The significance of visual information processing in reading: Insights from hemianopic dyslexia

Department of Psychology, University of Durham, UK.
Neuropsychologia (Impact Factor: 3.3). 02/2008; 46(10):2445-62. DOI: 10.1016/j.neuropsychologia.2008.04.016
Source: PubMed


We present the first comprehensive review of research into hemianopic dyslexia since Mauthner's original description of 1881. We offer an explanation of the reading impairment in patients with unilateral homonymous visual field disorders and clarify its functional and anatomical bases. The major focus of our review is on visual information processing, visuospatial attention and eye-movement control during reading. An advanced understanding of the basis of hemianopic dyslexia and its rehabilitation also increases our knowledge about normal reading and its underlying neural mechanisms. By drawing together various sources of evidence we illustrate the significance of bottom-up and attentional top-down control of visual information processing and saccadic eye-movements in reading. Reading depends critically on the cortical-subcortical network subserving the integration of visual, attentional and oculomotor processes involved in text processing.

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Available from: Josef Zihl, May 03, 2014
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    • ") amongst others have also shown that visual search training does not translate to improved reading speed. Indeed, search strategies do not address the small, step-wise eye scanning or specific part of the visual field that is required to read left-to-right text (Zihl 1995, see Schuett 2008 for review). Hemianopic alexia is an important consequence of hemianopia and can be particularly debilitating. "
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    ABSTRACT: Homonymous visual field loss is a common consequence of stroke and traumatic brain injury. It is associated with an adverse functional prognosis and has implications on day-to-day activities such as driving, reading, and safe navigation. Early recovery is expected in around half of cases, and may be associated with a return in V1 activity. In stable disease, recovery is unlikely beyond 3 and certainly 6 months. Rehabilitative approaches generally target three main areas, encompassing a range of techniques with variable success: visual aids aim to expand or relocate the affected visual field; eye movement training builds upon compensatory strategies to improve explorative saccades; visual field restitution aims to improve visual processing within the damaged field itself. All these approaches seem to offer modest improvements with repeated practice, with none clearly superior to the rest. However, a number of areas are demonstrating particular promise currently, including simple web-based training initiatives, and work on neuroimaging and learning. The research interest in this area is encouraging, and it is to be hoped that future trials can better untangle and control for the number of complicated confounds, so that we will be in a much better position to evaluate and select the most appropriate therapy for patients.
    Revue Neurologique 09/2012; 168(10):754-61. DOI:10.1016/j.neurol.2012.07.015 · 0.66 Impact Factor
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    • "Compensatory oculomotor training is based on relearning eye movement control with visual field loss, leading to substantial improvements in reading and visual exploration performance. It is possibly best understood as a substitution of the visual bottom–up control of visual information processing and eye movements for a (training-induced) attentional top– down control (Zihl, 1995a, b, 2011; Schuett et al., 2008a, b). Nonetheless, our study not only confirms earlier studies investigating the therapeutic effect of compensatory visual exploration training (Kerkhoff et al., 1992a, 1994; Zihl, 1995b, 2011; Nelles et al., 2001; Pambakian et al., 2004; Bolognini et al., 2005; Passamonti et al., 2009; Roth et al., 2009; Keller and Lefin-Rank, 2010; Lane et al., 2010; Mannan et al., 2010) and reading training (Kerkhoff et al., 1992b; Zihl, 1995a, 2011; Spitzyna et al., 2007; Schuett et al., 2008b). "
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    ABSTRACT: Reading and visual exploration impairments in unilateral homonymous visual field disorders are frequent and disabling consequences of acquired brain injury. Compensatory therapies have been developed, which allow patients to regain sufficient reading and visual exploration performance through systematic oculomotor training. However, it is still unclear whether the reading and visual exploration impairments require specific compensatory training for their improvement. We present the first cross-over rehabilitation study to determine whether the training-related performance improvements are task-specific, or whether there is a transfer of training-related improvements between reading and visual exploration. We compared the therapeutic effects of compensatory oculomotor reading and visual exploration training in 36 patients with unilateral homonymous visual field loss in a cross-over design. In addition, we explored whether the training sequence determines the overall treatment outcome. Our findings demonstrate that the training-related improvements in reading and visual exploration are highly specific and task-dependent, and there was no effect of training sequence.
    Brain 03/2012; 135(Pt 3):912-21. DOI:10.1093/brain/awr356 · 9.20 Impact Factor
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    • "Hemianopia is the most common field defect (loss of both monocular hemifields), followed by quadranopia (vision loss in the upper or lower quadrant), and paracentral scotoma (small island-like parafoveal field defect) (Zihl, 2000; Zhang et al., 2006). It is well-known that these patients show severe impairments of reading (Schuett et al., 2008) and visual exploration (Zihl, 2000). It is not well-known, however, that patients with unilateral homonymous hemianopia also frequently suffer from a persistent spatial distortion that is characterized by * Corresponding author. "

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