Processing In Developmental Dyslexia Research Articles

Automatic metaphor processing in developmental dyslexia

IntroductionPrevious research found metaphor impairments with dyslexia; however, it is unclear if difficulties are due to initial activation of the metaphorical meaning or to subsequent discourse integration processes. The study examines the presence of early automatic processing of metaphors in adults with developmental dyslexia, considering the role of executive functions and metaphor familiarity. MethodsUsing a sentence recall task and a semantic judgment task from the Metaphor Interference Effect (MIE) paradigm, we evaluated two early stages of metaphor comprehension, namely the generation of the figurative meaning and the suppression of the literal meaning. High and low familiar metaphors, and their scrambled counterparts, were aurally presented to participants, who were asked to judge whether sentences were literally true or literally false. Afterwards, they were provided ten minutes to recall the sentences they heard to verify the depth of processing for each type of stimulus. A total of 26 participants with dyslexia were included in the experimental group, and 31 in the control group. ResultsIndividuals with dyslexia showed a MIE and an accuracy rate that are similar to participants without dyslexia. Inhibition correlated with the MIE size only for high familiar metaphors, and working memory seemed to play no role in the process. In the recall task, both groups demonstrated a better encoding of the metaphorical sentences compared to scrambled metaphors, but participants with dyslexia recalled less metaphors than did the control group, showing that metaphors are no exception to the limitations in sentence retrieval typically found in dyslexia. ConclusionsOur findings suggest that individuals with dyslexia are comparable to participants without dyslexia in their ability to automatically compute metaphorical meanings. Thus, difficulties in metaphor comprehension in people with dyslexia that have been detected in previous studies might depend on meaning construction in context rather than online semantic processing.

Shared and task-specific brain functional differences across multiple tasks in children with developmental dyslexia

Different tasks have been used in examining the neural functional differences associated with developmental dyslexia (DD), and consequently, different findings have been reported. However, very few studies have systematically compared multiple tasks in understanding what specific task differences each brain region is associated with. In this study, we employed an auditory rhyming task, a visual rhyming task, and a visual spelling task, in order to investigate shared and task-specific neural differences in Chinese children with DD. First, we found that children with DD had reduced activation in the opercular part of the left inferior frontal gyrus (IFG) only in the two rhyming tasks, suggesting impaired phonological analysis. Children with DD showed functional differences in the right lingual gyrus/inferior occipital gyrus only in the two visual tasks, suggesting deficiency in their visuo-orthographic processing. Moreover, children with DD showed reduced activation in the left dorsal inferior frontal gyrus and increased activation in the right precentral gyrus across all of the three tasks, suggesting neural signatures of DD in Chinese. In summary, our study successfully separated brain regions associated with differences in orthographic processing, phonological processing, and general lexical processing in DD. It advances our understanding about the neural mechanisms of DD.

Electrophysiological signatures of visual temporal processing deficits in developmental dyslexia.

Developmental dyslexia (DD) is a common neurodevelopmental disorder that affects reading ability despite normal intelligence and education. In search of core deficits, previous evidence has linked DD with impairments in temporal aspects of perceptual processing, which might underlie phonological deficits as well as inefficient graphemic parsing during reading. However, electrophysiological evidence for atypical temporal processing in DD is still scarce in the visual modality. Here, we investigated the efficiency of both temporal segregation and integration of visual information by means of event-related potentials (ERPs). We confirmed previous evidence of a selective segregation deficit in dyslexia for stimuli presented in rapid succession (<80 ms), despite unaffected integration performance. Importantly, we found a reduced N1 amplitude in DD, a component related to the allocation of attentional resources, which was independent of task demands (i.e., evident in both segregation and integration). In addition, the P3 amplitude, linked to working memory and processing load, was modulated by task demands in controls but not in individuals with DD. These results suggest that atypical attentional sampling in dyslexia might weaken the quality of information stored in visual working memory, leading to behavioral and electrophysiological signatures of atypical temporal segregation. These results are consistent with some existing theories of dyslexia, such as the magnocellular theory and the "Sluggish Attentional Shifting" framework, and represent novel evidence for neural correlates of decreased visual temporal resolution in DD.

Lateralization of word and face processing in developmental dyslexia and developmental prosopagnosia

In right-handed adults, face processing is lateralized to the right hemisphere and visual word processing to the left hemisphere. According to the many-to-many account (MTMA) of functional cerebral organization this lateralization pattern is partly dependent on the acquisition of literacy. Hence, the MTMA predicts that: (i) processing of both words and faces should show no or at least less lateralization in individuals with developmental dyslexia compared with controls, and (ii) lateralization in word processing should be normal in individuals with developmental prosopagnosia whereas lateralization in face processing should be absent. To test these hypotheses, 21 right-handed adults with developmental dyslexia and 21 right-handed adults with developmental prosopagnosia performed a divided visual field paradigm with delayed matching of faces, words and cars. Contrary to the predictions, we find that lateralization effects in face processing are within the normal range for both developmental dyslexics and prosopagnosics. Moreover, the group with developmental dyslexia showed right hemisphere lateralization for word processing. We argue that these findings are incompatible with the specific predictions of the MTMA.

The inseparability of visual processes in developmental dyslexia and the inseparability of visual categories in developmental prosopagnosia

The inseparability of visual processes in developmental dyslexia and the inseparability of visual categories in developmental prosopagnosia

Increased reliance on top-down information to compensate for reduced bottom-up use of acoustic cues in dyslexia

Speech recognition is a complex human behavior in the course of which listeners must integrate the detailed phonetic information present in the acoustic signal with their general linguistic knowledge. It is commonly assumed that this process occurs effortlessly for most people, but it is still unclear whether this also holds true in the case of developmental dyslexia (DD), a condition characterized by perceptual deficits. In the present study, we used a dual-task setting to test the assumption that speech recognition is effortful for people with DD. In particular, we tested the Ganong effect (i.e., lexical bias on phoneme identification) while participants performed a secondary task of either low or high cognitive demand. We presumed that reduced efficiency in perceptual processing in DD would manifest in greater modulation in the performance of primary task by cognitive load. Results revealed that this was indeed the case. We found a larger Ganong effect in the DD group under high than under low cognitive load, and this modulation was larger than it was for typically developed (TD) readers. Furthermore, phoneme categorization was less precise in the DD group than in the TD group. These findings suggest that individuals with DD show increased reliance on top-down lexically mediated perception processes, possibly as a compensatory mechanism for reduced efficiency in bottom-up use of acoustic cues. This indicates an imbalance between bottom-up and top-down processes in speech recognition of individuals with DD.

Sleep-Related Declarative Memory Consolidation in Children and Adolescents with Developmental Dyslexia.

Sleep has a crucial role in memory processes, and maturational changes in sleep electrophysiology are involved in cognitive development. Albeit both sleep and memory alterations have been observed in Developmental Dyslexia (DD), their relation in this population has been scarcely investigated, particularly concerning topographical aspects. The study aimed to compare sleep topography and associated sleep-related declarative memory consolidation in participants with DD and normal readers (NR). Eleven participants with DD and 18 NR (9–14 years old) underwent a whole-night polysomnography. They were administered a word pair task before and after sleep to assess for declarative memory consolidation. Memory performance and sleep features (macro and microstructural) were compared between the groups, and the intercorrelations between consolidation rate and sleep measures were assessed. DD showed a deeper worsening in memory after sleep compared to NR and reduced slow spindles in occipito-parietal and left fronto-central areas. Our results suggest specific alterations in local sleep EEG (i.e., sleep spindles) and in sleep-dependent memory consolidation processes in DD. We highlight the importance of a topographical approach, which might shed light on potential alteration in regional cortical oscillation dynamics in DD. The latter might represent a target for therapeutic interventions aimed at enhancing cognitive functioning in DD.

A Temporal Sampling Basis for Visual Processing in Developmental Dyslexia.

Knowledge of oscillatory entrainment and its fundamental role in cognitive and behavioral processing has increasingly been applied to research in the field of reading and developmental dyslexia. Growing evidence indicates that oscillatory entrainment to theta frequency spoken language in the auditory domain, along with cross-frequency theta-gamma coupling, support phonological processing (i.e., cognitive encoding of linguistic knowledge gathered from speech) which is required for reading. This theory is called the temporal sampling framework (TSF) and can extend to developmental dyslexia, such that inadequate temporal sampling of speech-sounds in people with dyslexia results in poor theta oscillatory entrainment in the auditory domain, and thus a phonological processing deficit which hinders reading ability. We suggest that inadequate theta oscillations in the visual domain might account for the many magno-dorsal processing, oculomotor control and visual deficits seen in developmental dyslexia. We propose two possible models of a magno-dorsal visual correlate to the auditory TSF: (1) A direct correlate that involves “bottom-up” magnocellular oscillatory entrainment of the visual domain that occurs when magnocellular populations phase lock to theta frequency fixations during reading and (2) an inverse correlate whereby attending to text triggers “top-down” low gamma signals from higher-order visual processing areas, thereby organizing magnocellular populations to synchronize to a theta frequency to drive the temporal control of oculomotor movements and capturing of letter images at a higher frequency.

Investigating the role of temporal processing in developmental dyslexia: Evidence for a specific deficit in rapid visual segmentation.

The current study investigates the role of temporal processing in the visual domain in participants with developmental dyslexia (DD), the most common neurodevelopmental disorder, which is characterized by severe and specific difficulties in learning to read despite normal intelligence and adequate education. Specifically, our aim was to test whether DD is associated with a general impairment of temporal sensory processing or a specific deficit in temporal integration (which ensures stability of object identity and location) or segregation (which ensures sensitivity to changes in visual input). Participants with DD performed a task that measured both temporal integration and segregation using an identical sequence of two displays separated by a varying interstimulus interval (ISI) under two different task instructions. Results showed that participants with DD performed worse in the segregation task, with a shallower slope of the psychometric curve of percentage correct as a function of the ISI between the two target displays. Moreover, we found also a relationship between temporal segregation performance and text, words, and pseudowords reading speeds at the individual level. In contrast, no significant association between reading (dis)ability and temporal integration emerged. The current findings provide evidence for a difference in the fine temporal resolution of visual processing in DD and, considering the growing evidence about a link between visual temporal segregation and neural oscillations at specific frequencies, they support the idea that DD is characterized by an altered oscillatory sampling within the visual system.

Double Trouble: Visual and Phonological Impairments in English Dyslexic Readers.

Developmental dyslexia is a reading disorder characterized by problems in accurate or fluent reading. A deficiency in phonological processing is thought to underpin the reading difficulties of individuals with developmental dyslexia and a variety of explanations have been proposed including deficits in phonological awareness and verbal memory. Recent investigations have begun to suggest that developmental deficits in the acquisition of reading may also co-occur with visual processing deficits, which are particularly salient for visually complex stimuli, yet these deficits have received relatively little attention from researchers. To further explore the nature of phonological and visual processing in developmental dyslexia, we administered a series of non-reading tasks tapping both domains. Unsurprisingly, individuals with developmental dyslexia performed worse than typically developing readers in phonological tasks. More intriguingly, they also struggled with visual tasks, specifically when discriminating between novel visual patterns, and in visuo-spatial working memory, which requires greater attentional control. These findings highlight that individuals with developmental dyslexia present not only with phonological impairments but also difficulties in processing visual materials. This aspect has received limited attention in previous literature and represents an aspect of novelty of this study. The dual phonological and visual impairments suggest that developmental dyslexia is a complex disorder characterized by deficits in different cognitive mechanisms that underpin reading.

A neural oscillations perspective on phonological development and phonological processing in developmental dyslexia

AbstractChildren's ability to reflect upon and manipulate the sounds in words (“phonological awareness”) develops as part of natural language acquisition, supports reading acquisition, and develops further as reading and spelling are learned. Children with developmental dyslexia typically have impairments in phonological awareness. Many developmental factors contribute to individual differences in phonological development. One important source of individual differences may be the child's sensory/neural processing of the speech signal from an amplitude modulation (~energy or intensity variation) perspective, which may affect the quality of the sensory/neural representations (“phonological representations”) that support phonological awareness. During speech encoding, brain electrical rhythms (oscillations, rhythmic variations in neural excitability) recalibrate their temporal activity to be in time with rhythmic energy variations in the speech signal. The accuracy of this neural alignment or “entrainment” process is related to speech intelligibility. Recent neural studies demonstrate atypical oscillatory function at slower rates in children with developmental dyslexia. Potential relations with the development of phonological awareness by children with dyslexia are discussed.

Own-race and other-race face recognition problems without visual expertise problems in dyslexic readers

Both intact and deficient neural processing of faces has been found in dyslexic readers. Similarly, behavioral studies have shown both normal and abnormal face processing in developmental dyslexia. We tested whether dyslexic adults are impaired in tests of own-race and other-race face recognition. As both face and word recognition rely considerably on visual expertise, we wished to investigate whether face recognition problems of dyslexic readers might stem from difficulties with experience-driven expert visual processing. We utilized the finding that people tend to be worse at discriminating other-race faces compared to own-race faces, the so-called other-race effect, thought to reflect greater experience with own-race faces. If visual expertise is compromised in dyslexic readers, so that their visual system is not effectively shaped by experience, then they might show a diminished other-race effect. Matched dyslexic and typical readers completed two tests of own- and other-race face recognition. The results show that dyslexic readers have problems with recognizing faces, and these difficulties are not fully accounted for by general problems with attention or memory. However, recognition is compromised for both own- and other-race faces, and the strength of the other-race effect does not differ between dyslexic and typical readers. There was individual variability in both groups, and an exploratory analysis revealed that while dyslexic readers with no university education showed deficits in face recognition, the dyslexic participants with higher education did not. We conclude that dyslexic readers as a group have face recognition problems. These are potentially modulated by educational level but compromised visual expertise cannot demonstrably account for the face recognition problems associated with dyslexia. We discuss the implications of these findings for theoretical accounts of dyslexia and for theories of word and face recognition.

Transcranial electrical stimulation improves phoneme processing in developmental dyslexia

BackgroundAbout 10% of the western population suffers from a specific disability in the acquisition of reading and writing skills, known as developmental dyslexia (DD). Even though DD starts in childhood it frequently continuous throughout lifetime. Impaired processing of acoustic features at the phonematic scale based on dysfunctional auditory temporal resolution is considered as one core deficit underlying DD. Recently, the efficacy of transcranial electrical stimulation (tES) to modulate auditory temporal resolution and phoneme processing in healthy individuals has been demonstrated. ObjectiveThe present work aims to investigate online effects of tES on phoneme processing in individuals with DD. MethodUsing an established phoneme-categorization task, we assessed the immediate behavioral and electrophysiological effects of transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) over bilateral auditory cortex in children and adolescents with DD (study 1) and adults with DD (study 2) on auditory phoneme processing acuity. ResultsOur data revealed that tACS improved phoneme categorization in children and adolescents with DD, an effect that was paralleled by an increase in evoked brain response patterns representing low-level sensory processing. In the adult sample we replicated these findings and additionally showed a more pronounced impact of tRNS on phoneme-categorization acuity. ConclusionThese results provide compelling evidence for the potential of both tACS and tRNS to increase temporal precision of the auditory system in DD and suggest transcranial electrical stimulation as potential intervention in DD to foster the effect of standard phonology-based training.

Visual-spatial attention processing in developmental dyslexia

Visual-spatial attention processing in developmental dyslexia

Mirrors are hard to break: A critical review and behavioral evidence on mirror-image processing in developmental dyslexia

The relation between reversal errors (e.g., d for b, Я for R) and developmental dyslexia has been elusive. In this study, we investigated the roles of reading level, visual category, and orientation processing in this relation. Children with developmental dyslexia, chronological-age-matched controls, and reading-level-matched controls performed two “same–different” matching tasks on reversible (e.g., b) and nonreversible (e.g., e) letters and on geometric shapes (e.g., ▪). In the orientation-based task, orientation processing was explicitly required; in the shape-based task, orientation processing would be automatic inasmuch as it was task irrelevant and would hinder successful performance. Two orientation contrasts were examined: mirror images (e.g., d–b) and plane rotations (e.g., d–p). For the latter, dyslexics behaved as controls; all were worse on shape-based judgments of plane rotation than on identical (e.g., d–d) pairs and were better able to attend to orientation than to shape. In contrast, for mirror images and across visual categories, dyslexics showed an advantage over typical readers on shape-based judgments. Both control groups had worse performance on shape-based judgments of mirror images than of identical pairs and exhibited similar magnitudes of mirror interference. Dyslexic children were the only group whose shape-based judgments were immune to mirror-image differences because they failed to automatize mirror discrimination during visual object processing. This deficit is not a consequence of reading level, is found across visual categories, and is specific to mirror images.

Age, dyslexia subtype and comorbidity modulate rapid auditory processing in developmental dyslexia.

The nature of Rapid Auditory Processing (RAP) deficits in dyslexia remains debated, together with the specificity of the problem to certain types of stimuli and/or restricted subgroups of individuals. Following the hypothesis that the heterogeneity of the dyslexic population may have led to contrasting results, the aim of the study was to define the effect of age, dyslexia subtype and comorbidity on the discrimination and reproduction of non-verbal tone sequences. Participants were 46 children aged 8–14 (26 with dyslexia, subdivided according to age, presence of a previous language delay, and type of dyslexia). Experimental tasks were a Temporal Order Judgment (TOJ) (manipulating tone length, ISI and sequence length), and a Pattern Discrimination Task. Dyslexic children showed general RAP deficits. Tone length and ISI influenced dyslexic and control children's performance in a similar way, but dyslexic children were more affected by an increase from 2 to 5 sounds. As to age, older dyslexic children's difficulty in reproducing sequences of 4 and 5 tones was similar to that of normally reading younger (but not older) children. In the analysis of subgroup profiles, the crucial variable appears to be the advantage, or lack thereof, in processing long vs. short sounds. Dyslexic children with a previous language delay obtained the lowest scores in RAP measures, but they performed worse with shorter stimuli, similar to control children, while dyslexic-only children showed no advantage for longer stimuli. As to dyslexia subtype, only surface dyslexics improved their performance with longer stimuli, while phonological dyslexics did not. Differential scores for short vs. long tones and for long vs. short ISIs predict non-word and word reading, respectively, and the former correlate with phonemic awareness. In conclusion, the relationship between non-verbal RAP, phonemic skills and reading abilities appears to be characterized by complex interactions with subgroup characteristics.

The deficit of letter processing in developmental dyslexia: combining evidence from dyslexics, typical readers and illiterate adults

To clarify the link between anomalous letter processing and developmental dyslexia, we examined the impact of surrounding contours on letter vs. pseudo-letter processing by three groups of children - phonological dyslexics and two controls, one matched for chronological age, the other for reading level - and three groups of adults differing by schooling and literacy - unschooled illiterates and ex-illiterates, and schooled literates. For pseudo-letters, all groups showed congruence effects (CE: better performance for targets surrounded by a congruent than by an incongruent shape). In contrast, for letters, only dyslexics exhibited a CE, strongly related to their phonological recoding abilities even after partialling out working memory, whereas the reverse held true for the pseudo-letter CE. In illiterate adults, the higher letter knowledge, the smaller their letter CE; their letter processing was immune (to some extent) to inference from surrounding information. The absence of a letter CE in illiterates and the positive CE in dyslexics have their origin in different aspects of the same ability, i.e. phonological recoding.

Enhanced Recognition Memory after Incidental Encoding in Children with Developmental Dyslexia

Developmental dyslexia (DD) has previously been associated with a number of cognitive deficits. Little attention has been directed to cognitive functions that remain intact in the disorder, though the investigation and identification of such strengths might be useful for developing new, and improving current, therapeutical interventions. In this study, an old/new recognition memory paradigm was used to examine previously untested aspects of declarative memory in children with DD and typically developing control children. The DD group was not only not impaired at the task, but actually showed superior recognition memory, as compared to the control children. These findings complement previous reports of enhanced cognition in other domains (e.g., visuo-spatial processing) in DD. Possible underlying mechanisms for the observed DD advantage in declarative memory, and the possibility of compensation by this system for reading deficits in dyslexia, are discussed.

I can read it in your eyes: What eye movements tell us about visuo-attentional processes in developmental dyslexia

Most studies today agree about the link between visual-attention and oculomotor control during reading: attention seems to affect saccadic programming, that is, the position where the eyes land in a word. Moreover, recent studies show that visuo-attentional processes are strictly linked to normal and impaired reading. In particular, a large body of research has found evidence of defective visuo-attentional processes in dyslexics. What do eye movements tell us about visuo-attentional deficits in developmental dyslexia? The purpose of this paper is to explore the link between oculomotor control and dyslexia, taking into account its heterogeneous manifestation and comorbidity. Clinical perspectives in the use of the eye-movements approach to better explore and understand reading impairments are discussed.

Event-related potentials reveal anomalous morphosyntactic processing 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.