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Abstract:
Abstract: Based on pioneering neuroimaging studies of verbal
working memory, it has been proposed that: posterior parietal
cortex (PPC) provides a phonological buffer for "pure storage" of
component speech units; inferior prefrontal cortex (IPFC), SMA, and
premotor cortex form a circuit for articulatory rehearsal that
refreshes the phonological buffer; and dorsolateral prefrontal
cortex (DLPFC) implements executive processes for temporal coding,
serial-order control, and other related supervisory functions. Yet
these proposals may be somewhat incomplete and inaccurate. Precise
computational modeling of quantitative behavioral data from the
verbal serial memory-span task reveals that it entails executive
processes, temporal coding, serial-order control, and associative
chaining of speech units. Furthermore, focal lesions of PPC and
IPFC cause different patterns of deficits in serial memory span,
sequential oral and manual movement, and other basic
perceptual-motor performance, whereas lesions of DLPFC cause
relatively little such deficits. Given these insights, we reach
four tentative inferences: (1) executive processes of temporal
coding and serial-order control take place at least partly in IPFC;
(2) PPC is a storage site of amodal associative-chain links; (3)
the site of temporary storage for component speech units remains to
be discovered; (4) other putative functions of executive processes
in DLPFC remain to be elucidated.
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