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Specific rather than a general neural adaptation deficit in children with dyslexia when processing print
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Poster E126 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Also presenting in Lightning Talks E, Thursday, October 26, 10:00 - 10:15 am CEST, Auditorium
Sarah Di Pietro1,2,3, Alexandra Brem1, David Tanner1, Silvia Brem1,2,3; 1Department of Child and Adolescent Psychiatry and Psychotherapy, University Hospital of Psychiatry Zurich, University of Zurich, Switzerland, 2Neuroscience Center Zurich, University of Zurich and ETH Zurich, Switzerland, 3URPP Adaptive Brain Circuits in Development and Learning (AdaBD), University of Zurich, Switzerland
Repeated stimulus presentation leads to reduced neural activity, also called adaptation effect, in brain regions involved in processing the presented information (Grill-Spector et al., 2006). Neural adaptation (NA) paradigms can thus be used to assess the magnitude and spatial location of selective neural processing in specific cortical networks. In written word processing, this effect is expected to be specific to areas within the reading network, for example the ventral occipitotemporal cortex (vOTC) including the visual word form area, and its electrophysiological correlate, the occipitotemporal N1 event-related potential (ERP) (Price, 2012; Maurer et al., 2005). Neural adaptation to objects is expected to occur in posterior occipital object processing regions. A recent study showed a general deficit in NA to speech, print and object processing in adults with developmental dyslexia, suggesting dysfunctional adaptation as a core impairment in dyslexia (Perrachione et al., 2016). We aimed to investigate whether this NA effect for written words occurs in children and sought to clarify its association with reading skills. A group of 85 fifth grade children with varying reading skills (11.4 ± .4 years) performed a visual adaptation paradigm during simultaneous high-density EEG-fMRI, consisting of block-wise presentation of repeated and non-repeated words, objects and pseudowords. To derive adaptation effects, we performed one-sample t-tests on a whole-brain level for fMRI data. For EEG data, we computed the ERPs for each condition (repeated, non-repeated) and part (words, pseudowords, objects) and extracted the mean amplitudes of the left visual occipitotemporal negativity N1 (170-230 ms) and the subsequent occipitotemporal positivity P2 (290-350 ms). These ERP amplitudes were then entered in linear mixed models with factors condition (repeated, non-repeated) and hemisphere (left, right) for each part separately. Children’s reading skills were added as a covariate in the fMRI and ERP analyses. Our fMRI results reveal NA effects to words, objects and pseudowords in bilateral vOTC, to words in the superior temporal cortex, and to pseudowords in the precentral gyrus. These results were paralleled by NA effects in the N1 and the P2 ERPs. For pseudowords, poor reading skills were associated with reduced NA BOLD signal in the left vOTC and in the frontal cortex. No association between reading skills and NA was found for words or objects. Reading skills also modulated the NA effect in the P2 ERP during pseudoword and object processing, with stronger NA effects in children with better reading skills. As expected, we found an NA effect for all parts in the occipitotemporal cortex and additionally some effects in other areas of the reading network for words and pseudowords, confirming the feasibility of measuring the neural adaptation effect with this paradigm. Contrary to previous findings (Perrachione et al., 2016), however, our results speak against a general neural adaptation deficit as a cause for dyslexia in children because a consistent reduction in the NA effect in fMRI and ERPs in poor readers was only detected when processing pseudowords. Rather, our data suggest a specific NA deficit in the visual domain when children with dyslexia process phonologically demanding pseudowords.
Topic Areas: Reading,