Lexical effects in left neglect dyslexia: A study in Italian patients.

This study investigated whether and to what extent the reading performance of six Italian right brain-damaged patients with left neglect dyslexia was affected by lexical variables. The lexicality of responses (either words or nonwords) and the distribution of substitution vs. omission neglect errors were measured. Patients were given the following tasks: (i) Reading aloud monomorphemic words of different frequencies and nonwords with different degrees of similarity to real words (Experiment 1); (ii) Reading aloud morphologically complex (suffixed) derived words and morphologically complex (suffixed) nonwords (Experiment 2). Patients could be distinguished in terms of their sensitivity to the lexical status of the target. Four patients exhibited lexicality effects in their reading performance, while two patient did not. The dissociation is discussed in terms of the interaction between defective visuo-spatial analysis, which characterises neglect, and higher-order lexical knowledge. The suggestion is made that lexical effects in neglect dyslexia reflect a relative preservation of visuo-spatial processing of the left side of the letter string, its absence a more severe neglect disorder. This interpretation of the occurrence of lexical effects in left neglect dyslexia in terms of severity of the spatial disorder is specific to the domain of reading, however, and does not extend to other manifestations of unilateral spatial neglect. Finally, the relationship between error type (omissions vs. substitutions) and the absence vs. presence of lexical effects is considered.