Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup

Abstract The magnocellular-dorsal system is well isolated by high temporal frequency. However, temporal processing thresholds have seldom been explored in developmental dyslexia nor its subtypes. Hence, performances on two, four-alternative forced-choice achromatic flicker fusion threshold tasks mod...

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Autores principales:	Jessica L. Peters, Edith L. Bavin, Alyse Brown, David P. Crewther, Sheila G. Crewther
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2020
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/73456042f443442ba12d0df47974ef05
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spelling	oai:doaj.org-article:73456042f443442ba12d0df47974ef052021-12-02T11:43:35ZFlicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup10.1038/s41598-020-78552-32045-2322https://doaj.org/article/73456042f443442ba12d0df47974ef052020-12-01T00:00:00Zhttps://doi.org/10.1038/s41598-020-78552-3https://doaj.org/toc/2045-2322Abstract The magnocellular-dorsal system is well isolated by high temporal frequency. However, temporal processing thresholds have seldom been explored in developmental dyslexia nor its subtypes. Hence, performances on two, four-alternative forced-choice achromatic flicker fusion threshold tasks modulated at low (5%) and high (75%) temporal contrast were compared in dyslexic and neurotypical children individually matched for age and intelligence (8–12 years, n = 54 per group). As expected, the higher modulation resulted in higher flicker fusion thresholds in both groups. Compared to neurotypicals, the dyslexic group displayed significantly lower ability to detect flicker at high temporal frequencies, both at low and high temporal contrast. Yet, discriminant analysis did not adequately distinguish the dyslexics from neurotypicals, on the basis of flicker thresholds alone. Rather, two distinct dyslexic subgroups were identified by cluster analysis – one characterised by significantly lower temporal frequency thresholds than neurotypicals (referred to as ‘Magnocellular-Deficit’ dyslexics; 53.7%), while the other group (‘Magnocellular-Typical’ dyslexics; 46.3%) had comparable thresholds to neurotypicals. The two dyslexic subgroups were not differentially associated with phonological or naming speed subtypes and showed comparable mean reading rate impairments. However, correlations between low modulation flicker fusion threshold and reading rate for the two subgroups were significantly different (p = .0009). Flicker fusion threshold performances also showed strong classification accuracy (79.3%) in dissociating the Magnocellular-Deficit dyslexics and neurotypicals. We propose that temporal visual processing impairments characterize a previously unidentified subgroup of dyslexia and suggest that measurement of flicker fusion thresholds could be used clinically to assist early diagnosis and appropriate treatment recommendations for dyslexia.Jessica L. PetersEdith L. BavinAlyse BrownDavid P. CrewtherSheila G. CrewtherNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 10, Iss 1, Pp 1-10 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Jessica L. Peters Edith L. Bavin Alyse Brown David P. Crewther Sheila G. Crewther Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
description	Abstract The magnocellular-dorsal system is well isolated by high temporal frequency. However, temporal processing thresholds have seldom been explored in developmental dyslexia nor its subtypes. Hence, performances on two, four-alternative forced-choice achromatic flicker fusion threshold tasks modulated at low (5%) and high (75%) temporal contrast were compared in dyslexic and neurotypical children individually matched for age and intelligence (8–12 years, n = 54 per group). As expected, the higher modulation resulted in higher flicker fusion thresholds in both groups. Compared to neurotypicals, the dyslexic group displayed significantly lower ability to detect flicker at high temporal frequencies, both at low and high temporal contrast. Yet, discriminant analysis did not adequately distinguish the dyslexics from neurotypicals, on the basis of flicker thresholds alone. Rather, two distinct dyslexic subgroups were identified by cluster analysis – one characterised by significantly lower temporal frequency thresholds than neurotypicals (referred to as ‘Magnocellular-Deficit’ dyslexics; 53.7%), while the other group (‘Magnocellular-Typical’ dyslexics; 46.3%) had comparable thresholds to neurotypicals. The two dyslexic subgroups were not differentially associated with phonological or naming speed subtypes and showed comparable mean reading rate impairments. However, correlations between low modulation flicker fusion threshold and reading rate for the two subgroups were significantly different (p = .0009). Flicker fusion threshold performances also showed strong classification accuracy (79.3%) in dissociating the Magnocellular-Deficit dyslexics and neurotypicals. We propose that temporal visual processing impairments characterize a previously unidentified subgroup of dyslexia and suggest that measurement of flicker fusion thresholds could be used clinically to assist early diagnosis and appropriate treatment recommendations for dyslexia.
format	article
author	Jessica L. Peters Edith L. Bavin Alyse Brown David P. Crewther Sheila G. Crewther
author_facet	Jessica L. Peters Edith L. Bavin Alyse Brown David P. Crewther Sheila G. Crewther
author_sort	Jessica L. Peters
title	Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
title_short	Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
title_full	Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
title_fullStr	Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
title_full_unstemmed	Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
title_sort	flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup
publisher	Nature Portfolio
publishDate	2020
url	https://doaj.org/article/73456042f443442ba12d0df47974ef05
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Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup

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