Seeing is knowing? Visual word recognition with and without Dyslexia N Taroyan |
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Department of Psychology, Sheffield Hallam University, United Kingdom
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| In this study Event Related Potentials (ERPs) technique was used to investigate whether higher order (phonological and semantic) stages of visual word recognition take place simultaneously or following processing in earlier visual features stages. Thirteen dyslexic (4 female) and 15 non-dyslexic (6 female) native English speaking young adults were tested in visual orthographic (words and pseudohomophones, W and PH1) and phonological (pseudowords and pseudohomophones, PW and PH2) lexical decision tasks. Reaction times (RTs) showed the following latency across 4 conditions: W<PH1<PH2<PW. Analysis of occipito-parietal ERP activation revealed the amplitude of P1, N1, P2, N2 and P3 components was significantly larger in the first compared to the second task in controls but not dyslexics. The latency of these components was longer in dyslexics. The amplitude of N2 and P3 components was larger and their latency longer in PH2 compared to PW condition in controls only. Overall results suggest that low level visual task required less effort than phonological task hence larger amplitude of ERPs in latter, whereas the larger amplitude of N2 and P3 in PH2 compared to PW condition in controls showed higher order processing of phonology and semantics takes place at around and no earlier than 250-300ms. |
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