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Abstract:
An important issue in current theories of speech perception
is the role played by the planum temporale area in the superior
temporal gyrus. 15 O- PET brain imaging was performed on 12 healthy
subjects who listened to series of consonant-vowel syllables or
musical chords. The syllables consisted of the six stop-consonants
paired with the vowel /a/. The stimuli were presented dichotically,
i.e. two different syllables or chords at the same time, one in
each ear. The subjects were instructed to press a response-button
whenever a pre-determined target (CV-syllable or musical chord) was
heard. PET-scanning was done with an 18-ring GE-Advance scanner.
The behavioral results showed a right ear advantage to the
CV-syllables, and a left ear advantage for the musical chords. The
PET data were analyzed from 2 mm thick axial slices going from - 12
mm to + 20 mm, thus covering a region from the medial to the
superior temporal gyrus. The PET results showed significant
bilateral activation to the CV-syllables in more ventral temporal
areas, that extended into the planum temporale, with increasing
asymmetry of activation in more superior slices. For the musical
chords, there were no activation in ventral regions, only in the
superior temporal plane, with a reversed asymmetry. It is concluded
that phonological stimuli also activate areas in the medial
temporal lobe outside of the planum temporale area.
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