The current status of the magnocellular theory of developmental dyslexia

Stein, John

doi:10.1016/j.neuropsychologia.2018.03.022

Cited by 136 publications

(150 citation statements)

References 145 publications

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“…As such, our results contradict claims that a single mechanism, either phonological or sensory, can be considered the "fundamental" or "core" deficit of dyslexia. In particular, our work opposes the recent claim that the majority of individuals with dyslexia have a magnocellular processing deficit (Stein, 2018); if the DDM is accepted as a reasonable model of behavior on the motion discrimination task-a starting point with considerable basis (Huang-Pollock et al, 2017;Palmer et al, 2005;Ratcliff & McKoon, 2008)-then we conclude that a minority of children with dyslexia are best modeled as having a motion encoding deficit.…”

Section: Discussioncontrasting

confidence: 98%

Bridging sensory and language theories of dyslexia: towards a multifactorial model

O’Brien

Yeatman

2019

Preprint

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Our research provides direct evidence that a single-mechanism, or core-deficit, model of dyslexia cannot account for the range of linguistic and sensory outcomes in children.• Individual differences in visual motion processing, perceptual decision making, phonological awareness and rapid naming each account for unique variance in reading skill. • Our data support an additive risk-factor model, in which multiple independent dimensions each confer risk for reading difficulties. AbstractCompeting theories of dyslexia posit that reading disability arises from impaired sensory, phonological, or statistical learning mechanisms. Importantly, many theories posit that dyslexia reflects a cascade of impairments emanating from a "core deficit". Here we collect a battery of psychophysical and language measures in 106 school-aged children to investigate whether dyslexia is best conceptualized under a core-deficit model, or as a disorder with heterogenous origins. Specifically, by capitalizing on the drift diffusion model to separate sensory encoding from task-related influences on performance in a visual motion discrimination experiment, we show that deficits in motion perception, decision making and phonological processing manifest largely independently. Based on statistical models of how variance in reading skill is parceled across measures of sensory encoding, phonological processing and decision-making, our results challenge the notion that a unifying deficit characterizes dyslexia. Instead, these findings indicate a model where reading skill is explained by several distinct, additive predictors, or risk factors, of reading (dis)ability.

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Section: Discussioncontrasting

confidence: 98%

Bridging sensory and language theories of dyslexia: towards a multifactorial model

O’Brien

Yeatman

2019

Preprint

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“…Future studies may examine which stimulus properties in auditory domain, if any, may relate with atypical metacognitive performance. For example, metacognitive performance among patients may be atypically modulated by some auditory properties that are supported by magnocellular function such as temporal features [44,45], which would suggest that altered magnocellular function may underlie the metacognitive atypicality among patients across sensory modalities.…”

Section: Discussionmentioning

confidence: 99%

Atypical spatial frequency dependence of visual metacognition among schizophrenia patients

Koizumi¹,

Hori

Maniscalco

et al. 2019

Preprint

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Although a potential link between altered metacognition and schizophrenia has been speculated, studies have yielded inconsistent results. This may be partly because such findings would depend on the stimulus properties. Here we tested the hypothesis that metacognitive performance may be atypically modulated by spatial-frequency of visual stimuli among individuals with schizophrenia, given their altered magnocellular function. In Experiment 1, we used the signal detection theoretic measure meta-d' to quantify metacognitive performance of healthy participants in a visual detection task with confidence ratings. We then compared metacognitive performance between patients and controls with high and low spatial-frequency (HSF/LSF) stimuli outside and inside of an fMRI scanner (Experiment 2 and 3). Experiment 1 revealed that metacognitive performance is typically better after yes-(stimulus-presence) rather than after no-(stimulus-absence) responses. Experiment 2 revealed that control subjects showed such 'yes-response advantage' with HSF stimuli but not with LSF stimuli, while such spatial-frequency dependency was absent among the patients. Experiment 3 showed that the patients and controls differ in the functional connectivity between the dorsolateral prefrontal cortex (DLPFC) and visual or parietal cortices as well as in the multivoxel decoding accuracy of perceptual confidence in DLPFC, in a spatial-frequency-dependent manner. While individuals without schizophrenia may flexibly adapt differential metacognitive computations across spatialfrequency range, patients may employ a different mechanism that is not dependent on spatialfrequency. Because visual stimuli of low spatial-frequency have been linked to top-down processing in predictive coding, this may reflect atypical functioning in these processes in schizophrenia.

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“…Third, it affects phonological representations through orthographic representations [48]. For the most recent version of the MDT, see [56].…”

Section: Dyslexia and The Most Researched Causal Theories Of This Dismentioning

confidence: 99%

Neuroimaging Reveals Heterogeneous Neural Correlates of Reading Deficit in Individuals with Dyslexia Consistent with a Multiple Deficit Model

Reid¹

2019

Neuroimaging - Structure, Function and Mind

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Neuroimaging has become a powerful way of studying in vivo brain function and structure. The aim here is to comprehensively review Reid's fMRI study which is the first to use a multiple case approach to investigate individual differences among 18 participants with dyslexia (DPs) and 16 control participants (CPs) and to directly test the predictions of the main dyslexia theories on reading deficit. The results show that the neural correlates of reading deficit for all DPs (except one) are consistent with more than one theory, supporting a multiple deficit model. Striking individual differences between DPs were found; even if the neural correlates of reading deficit in two DPs were consistent with the same theory, the affected brain areas could differ. To make progress, research on causes of reading deficit in dyslexia would need to (1) focus on the multiple deficit model, (2) use neuroimaging to test a further refined set of brain areas (including areas hypothesised by other dyslexia theories) in longitudinal designs, (3) control the effects of co-occurring neurodevelopmental disorders, (4) use high-field MRI (including diffusion techniques), multiband fMRI and MEG with optically pumped magnetometers, (5) progress imaging genetics and (6) pursue neuroimaging intergenerational transmission of brain circuity.

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The current status of the magnocellular theory of developmental dyslexia

Cited by 136 publications

References 145 publications

Bridging sensory and language theories of dyslexia: towards a multifactorial model

Bridging sensory and language theories of dyslexia: towards a multifactorial model

Atypical spatial frequency dependence of visual metacognition among schizophrenia patients

Neuroimaging Reveals Heterogeneous Neural Correlates of Reading Deficit in Individuals with Dyslexia Consistent with a Multiple Deficit Model

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