Vision and Attention. II: Is Visual Attention a Mechanism Through Which a Deficient Magnocellular Pathway Might Cause Reading Disability?

Steinman, Scott B.; Steinman, Barbara; Garzia, Ralph P.

doi:10.1097/00006324-199809000-00023

Cited by 46 publications

(36 citation statements)

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“…This finding was later used to test the hypothesis that transient visual attention might be the mechanism through which an Mpathway deficit could implicate visual impairments in dyslexia (Steinman et al, 1998). As predicted, adults with a reading disability were impaired on the line motion illusion task, suggested to be the manifestation of deficient transient attention.…”

Section: Attention Mechanisms In Readingmentioning

confidence: 87%

“…Indeed, a number of studies have demonstrated visual attention defects in dyslexia (Brannan and Williams, 1987;Casco et al, 1998;Facoetti et al, 2000;Omtzigt et al, 2002;Steinman et al, 1998;Vidyasagar and Pammer, 1999). Vidyasagar and Pammer (1999) proposed that if the M-system, leading to parietal cortex, is involved in gating all visual input going through striate cortex, then a deficit in this system would not only result in difficulties in the predicted M-type functions such as low contrast sensitivity at high temporal and low spatial frequencies, but also P-type functions normally attributed to the ventral stream.…”

Section: Attention Mechanisms In Readingmentioning

confidence: 99%

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Towards an understanding of the role of the ‘magnocellular advantage’ in fluent reading

Laycock

Crewther

2008

Neuroscience & Biobehavioral Reviews

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Section: Attention Mechanisms In Readingmentioning

confidence: 87%

Section: Attention Mechanisms In Readingmentioning

confidence: 99%

Towards an understanding of the role of the ‘magnocellular advantage’ in fluent reading

Laycock

Crewther

2008

Neuroscience & Biobehavioral Reviews

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“…At present, the mechanism by which impaired visual processing contributes to poor outcome is unknown, although the M pathway in particular contributes to processes that may be critical for real world function, such as object recognition (Doniger et al, 2002), motion processing (Chen et al, 1999), visual attention (Steinman et al, 1998;Vidyasagar, 1999) or reading (Cornelissen et al, 1998;Demb et al, 1998;Greatrex and Drasdo, 1995;Livingstone et al, 1991;Romani et al, 2001;Stein and Walsh, 1997). Alternatively, VEP components may simply serve as phenotypic markers for poor outcome forms of the disorder.…”

Section: Discussionmentioning

confidence: 99%

Impairments in generation of early-stage transient visual evoked potentials to magno- and parvocellular-selective stimuli in schizophrenia

Schechter

Butler

Zemon

et al. 2005

Clinical Neurophysiology

136

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Objective-Patients with schizophrenia demonstrate significant impairments of early visual processing, potentially implicating dysfunction of the magnocellular visual pathway. The present study evaluates transient visual evoked potential (tVEP) responses to stimuli biased toward the magnocellular (M) or parvocellular (P) systems in patients with schizophrenia vs. normal volunteers first to evaluate relative contributions of M and P systems to specific tVEP components in schizophrenia and, second, to evaluate integrity of early M and P processing in schizophrenia.Methods-Seventy-four patients with schizophrenia and schizoaffective disorder were compared with 59 control subjects using separate stimuli to assess the tVEP response to M, P and mixed M/P conditions. Stimuli were biased toward M vs. P processing by manipulation of chromatic and achromatic contrast. C1, P1, N1 and P2 components were compared between patients and controls. All subjects showed 20/32 vision or better.Results-Waveforms were obtained to low contrast (M), chromatic contrast (P) and high contrast (mixed M/P) stimuli in both patients and controls. C1 was present to P and mixed M/P stimuli. Patients showed a significant reduction in amplitude and an increase in latency of the C1 component. P1 was elicited primarily by M and mixed M/P stimuli, whereas N1 was elicited primarily by P and mixed M/P stimuli. Patients showed reductions in both P1 and N1 amplitudes across conditions. However, only reductions in P1 amplitude survived covariation for between group differences in visual acuity. Further, P1 amplitude reductions in the M condition correlated with a proxy measure of global outcome.Conclusions-M-and P-selective stimuli elicit differential components of the tVEP. Patients with schizophrenia show significant reductions in response even to simple visual stimuli. Deficits, particularly within the M system, may correlate significantly with global outcome and level of community functioning.Significance-Whereas deficits in high-order cognitive processing have been extensively documented in schizophrenia, integrity of early-stage sensory processing has been studied to a lesser degree. The present findings suggest that deficits in early-stage visual processing are significantly

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“…The interpretation of the assortment of visual processing difficulties identified in DD has resulted in at least two schools of thought: The first of these stems from research that has demonstrated that many dyslexic readers' visual processing skills are different from their peers: they are less sensitive than controls to dynamic visual stimuli, especially those of low contrast, low luminance, low spatial frequencies, and high temporal frequencies (Lovegrove et al, 1982;Lovegrove, Martin, & Slaghuis, 1986;Livingstone, Rosen, Drislane, & Galaburda, 1991;Mason, Cornelissen, Fowler, & Stein, 1993;Cornelissen, Richardson, Mason, & Stein, 1995) and they show reduced sensitivity to the coherent motion in random dot kinematograms (Cornelissen et al, 1995;Hansen, Stein, Orde, Winter, & Talcott, 2001;Pammer & Wheatley, 2001). In addition, performance differences between dyslexics and controls have been found for tasks that measure temporal and spatial properties of visual attention (Bouma & Legein, 1977;Brannan & Williams, 1987;Steinman, Steinman, & Garzia, 1998;Facoetti & Molteni, 2001). With some exceptions (Gross-Glenn et al, 1995;Walther-M .…”

Section: Mechanisms Of Visual Encoding and The Relation To Text Presementioning

confidence: 99%

Visual encoding mechanisms and their relationship to text presentation preference

Pammer¹,

Lavis²,

Cornelissen³

2004

Dyslexia

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This study was designed to investigate the importance of spatial encoding in reading, with particular emphasis on visuo-spatial encoding mechanisms. Thirty one school children participated in the first study in which they were measured on their ability to solve a centrally presented spatial encoding task, as well as their sensitivity to the frequency doubling illusion across the retina. We found that both spatial frequency doubling sensitivity and performance in the spatial encoding task were correlated with reading, however these tasks were unrelated to each other. Furthermore, frequency doubling sensitivity was correlated with contextual reading, but not single-word reading, while the central spatial encoding task was correlated with both reading tasks. These findings may have functional implications for text presentation preference. Accordingly, in Experiment 2 we demonstrated that children with poor FDT sensitivity read more accurately when words were presented singularly rather than in a whole-text format. In conclusion, we suggest that contextual reading may depend upon two separate and functionally distinct visual encoding mechanisms--one central, important for the spatial discrimination of letters within words, and the other, a spotlighting mechanism important for spatial localization within a body of text. While both mechanisms may constrain reading efficiency, neither mechanism enforces an absolute limit on reading ability.

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Vision and Attention. II: Is Visual Attention a Mechanism Through Which a Deficient Magnocellular Pathway Might Cause Reading Disability?

Cited by 46 publications

References 0 publications

Towards an understanding of the role of the ‘magnocellular advantage’ in fluent reading

Towards an understanding of the role of the ‘magnocellular advantage’ in fluent reading

Impairments in generation of early-stage transient visual evoked potentials to magno- and parvocellular-selective stimuli in schizophrenia

Visual encoding mechanisms and their relationship to text presentation preference

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