Different Impairments Contribute to Neglect Dyslexia

Abstract

We report investigations of the reading abilities of SP, a right-handed woman who had suffered a sub-arachnoid haemorrhage from a right middle cerebral artery aneurysm. When reading text SP showed “neglect dyslexia”. She omitted words from the left side of the page and often misread the beginnings of words, either by deleting (e.g. WANT read as “ant”) or substituting (BAND read as “sand”) their initial letters. SP's tendency to omit words was markedly affected by their position along the left-right axis, yet the same variable did not affect her tendency to make initial-letter misreadings in the same way. When words were presented so that their beginnings fell in the hemianopic region of her visual field she showed a marked tendency to make misreadings involving the deletion of initial letters. In contrast, when words were presented so that they had fallen entirely in the intact part of her field of vision, SP made errors that were mostly initial-letter substitutions. We thus suggest that neglect dyslexia involves different underlying impairments, which are often (but not inevitably) present in combination with each other. Words are omitted from the left side of the page because of defective location of line beginnings. Initial-letter deletions occur primarily when the patient fails to make adequate compensatory eye movements to words that have been fixated with their beginnings falling in the hemianopic area of the visual field. Initial-letter substitutions, however, reflect damage to mechanisms involved in letter and word recognition.