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Abstract:
Recent memory research focuses on brain activity associated
with encoding and retrieval. The present experiment utilizes fMRI
to disentangle the neural mechanisms subserving encoding and
retrieval using nonverbal auditory information. 15 subjects were
presented with novel sounds embedded in a tonesequence. In the
study phase of an intentional memory task subjects were required
either to judge the sounds loudness or to decide whether or not a
sound could be verbally described (e.g. ringing bell). In the
following test phase subjects performed a recognition test. During
the entire experiment echo planar images (TE=40ms, TR=1s) of eight
axial slices were acquired. In the study phase the right
dorsolateral and inferior prefrontal cortices (PFC) were activated
in the both conditions. In the VERBAL condition additional
activation of the left inferior PFC was obtained. Retrieval related
fMRI activity varied as a function of encoding condition: in the
LOUDNESS condition we detected an activation focus in the right
inferior PFC while in the VERBAL condition an activation in the
left dorsolateral PFC was observed. These findings indicate that
the right dorsolateral PFC is engaged in encoding of nonverbal
auditory information independent of encoding condition.
Furthermore, the lateralization of PFC activity during retrieval of
nonverbal material depends on the availability of verbal codes,
with left hemispheric involvement for verbally and right
hemispheric activation for nonverbally coded information.
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