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Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia

(1) Background—the magnocellular hypothesis proposes that impaired development of the visual timing systems in the brain that are mediated by magnocellular (M-) neurons is a major cause of dyslexia. Their function can now be assessed quite easily by analysing averaged visually evoked event-related p...

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Autor principal: Stein, John
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7824745/
https://www.ncbi.nlm.nih.gov/pubmed/33466235
http://dx.doi.org/10.3390/brainsci11010048
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author Stein, John
author_facet Stein, John
author_sort Stein, John
collection PubMed
description (1) Background—the magnocellular hypothesis proposes that impaired development of the visual timing systems in the brain that are mediated by magnocellular (M-) neurons is a major cause of dyslexia. Their function can now be assessed quite easily by analysing averaged visually evoked event-related potentials (VERPs) in the electroencephalogram (EEG). Such analysis might provide a useful, objective biomarker for diagnosing developmental dyslexia. (2) Methods—in adult dyslexics and normally reading controls, we recorded steady state VERPs, and their frequency content was computed using the fast Fourier transform. The visual stimulus was a black and white checker board whose checks reversed contrast every 100 ms. M- cells respond to this stimulus mainly at 10 Hz, whereas parvocells (P-) do so at 5 Hz. Left and right visual hemifields were stimulated separately in some subjects to see if there were latency differences between the M- inputs to the right vs. left hemispheres, and these were compared with the subjects’ handedness. (3) Results—Controls demonstrated a larger 10 Hz than 5 Hz fundamental peak in the spectra, whereas the dyslexics showed the reverse pattern. The ratio of subjects’ 10/5 Hz amplitudes predicted their reading ability. The latency of the 10 Hz peak was shorter during left than during right hemifield stimulation, and shorter in controls than in dyslexics. The latter correlated weakly with their handedness. (4) Conclusion—Steady state visual ERPs may conveniently be used to identify developmental dyslexia. However, due to the limited numbers of subjects in each sub-study, these results need confirmation.
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spelling pubmed-78247452021-01-24 Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia Stein, John Brain Sci Article (1) Background—the magnocellular hypothesis proposes that impaired development of the visual timing systems in the brain that are mediated by magnocellular (M-) neurons is a major cause of dyslexia. Their function can now be assessed quite easily by analysing averaged visually evoked event-related potentials (VERPs) in the electroencephalogram (EEG). Such analysis might provide a useful, objective biomarker for diagnosing developmental dyslexia. (2) Methods—in adult dyslexics and normally reading controls, we recorded steady state VERPs, and their frequency content was computed using the fast Fourier transform. The visual stimulus was a black and white checker board whose checks reversed contrast every 100 ms. M- cells respond to this stimulus mainly at 10 Hz, whereas parvocells (P-) do so at 5 Hz. Left and right visual hemifields were stimulated separately in some subjects to see if there were latency differences between the M- inputs to the right vs. left hemispheres, and these were compared with the subjects’ handedness. (3) Results—Controls demonstrated a larger 10 Hz than 5 Hz fundamental peak in the spectra, whereas the dyslexics showed the reverse pattern. The ratio of subjects’ 10/5 Hz amplitudes predicted their reading ability. The latency of the 10 Hz peak was shorter during left than during right hemifield stimulation, and shorter in controls than in dyslexics. The latter correlated weakly with their handedness. (4) Conclusion—Steady state visual ERPs may conveniently be used to identify developmental dyslexia. However, due to the limited numbers of subjects in each sub-study, these results need confirmation. MDPI 2021-01-05 /pmc/articles/PMC7824745/ /pubmed/33466235 http://dx.doi.org/10.3390/brainsci11010048 Text en © 2021 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Stein, John
Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title_full Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title_fullStr Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title_full_unstemmed Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title_short Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia
title_sort reduced visual magnocellular event-related potentials in developmental dyslexia
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7824745/
https://www.ncbi.nlm.nih.gov/pubmed/33466235
http://dx.doi.org/10.3390/brainsci11010048
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