Abstract
The main diagnostic criterion for developmental dyslexia (DD) in transparent orthographies is a remarkable reading speed deficit, which is often accompanied by spelling difficulties. These deficits have been traced back to both deficits in orthographic and phonological processing. For a better understanding of the reading speed deficit in DD it is necessary to clarify which processing steps are degraded in children with DD during reading. In order to address this question the present study used EEG to investigate three reading related ERPs: the N170, N400 and LPC. Twenty-nine children without DD and 52 children with DD performed a phonological lexical decision (PLD)—task, which tapped both orthographic and phonological processing. Children were presented with words, pseudohomophones, pseudowords and false fonts and had to decide whether the presented stimulus sounded like an existing German word or not. Compared to control children, children with DD showed deficits in all the investigated ERPs. Firstly, a diminished mean area under the curve for the word material-false font contrasts in the time window of the N170 was observed, indicating a reduced degree of print sensitivity; secondly, N400 amplitudes, as suggested to reflect the access to the orthographic lexicon and grapheme-phoneme conversion, were attenuated; and lastly, phonological access as indexed by the LPC was degraded in children with DD. Processing differences dependent on the linguistic material in children without DD were observed only in the LPC, suggesting that similar reading processes were adopted independent of orthographic familiarity. The results of this study suggest that effective treatment should include both orthographic and phonological training. Furthermore, more longitudinal studies utilizing the same task and stimuli are needed to clarify how these processing steps and their time course change during reading development.
Highlights
Reading and writing are fundamental skills for daily life that allow us to integrate properly into a community and they are crucial for acquiring knowledge and transmitting information
The present study was designed to investigate the single processing steps underlying phonological lexical decision (PLD) in order to provide a temporal model of reading processes in normal developing children and to further clarify which processing steps are degraded in children with developmental dyslexia (DD) during reading
In adults it has been found that N400 amplitudes were www.frontiersin.org smaller to orthographic familiar word forms compared to unfamiliar word forms (e.g., Braun et al, 2006; Briesemeister et al, 2009). These results suggest that less effort was needed in order to find a fitting orthographic representation for familiar words in the orthographic lexicon, whereas the search was prolonged and grapheme-phoneme correspondence rules had to be applied in case of unfamiliar word forms resulting in enhanced N400 amplitudes
Summary
Reading and writing are fundamental skills for daily life that allow us to integrate properly into a community and they are crucial for acquiring knowledge and transmitting information. Despite adequate teaching some children fail to develop age appropriate reading and spelling skills. These children suffer from developmental dyslexia (DD), which is one of the most common specific developmental disorders affecting around 4–9% of school-aged children (Shaywitz et al, 1990; Katusic et al, 2001; Esser et al, 2002). DD is characterized by severe problems in learning to read properly and is often accompanied by a comorbid spelling disorder. These difficulties are not the direct result of below-average general intelligence, inadequate schooling and neurological or sensory deficits (Dilling, 2006). DD accompanies the individuals throughout their lifespan and interferes with academic achievement, professional success and mental health (Esser et al, 2002)
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