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Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex

fMRI studies using a region-of-interest approach have revealed that the ventral portion of the left occipito-temporal cortex, which is specialized for orthographic processing of visually presented words (and includes the so-called “visual word form area”, VWFA), is characterized by a posterior-to-an...

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Autores principales: Olulade, O.A., Flowers, D.L., Napoliello, E.M., Eden, G.F.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375638/
https://www.ncbi.nlm.nih.gov/pubmed/25844326
http://dx.doi.org/10.1016/j.nicl.2015.02.013
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author Olulade, O.A.
Flowers, D.L.
Napoliello, E.M.
Eden, G.F.
author_facet Olulade, O.A.
Flowers, D.L.
Napoliello, E.M.
Eden, G.F.
author_sort Olulade, O.A.
collection PubMed
description fMRI studies using a region-of-interest approach have revealed that the ventral portion of the left occipito-temporal cortex, which is specialized for orthographic processing of visually presented words (and includes the so-called “visual word form area”, VWFA), is characterized by a posterior-to-anterior gradient of increasing selectivity for words in typically reading adults, adolescents, and children (e.g. Brem et al., 2006, 2009). Similarly, the left inferior frontal cortex (IFC) has been shown to exhibit a medial-to-lateral gradient of print selectivity in typically reading adults (Vinckier et al., 2007). Functional brain imaging studies of dyslexia have reported relative underactivity in left hemisphere occipito-temporal and inferior frontal regions using whole-brain analyses during word processing tasks. Hence, the question arises whether gradient sensitivities in these regions are altered in dyslexia. Indeed, a region-of-interest analysis revealed the gradient-specific functional specialization in the occipito-temporal cortex to be disrupted in dyslexic children (van der Mark et al., 2009). Building on these studies, we here (1) investigate if a word-selective gradient exists in the inferior frontal cortex in addition to the occipito-temporal cortex in normally reading children, (2) compare typically reading with dyslexic children, and (3) examine functional connections between these regions in both groups. We replicated the previously reported anterior-to-posterior gradient of increasing selectivity for words in the left occipito-temporal cortex in typically reading children, and its absence in the dyslexic children. Our novel finding is the detection of a pattern of increasing selectivity for words along the medial-to-lateral axis of the left inferior frontal cortex in typically reading children and evidence of functional connectivity between the most lateral aspect of this area and the anterior aspects of the occipito-temporal cortex. We report absence of an IFC gradient and connectivity between the lateral aspect of the IFC and the anterior occipito-temporal cortex in the dyslexic children. Together, our results provide insights into the source of the anomalies reported in previous studies of dyslexia and add to the growing evidence of an orthographic role of IFC in reading.
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spelling pubmed-43756382015-04-03 Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex Olulade, O.A. Flowers, D.L. Napoliello, E.M. Eden, G.F. Neuroimage Clin Regular Article fMRI studies using a region-of-interest approach have revealed that the ventral portion of the left occipito-temporal cortex, which is specialized for orthographic processing of visually presented words (and includes the so-called “visual word form area”, VWFA), is characterized by a posterior-to-anterior gradient of increasing selectivity for words in typically reading adults, adolescents, and children (e.g. Brem et al., 2006, 2009). Similarly, the left inferior frontal cortex (IFC) has been shown to exhibit a medial-to-lateral gradient of print selectivity in typically reading adults (Vinckier et al., 2007). Functional brain imaging studies of dyslexia have reported relative underactivity in left hemisphere occipito-temporal and inferior frontal regions using whole-brain analyses during word processing tasks. Hence, the question arises whether gradient sensitivities in these regions are altered in dyslexia. Indeed, a region-of-interest analysis revealed the gradient-specific functional specialization in the occipito-temporal cortex to be disrupted in dyslexic children (van der Mark et al., 2009). Building on these studies, we here (1) investigate if a word-selective gradient exists in the inferior frontal cortex in addition to the occipito-temporal cortex in normally reading children, (2) compare typically reading with dyslexic children, and (3) examine functional connections between these regions in both groups. We replicated the previously reported anterior-to-posterior gradient of increasing selectivity for words in the left occipito-temporal cortex in typically reading children, and its absence in the dyslexic children. Our novel finding is the detection of a pattern of increasing selectivity for words along the medial-to-lateral axis of the left inferior frontal cortex in typically reading children and evidence of functional connectivity between the most lateral aspect of this area and the anterior aspects of the occipito-temporal cortex. We report absence of an IFC gradient and connectivity between the lateral aspect of the IFC and the anterior occipito-temporal cortex in the dyslexic children. Together, our results provide insights into the source of the anomalies reported in previous studies of dyslexia and add to the growing evidence of an orthographic role of IFC in reading. Elsevier 2015-02-26 /pmc/articles/PMC4375638/ /pubmed/25844326 http://dx.doi.org/10.1016/j.nicl.2015.02.013 Text en © 2015 The Authors. Published by Elsevier Inc. http://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Regular Article
Olulade, O.A.
Flowers, D.L.
Napoliello, E.M.
Eden, G.F.
Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title_full Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title_fullStr Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title_full_unstemmed Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title_short Dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
title_sort dyslexic children lack word selectivity gradients in occipito-temporal and inferior frontal cortex
topic Regular Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375638/
https://www.ncbi.nlm.nih.gov/pubmed/25844326
http://dx.doi.org/10.1016/j.nicl.2015.02.013
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