Seeing is knowing? Visual word recognition in non-dyslexic and dyslexic readers: An ERP study

Abstract

The aim of the current study was to investigate whether phonological/semantic processing of the word takes place simultaneously with, or following, the early processing of its visual features. Event related potentials (ERPs) were recorded in thirteen dyslexic (4 female) and fourteen non-dyslexic (6 female) native English speaking young adults in two lexical decision tasks. In Task 1 participants had to make an orthographic lexical decision to distinguish frequently used words (W) from pseudohomophones (PH1) focusing on visual properties of stimuli. In Task 2 they had to make a phonological lexical decision -to pseudohomophones (PH2) and pseudowords (PW) and decide whether stimuli sounded like real words -focusing on non-visual higher order, i.e., phonological and semantic, processing of the stimuli. The behavioural performance was less good and the ERP peaks' latency longer in dyslexics compared to controls. Similarly to Twomey, Kawabata Duncan, Price & Devlin (2011), the reaction times (RTs) and the number of errors (reversed for the controls in Task 2) increased across four conditions for both groups in the following order: W< PH1< PH2< PW. The ERPs were larger in Task 2 compared to Task 1 starting at 100 ms (P1) for the controls and from about 220 ms (P2) for the dyslexics. The latency of N2 peak in left occipito-temporal sites was larger (as was the number of errors) in PH2 compared to PW condition in controls only, which indicates phonological/semantic specific processing at a time latency of 250-260 ms. Thus, the visual task required less effort than the phonological task, dyslexics' behavioural performance was less good and the brain activation delayed compared to controls. Combined behavioural and ERP results of this study indicated that phonological/semantic processing of the word took place 150 ms after processing of its visual features in controls and possibly later in dyslexics.

Individual Differences in Performance Speed Are Associated With a Positivity/Negativity Bias. An ERP and Behavioral Study

“…A late P300 was identified in some individuals, however it was not present in all participants and, therefore, was excluded from further analysis. Each participant's ERP peak amplitudes were computed within the time windows established in the group average ERPs and automatically measured at the peak maximum (e.g., Taroyan, 2015). Peak amplitudes and latencies for all single channels were averaged into side-specific area groups (O, PO and P, for left and right hemisphere separately; see Figure 1) in order to optimize signal to noise ratio and increase statistical power (Oken and Chiappa, 1986).…”

Contrasting L1 profiles through early orthographic and phonological processing of written English

“…Overall, though, no evidence was found that suggests differences in lexicality, orthographic or phonological, influence P1-O amplitude. Therefore, in contrast to some previous findings (e.g., Segalowitz & Zheng, 2009;Taroyan, 2015), P1-O amplitude does not appear to reflect either orthographic or phonological lexicality when stimulus conditions are closely controlled.…”

“…This follows several reports from Hauk and colleagues (e.g., Hauk, Davis, et al, 2006;Hauk et al, 2012;Hauk, Patterson, et al, 2006) and others (e.g., Emmorey et al, 2017), supporting the notion that P1-O amplitude does not reflect lexicality or word recognition per se (Gibbons et al, 2022;D. Zhang et al, 2014), refuting claims of larger P1 amplitudes to real words (e.g., Segalowitz & Zheng, 2009) and to pseudowords (e.g., Taroyan, 2015). Not only did the results of the current study suggest that P1-O amplitude did not differ based on orthographic lexicality, but, importantly, did not meaningfully differ in any group.…”

“…Such discrepancies could be due to different task methodologies, though even in comparable LDTs, the amplitude of the P1 at occipital sites has been reported to be larger to real words (Segalowitz & Zheng, 2009), smaller to real words (Taroyan & Nicolson, 2009), and "virtually identical" to real words compared with pseudowords (Hauk, Davis, et al, 2006, p. 1389. Furthermore, in a study directly comparable to the current research due to using orthographic and phonological LDTs with native English participants, there were no reported differences in P1 amplitudes between real words and pseudohomophones or between pseudohomophones and pseudowords at occipital or other areas (Taroyan, 2015).…”

The N170 as a marker of Reading Proficiency

“…Nevertheless, adult dyslexics seem to have a more diffuse, bilateral reduction of ERP responses. Schulte-Körne et al (2004b) did not find any differences in the P200 amplitude and latency in dyslexic children while another study (Taroyan, 2015) found longer latencies for dyslexics. In another study by Schulte-Körne, Bartling, Deimel, and Remschmidt (2004a) the researchers investigated in-motion-onset visual evoked potentials (i.e.…”