Analysis of Disorder Structure in Surface Dyslexia Whose LARC Errors Appear in Real Words and Lexicalization Errors Appear in Nonwords

Abstract

  We report a case of a patient with Gogi aphasia who presented with surface dyslexia due to herpes simplex encephalitis. To investigate the mechanism of the disability, we performed a real-word and nonword oral reading task, a letter recognition task, and a lexical judgment task using Kanji stimuli. The results showed frequency and consistency effects in the real-word oral reading task, and legitimate alternative reading of components (LARC) errors appeared more frequently in reading words. The percentage of correct answers for nonwords was high, but patients recognized some nonword stimuli as lexicalization errors. For most words, the first letter was read aloud correctly, even when the words had errors. In the character recognition and lexicalization tasks, many errors were observed, in which non-existent Kanji and nonwords were identified as Japanese. Analysis using a dual route cascaded model suggested that LARC errors appeared in real words due to a failure of the semantic system. For nonwords, we hypothesized that the lexical root was incorrectly activated due to impairments in character recognition and lexical judgment, and lexicalization errors appeared in the representation of real words recalled from the first letter sound.