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Abstract:
Using event related fMRI, we investigated the spatio-temporal
pattern of activation during language tasks that involved listening
to and then silently repeating speech. Previous work has suggested
both (i) that frontal (as well as temporal) cortex participates in
language perception, and (ii) that temporal (as well as frontal)
cortex participates in language expression. We sought to address
several questions: Would frontal and/or parietal cortex be active
during the receptive phase of the trial? Would temporal lobe
regions remain active during the expressive phase of the trial? Are
there areas active during both during receptive and expressive
phases suggestive of overlap in processing systems for perception
and production? In one task, presented subjects with four
auditorily presented pseudowords and asked them to rehearse the
list until they heard a tone. The tone was followed by several
seconds of a silent period followed by a new list of pseudowords,
and so on. Using multiple regression, we then examined activations
associated with just the auditory perception component, just with
the rehearsal component, or with both. We found that primary
auditory cortex and surrounding fields (bilaterally) responded just
to the presentation of the auditory stimuli, that left frontal
regions responded just during the rehearsal component, and that
left posterior superior temporal gyrus responded during both
components of the task. Similar results have been obtained in a
variant of this task using jabberwocky stimuli. These results,
together with several additional lines of evidence, suggest the
left posterior superior temporal gyrus supports phonemic aspects of
both speech perception and production.
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