Early cognitive neuropsychological profiles and development of reading skills

The present thesis sought to investigate the precise relationship between the cognitive and psychophysiological profiles of developing readers, of established readers and of failed readers. Phonological processing tasks and visuospatial tasks were used to assess relevant auditory and visual cognitive skills; handedness and EEG measures were used to provide indices of cortical organisation and activation. A 21/2 year longitudinal investigation of some 150 pre-readers provided evidence of mutually facilitative relationships between and within specific types of phonological skill and phonological memory. Early significance of visual skills was subsequently superseded by the importance of these phonological skills. The acquisition of early reading skills was associated with a shift towards increased dextrality as measured by hand skill and hand preference; this relationship was not evident in subsequent stages. Cross-sectional studies comparing dyslexic children with chronological- and reading-age matched controls extended these findings. The dyslexic readers displayed impaired phonological processing and phonological memory skills relative to chronological-age matched competent readers; similarities were observed between dyslexics and reading-age matched controls. Visual perceptual skills failed to differentiate between the chronological-age matched competent and impaired readers, although both out-performed younger control readers. ERP measures consistently demonstrated diffuse patterns of bilateral activation in dyslexic readers as opposed to asymmetric activity lateralised to the left hemisphere in control readers. Between group comparisons of inter-hemispheric activity revealed greater levels of right-hemisphere involvement in the dyslexic samples; between group comparisons of intra-hemispheric activity revealed evidence of greater involvement of fronto-central regions in the dyslexic samples. It is proposed that these data provide supportive evidence for the central involvement of phonological processing skills in the development of reading, underpinned by the normal development of asymmetric patterns of cortical lateralisation. Children where this development is delayed or deficient will display the reading difficulties characteristic of developmental dyslexia

Convergent and divergent fMRI responses in children and adults to increasing language production demands

In adults, patterns of neural activation associated with perhaps the most basic language skill—overt object naming—are extensively modulated by the psycholinguistic and visual complexity of the stimuli. Do children's brains react similarly when confronted with increasing processing demands, or they solve this problem in a different way? Here we scanned 37 children aged 7–13 and 19 young adults who performed a well-normed picture-naming task with 3 levels of difficulty. While neural organization for naming was largely similar in childhood and adulthood, adults had greater activation in all naming conditions over inferior temporal gyri and superior temporal gyri/supramarginal gyri. Manipulating naming complexity affected adults and children quite differently: neural activation, especially over the dorsolateral prefrontal cortex, showed complexity-dependent increases in adults, but complexity-dependent decreases in children. These represent fundamentally different responses to the linguistic and conceptual challenges of a simple naming task that makes no demands on literacy or metalinguistics. We discuss how these neural differences might result from different cognitive strategies used by adults and children during lexical retrieval/production as well as developmental changes in brain structure and functional connectivity

Visual dysfunction : a contributing factor in memory deficits, and therefore learning difficulties?

This thesis is based on Educational Therapy (ET) practice which has found eye muscle imbalance is a key factor to be addressed in management of learning difficulties (LD). This level of oculo-motor (o-m) function is a \u27hidden\u27 handicap as individuals are unaware of the problem; it is not routinely tested; and is not generally included in learning difficulties research. O-m function is omitted in standard paediatric optometry tests, and in school vision screening. Eye exercises increase the range of binocular fields of vision by employing stereopsis glasses and red/green slides. Central vision loss was uncovered when students reported words, seen by only the right eye, disappear or switch on and off . When the left eye was covered, right eye vision returned but was lost again with binocular vision, even though larger shapes on the screen remained complete. In effect, global vision was unaffected while right eye central (foveal) vision was suppressed. This is considered significant because students attending ET have learning difficulties with phonemic memory, spelling and reading deficits, which are predominantly left hemisphere processes. The aim of this three-part study, consisting of School Survey, ET Intervention study and Case studies, was to: a) determine whether o-m dysfunction was found in a girls\u27 school population and/or was associated with LD; b) set up an Intervention study to explore the effects of vision training on the outcomes of a subsequent week-long word-skills programme in the ET practice. Two case studies we\u27re also examined, that of matched senior school boys whose outcomes were significantly different; and c) examine more closely the common pattern of muscle imbalance in two case studies of current junior school students. This tested the therapy assumption that mal-adaptive sensory feedback was contributing to o-m dysfunction. This notion is based on the Luria (1973) Model of Levels of Neural Function which provides the framework for ET practice, and the Developmental Model of LD that has evolved in application and explanation. Part 1 School Survey. This exploratory, cross-sectional study included a randomised sample of 277 participants in a private girl\u27s school. A 7-10 minute screening was provided by five optometrists, with an expanded protocol including o-m function. Also assessed were academic standards of reading comprehension and spelling, reasoning, visual perception, phonological skills, auditory, visual and phonemic memory, and arm dominance. Results showed visual dysfunction and mixed eye dominance in approximately equal numbers. Of the 47% girls with visual dysfunction, not all had literacy problems; however, LD students had corresponding degrees of o-m dysfunction, memory deficit and mixed hand / arm dominance. Part 2 Intervention study. The Research Question for the Intervention Study was: Does the difference in learning standards depend on which eye is disadvantaged in the case of weak binocularity? This question was answered by determining the outcomes to literacy levels once normal binocular o-m function and stable eye dominance were established. Twenty-four students (6 to 18 years) had Behavioural Optometry assessment prior to commencing therapy and were found to have o-m dysfunction, undetected by previous standard optometry tests. Eye exercise results showed 62.5% of the group had changed from left to right eye dominance. The dominance criterion was set by this group, indicated by the right eye holding fixation through full range of fusional reserves (binocular overlap), together with superior eye-tracking speed \u3e20% by the right, compared to the left, eye. Associated significant gains in literacy and phonemic memory were also achieved by the newly established \u27right-eyed\u27 group. In spite of undergoing identical treatment, the \u27left-eyed\u27 group retained limited foveal binocularity, and made less progress in literacy outcomes. Part 3 Two current Case Studies. Present ET practice benefited from insights gained from the 36% \u27unsuccessful\u27 participants of the previous study. Better therapy outcomes are achieved from an integrative motor-sensory approach, supported by Podiatry and Cranial Osteopathy. This detailed study involved two junior school boys who exemplified a common pattern of physical anomalies. For example, RW (8-year old male) had \u27minimal brain damage\u27 and LD that co-occur with unstable feet and o-m control, postural muscle imbalance, poor balance, motor co-ordination and dyspraxia. After 18, two-hour therapy sessions over nine months, he is now reading well, his motor co-ordination, eye tracking and writing are within the ‘low normal range’, and he is interacting competently with his peers. Learning difficulties can be conceptualised as a profile of immaturities. The results of this three part study have shown that once the \u27hidden\u27 handicap of right eye suppression is overcome with balanced binocular fields of vision, learning difficulties arc ameliorated. This is affirmed by the positive gains achieved by these students, not only in literacy skills but also \u27outgrowing\u27 immaturity in motor-sensory-perceptual development

Functional and structural connectivity of reading networks in the adult brain

Language processing draws upon many distributed regions in the brain. Reading in particular is a skill that emerges from the interaction between brain regions involved in phonological and orthographical processing. This project examined the reading network in adults (18-35 years old) with and without developmental dyslexia. Each participant was assessed on a comprehensive battery of standardised neuropsychological tests, which assessed IQ, reading accuracy and comprehension, spelling, phonological processing, working memory, grammatical understanding, motor coordination, and expressive and receptive language skills. In addition, each participant underwent a non-invasive MRI scan, during which structural and functional images were acquired. More specifically, T1-weighted and diffusion-weighted images were acquired to assess structural networks in the brain, whereas a simple reading task and resting-state fMRI were acquired to assess the functional networks involved in reading. Individuals with dyslexia were found to show reduced activation and reduced connectivity in regions typically associated with skilled reading. Moreover, results suggested that they rely on more effortful processing and attentional mechanisms instead to compensate for their reading difficulties. All in all, results indicated that individuals with developmental dyslexia had abnormal functional and structural brain networks related to reading performance, as well as other functions, such as working memory. These findings suggest that for successful reading remediation, it is important to focus on the integration of phonology with orthography, as well as with working memory. Literacy problems such as developmental dyslexia are thus better characterised as a complex disorder with multiple deficits rather than by a single phonological deficit