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Abstract:
Posterior left inferior prefrontal cortex (pLIPC) has been
posited to mediate the control of phonological representations.
Moreover, during incidental episodic encoding of familiar verbal
stimuli (native language words), the magnitude of pLIPC activation
under semantic orienting conditions is predictive of subsequent
recognition memory. In the present study, event-related fMRI
assessed whether pLIPC activation is (a) greater during
phonological processing of unfamiliar words that require
construction of novel phonological representations, and (b)
predictive of subsequent memory when incidental encoding is
performed under phonological orienting conditions. During scanning,
subjects made a syllable judgment (2 or 3 syllables?) for English,
pseudo-English, and foreign words (BOLD EPI, 1.5T, 21 axial slices,
TR=2 sec). Behaviorally, reaction times were comparable across all
word classes, and performance accuracy was high. Functionally,
pLIPC activation was greater during phonological analysis of
unfamiliar (pseudo-English and foreign) relative to familiar
(English) words. Moreover, the magnitude of activation during the
phonological encoding task was positively correlated with
subsequent memory. As this pattern was observed for non-words with
no available semantic representation, this pLIPC activity must
reflect differences in phonological encoding. Collectively, these
data suggest that pLIPC may mediate the on-line construction of
phonological representations for stimuli when there is no
pre-existing representation in LTM, and in so doing may foster
their episodic encoding.
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