The time course of reading processes in children with and without dyslexia: an ERP study

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.

Lexical and sublexical orthographic processing: An ERP study with skilled and dyslexic adult readers

“…Jost, Raith, & Maurer, 2014). Moreover, another result supporting the claim that the N1 reflects a specific brain training effect comes from studies with populations of different reading expertise: the N1 response is attenuated in groups lacking reading expertise such as dyslexic children (Araújo, Faísca, Bramão, Petersson, & Reis, 2012;Hasko, Groth, Bruder, Bartling, & Schulte-Körne, 2013; and adults Mahé, Bonnefond, Gavens, Dufour, & Doignon-Camus, 2012). This finding indicates that perceptual coding of orthographic properties might be compromised in dyslexia, contributing to a deficient development of automatic and fluent reading.…”

“…One set of studies described similar brain activation patterns for words and pseudowords observed around the peak of the N1 (Araújo et al, 2012;Bentin et al, 1999;Hasko et al, 2013;Kast, Elmer, Jancke, & Meyer, 2010;Maurer et al, 2005), and no modulation by different levels of word frequency (Araújo et al, 2012). These findings suggest that the N1-evoked response might arise at the earliest prelexical stages of the orthographic system.…”

“…The research on this topic is rather mixed: some studies have found distinct neurophysiological manifestations between pseudowords and words (Hauk, Coutout, Holden, & Chen, 2012;Hauk, Pulvermuller, Ford, Marslen-Wilson, & Davis, 2009;Taroyan & Nicolson, 2009), and significant effects of frequency (Hauk & Pulvermuller, 2004;Sereno, Brewer, & O'Donnell, 2003;Sereno et al, 1998), while others have reported no effect of lexicality or frequency in the N1 time window (Araújo et al, 2012;Hasko et al, 2013;Maurer et al, 2005), suggesting therefore that lexical access is located later on in processing. In this study we manipulated the variable orthographic lexicality (words vs. pseudowords) as a property of the word as a whole, and also compared the N1-evoked response to pseudohomophones as a way to minimize phonological familiarity confound.…”

“…With respect to dyslexia, research has suggested that the N1-response is a neural correlate of the disorder, based on absent differences in electrophysiological responses to words vs. symbol strings (Araújo et al, 2012;Hasko et al, 2013;Helenius et al, 1999;Mahé et al, 2012). Some have been acknowledged that dysfunctions are critical already at the letter level (Kronschnabel, Schmid, Maurer, & Brandeis, 2013;.…”

“…One possibility has to do with developmental aspects. Most of the studies reporting null lexicality or frequency effects were conducted in the early reading stages of reading development (e.g., in ten-year-old children, Araújo et al, 2012; in eight-year-old children, Hasko et al, 2013). Presumably, when the reading process is not yet fully automatized (as in young children) N1 is likely an index of pre-lexical processing only, but with increasing reading expertise (adults) it might reflect sensitivity to lexical orthographic information as well.…”