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Abstract:
Conceptual knowledge can be roughly divided into objects
(prototypically referred to by nouns) and actions (prototypically
referred to by verbs). We investigated the neural substrates of
these two categories using functional magnetic resonance imaging.
Actions, unlike objects, imply motion through space and therefore
might differentially engage posterior structures in the "where"
visual processing stream. Additionally, observations in
brain-damaged patients suggest that left prefrontal cortex may
impair verb naming more than noun naming. Participants matched
pictures of objects and pictures of actions. Matching actions
produced greater activation in and around human motion cortex (MT)
than matching objects. By contrast, activation in premotor and
prefrontal areas (BA 6, 44 and 45) did not differ. To further
investigate the neural mediation of verb knowledge, participants
judged the plausibility of sentences in which the verb referred to
concrete actions (i.e., "hit") or abstract states (i.e., "love").
Both verb types activated similar left premotor/frontal, anterior
and posterior temporal cortices. The posterior temporal activation
in the sentence task was slightly anterior and more left
lateralized than the motion areas engaged by action matching. Verb
knowledge is mediated by a distributed system that includes
premotor/prefrontal cortex, posterior and anterior superior
temporal cortices. Probing this knowledge through sentence
judgments appears to preferentially activate the left hemisphere in
contrast to when this knowledge is probed by associating
pictures.
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