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John F. Stein - One of the best experts on this subject based on the ideXlab platform.

  • Two Visual Motion Processing Deficits in Developmental Dyslexia Associated with Different Reading Skills Deficits
    Journal of cognitive neuroscience, 2004
    Co-Authors: Jeremy Wilmer, Yue Chen, Alexandra J. Richardson, John F. Stein
    Abstract:

    Developmental dyslexia is associated with deficits in the Processing of visual Motion stimuli, and some evidence suggests that these Motion Processing deficits are related to various reading subskills deficits. However, little is known about the mechanisms underlying such associations. This study lays a richer groundwork for exploration of such mechanisms by more comprehensively and rigorously characterizing the relationship between Motion Processing deficits and reading subskills deficits. Thirty-six adult participants, 19 of whom had a history of developmental dyslexia, completed a battery of visual, cognitive, and reading tests. This battery combined Motion Processing and reading subskills measures used across previous studies and added carefully matched visual Processing control tasks. Results suggest that there are in fact two distinct Motion Processing deficits in developmental dyslexia, rather than one as assumed by previous research, and that each of these deficits is associated with a different type of reading subskills deficit. A deficit in detecting coherent Motion is selectively associated with low accuracy on reading subskills tests, and a deficit in discriminating velocities is selectively associated with slow performance on these same tests. In addition, evidence from visual Processing control tasks as well as self-reports of ADHD symptoms suggests that these Motion Processing deficits are specific to the domain of visual Motion, and result neither from a broader visual deficit, nor from the sort of generalized attention deficit commonly comorbid with developmental dyslexia. Finally, dissociation between these two Motion Processing deficits suggests that they may have distinct neural and functional underpinnings. The two distinct patterns of Motion Processing and reading deficits demonstrated by this study may reflect separable underlying neurocognitive mechanisms of developmental dyslexia.

F Steinjohn - One of the best experts on this subject based on the ideXlab platform.

Yue Chen - One of the best experts on this subject based on the ideXlab platform.

  • Compromised late-stage Motion Processing in schizophrenia.
    Biological psychiatry, 2004
    Co-Authors: Yue Chen, Deborah L. Levy, Summer Sheremata, Philip S. Holzman
    Abstract:

    Abstract Background Visual Motion Processing is compromised in schizophrenia, as shown in deficient velocity discrimination. Processing of Motion signals comprises progressive stages along the geniculate-striate-extrastriate-cortex pathway. Based on neurophysiologic and brain lesion studies, a velocity discrimination deficit can implicate early-stage Motion Processing if it is contrast-dependent or late-stage Motion Processing if it is contrast-independent. Methods To determine which stage underlies the deficient velocity discrimination in schizophrenia, we examined the effects of visual contrast on velocity discrimination. We measured velocity discrimination thresholds in schizophrenia patients ( n = 34) and normal control subjects ( n = 17) at both low and high contrasts, using each subject's contrast detection threshold to equate contrast levels. Results Schizophrenia patients showed poor velocity discrimination that improved little with high contrast, whereas normal control subjects showed enhanced velocity discrimination with increased contrast. Conclusions The finding that the velocity discrimination deficit in schizophrenia is independent of contrast modulation implicates the later, rather than the earlier, stages of Motion Processing, which is mediated in the extrastriate cortex.

  • Two Visual Motion Processing Deficits in Developmental Dyslexia Associated with Different Reading Skills Deficits
    Journal of cognitive neuroscience, 2004
    Co-Authors: Jeremy Wilmer, Yue Chen, Alexandra J. Richardson, John F. Stein
    Abstract:

    Developmental dyslexia is associated with deficits in the Processing of visual Motion stimuli, and some evidence suggests that these Motion Processing deficits are related to various reading subskills deficits. However, little is known about the mechanisms underlying such associations. This study lays a richer groundwork for exploration of such mechanisms by more comprehensively and rigorously characterizing the relationship between Motion Processing deficits and reading subskills deficits. Thirty-six adult participants, 19 of whom had a history of developmental dyslexia, completed a battery of visual, cognitive, and reading tests. This battery combined Motion Processing and reading subskills measures used across previous studies and added carefully matched visual Processing control tasks. Results suggest that there are in fact two distinct Motion Processing deficits in developmental dyslexia, rather than one as assumed by previous research, and that each of these deficits is associated with a different type of reading subskills deficit. A deficit in detecting coherent Motion is selectively associated with low accuracy on reading subskills tests, and a deficit in discriminating velocities is selectively associated with slow performance on these same tests. In addition, evidence from visual Processing control tasks as well as self-reports of ADHD symptoms suggests that these Motion Processing deficits are specific to the domain of visual Motion, and result neither from a broader visual deficit, nor from the sort of generalized attention deficit commonly comorbid with developmental dyslexia. Finally, dissociation between these two Motion Processing deficits suggests that they may have distinct neural and functional underpinnings. The two distinct patterns of Motion Processing and reading deficits demonstrated by this study may reflect separable underlying neurocognitive mechanisms of developmental dyslexia.

Oliver Braddick - One of the best experts on this subject based on the ideXlab platform.

  • normal and anomalous development of visual Motion Processing Motion coherence and dorsal stream vulnerability
    Neuropsychologia, 2003
    Co-Authors: Oliver Braddick, J Atkinson, J Wattambell
    Abstract:

    Directional Motion Processing is a pervasive and functionally important feature of the visual system. Behavioural and VEP studies indicate that it appears as a cortical function after about 7 weeks of age, with global Processing, Motion based segmentation, and the use of Motion in complex perceptual tasks emerging shortly afterwards. A distinct, subcortical Motion system controls optokinetic nystagmus (OKN) from birth, showing characteristic monocular asymmetries which disappear as binocular cortical function takes over in normal development. Asymmetries in cortical responses are linked to this interaction in a way that is not yet fully understood. Beyond infancy, a range of developmental disorders show a deficit of global Motion compared to global form Processing which we argue reflects a general 'dorsal-stream vulnerability'.

  • Motion Processing: Where is the naso-temporal asymmetry?
    Current biology : CB, 1996
    Co-Authors: Oliver Braddick
    Abstract:

    Strabismic (cross-eyed) humans and animals show an imbalance between opposite directions of eye movement. Both midbrain and cortical origins for this asymmetry have been proposed, but there is no sign of it in the main Motion-Processing area of visual cortex.

  • Segmentation versus integration in visual Motion Processing.
    Trends in neurosciences, 1993
    Co-Authors: Oliver Braddick
    Abstract:

    Reliable Motion perception requires processes that integrate visual Motion signals from neighbouring locations in the visual field, which should have the effect of smoothing out spatial variations in velocity. However, we also require Motion Processing to be very sensitive to local velocity differences, so that moving objects appear sharply distinct from their background and specific differential properties of optic flow associated with the observer's Motion can be detected. Perceptual experiments give evidence both for integrative processes, which lead to spreading of perceived Motion, and for differential processes, which lead to Motion contrast and segmentation. Current and future experiments might allow tests of theoretical schemes that employ adaptive networks and/or multiple representations in order to reconcile the conflicting demands of integration and segmentation.

Jeremy Wilmer - One of the best experts on this subject based on the ideXlab platform.

  • Two Visual Motion Processing Deficits in Developmental Dyslexia Associated with Different Reading Skills Deficits
    Journal of cognitive neuroscience, 2004
    Co-Authors: Jeremy Wilmer, Yue Chen, Alexandra J. Richardson, John F. Stein
    Abstract:

    Developmental dyslexia is associated with deficits in the Processing of visual Motion stimuli, and some evidence suggests that these Motion Processing deficits are related to various reading subskills deficits. However, little is known about the mechanisms underlying such associations. This study lays a richer groundwork for exploration of such mechanisms by more comprehensively and rigorously characterizing the relationship between Motion Processing deficits and reading subskills deficits. Thirty-six adult participants, 19 of whom had a history of developmental dyslexia, completed a battery of visual, cognitive, and reading tests. This battery combined Motion Processing and reading subskills measures used across previous studies and added carefully matched visual Processing control tasks. Results suggest that there are in fact two distinct Motion Processing deficits in developmental dyslexia, rather than one as assumed by previous research, and that each of these deficits is associated with a different type of reading subskills deficit. A deficit in detecting coherent Motion is selectively associated with low accuracy on reading subskills tests, and a deficit in discriminating velocities is selectively associated with slow performance on these same tests. In addition, evidence from visual Processing control tasks as well as self-reports of ADHD symptoms suggests that these Motion Processing deficits are specific to the domain of visual Motion, and result neither from a broader visual deficit, nor from the sort of generalized attention deficit commonly comorbid with developmental dyslexia. Finally, dissociation between these two Motion Processing deficits suggests that they may have distinct neural and functional underpinnings. The two distinct patterns of Motion Processing and reading deficits demonstrated by this study may reflect separable underlying neurocognitive mechanisms of developmental dyslexia.