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Abstract:
This fMRI study investigated the functional neuroanatomy of
auditory and visual verbal working memory using an event-related
design to determine whether there were modality-specific
differences in the timecourse and location of activation during
retention. Five subjects were presented with three consonant-vowel
syllables (e.g. ba co di) sequentially (500 ms per syllable) in the
auditory modality during one MRI scanning session, and in the
visual modality during another. Two conditions were compared, one
in which subjects retained the syllables subvocally during the
14-second delay interval following stimulus presentation, and one
in which they did not. Probe tasks following the delay interval
ensured that subjects were performing the experiment according to
instructions. Paired t-tests compared each of the timepoints to the
baseline. The results showed significant activity in the
modality-specific sensory cortices during timepoints early in the
retention interval due to stimulus processing. In the auditory
memory condition, superior temporal activation persisted later into
the retention interval compared to the visual memory condition,
where activity in this temporal region only appeared
inconsistently. Four of the five subjects demonstrated frontal
activity in both the auditory and visual memory conditions,
although there were individual differences in the location and
timecourse of activation for these subjects. These results suggest
the presence of modality-specific differences in the retention of
verbal information.
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