Brain, Vol 121, Issue 5 843-850, Copyright © 1998 by Oxford University Press
R Fukatsu, T Fujii and A Yamadori
We studied a patient who manifested a bilateral reading disorder through
the somaesthetic modality, without deficit of elementary tactile sensation
or tactile object naming, due to a left parietal infarct. Detailed
investigation established the following points. (i) The patient showed
normal function on elementary somaesthetic examination, normal function on
high level tactile perception, except for minimal impairment of the right
hand on the two-point discrimination test, and normal latencies on the
somatosensory evoked potential in both hands. (ii) The patient had
difficulty in reading letters using any somaesthetic strategy
(graphaesthesia, directional joint kinaesthesia and active touch) with
either hand. (iii) On a same- different judgement task, the patient's
performance with the right hand was slightly defective on graphaesthesia
and active touch, but performance with the left hand was within the normal
range for all of the strategies. The patient's disorder was highly category
specific and modality specific, indicating that somaesthetic letter reading
can be disrupted not only independent of other high level somaesthetic
functions, like object recognition, but also independent of other modes of
reading functions, such as visual reading. A lesion involving the
intraparietal sulcus, the upper part of the inferior parietal lobule and
the adjacent white matter in the left hemisphere may be capable of
compromising the pathways for somaesthetic letter reading with both hands.
ARTICLES
Pure somaesthetic alexia: somaesthetic-verbal disconnection for letters
Department of Neurology, Miyagi National Hospital, Japan.
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