Lexical decision with left, right and center visual field presentation: a comparison between dyslexic and regular readers by means of electrophysiological and behavioral measures

Abstract

This study examined the differences in processing between regular and dyslexic readers in a lexical decision task in different visual field presentations (left, right, and center). The research utilized behavioral measures that provide information on accuracy and reaction time and electro-physiological measures that permit the examination of brain activity during cognitive processing. Two groups of university students, regular and dyslexic readers, were matched on age, gender, intelligence, socioeconomic status, and handedness. A lexical decision task was used in order to examine the processes during word recognition. Subjects were required to decide whether a sequence of letters constituted a real word existing in spoken language or whether the stimulus seen was not an accurate word. For the behavioral measures, it was found that the dyslexics read slower and with more errors than the regular readers. Moreover, the ERP components appeared later in dyslexics as compared to regular readers in this task. The performance of the dyslexics improved and even approached that of the regular readers when the stimuli were presented to the left visual field. Thus, it seems that the dyslexics were relying more on their right hemisphere for linguistic processing, whereas the regular readers were relying more on their language areas in the left hemisphere.