Ra. Poldrack et al., Functional specialization for semantic and phonological processing in the left inferior prefrontal cortex, NEUROIMAGE, 10(1), 1999, pp. 15-35
Neuroimaging and neuropsychological studies have implicated left inferior p
refrontal cortex (LIPC) in both semantic and phonological processing. In th
is study, functional magnetic resonance imaging was used to examine whether
separate LIPC regions participate in each of these types of processing. Pe
rformance of a semantic decision task resulted in extensive LIPC activation
compared to a perceptual control task. Phonological processing of words an
d pseudowords in a syllable-counting task resulted in activation of the dor
sal aspect of the left inferior frontal gyrus near the inferior frontal sul
cus (BA44/45) compared to a perceptual control task, with greater activatio
n for nonwords compared to words. In a direct comparison of semantic and ph
onological tasks, semantic processing preferentially activated the ventral
aspect of the left inferior frontal gyrus (BA 47/45). A review of the liter
ature demonstrated a similar distinction between left prefrontal regions in
volved in semantic processing and phonological/lexical processing. The resu
lts suggest that a distinct region in the left inferior frontal cortex is i
nvolved in semantic processing, whereas other regions may subserve phonolog
ical processes engaged during both semantic and phonological tasks. (C) 199
9 Academic Press.