VARIETIES OF PURE ALEXIA - THE CASE OF FAILURE TO ACCESS GRAPHEMIC REPRESENTATIONS

We document the case of a patient (GV) who, following a left posterior brain lesion, showed a selective and severe deficit in naming visual objects and in reading letters, words, and numerals. Three sets of fin dings are critical for the interpretation of the patient's alexia. Fir st, despite intact visual processing abilities and preserved ability t o recognise the shape and orientation of letters, GV could not determi ne whether a pair of letters had the same name. Second, she should not access the orthographic structure and meaning of visually presented w ords, although she could access meaning from orally spelled words and she could access orthographic structure from meaning in written words. Third, GV could access partial semantic information from pictures and Arabic numerals. Based on this pattern of results, we conclude that t he form of alexia manifested by our patient results from failure to ac cess the graphemic representations of letters and words from normally processed visual input. The findings further suggest that access to le tter forms and grapheme representations are sequentially ordered stage s of processing in word recognition. The results also suggest that gra phemic processing may be a distinct property of the left hemisphere.