Short report
Intact verbal description of letters with diminished awareness of
their forms
Kyoko Suzuki, Atsushi Yamadori
Section of
Neuropsychology, Division of Disability Science, Tohoku University
Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai
980-8575, Japan
Correspondence to: Dr K Suzuki kyon{at}mail.cc.tohoku.ac.jp
Received 19 August
1999 and in revised form 23 December 1999;
Accepted 5
January 2000
Visual processing and its conscious awareness can be
dissociated. To examine the extent of dissociation between ability to read characters or words and to be consciously aware of their forms,
reading ability and conscious awareness for characters were examined
using a tachistoscope in an alexic patient. A right handed woman with
14 years of education presented with incomplete right hemianopia,
alexia with kanji (ideogram) agraphia, anomia, and amnesia. Brain MRI
disclosed cerebral infarction limited to the left lower bank of the
calcarine fissure, lingual and parahippocampal gyri, and an old
infarction in the right medial frontal lobe. Tachistoscopic examination
disclosed that she could read characters aloud in the right lower
hemifield when she was not clearly aware of their forms and only noted
their presence vaguely. Although her performance in reading kanji was
better in the left than the right field, she could read kana
(phonogram) characters and Arabic numerals equally well in both fields.
By contrast, she claimed that she saw only a flash of light in 61% of
trials and noticed vague forms of stimuli in 36% of trials. She never
recognised a form of a letter in the right lower field precisely. She
performed judgment tasks better in the left than right lower hemifield
where she had to judge whether two kana characters were the same or different. Although dissociation between performance of visual recognition tasks and conscious awareness of the visual experience was
found in patients with blindsight or residual vision, reading (verbal
identification) of characters without clear awareness of their forms
has not been reported in clinical cases. Diminished awareness of forms
in our patient may reflect incomplete input to the extrastriate cortex.
Keywords: blindsight; alexia; consciousness; letter discrimination
© 2000 by Journal of Neurology, Neurosurgery, and Psychiatry
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