure learning in typical and dyslexic readers

Statistical learning, or the ability to extract statistical regularities from the sensory environment, plays a critical role in language acquisition and reading development. Here we employed electroencephalography (EEG) with frequency-tagging measures to track the temporal evolution of speech-structure learning in individuals with reading difficulties due to developmental dyslexia and in typical readers. We measured EEG while participants listened to (a) a structured stream of repeated tri-syllabic pseudowords, (b) a random stream of the same isochronous syllables, and (c) a series of tri-syllabic real Dutch words. Participants' behavioral learning outcome (pseudoword recognition) was measured after training. We found that syllable-rate tracking was comparable between the two groups and stable across both the random and structured streams of syllables. More importantly, we observed a gradual emergence of the tracking of tri-syllabic pseudoword structures in both groups. Compared to the typical readers, however, in the dyslexic readers this implicit speech structure learning seemed to build up at a slower pace. A brain-behavioral correlation analysis showed that slower learners (i.e., participants who were slower in establishing the neural tracking of pseudowords) were less skilled in phonological awareness. Moreover, those who showed stronger neural tracking of real words tended to be less fluent in the visual-verbal conversion of linguistic symbols. Taken together, our study provides an online neurophysiological approach to track the progression of implicit learning processes and gives insights into the learning difficulties associated with dyslexia from a dynamic perspective.

The relationship of domain-general serial order memory and reading ability in school children with and without dyslexia

Recent evidence suggests that reading development when learning alphabetic languages is related to the underlying cognitive ability to maintain the serial order of information in short-term memory (STM). However, it remains unclear at which time point in reading development serial order STM is most important. Here, we established a crucial link between the reading development of primary school children and their serial order STM performance for both verbal and nonverbal materials. In a large cohort study of 113 Italian-speaking elementary school children in Grades 1-4, we investigated this relationship by implementing a novel double-probe design. In Experiment 1, we found that serial order STM performance was related to children's reading abilities, especially in Grades 2 and 3, corresponding to the training phase of grapheme-phoneme decoding skills. In Experiment 2, we assessed children with developmental dyslexia (DD) and found that their serial order STM performance was significantly lower than that of chronological age-matched controls (CA). It also differed from that of reading age-matched controls when accounting for individual reading performance. Furthermore, the CA group displayed an implicit serial order facilitation for item memory, whereas this implicit recruitment of serial order abilities was completely absent in children with DD. Our results suggest that the domain-general cognitive ability to maintain the serial order of information interacts with the development of reading competency, especially during a middle training phase of word reading, and this particular relationship is markedly impaired in children with DD.

Music-related abilities among readers with dyslexia

Research suggests that a central difficulty in dyslexia may be impaired rapid temporal processing. Good temporal processing is also needed for musical perception, which relies on the ability to detect rapid changes. Our study is the first to measure the perception of adults with and without dyslexia on all three dimensions of music (rhythm, pitch, and spectrum), as well as their capacity for auditory imagery and detection of slow changes, while controlling for working memory. Participants were undergraduate students, aged 20-35 years: 26 readers with dyslexia and 30 typical readers. Participants completed a battery of tests measuring aptitude for recognizing the similarity/difference in tone pitch or rhythm, spectral resolution, vividness/control of auditory imagination, the ability to detect slow changes in auditory stimuli, and working memory. As expected, readers with dyslexia showed poorer performance in pitch and rhythm than controls, but outperformed them in spectral perception. The data for each test was analyzed separately while controlling for the letter-number sequencing score. No differences between groups were found in slow-change detection or auditory imagery. Our results demonstrated that rapid temporal processing appears to be the main difficulty of readers with dyslexia, who demonstrated poorer performance when stimuli were presented quickly rather than slowly and better performance on a task when no temporal component was involved. These findings underscore the need for further study of temporal processing in readers with dyslexia. Remediation of temporal processing deficits may unmask the preserved or even superior abilities of people with dyslexia, leading to enhanced ability in all areas that utilize the temporal component.

Dyslexia as a multi-deficit disorder: Working memory and auditory temporal processing

Dyslexia is difficulty in acquiring reading skills despite adequate intelligence and sufficient reading opportunities. Its origin is still under debate. Studies usually focus on a singular cause for dyslexia; however, some researchers argue that dyslexia reflects multiple deficits. Two of the abilities under investigation in dyslexia are working memory (WM) and auditory temporal processing (ATP). In order to better evaluate the relative roles of WM and ATP in dyslexia, in the present study, we tested the contribution of WM and ATP to different types of reading performance and phonological awareness in dyslexia, using a multidimensional approach. Seventy-eight adults with dyslexia and 23 normal-reading adults performed WM and ATP tasks, as well as reading and phonological awareness tests. Readers with dyslexia showed poorer performance on all tests. Both WM and ATP were significant predictors of reading performance and phonological awareness among participants with dyslexia. Dividing participants with dyslexia according to their performance level on WM and ATP tasks revealed group differences in reading and phonological awareness tests. Both WM and ATP contribute to dyslexia, and varying levels of difficulties in both of these abilities are observed among this population. This is strong evidence in favor of the multi-deficit approach in dyslexia, and suggests that researchers should consider this approach in future studies of dyslexia.

Dysfunction of Rapid Neural Adaptation in Dyslexia

Identification of specific neurophysiological dysfunctions resulting in selective reading difficulty (dyslexia) has remained elusive. In addition to impaired reading development, individuals with dyslexia frequently exhibit behavioral deficits in perceptual adaptation. Here, we assessed neurophysiological adaptation to stimulus repetition in adults and children with dyslexia for a wide variety of stimuli, spoken words, written words, visual objects, and faces. For every stimulus type, individuals with dyslexia exhibited significantly diminished neural adaptation compared to controls in stimulus-specific cortical areas. Better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation. These results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development. Reduced neurophysiological adaptation may relate to prior reports of reduced behavioral adaptation in dyslexia and may reveal a difference in brain functions that ultimately results in a specific reading impairment.

Dysfunction of Rapid Neural Adaptation in Dyslexia

Identification of specific neurophysiological dysfunctions resulting in selective reading difficulty (dyslexia) has remained elusive. In addition to impaired reading development, individuals with dyslexia frequently exhibit behavioral deficits in perceptual adaptation. Here, we assessed neurophysiological adaptation to stimulus repetition in adults and children with dyslexia for a wide variety of stimuli, spoken words, written words, visual objects, and faces. For every stimulus type, individuals with dyslexia exhibited significantly diminished neural adaptation compared to controls in stimulus-specific cortical areas. Better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation. These results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development. Reduced neurophysiological adaptation may relate to prior reports of reduced behavioral adaptation in dyslexia and may reveal a difference in brain functions that ultimately results in a specific reading impairment.

A Computational Model of Implicit Memory Captures Dyslexics' Perceptual Deficits

Dyslexics are diagnosed for their poor reading skills, yet they characteristically also suffer from poor verbal memory and often from poor auditory skills. To date, this combined profile has been accounted for in broad cognitive terms. Here we hypothesize that the perceptual deficits associated with dyslexia can be understood computationally as a deficit in integrating prior information with noisy observations. To test this hypothesis we analyzed the performance of human participants in an auditory discrimination task using a two-parameter computational model. One parameter captures the internal noise in representing the current event, and the other captures the impact of recently acquired prior information. Our findings show that dyslexics' perceptual deficit can be accounted for by inadequate adjustment of these components; namely, low weighting of their implicit memory of past trials relative to their internal noise. Underweighting the stimulus statistics decreased dyslexics' ability to compensate for noisy observations. ERP measurements (P2 component) while participants watched a silent movie indicated that dyslexics' perceptual deficiency may stem from poor automatic integration of stimulus statistics. This study provides the first description of a specific computational deficit associated with dyslexia.

SIGNIFICANCE STATEMENT

This study presents the first attempt to specify the mechanisms underlying dyslexics' perceptual difficulties computationally by applying a specific model, inspired by the Bayesian framework. This model dissociates between the contribution of sensory noise and that of the prior statistics in an auditory perceptual decision task. We show that dyslexics cannot compensate for their perceptual noise by incorporating prior information. By contrast, adequately reading controls' usage of previous information is often close to optimal. We used ERP measurements to assess the neuronal stage of this deficit. We found that unlike their peers, dyslexics' ERP responses are not sensitive to the relations between the current observation and the prior observation, indicating that they cannot establish a reliable prior.

From temporal processing to developmental language disorders: mind the gap

The 'rapid temporal processing' and the 'temporal sampling framework' hypotheses have been proposed to account for the deficits in language and literacy development seen in specific language impairment and dyslexia. This paper reviews these hypotheses and concludes that the proposed causal chains between the presumed auditory processing deficits and the observed behavioural manifestation of the disorders are vague and not well established empirically. Several problems and limitations are identified. Most data concern correlations between distantly related tasks, and there is considerable heterogeneity and variability in performance as well as concerns about reliability and validity. Little attention is paid to the distinction between ostensibly perceptual and metalinguistic tasks or between implicit and explicit modes of performance, yet measures are assumed to be pure indicators of underlying processes or representations. The possibility that diagnostic categories do not refer to causally and behaviourally homogeneous groups needs to be taken seriously, taking into account genetic and neurodevelopmental studies to construct multiple-risk models. To make progress in the field, cognitive models of each task must be specified, including performance domains that are predicted to be deficient versus intact, testing multiple indicators of latent constructs and demonstrating construct reliability and validity.

Perceptual learning is specific to the trained structure of information

What do we learn when we practice a simple perceptual task? Many studies have suggested that we learn to refine or better select the sensory representations of the task-relevant dimension. Here we show that learning is specific to the trained structural regularities. Specifically, when this structure is modified after training with a fixed temporal structure, performance regresses to pretraining levels, even when the trained stimuli and task are retained. This specificity raises key questions as to the importance of low-level sensory modifications in the learning process. We trained two groups of participants on a two-tone frequency discrimination task for several days. In one group, a fixed reference tone was consistently presented in the first interval (the second tone was higher or lower), and in the other group the same reference tone was consistently presented in the second interval. When following training, these temporal protocols were switched between groups, performance of both groups regressed to pretraining levels, and further training was needed to attain postlearning performance. ERP measures, taken before and after training, indicated that participants implicitly learned the temporal regularity of the protocol and formed an attentional template that matched the trained structure of information. These results are consistent with Reverse Hierarchy Theory, which posits that even the learning of simple perceptual tasks progresses in a top-down manner, hence can benefit from temporal regularities at the trial level, albeit at the potential cost that learning may be specific to these regularities.

Auditory frequency discrimination in adults with dyslexia: a test of the anchoring hypothesis

PURPOSE

A recent hypothesis ascribes dyslexia to a perceptual anchoring deficit. Supporting results have so far been obtained only in children with dyslexia and additional learning difficulties, but the hypothesis has been argued to apply to all individuals with dyslexia.

METHOD

The authors measured auditory frequency discrimination thresholds in 54 young adults (native speakers of Dutch; 25 individuals with dyslexia; 29 age- and education-matched controls), with a 2-alternative forced-choice staircase paradigm. There were 2 conditions: 1 in which 1 tone in each pair had a fixed frequency across trials (standard), and 1 in which both tones varied in frequency (no standard). Presence of a standard stimulus allows the creation of a stimulus-specific representation in short-term-memory (perceptual anchor).

RESULTS

The standard condition yielded significantly lower discrimination thresholds in both controls and individuals with dyslexia; both groups benefited equally from the presence of an invariant stimulus.

CONCLUSION

There is no difference between this group of adults with dyslexia and controls in their capacity to form a perceptual anchor. The implication is that an anchoring deficit cannot be generalized to all cases of dyslexia.

A taxometric investigation of developmental dyslexia subtypes

Long-standing issues with the conceptualization, identification and subtyping of developmental dyslexia persist. This study takes an alternative approach to examine the heterogeneity of developmental dyslexia using taxometric classification techniques. These methods were used with a large sample of 671 children ages 6-8 who were diagnosed with severe reading disorders. Latent characteristics of the sample are assessed in regard to posited subtypes with phonological deficits and naming speed deficits, thus extending prior work by addressing whether these deficits embody separate classes of individuals. Findings support separate taxa of dyslexia with and without phonological deficits. Different latent structure for naming speed deficits was found depending on the definitional criterion used to define dyslexia. Non-phonologically based forms of dyslexia showed particular difficulty with naming speed and reading fluency.

Perceptual anchoring in preschool children: not adultlike, but there

BACKGROUND

Recent studies suggest that human auditory perception follows a prolonged developmental trajectory, sometimes continuing well into adolescence. Whereas both sensory and cognitive accounts have been proposed, the development of the ability to base current perceptual decisions on prior information, an ability that strongly benefits adult perception, has not been directly explored. Here we ask whether the auditory frequency discrimination of preschool children also improves when given the opportunity to use previously presented standard stimuli as perceptual anchors, and whether the magnitude of this anchoring effect undergoes developmental changes.

METHODOLOGY/PRINCIPAL FINDINGS

Frequency discrimination was tested using two adaptive same/different protocols. In one protocol (with-reference), a repeated 1-kHz standard tone was presented repeatedly across trials. In the other (no-reference), no such repetitions occurred. Verbal memory and early reading skills were also evaluated to determine if the pattern of correlations between frequency discrimination, memory and literacy is similar to that previously reported in older children and adults. Preschool children were significantly more sensitive in the with-reference than in the no-reference condition, but the magnitude of this anchoring effect was smaller than that observed in adults. The pattern of correlations among discrimination thresholds, memory and literacy replicated previous reports in older children.

CONCLUSIONS/SIGNIFICANCE

The processes allowing the use of context to form perceptual anchors are already functional among preschool children, albeit to a lesser extent than in adults. Nevertheless, immature anchoring cannot fully account for the poorer frequency discrimination abilities of young children. That anchoring is present among the majority of typically developing preschool children suggests that the anchoring deficits observed among individuals with dyslexia represent a true deficit rather than a developmental delay.