Comprehension of Written Words in Word-meaning Deafness:

Implications from a Study with Words Written in Atypical Usage of Japanese Kana Letters

Abstract

  It is generally thought that the mechanism underlying word-meaning deafness (WMD) is impairment in access from auditory word form to semantics. In Japanese writing, words usually written in kanji (morphograms) can alternately also be written in kana (syllabograms) . Some researchers have hypothesized that such atypically kana-written words undergo letter-by-letter conversion via the auditory word form before accessing semantics. If so, patients with WMD would have difficulty in the comprehension of atypically kana-written words as well as aurally presented words. We studied comprehension of words printed in the atypical kana-written form in a patient with WMD.
  A right-handed Japanese male in his early 60s presented with WMD following traumatic brain injury. He showed impaired comprehension of aurally presented words but flawless comprehension of visually pre sented words. His ability to perform the phoneme discrimination task, the auditory and written lexical decision task, and repetition of words and non-words were preserved. We considered these performances as those typical of WMD. When he was unable to comprehend aurally presented words, he sometimes wrote them down exactly and understood their meanings. We investigated whether he could comprehend words written atypically in kana letters. He pointed to the pictures that corresponded to the presented words swiftly, showing flawless acquisition of their meanings. For individual kana letters and kana-written non-words, however, his reading aloud was moderately impaired.
  These findings suggest that in WMD, aurally perceived word forms may neither access semantic memory nor directly retrieve visual word forms that would be understood flawlessly. By contrast, written words may access semantic memory via orthographic word form, even if they are printed in an unusual style with kana letters.
  Brain magnetic resonance imaging revealed abnormal-intensity areas in the anterior part of the left superior and middle temporal gyri and in the posterior superior temporal region around the superior temporal sulcus. We believe that the semantic memory was preserved, as the anterior temporal lesion was partial and due to traumatic etiology. The posterior superior temporal lesion may be responsible for the disconnection between the auditory word form and the semantic memory, while the preservation of the inferior part of the left temporal lobe may explain the flawless access from the visual word form to the semantic memory