Neglect dyslexia with a stimulus-centred deficit and without visuospatial neglect

This paper reports a single case of ipsilesional left neglect dyslexia and interprets it according to the three-level model of visual word recognition proposed by Caramazza and Hillis (1990). The three levels reflect a progre ssion from the physical stimulus to an abstract representation of a word. R R was not impaired at the first, retinocentric, level, which represents the individual features of letters within a word according to the location of the word in the visual field: She made the same number of errors to words p resented in her left visual field as in her right visual field. A deficit a t this level should also mean the patient neglects all stimuli. This did no t occur with RR: She did not neglect when naming the items in rows of objec ts and rows of geometric symbols. In addition, although she displayed signi ficant neglect dyslexia when making visual matching judgements on pairs of words and nonwords, she did not do so to pairs of nonsense letter shapes, s hapes which display the same level of visual complexity as letters in words . RR was not impaired at the third, graphemic, level, which represents the ordinal positions of letters within a word: She continued to neglect the le ftmost (spatial) letter of words presented in mirror-reversed orientation a nd she did not neglect in oral spelling. By elimination, these results sugg est RR's deficit affects a spatial reference frame where the representation al space is bounded by the stimulus: A stimulus-centred level of representa tion. We define five characteristics of a stimulus-centred deficit, as mani fest in RR. First, it is not the case that neglect dyslexia occurs because the remaining letters in a string attract or capture attention away from th e leftmost letter(s). Second, the deficit is continuous across the letter s tring. Third, perceptually significant features, such as spaces, define pot ential words. Fourth, the whole, rather than part, of a letter is neglected . Fifth, category information is preserved. It is concluded that the Carama zza-Hillis model accounts well for RR's data, although we conclude that neg lect dyslexia can be present when a more general visuospatial neglect is ab sent.