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Abstract:
Neuropsychological evidence from brain damaged patients
suggests that the processing of verbs and nouns dissociate, but the
neuroanatomical characteristics of this dissociation remain
unclear, especially in input tasks. We hypothesized that such a
dissociation is related to the nature of lexical processing
associated with these two categories. To examine this question we
manipulated both grammatical category and processing mode of Hebrew
words. Twelve healthy right-handed subjects were scanned in a 1.5T
scanner while listening to 16 blocks comprising either verbs or
nouns. For each block, subjects were instructed to make either a
semantic decision ("Does the word belong to a given semantic
category?"), or a morphological decision ("Is the word inflected in
plural?"). The results showed different patterns of activation
across distinct language areas. In the posterior portion of left
superior temporal sulcus, the overall activation for verbs was
greater than the activation for nouns. Within the inferior
prefrontal cortex we observed two subregions distinguished by their
differential response to the experimental conditions - one of them
favoring verbs and morphological processing while the other
revealing a strong effect of the semantic classification task only.
These results support the notion of distributed brain
representations for lexical entries, which depend on both semantic
and grammatical properties.
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