Phonological, orthographic, and semantic processing during sentence reading in adults with dyslexia: Behavioral and neural correlates

Abstract

The reported study used behavioral measures and event-related potentials (ERPs) to investigate phonological, orthographic, and semantic processing during sentence reading in adults with dyslexia. Twenty-seven nonimpaired (13 men, 20-31 years) and 25 dyslexic (11 men, 20-32 years) readers were presented with sentences that included four possible endings: a congruent ending in which the last word was semantically related to the sentence, an incongruent ending with no semantic relationship, a homophone which was based on a congruent word, and an orthographically similar word to a congruent word. The participants were asked to decide if the sentence-final word was semantically related to the sentence. Response accuracy, reaction times, and both amplitude and peak latency of the N400 were investigated. The N400 component has been reported as a brain measure that reflects the integration of phonological and orthographic processes into meaning during word reading. The behavioral results revealed that the dyslexic readers were less accurate overall compared to the nonimpaired readers. In addition, the dyslexic readers had longer reaction times for the phonological, orthographic, and incongruent conditions compared to the nonimpaired readers. The N400 results showed that the dyslexic readers produced larger amplitude compared to the nonimpaired readers for the congruent (p = 0.021) and orthographic (p = 0.041) conditions. Moreover, the dyslexic readers had longer latency than the nonimpaired readers for the congruent (p = 0.012), orthographic (p = 0.015), and incongruent (p = 0.011) conditions. The behavioral and ERP findings suggest that adults with dyslexia are impaired in phonological, orthographic, and semantic processing during sentence reading.

Keywords: Dyslexia; ERP; N400; Orthography; Phonology; Semantic processing.