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Abstract:
Humans can maintain and manipulate different kinds of
information in a short-term or working memory. Considerable
evidence suggests that this information may be represented verbally
or non-verbally. However, less is known about whether transient
verbal representations are also segregated by modality. We
investigated this question in JD, a right-handed 46 year-old man
with a left temporal-parietal intracerebral lesion from a ruptured
AVM. He read, repeated, and named pictures well but was
significantly impaired in writing. For example, he wrote "callpy"
for "club" and "eheather" for "earth." His individual letters were
well formed, suggesting that his dysgraphia was not dyspraxic.
Furthermore, his errors were not influenced by the frequency,
regularity, or lexical status (i.e., words or nonwords) of the
targets suggesting that his dysgraphia was not lexical. He was
similarly impaired in oral spelling as in writing, suggesting a
selective impairment of a graphemic output buffer, which maintains
representations of letter shapes and names. His preserved
repetition and reading suggests that he did not also have an
analogous deficit of the phonological output buffer. Although
working memory deficits are most often associated with frontal lobe
damage, JDs temporal-parietal lesion suggests that frontal and
temporal-parietal regions interact in highly specific ways with
respect to the information being maintained or manipulated.
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