Speech therapy and hyperbaric oxygen for aphasia after carbon monoxide intoxication.

Acute carbon monoxide (CO) intoxication may result in delayed neurological sequelae, which can include amnesia, ataxia, aphasia, emotional lability, disorientation, dysphagia, and other manifestations. A 27-year-old man reported symptoms of aphasia with agraphia and alexia in a review after CO intoxication. The patient received outpatient speech therapy, as well as repeated sessions of hyperbaric oxygen for 15 days, interspersing speech therapy with hyperbaric oxygen therapy for two months. After this period of combined treatment the aphasic symptomatology remitted, and oral and written language was normal. The complete disappearance of aphasia with agraphia and alexia confirms the efficacy of the combined intervention. More data from large clinical studies are needed to assess the outcomes of hyperbaric oxygen treatment in patients with delayed neurological sequelae after CO intoxication, but this case suggests it may be a good therapeutic option in combination with specific speech therapy.

Neural signatures of phonological deficits in Chinese developmental dyslexia.

There has been debate on whether phonological deficits explain reading difficulty in Chinese, since Chinese is a logographic language which does not employ grapheme-phoneme-correspondence rules and remote memorization seems to be the main method to acquire reading. In the current study, we present neuroimaging evidence that the phonological deficit is also a signature of Chinese dyslexia. Specifically, we found that Chinese children with dyslexia (DD) showed reduced brain activation in the left dorsal inferior frontal gyrus (dIFG) when compared to both age-matched controls (AC) and reading-matched controls (RC) during an auditory rhyming judgment task. This suggests that the phonological processing deficit in this region may be a signature of dyslexia in Chinese, rather than a difference due to task performance or reading ability, which was matched on DD and RC. At exactly the same region of the left dIFG, we found a positive correlation between brain activation and reading skill in DD, suggesting that the phonological deficit is associated with the severity of dyslexia. We also found increased brain activation in the right precentral gyrus in DD than both AC and RC, suggesting a compensation of reliance on articulation. Functional connectivity analyses revealed that DD had a weaker connection between the left superior temporal gyrus (STG) and fusiform gyrus (FG) than the two control groups, suggesting that the reduced connection between phonology and orthography is another neural signature of dyslexia. In contrast, DD showed greater connectivity between the left dIFG and the left inferior parietal lobule (IPL) than both control groups, suggesting a reduced segregation between the language network and default mode network in dyslexic children. We also found that connectivity between the left STG and the left dIFG was sensitive to task performance and/or reading skill rather than being dyslexic or not, because AC was greater than both RC and DD, while the connectivity between the left middle occipital gyrus (MOG) and left STG was sensitive to age, because both AC and DD were greater than RC. In summary, our study provides the very first neurological evidence of phonological deficits in Chinese developmental dyslexia and we successfully distinguished variations of brain activity/functional connectivity due to age, performance, and dyslexia by comparing AC, RC, and DD.

[Clinical and neurophysiological data of neurofeedback therapy in children with ADHD]. / Wyniki kliniczne i neurofizjologiczne terapii neurofeedback u dzieci z zespolem ADHD.

INTRODUCTION: ADHD occurs in 3% of school-age children (and in 70% of them in adulthood) and represents an important medical and social problem. It is characterized by attention deficits, hyperactivity and impulsiveness. Neurofeedback therapy (EEG biofeedback, NF) is carried out based on the analysis of EEG. OBJECTIVE: To investigate the effect of NF therapy on clinical status and parameters of the EEG in ADHD. MATERIALS AND METHODS: In the years 2007-2014, 287 children (191 boys), aged 6-17 years were included into the study. Some children with ADHD had other coexisting disorders like: tics, dyslexia, emotional or behavior disorders. Visual analysis of EEG was made and 7 selected parameters of bioelectrical activity were assessed. EEG tracing before and after NF therapy were compared. NF therapy lasted from 9 months to 3 years (mean 1.5 years). 60-240 NF training sessions were performed with the use of NF device, video-games and 16-channel Elmiko devices. Statistical analysis of the results was made. RESULTS: Children with ADHD additionally presented low self-esteem, anxiety and sleep disorders. The baseline theta/beta ratio in children with ADHD and ADHD with cooccurring dyslexia was >4.0 and in children with ADHD and coexisting tics 3.0-3.8, with coexisting behavioral disorders 3.7-4.0 and emotional disorders 3.3-3.7. After therapy, this ratio decreased significantly in all groups, but most significantly in ADHD and ADHD with dyslexia group. In the group with dyslexia theta and alpha activity in the left fronto-temporo-parietal region (the speech centers) has been increased. In children with ADHD and behavior disorders right-sided paroxysmal changes in the form of slow and sharp waves in the temporo-centro-parietal regions were found. In emotionally disturbed children increased fast beta activity in the right hemisphere (anxiety, fear) was observed. Initially NF therapy reduced hyperactivity and impulsivity of children, subsequently improvement of attention was observed and eventually reduction of emotional and behavior disturbances was noticed. Noticeable improvement in the self-esteem was observed as well. The therapy had a positive impact on the spatial organization of EEG in each group. It proved to be particularly useful in children with ADHD and dyslexia. CONCLUSIONS: Neurofeedback therapy is a valuable tool with beneficial impact on children with ADHD and accompanying disorders. Characteristics of brain bioelectric activity provides a reliable basis to establish individual EEG bio-feedback protocols of therapy in children and monitor the effectiveness of treatment. In the last 4 years the number of children with ADHD and cooccurring tics who applied for neurofeedback therapy has increased significantly.

Calidad de vida a los 6 meses tras un ictus / Quality of life 6 months after a stroke

Objetivo. Describir la calidad de vida (CV) de los pacientes a los 6 meses de evolución del ictus y su relación con variables sociodemográficas, clínicas y funcionales. Material y métodos. Estudio multicéntrico de cohortes longitudinal (n = 157). Los pacientes incluidos ingresaron en la fase subaguda tras un ictus en 2 Servicios de Rehabilitación. Se recogieron los siguientes datos a los 6 meses postictus: género, edad, riesgo social, comorbilidad, disfagia, afasia, estado cognitivo, depresión y grado de discapacidad evaluado mediante el índice de Barthel modificado. Se evaluó la influencia de estas variables en la CV, para lo que se empleó la escala específica de calidad de vida para el ictus ECVI-38. Resultados. La media de edad fue de 70,93 ± 11,85 años; fue significativamente superior en las mujeres. El paciente tipo presentó una elevada comorbilidad, un bajo riesgo social y dependencia moderada. La puntuación media total de la escala ECVI-38 fue de 35,30 ± 16,17 y los dominios más afectados los referentes a las actividades comunes y básicas de la vida diaria. Las variables que más se relacionan con la CV fueron el género, la afasia, la disfagia, la depresión, el déficit cognitivo y el estado funcional. El dolor de elevada intensidad estuvo presente en un 21% de los pacientes. Conclusión. Son muy diversas las variables que influyen en la CV del paciente con ictus que se deben considerar, para su potencial abordaje, en la planificación de las intervenciones rehabilitadoras (AU)

Objective. To describe quality of life (QoL) in patients at 6 months poststroke and its relationship with sociodemographic, clinical and functional characteristics. Material and method. This multicenter longitudinal cohort study (n = 157) included patients from 2 hospital rehabilitation services who were admitted for stroke in the subacute phase. The following data were gathered at 6 months poststroke: gender, age, social risk, comorbidity, dysphagia, aphasia, cognitive status, depression, and disability measured by the modified Barthel Index. The influence of these variables on QoL was evaluated using the stroke-specific quality of life scale, ECVI-38. Results. The mean age was 70.93 ± 11.85 years and was significantly higher in women. Most of the patients had high comorbidity, low social risk and moderate dependence. The mean total score on the ECVI-38 scale was 35.30 ± 16.17 and the most affected domains were those concerning common and basic activities of daily living. The variables associated with QoL were gender, aphasia, dysphagia, depression, cognitive impairment, and functional status. High-intensity pain was present in 21% of patients. Conclusion. Numerous variables influence QoL in patients with stroke and should be considered in the planning of rehabilitation interventions (AU)

Neurociencia y Educación: ¿podemos ir de la investigación básica a su aplicación? Un posible marco de referencia desde la investigación en dislexia1 / Neurociencia y Educación: ¿podemos ir de la investigación básica a su aplicación? Un posible marco de referencia desde la investigación en dislexia

La neurociencia podría transformar la educación, pues proporciona nuevos métodos para comprender el aprendizaje y el desarrollo cognitivo, sus mecanismos causales y una forma empírica de evaluar la eficacia de diferentes pedagogías. No obstante, éste sería un objetivo a largo plazo. Desde la neurociencia educativa se debería empezar estudiando cómo los sistemas cognitivos se construyen sobre los sensoriales a lo largo del desarrollo. Aquí me centraré en el lenguaje. Pequeñas diferencias individuales iniciales en una función sensorial, por ejemplo la auditiva, podrían ser el origen de notables diferencias individuales en el desarrollo lingüístico. La neurociencia podría proporcionar una comprensión detallada de los mecanismos causales del desarrollo que vinculan la audición, el desarrollo fonológico y el desarrollo de la alfabetización. Este tipo de investigación neurocientífica básica podría orientar al campo de la educación y la pedagogía explorando los efectos que sobre estos mecanismos ejercen diferentes contextos pedagógicos y de aprendizaje

Neuroscience has the potential to transform education because it provides novel methods for understanding human learning and cognitive development. It therefore offers deeper understanding of causal mechanisms in learning and an empirical approach to evaluating the efficacy of different pedagogies. However, this will be a long-term enterprise and there will be few immediate pay-offs. Here I set out one possible framework for linking basic research in neuroscience to pedagogical questions in education. I suggest that the developing field of educational neuroscience must first study how sensory systems build cognitive systems over developmental time. I focus on one cognitive system, language, the efficient functioning of which is critical for reading acquisition. Small initial differences in sensory function, for example auditory function, have the potential to cause large differences in linguistic performance over the learning trajectory. The tools offered by neuroscience can enable better understanding of the causal developmental mechanisms linking audition, phonological development and literacy development, in fine-grained detail. Following this basic research, neuroscience can then inform education and pedagogy by exploring the effects on these neural mechanisms of different learning contexts and pedagogies

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.

Impaired Statistical Learning in Developmental Dyslexia.

PURPOSE: Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined if individuals with DD are capable of extracting statistical regularities across sequences of passively experienced speech and nonspeech sounds. Such statistical learning is believed to be domain-general, to draw upon procedural learning systems, and to relate to language outcomes. METHOD: DD and control groups were familiarized with a continuous stream of syllables or sine-wave tones, the ordering of which was defined by high or low transitional probabilities across adjacent stimulus pairs. Participants subsequently judged two 3-stimulus test items with either high or low statistical coherence as being the most similar to the sounds heard during familiarization. RESULTS: As with control participants, the DD group was sensitive to the transitional probability structure of the familiarization materials as evidenced by above-chance performance. However, the performance of participants with DD was significantly poorer than controls across linguistic and nonlinguistic stimuli. In addition, reading-related measures were significantly correlated with statistical learning performance of both speech and nonspeech material. CONCLUSION: Results are discussed in light of procedural learning impairments among participants with DD.

The level of audiovisual print-speech integration deficits in dyslexia.

The classical phonological deficit account of dyslexia is increasingly linked to impairments in grapho-phonological conversion, and to dysfunctions in superior temporal regions associated with audiovisual integration. The present study investigates mechanisms of audiovisual integration in typical and impaired readers at the critical developmental stage of adolescence. Congruent and incongruent audiovisual as well as unimodal (visual only and auditory only) material was presented. Audiovisual presentations were single letters and three-letter (consonant-vowel-consonant) stimuli accompanied by matching or mismatching speech sounds. Three-letter stimuli exhibited fast phonetic transitions as in real-life language processing and reading. Congruency effects, i.e. different brain responses to congruent and incongruent stimuli were taken as an indicator of audiovisual integration at a phonetic level (grapho-phonological conversion). Comparisons of unimodal and audiovisual stimuli revealed basic, more sensory aspects of audiovisual integration. By means of these two criteria of audiovisual integration, the generalizability of audiovisual deficits in dyslexia was tested. Moreover, it was expected that the more naturalistic three-letter stimuli are superior to single letters in revealing group differences. Electrophysiological and hemodynamic (EEG and fMRI) data were acquired simultaneously in a simple target detection task. Applying the same statistical models to event-related EEG potentials and fMRI responses allowed comparing the effects detected by the two techniques at a descriptive level. Group differences in congruency effects (congruent against incongruent) were observed in regions involved in grapho-phonological processing, including the left inferior frontal and angular gyri and the inferotemporal cortex. Importantly, such differences also emerged in superior temporal key regions. Three-letter stimuli revealed stronger group differences than single letters. No significant differences in basic measures of audiovisual integration emerged. Convergence of hemodynamic and electrophysiological signals appeared to be limited and mainly occurred for highly significant and large effects in visual cortices. The findings suggest efficient superior temporal tuning to audiovisual congruency in controls. In impaired readers, however, grapho-phonological conversion is effortful and inefficient, although basic audiovisual mechanisms seem intact. This unprecedented demonstration of audiovisual deficits in adolescent dyslexics provides critical evidence that the phonological deficit might be explained by impaired audiovisual integration at a phonetic level, especially for naturalistic and word-like stimulation.

The effect of auditory pacing on period stability and temporal consistency in children with and without dyslexia co-existing motor dysfunction.

The primary purpose of this study was to examine the effect of auditory pacing on period stability and temporal consistency of a dual motor task in children with and without dyslexia and with varying amounts of motor deficiency. Fifty-four children were divided into groups based on dyslexia diagnosis and score on the Movement Assessment Battery for Children-Second Edition (Movement ABC-2). Participants performed a dual motor task (clapping while walking) at a self-determined pace in a pretest block, practiced 4 blocks of 4 trials with a metronome pacing signal, and finished with a posttest block without auditory pacing. Measures of period stability (interclap/interheel strike intervals across trial blocks) and temporal consistency (coefficient of variation of period with trials) were taken. The results suggest that auditory pacing may improve period stability across groups, but does not appear to impact temporal consistency. Weak support existed for a general impairment of motor function in children diagnosed with dyslexia.

Characterizing the morphosyntactic processing deficit and its relationship to phonology in developmental dyslexia.

This study explores the morphosyntactic processing deficit in developmental dyslexia, addressing the on-going debate on the linguistic nature of the disorder, and directly testing the hypothesis that the deficit is based on underlying processing difficulties, such as acoustic and/or phonological impairments. Short German sentences consisting of a pronoun and a verb, either correct or containing a morphosyntactic violation, were auditorily presented to 17 German-speaking adults with dyslexia, and 17 matched control participants, while an EEG was recorded. In order to investigate the interaction between low-level phonological processing and morphosyntactic processing, the verbal inflections were manipulated to consist of different levels of acoustic salience. The event-related potential (ERP) results confirm altered morphosyntactic processing in participants with dyslexia, especially when morphosyntactic violations are expressed by both lexical and inflectional changes. Moreover, ERP data on phoneme discrimination and behavioural data on phonemic awareness and verbal short-term memory reveal phonological deficits in dyslexic participants. However, a causal relationship between phonological and morphosyntactic processing was not conclusive, because anomalous morphosyntactic processing in dyslexia is not directly mediated by acoustic salience, rather it correlates with high-level phonological skills and is mediated by lexical cues.

Are auditory and visual processing deficits related to developmental dyslexia?

The purpose of this study was to examine if children with dyslexia learning to read a consistent orthography (Greek) experience auditory and visual processing deficits and if these deficits are associated with phonological awareness, rapid naming speed and orthographic processing. We administered measures of general cognitive ability, phonological awareness, orthographic processing, short-term memory, rapid automatized naming, auditory and visual processing, and reading fluency to 21 Grade 6 children with dyslexia, 21 chronological age-matched controls and 20 Grade 3 reading age-matched controls. The results indicated that the children with dyslexia did not experience auditory processing deficits, but about half of them showed visual processing deficits. Both orthographic processing and rapid automatized naming deficits were associated with dyslexia in our sample, but it is less clear that they were associated with visual processing deficits.

Speech-in-noise perception deficit in adults with dyslexia: effects of background type and listening configuration.

Developmental dyslexia is associated with impaired speech-in-noise perception. The goal of the present research was to further characterize this deficit in dyslexic adults. In order to specify the mechanisms and processing strategies used by adults with dyslexia during speech-in-noise perception, we explored the influence of background type, presenting single target-words against backgrounds made of cocktail party sounds, modulated speech-derived noise or stationary noise. We also evaluated the effect of three listening configurations differing in terms of the amount of spatial processing required. In a monaural condition, signal and noise were presented to the same ear while in a dichotic situation, target and concurrent sound were presented to two different ears, finally in a spatialised configuration, target and competing signals were presented as if they originated from slightly differing positions in the auditory scene. Our results confirm the presence of a speech-in-noise perception deficit in dyslexic adults, in particular when the competing signal is also speech, and when both signals are presented to the same ear, an observation potentially relating to phonological accounts of dyslexia. However, adult dyslexics demonstrated better levels of spatial release of masking than normal reading controls when the background was speech, suggesting that they are well able to rely on denoising strategies based on spatial auditory scene analysis strategies.

Neocortical disruption and behavioral impairments in rats following in utero RNAi of candidate dyslexia risk gene Kiaa0319.

Within the last decade several genes have been identified as candidate risk genes for developmental dyslexia. Recent research using animal models and embryonic RNA interference (RNAi) has shown that a subset of the candidate dyslexia risk genes--DYX1C1, ROBO1, DCDC2, KIAA0319--regulate critical parameters of neocortical development, such as neuronal migration. For example, embryonic disruption of the rodent homolog of DYX1C1 disrupts neuronal migration and produces deficits in rapid auditory processing (RAP) and working memory--phenotypes that have been reported to be associated with developmental dyslexia. In the current study we used a modified prepulse inhibition paradigm to assess acoustic discrimination abilities of male Wistar rats following in utero RNA interference targeting Kiaa0319. We also assessed spatial learning and working memory using a Morris water maze (MWM) and a radial arm water maze. We found that embryonic interference with this gene resulted in disrupted migration of neocortical neurons leading to formation of heterotopia in white matter, and to formation of hippocampal dysplasia in a subset of animals. These animals displayed deficits in processing complex acoustic stimuli, and those with hippocampal malformations exhibited impaired spatial learning abilities. No significant impairment in working memory was detected in the Kiaa0319 RNAi treated animals. Taken together, these results suggest that Kiaa0319 plays a role in neuronal migration during embryonic development, and that early interference with this gene results in an array of behavioral deficits including impairments in rapid auditory processing and simple spatial learning.

Brain basis of phonological awareness for spoken language in children and its disruption in dyslexia.

Phonological awareness, knowledge that speech is composed of syllables and phonemes, is critical for learning to read. Phonological awareness precedes and predicts successful transition from language to literacy, and weakness in phonological awareness is a leading cause of dyslexia, but the brain basis of phonological awareness for spoken language in children is unknown. We used functional magnetic resonance imaging to identify the neural correlates of phonological awareness using an auditory word-rhyming task in children who were typical readers or who had dyslexia (ages 7-13) and a younger group of kindergarteners (ages 5-6). Typically developing children, but not children with dyslexia, recruited left dorsolateral prefrontal cortex (DLPFC) when making explicit phonological judgments. Kindergarteners, who were matched to the older children with dyslexia on standardized tests of phonological awareness, also recruited left DLPFC. Left DLPFC may play a critical role in the development of phonological awareness for spoken language critical for reading and in the etiology of dyslexia.

Impairments in speech and nonspeech sound categorization in children with dyslexia are driven by temporal processing difficulties.

Auditory processing problems in persons with dyslexia are still subject to debate, and one central issue concerns the specific nature of the deficit. In particular, it is questioned whether the deficit is specific to speech and/or specific to temporal processing. To resolve this issue, a categorical perception identification task was administered in thirteen 11-year old dyslexic readers and 25 matched normal readers using 4 sound continua: (1) a speech contrast exploiting temporal cues (/bA/-/dA/), (2) a speech contrast defined by nontemporal spectral cues (/u/-/y/), (3) a nonspeech temporal contrast (spectrally rotated/bA/-/da/), and (4) a nonspeech nontemporal contrast (spectrally rotated/u/-/y/). Results indicate that children with dyslexia are less consistent in classifying speech and nonspeech sounds on the basis of rapidly changing (i.e., temporal) information whereas they are unimpaired in steady-state speech and nonspeech sounds. The deficit is thus restricted to categorizing sounds on the basis of temporal cues and is independent of the speech status of the stimuli. The finding of a temporal-specific but not speech-specific deficit in children with dyslexia is in line with findings obtained in adults using the same paradigm (Vandermosten et al., 2010, Proceedings of the National Academy of Sciences of the United States of America, 107: 10389-10394). Comparison of the child and adult data indicates that the consistency of categorization considerably improves between late childhood and adulthood, particularly for the continua with temporal cues. Dyslexic and normal readers show a similar developmental progress with the dyslexic readers lagging behind both in late childhood and in adulthood.

Transtorno do processamento auditivo (central) em indivíduos com e sem dislexia / (Central) auditory processing disorders in individuals with and without dyslexia

TEMA: comparação do transtorno do processamento auditivo (central) em indivíduos com e sem dislexia. OBJETIVO: comparar o transtorno do processamento auditivo (central) em crianças brasileiras com e sem dislexia, por meio dos testes fala com ruído, dicótico de dígitos e padrão de freqüência. MÉTODO: foram avaliadas 40 crianças de 7:0 a 12:11 anos, sendo 20 pertencentes ao grupo com dislexia e 20 pertencentes ao grupo TPA(C). Os testes aplicados envolveram habilidades de fechamento auditivo, figura-fundo para sons lingüísticos e ordenação temporal. RESULTADOS: os indivíduos do grupo TPA (C) apresentaram maior probabilidade de alteração nos testes de fala com ruído e dicótico de dígitos do que os pertencentes ao grupo dislexia. CONCLUSÃO: os sujeitos do grupo dislexia apresentam padrões diferentes de transtorno de processamento auditivo (central), com alteração maior em testes que avaliam o processamento temporal do que em testes que avaliam outras habilidades auditivas.

BACKGROUND: comparison of (central) auditory processing disorders in children with and without dyslexia. AIM: to compare the (central) auditory processing disorders in Brazilian children with and without dyslexia using speech in noise, dichotic digits and pattern of frequency tests. METHOD: forty-five children with ages ranging between 7:0 and 12:11 years were assessed; twenty children composed the dyslexic group and twenty composed the (Central) auditory processing disorder group. The tests used involved closing aural, auditory figure-ground and temporal ordering abilities. RESULTS: individuals of the (Central) auditory processing disorder group presented a higher alteration probability in the speech in noise and dichotic digits tests than those from the dyslexic group. CONCLUSION: subjects from the dyslexic group presented different patterns of (central) auditory processing disorder, with greater alteration in the tests that evaluate the temporal processing when compared to the tests that evaluate other auditory abilities.

Behavioral and ERP evidence for amodal sluggish attentional shifting in developmental dyslexia.

The goal of this study was to examine the claim that amodal deficits in attentional shifting may be the source of reading acquisition disorders in phonological developmental dyslexia (sluggish attentional shifting, SAS, theory, Hari & Renvall, 2001). We investigated automatic attentional shifting in the auditory and visual modalities in 13 dyslexic young adults with a phonological awareness deficit and 13 control participants, matched for cognitive abilities, using both behavioral and ERP measures. We tested automatic attentional shifting using a stream segregation task (perception of rapid succession of visual and auditory stimuli as one or two streams). Results of Experiment 1(behavioral) suggested that in order to process two successive stimuli separately dyslexic participants required a significantly longer inter-stimulus interval than controls regardless of sensory modality. In Experiment 2 (ERPs), the same participants were tested by means of an auditory and a visual oddball tasks involving variations in the tempo of the same alternating stimuli as Experiment 1. P3b amplitudes elicited by deviant tempos were differently modulated between groups, supporting predictions made on the basis of observations in Experiment 1. Overall, these results support the hypothesis that SAS in dyslexic participants might be responsible for their atypical perception of rapid sequential stimulus sequences in both the auditory and the visual modalities. Furthermore, these results bring new evidence supporting the link between amodal SAS and the phonological impairment in developmental dyslexia.

Implicit phonological and semantic processing in children with developmental dyslexia: evidence from event-related potentials.

Dyslexia is characterized by a core phonological deficit, although recent studies indicate that semantic impairment also contributes to this condition. In this study, event-related potentials (ERP) were used to examine whether the N400 wave in dyslexic children is modulated by phonological or semantic priming, similarly to age-matched controls. ERPs were recorded while children listened to word lists in which the semantic and phonological congruency of the terminal words were manipulated. No overt judgments were made by participants. In control children the N400 amplitude to both semantically and phonologically incongruent words was enlarged relative to congruent words. Dyslexic children exhibited a dissociation of priming effects depending on whether semantic or phonological primes were used. Semantic priming elicited an N400 effect comparable to controls, though delayed. In phonological priming, the dyslexics differed from controls in both the phonologically incongruent and congruent conditions showing reduced N400 amplitude in the former and enhanced N400 in the latter. This pattern suggests that when faced with phonological priming, dyslexics show abnormal neural responses related to both integration of similarities between the consecutive stimuli and the ability to detect incongruent stimuli. Semantic priming seems relatively intact in dyslexics, however neural responses to contextual incongruency are delayed.

Multisensory spatial attention deficits are predictive of phonological decoding skills in developmental dyslexia.

Although the dominant approach posits that developmental dyslexia arises from deficits in systems that are exclusively linguistic in nature (i.e., phonological deficit theory), dyslexics show a variety of lower level deficits in sensory and attentional processing. Although their link to the reading disorder remains contentious, recent empirical and computational studies suggest that spatial attention plays an important role in phonological decoding. The present behavioral study investigated exogenous spatial attention in dyslexic children and matched controls by measuring RTs to visual and auditory stimuli in cued-detection tasks. Dyslexics with poor nonword decoding accuracy showed a slower time course of visual and auditory (multisensory) spatial attention compared with both chronological age and reading level controls as well as compared with dyslexics with slow but accurate nonword decoding. Individual differences in the time course of multisensory spatial attention accounted for 31% of unique variance in the nonword reading performance of the entire dyslexic sample after controlling for age, IQ, and phonological skills. The present study suggests that multisensory "sluggish attention shifting"-related to a temporoparietal dysfunction-selectively impairs the sublexical mechanisms that are critical for reading development. These findings may offer a new approach for early identification and remediation of developmental dyslexia.

(Central) auditory processing disorders in individuals with and without dyslexia.

BACKGROUND: Comparison of (central) auditory processing disorders in children with and without dyslexia. AIM: To compare the (central) auditory processing disorders in Brazilian children with and without dyslexia using speech in noise, dichotic digits and pattern of frequency tests. METHOD: Forty-five children with ages ranging between 7:0 and 12:11 years were assessed; twenty children composed the dyslexic group and twenty composed the (Central) auditory processing disorder group. The tests used involved closing aural, auditory figure-ground and temporal ordering abilities. RESULTS: Individuals of the (Central) auditory processing disorder group presented a higher alteration probability in the speech in noise and dichotic digits tests than those from the dyslexic group. CONCLUSION: Subjects from the dyslexic group presented different patterns of (central) auditory processing disorder, with greater alteration in the tests that evaluate the temporal processing when compared to the tests that evaluate other auditory abilities.