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Abstract:
Auditory scene analysis involves identifying the content of
sound sources in the environment as well as their locations.
Functional dissociations for these processes have yet to be clearly
demonstrated, although evidence suggesting such dissociations is
provided by anatomical and neurophysiological studies in non-human
primates. To determine if separate pathways for what and where
exist in the auditory system, we compared changes in regional brain
activity, as measured by fMRI, in a group of 12 young adults
performing an S1-S2 match-to-sample task. In the location task,
participants were asked to localize S2 relative to S1 (leftward,
same or rightward) regardless of pitch changes. In the pitch task,
participants judged whether S2 was lower, identical to or higher in
pitch than S1 regardless of its location. The same stimulus set was
used in both tasks. Accuracy and response times were similar in
both conditions. Comparing the locations of the two stimuli
generated greater activation in inferior and superior parietal
cortices and superior frontal gyrus than did pitch comparisons.
Conversely, judging the pitch changes generated greater activation
in auditory cortices and inferior frontal gyri. Results are
consistent with distinct neural systems underlying the processing
of sound identity and sound location similar to the what and where
systems observed in the visual modality.
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