Investigating which processes influence reading fluency in dyslexic and non-dyslexic groups

This thesis reports an investigation of the component processes underlying reading fluency. A current controversy in reading research is whether reading ability and development is determined solely by linguistic processes such as phonological (sound-based) skill, or whether it can also be influenced by non-linguistic processes such as visual processing of print, attention and general timing capacity. One way of addressing this problem is to investigate naming speed; the speed with which objects, colours, letters or digits can be named. Letter naming in particular represents a ‘microcosm’ of the processes required for fluent reading. The experiments in this thesis systematically manipulate the letter naming process to investigate a) what determines naming-speed performance and b) which processes, when aberrant, cause slower naming in dyslexic readers. Results suggest that non-dyslexic readers are better able to process multiple letter items simultaneously than dyslexic readers. Further, we find evidence suggesting a strong role for phonological retrieval in determining naming latencies and contributing to the naming-speed deficit. We also identify a strong attentional component and a role for visual processing in naming speed which discriminates dyslexic and non-dyslexic reading groups. The results support models emphasising the multi-componential nature of reading fluency and suggest that naming deficits in dyslexia reflect processing difficulties in non-phonological, as well as phonological domains

Literacy development in children with cerebral palsy

This thesis concerns the literacy difficulties of fifteen children with cerebral palsy (CP). The children were an opportunistic sample from two schools, and were initially selected on the basis that they had typical abilities in other school subjects. A review of the literature pertaining to the development of literacy and related aspects of cognitive development in typically-developing children and children with CP informed the development of the research strategy. The children's literacy, their general non-verbal and communication abilities, as well as a set of cognitive abilities that could be related to literacy impairments, were assessed. The findings revealed that most, but not all, of the children with CP had literacy difficulties with low scores in reading and spelling, and all the children had problems with handwriting. Standardised assessments showed that while the children had good verbal abilities, they had very low scores on a non-verbal test. The children with the most severe literacy difficulties also had the most problems with phonological processing. Almost all of the children had difficulties with visual and spatial perception; however the better readers had typical results in an assessment of visual sequential memory. Tests of working memory (WM) revealed a clear division between typical levels of performance on verbal recall measures, and very poor performance on the visual components of working memory tests. There were mixed results for the assessment of the central executive, but generally those children who were the more able in literacy had higher scores. Correlations suggested that visual sequential memory; phonological segmentation; verbal recall; and aspects of the central executive of working memory were most closely associated with the children's literacy abilities. Thus, the findings indicate that children with CP ha,ve specific cognitive impairments, including a new suggestion that poor visual sequential memory abilities could delay the development of reading and spelling skills

The brain beating and heart breathing: a unifying theory of the neuro- cardiac- respiratory control in infant and adult sudden unexpected deaths

Background: Sudden Infant Death Syndrome (SIDS) is characterized by the death of an infant that cannot be explained, despite a systematic case examination, including death scene investigation, autopsy and review of the clinical history. Nowadays, Sudden Unexpected Infant Death (SUID) is a wide-ranging concept used to describe any sudden and unexpected death, whether explained or unexplained, including SIDS, which occurs during the first year of life. Several differing and sometimes contradictory hypotheses of the underlying mechanisms of SIDS have been proposed. The most reliable seems to be the “triple risk hypothesis”. Based on this theory, unexpected infant deaths might arise as a consequence of the combination of three factors coming together: a vulnerable infant, a vulnerable phase of development and a final insult occurring in this window of vulnerability. Recently, a unified neuropathological theory contributes to describing SIDS. According to this, serotonergic neurons play a crucial homeostatic function in the cardiorespiratory brainstem centres. A high incidence of morphological abnormalities and biochemical defects of serotoninergic neurotransmission have been reported in the brainstem of SIDS victims. This brain region includes the main nuclei and structures that coordinate the vital activities, such as cardiovascular function and breathing, perinatal and after birth. Nevertheless, evidence suggests likely genomic complexity and a degree of overlap among SIDS, Sudden Intrauterine Death (SIUD), Sudden Cardiac Death (SCD) and Sudden Unexpected Death in Epilepsy (SUDEP). In SUDEP, which has clinical parallels with SIDS, alterations to medullary serotoninergic neural populations and autonomic dysregulation have been shown too. Molecular profiling of SUDEP cases and the investigation of genetic models have directed to the identification of putative SUDEP genes of which most are ion channel active along the neurocardiac, neuroautonomic, and neurorespiratory pathway. Concurrently, anomalous time- activation, transcription or regional expression of candidate neuro-cardiac-respiratory genes implicated for SUDEP, could be similarly involved in other unexpected sudden deaths. A small but significant proportion of infants who die suddenly and unexpectedly have been shown on postmortem genetic testing to have Developmental Serotonopathies, Cardiac Channelopathies and Autonomic Nervous System Dysregulation, with considerable implications for surviving and future family members. This has led to the demonstration that neuro-cardiac genes are expressed in both tissues (brain and heart) and recently in the respiratory system. Aim: Despite their decreasing incidence, SIDS and SUDEP are still important causes of death. There are many nuclei in the cardio and respiratory centres of the brain involved in unexpected and sudden deaths. Cardiac, sympathetic, and respiratory motor activities can be viewed as a unified rhythm controlled by brainstem neural circuits for effective and efficient gas exchange. We aim to describe abnormalities in these nuclei, in part because robust molecular or functional examination of these nuclei has not been carefully performed. We intend to perform detailed functional mapping of these brainstem nuclei. Specifically, the cardiorespiratory and cardioventilatory coupling can be understood as a unified vital rhythm controlled by brainstem neural circuits. By cardiorespiratory coupling, we mean the Respiratory Sinus Arrhythmia (RSA) that is characterized by a heart rate (HR) increasing during inspiration and an HR decrease during expiration. Conversely, Cardioventilatory coupling (CVC) is considered the influence of heartbeats and arterial pulse pressure on respiration with the tendency for the next inspiration to start at a preferred latency after the last heartbeat in expiration. We hypothesized that these two reflex systems are not separate, but constitute an integrated network. We defined this last concept as "unifying theory". By studying all the maps of the cardiorespiratory nuclei of the Literature, we integrated this concept into a reworking map of brainstem nuclei that could also explain the gasping and blocking cardiorespiratory of sudden deaths. The theory of a unique, unifying cardiorespiratory network, it has been recently demonstrated in some cases of arrhythmia, in some cases of SUDEP with striking systolic hypotensive changes and in some cases of SIDS too. Material and Methods: We investigated articles, reviews indexed in PubMed describing putative neuro-cardiac-respiratory genes and cardiorespiratory, and cardioventilatory coupling theories. Specifically, we evaluated cardiorespiratory brainstem nuclei and whole brains of fetal, infant and adult autopsies respectively to detect congenital errors in the cerebral development or malformations, but also to identify the “normal” or “dysplastic” brainstem centres. Results: Based on the Literature, we identified a brain-heart gene mapping and a scheme of cardiorespiratory brainstem nuclei network. Contemporary, we collected a large pool of fetal brain malformations and cardiorespiratory nuclei dysgenesis both in infants both in adult sudden deaths. We found dysgenesia, agenesia and hypoplasia of brainstem nuclei associated with SIDS cases, compared with post-mortem infant control cases. However, the arcuate nucleus showed insignificant inter-variations regarding adults autoptic cases. Discussion: Many intrinsic and extrinsic factors increase fetal, perinatal, infant, and adult sudden death susceptibility. The final common pathway for SIDS and SUDEP involves a failure to arouse and autoresuscitate in response to environmental challenge. The different risk factors, among these a prone position, can directly alter the function of cardiorespiratory nuclei and impair the ability of this network to coordinate cardiorespiratory–cardioventilatory coupling. Conclusions: Neuropathological analysis of the infant brainstem and neuro-cardiac-respiratory gene mapping represents a good tool to infer on the final events of SIDS and SUDEP, although nothing it is clear regarding the role of adult cardiorespiratory centres. An integrated study of postmortem neuropathology and molecular autopsies could help to understand the network of this beating-breathing-thinking unit

Down Syndrome

Down syndrome (DS), caused by the triplication of chromosome 21, is the most common genetic cause of intellectual disability (ID). Individuals with DS commonly exhibit unique neuropsychological profiles that emerge during specific developmental stages across the lifespan, often characterized by early developmental delay, cognitive strengths and weaknesses, behavior and mental health issues, and age-related cognitive decline, frequently resulting in early-onset Alzheimer’s disease. These profiles are unique compared to other individuals with ID and reflect the genetic mechanisms and neuroanatomic features underlying the distinct neuropsychological phenotype associated with DS. This Special Issue aims to highlight the recent advancements in understanding the neuropsychological phenotype associated with DS across the lifespan. The lifespan perspective will cover four developmental stages: (1) early childhood; (2) school age; (3) young adulthood, and (4) older adulthood. Authors contributed cutting-edge original research studies and comprehensive reviews that address a broad range of topics related to DS, including early developmental trajectories, cognitive functioning, language, adaptive skills, behavior and mental health, assessment and diagnosis, age-related cognitive decline, and medical issues related to the neuropsychological phenotype and neuroimaging

Cognitive and linguistic predictors of literacy in Namibian Herero-English bilingual school children

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Towards cerebral and behavioral representations of motor learning and its interaction with interference and sleep

Das Lernen neuer Bewegungen spielt eine fundamentale Rolle in der Natur. Menschliche Bewegungen sind in der Regel sehr komplex, auch wenn es auf den ersten Blick nicht so erscheint. Die meisten dieser komplexen Bewegungen werden im Laufe des Lebens erlernt und erfordern somit eine Lernfähigkeit des Individuums. Wie diese motorischen Lernprozesse funktionieren, ist im Detail bisher nicht bekannt. Dennoch ist ein tieferes Verständnis dieser Prozesse notwendig, um Trainingsprotokolle in der Rehabilitation oder im Sport zu verbessern. In der wissenschaftlichen Literatur liegen zahlreiche Befunde vor, die darauf hindeuten. dass Interferenzen im Üben einen Einfluss auf die spätere Gedächtnisleistung und somit die Konsolidierung haben. Solche Einflüsse können sowohl positiv als auch negativ sein, in Abhängigkeit davon, ob Interferenzen während des Übens oder aber in unterschiedlichen Übungseinheiten mit entgegengesetzten kinematischen oder dynamischen Bedingungen stattfinden. Die neuronalen Mechanismen, die entweder zu einem Vorteil oder einen Nachteil führen, sind bisher unbekannt. Das Ziel dieser Dissertationsschrift war es deshalb, in drei empirischen Arbeiten die neuronalen Grundlagen zu untersuchen, die entweder positive oder negative Effekte nach einem interferenzhaltigen Üben hervorrufen. Dabei wurde neben der motorischen Adaptation an Kraftfeldbedingungen auch das Elektroenzephalogramm (EEG) aufgezeichnet. Die erste Studie untersuchte, ob sehr instabile im Vergleich zu eher stabilen Übungsbedingungen zu einer besseren Konsolidierungsleistung führten. Dieses Phänomen, welches bereits als Kontextinterferenzeffekt bekannt ist, konnte hier mit einer motorischen Adaptationsaufgabe an veränderte dynamische Bedingungen bestätigt werden. Zusätzliche EEG-Analysen zeigten, dass diese positiven Effekte auf der Verhaltensebene mit Veränderungen in den Alpha-Frequenzen des parietalen Kortex in Verbindung zu stehen scheinen. Tiefgreifende Analysen deuten an, dass die positiven Befunde variablen Übens durch effektive Korrekturen auf Grund von Feedbackmechanismen hervorgerufen wurden. Jedoch sind zukünftige Studien notwendig, um diese Annahme zu bestätigen. Die Befunde aus der ersten Studie konnten auch in der zweiten Studie dieser Dissertationsschrift reproduziert werden. Zusätzlich wurde in dieser zweiten Studie untersucht, ob Schlaf einen Einfluss auf die Konsolidierungsfähigkeit einer Kraftfeldadaptationsaufgabe hat und ob solch ein Einfluss durch instabile Übungsbedingungen beeinflusst wird. Dazu wurden drei unterschiedliche Methoden kombiniert, nämlich: das Kraftfeldparadigma, das EEG und das Polysomnogramm. Die Ergebnisse zeigten keinen Hinweis auf einen Schlafeffekt, unabhängig von den Übungsbedingungen. Dennoch konnte im Polysomnogramm eine erhöhte Spindelaktivität in den niedrigen Frequenzbändern gefunden werden, welche mit der motorischen Leistung korrelierte. Die dritte Studie untersuchte, ob eine separate Übungseinheit, 24 Stunden nach der ersten Übungseinheit, einen negativen Einfluss auf den Wiederabruf der motorischen Aufgabe hat. Dabei bestand die Interferenz darin, dass das zu adaptierende Kraftfeld in der separaten Übungseinheit dem Kraftfeld der ersten Übungseinheit räumlich entgegengesetzt war. Dieses so genannte \u27ABA\u27 Paradigma führte zu einer verringerten motorischen Leistung im Wiederabruf der Aufgabe aus der ersten Übungseinheit, verglichen mit einer Kontrollgruppe, die keine separate Übungseinheit hatte. Die vergleichsweise bessere Leistung der Kontrollgruppe beim Wiederabruf trat zusammen mit einer erhöhten Leistung der Gamma-Frequenzen im EEG über frontalen Gehirnarealen auf. Dieser Effekt war jedoch nur von kurzer Dauer und verringerte sich während der Nachtestung. Insgesamt konnte diese Dissertationsschrift zeigen, dass EEG Aufnahmen während motorischer Adaptationsaufgaben an Robotermanipulanda möglich sind. Hohe Interferenzen während der Übungseinheit können einen positiven Einfluss auf die Konsolidierungsleistung haben, welche mit den Alpha-Frequenzen über parietalen Gehirnarealen in Verbindung steht. Es ist möglich, dass die positiven Befunde auf der Verhaltensebene durch Feedback-Korrekturmaßnahmen während der Bewegungsdurchführung hervorgerufen wurden. Außerdem konnte die zweite Studie zeigen, dass die Leistung im EEG Alpha Band die behaviorale Konsolidierungsleistung prädizieren kann, sofern das Üben unter eher stabilen Bedingungen stattfand. Wenn Interferenzen jedoch durch unterschiedliche Übungseinheiten mit gegen-sätzlichen Kraftfeldrichtung hervorgerufen werden, verringert diese Interferenz die motorische Leistung beim Wiederabruf. Dieser verringerte Wiederabruf fällt jedoch weniger stark aus, wenn das Üben mittels eingestreuter \u27catch trials\u27 variabler gestaltet wird. Somit scheint die Konsolidierung motorischer Erinnerungen nicht nur auf den Faktor \u27Zeit\u27 zu beruhen. Unterschiedliche Resultate ähnlicher Studien lassen vermuten, dass \u27Zeit\u27, aber nicht \u27Schlaf\u27, ein wichtiger Faktor für die Konsolidierung von Adaptationsaufgabe darstellt, es jedoch noch weitere Faktoren wie zum Beispiel die Übungsvariabilität gibt, die den uneinheitlichen Forschungsstand hervorrufen

Procedural and declarative memory and language ability in children

Impaired procedural learning has been suggested as a possible cause of developmental language disorder and dyslexia (Nicolson & Fawcett, 2007; Ullman & Pierpont, 2005). However, studies investigating this hypothesis have so far delivered inconsistent results. These studies typically use extreme group designs, frequently with small sample sizes and measures of procedural learning with unreported reliability. This thesis first used a meta-analysis to examine the existing evidence for a procedural deficit in language disorders. The experimental studies then took a different approach to previous studies, using a concurrent correlational design to test large samples of children unselected for ability on a wide range of implicit (serial reaction time, Hebb serial learning, contextual cueing and probabilistic category learning) and declarative learning tasks and literacy, language and arithmetic attainment measures. The reliability of the tasks was also carefully assessed. A final study explored the hypothesis from an extreme group design perspective, comparing a typically developing sample with a group of dyslexic children matched for reading ability. None of the studies found evidence of a relationship between procedural learning and language-related abilities. By contrast, a relationship between verbal declarative learning and attainment was found replicating earlier studies. Crucially, the first large-scale study showed that procedural learning tasks of a similar length to those typically used in earlier studies had unacceptably low reliability and correlated poorly with each other and with attainment. The second large-scale study, used extended procedural learning tasks that had proved reliable in adults, but found similar low levels of reliability in children. Additionally, the level of attention children paid during these extended tasks accounted entirely for the relationship between procedural learning and attainment. The results in this thesis highlight the importance of establishing task reliability, as well as considering the potential effects of individual differences in basic cognitive processes such as attention in all investigations of procedural learning

Sensory processing in children and adults with learning difficulties

Sensory processing refers to the ability to register and modulate sensory information in order to enable and learn adaptive responses to the environment and facilitate engagement in daily activities, and it depends on the maturation of the nervous system. Previous studies have indicated failures in sensory processing in neurodevelopmental disorders, however, the characteristics and extent of such problems are not clear with respect to other learning difficulties due to inconsistent literature, lack of systematic approaches, and a strong emphasis on phonological processing alone. Four studies were designed to compare sensory processing profile of participants with and without learning difficulties, using Dunn’s framework (1997) of four quadrants: Registration, Seeking, Avoiding and Sensitivity. Study 1 investigated the relationship between multisensory processing and literacy skills in children. Study 2 investigated sensory profile and learning difficulties in adolescents. Study 3 investigated sensory profile and its association with reading difficulties in adults. Study 4 focused on children and comorbidity as a variable that may influence the sensory profile. Results identified clear differences in the sensory profile between groups with and without learning difficulties. Accordingly, children with learning difficulties would present a profile of high frequency of sensory-related behaviours which is widespread across the sensory dimensions, while adults would have high frequency of such behaviours in only one quadrant of the sensory profile. Regression analyses showed that Registration (a profile of high neurological threshold and passive regulation) predicts the likelihood of presenting learning difficulties at all ages. Furthermore, low scores in Seeking (lack of active behaviours) were associated with learning difficulties in children. The findings suggest an atypical frequency of sensory-related behaviours associated with a range of learning difficulties. Future research should assess the sensory abilities across the ages, including performance in cross-modal tasks, and the use of neuroimaging techniques to obtain more insights of brain functioning