Auditory context effects in picture naming investigated with event-related fMRI |
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Authors: | Greig I de Zubicaray Katie L McMahon |
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Institution: | 1. Centre for Magnetic Resonance, University of Queensland, 4072, Brisbane, QLD, Australia
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Abstract: | Naming an object entails a number of processing stages, including retrieval of a target lexical concept and encoding of its
phonological word form. We investigated these stages using the picture-word interference task in an fMRI experiment. Participants
named target pictures in the presence of auditorily presented semantically related, phonologically related, or unrelated distractor
words or in isolation. We observed BOLD signal changes in left-hemisphere regions associated with lexical-conceptual and phonological
processing, including the midto-posterior lateral temporal cortex. However, these BOLD responses manifested as signal reductions
for all distractor conditions relative to naming alone. Compared with unrelated words, phonologically related distractors
showed further signal reductions, whereas only the pars orbitalis of the left inferior frontal cortex showed a selective reduction
in response in the semantic condition. We interpret these findings as indicating that the word forms of lexical competitors
are phonologically encoded and that competition during lexical selection is reduced by phonologically related distractors.
Since the extended nature of auditory presentation requires a large portion of a word to be presented before its meaning is
accessed, we attribute the BOLD signal reductions observed for semantically related and unrelated words to lateral inhibition
mechanisms engaged after target name selection has occurred, as has been proposed in some production models. |
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