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Abstract:
Patients with pure alexia have difficulty accessing
orthographic representations of visually-presented words, the
result of left occipital damage. When reading, these patients
decode each letter in the word ("letter-by-letter reading"). This
compensatory strategy may have its neural instantiation in other
parts of the left hemisphere, in the right hemisphere, or in
lesion-adjacent regions. We used fMRI to examine the cortical
activation of patients with pure alexia as they viewed words. The
task, a one-back matching task, was performed with different
orthographic stimulus types in different runs (real words,
pseudowords, consonant strings, and false fonts). For normal
readers, different activation patterns had been revealed for the
different string types: Unlike words and pseudowords, consonant
strings and false fonts resulted in activation of left parietal
areas, and increased bilateral activation overall (1). In contrast,
activation of the left parietal lobe and greater bilateral
activation were seen when the pure alexic patients performed the
task with real words as well as consonant strings. These results
support the behavioral data suggesting that patients with pure
alexia process visually-presented real words as if they were
unrelated letter strings.
(1) Tagamets, M-A., Novick, J.M., Chalmers, M.L., Friedman, R.B.
J.Cog. Neuro., 2000, 12:2, 281-297.
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