Neurology of developmental dyslexia

Department of Neurology, Beth Israel Hospital, Boston, Massachusetts.
Current Opinion in Neurobiology (Impact Factor: 6.77). 05/1993; 3(2):237-42. DOI: 10.1016/0959-4388(93)90216-L
Source: PubMed

ABSTRACT Developmental dyslexia was until recently considered to belong solely in the domain of educational psychology. With the advent of better theories on language and reading, and better methods for assessing the structure and function of living human brains and for determining genetic transmission, dyslexia is now poised to become a focal concern of cognitive neuroscience, neurology, and genetic research. Still unresolved are questions relating to how much a reading disability represents a normal variation or a separate pathological entity, and whether the cognitive disorder is primarily cognitive, or secondary to a disorder in early perception. Recent findings from neuroanatomy, neurophysiology, neuropsychology, and genetics research are reviewed. (This review is an updated version of a review first published in Current Opinion In Neurology and Neurosurgery 1992, 5:71-76.)

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Available from: Albert M Galaburda, Aug 18, 2015
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    • "Moreover, functional magnetic resonance imaging studies devoted to exploring visual processing abilities in individuals with DD revealed little activation in portions of the magnocellular visual system in response to the perception of subtle changes in motion (Eden et al., 1996). Irregular brain morphology has also been detected in regions associated with executive functions and in subcortical areas (Galaburda, 1993; Hynd et al., 1995; Riccio & Hynd, 1996). Finally, observations made with magnetic resonance spectroscopy (Rae et al., 1998), positron emission tomography (Nicolson et al., 1999) and "
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    ABSTRACT: The reduced verbal long-term memory capacities often reported in dyslexics are generally interpreted as a consequence of their deficit in phonological coding.The present study was aimed at evaluating whether the learning deficit exhibited by dyslexics was restricted only to the verbal component of the long-term memory abilities or also involved visual-object and visual-spatial domain. A further goal of the present study was to investigate the predictive value of non-verbal long-term memory abilities with respect to word and non-word reading in dyslexic children.In accordance with these aims, performances of 60 dyslexic children were compared with that of 65 age-matched normal readers on verbal, visual-spatial and visual-object task.Results documented a generalized impairment of episodic long-term memory capacities in dyslexic children and the results did not vary as a function of children's age.Furthermore, in addition to verbal measures, also individual differences in non-verbal long-term memory tasks turn out to be good predictors of reading difficulties in dyslexics.Our findings indicate that the long-term memory deficit in dyslexia is not limited to the dysfunction of phonological components but also involves visual-object and visual-spatial aspect, thus suggesting that dyslexia is associated to multiple cognitive deficits.
    Dyslexia 08/2010; 16(3):213-25. DOI:10.1002/dys.410 · 1.12 Impact Factor
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    • "The volume of visual area 17 in the rat is asymmetric across the hemispheres and this asymmetry is negatively correlated with the density of callosal terminations in this area (Rosen, Galaburda, & Sherman, 1990). One model postulates that brain symmetry is due to faulty pruning mechanisms that leave more interhemispheric connections and more neurons in the right perisylvian region (Galaburda, 1993, 1995). It may also result from abnormalities in neuron number caused by either increased progenitor proliferation or decreased normal developmental apoptosis that occurs during neurogenesis (Geschwind & Miller, 2001). "
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    ABSTRACT: The corpus callosum is the largest commissure in the brain and acts as a "bridge" of nerve fibres connecting the two cerebral hemispheres. It plays a crucial role in interhemispheric integration and is responsible for normal communication and cooperation between the two hemispheres. Evolutionary pressures guiding brain size are accompanied by reduced interhemispheric and enhanced intrahemispheric connectivity. Some lines of evidence suggest that the speed of transcallosal conduction is limited in large brains (e.g., in humans), thus favouring intrahemispheric processing and brain lateralisation. Patterns of directional symmetry/asymmetry of transcallosal transfer time may be related to the degree of brain lateralisation. Neural network modelling and electrophysiological studies on interhemispheric transmission provide data supporting this supposition.
    Laterality 09/2009; 16(1):35-74. DOI:10.1080/13576500903154231 · 1.13 Impact Factor
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    • "Converging findings indicate that both the dorsal component and the ventral component are impaired in dyslexia, which is functionally manifested by decreased activity. Evidence comes from functional neuroimaging studies (Brunswick et al., 1999; Paulescu et al., 2001; Shaywitz et al., 1998; Temple, 2002) as well as from anatomical accounts (Beaulieu et al., 2005; Gaillard et al., 2006; Galaburda, 1992; Klingberg et al., 2000; Niogi & McCandliss, 2006). To the contrary, activation in inferior frontal and right hemisphere posterior regions is heightened in reading-disabled individuals, relative to nonimpaired readers (Brunswick et al., 1999; Shaywitz et al., 2002). "
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    ABSTRACT: In this chapter we will engage in a theoretical quest for ways to ameliorate reading fluency in dyslexics. In the first section we will provide an overview of research on dyslexia and dyslexia treatment and we will discuss the limitations of traditional interventions to ameliorate the poor reading fluency of dyslexic children. In the second section of the chapter we will have a closer look on reading fluency, often referred to as the "neglected" aspect of reading. We will discuss the essential role of extensive reading experience in the development of reading fluency and focus on repeated reading, the most familiar and most researched approach to fluency training. A state of the art overview of insights from cognitive neuroscience, concerning fluent and disrupted reading, will be given in the third section of the chapter. In this light we will discuss cognitive, neurobiological and connectionist models on reading development and additionally focus on other areas of skill learning, such as chess. In the fourth section we will amalgamate the various insights, draw several conclusions regarding fluency-oriented instructional practices, and proposed some new directions for dyslexia treatment. Additionally, we will demonstrate the unique possibilities provided by edugames, or computer-game training, for the implementation of the proposed educational principles. As an example we will present an edugame, called LexyLink, which we developed in our own laboratory and which we are currently testing in our institute.
    Educational Psychology: Cognition and Learning, Individual Differences and Motivation, Edited by Larson, 01/2009: chapter 3: pages 115-143; Nova Science Publishers., ISBN: 978-1-60692-276-7
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