HOWARD ET AL (1992)
“The cortical localization of the lexicons: PET evidence.”

Abstract

The results are consistent with the localization of a lexicon for spoken word recognition in Wernicke’s area and a lexicon for written word recognition further back in the temporal lobe. [very close the the angular gyrus, the classical localization of visual word forms: Dejerine, 1891]

The proposal for the location of a visual word-form system differs from that by Petersen et al (1990), who identified this in left medial extrastriate cortex. There was however a weak trend implicating this location in the present study, some apparent involvement of the left temporal region in Petersen et al’s (1990) data.

Subjects were 12 normal r-handed adults. Each S had six scans in a session of 90 mins., one each control task, and two scans for each experimental task.

Tasks

  1. Word reading (visual presentation +speaking)
  2. Word repetition (auditory presentation + speaking)
  3. “see and say”: a series of “False-font” stimuli: Ss required to say the word “crime” after each control non-word, non-letter visual stimulus.
  4. “hear and say”: auditory presentation of words re-recorded backwards, and Ss required to say “crime” after hearing each non-word auditory stimulus.

Results

Sensory Processing. Comparing the activation patterns for same verbal response given to false-font visual stimulation and words recorded backwards suggests that the letter-like strings evoke bilateral activation in primary and secondary visual cortex (striate and extrastriate areas) whereas the arbitrary auditory stimulation activate primary and secondary auditory cortex.

Visual word processing. When word reading is compared with “see and say” (false-fonts, š say “crime”) the significant difference in activation is in the left temporal lobe (posterior middle temporal gyrus)

Auditory word processing When word repetition is compared with “hear and say” (words backwards š say “crime”) the significant difference in activation is again in the left temporal lobe: close to be slightly in front of the classical location of Wernicke’s area.

Conclusion