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Abstract:
Neuroimaging studies and studies of neurologically impaired
patients suggest that different kinds of knowledge involve
different neural substrates. Verb representations are hypothesized
to recruit frontal areas implicated in action, and semantic
representation of objects to reflect sensory-motor features such as
perceptual appearance and characteristic motion. These hypotheses
confound semantics and form class. In the present BOLD fMRI study,
we compare cortical representation of motion verbs (e.g., climb)
and manipulable objects (e.g., ladder). These word types are
semantically similar in that their essential features involve motor
activity; however, they afford contrasting grammatical form classes
(i.e., nouns and verbs). Young healthy subjects judged
consecutively presented written words, blocked by type, for
"pleasantness." This task promotes deep semantic processing,
imposes minimal cognitive demands, and allows a uniform task across
contrasting stimuli. Relative to motion verbs, implements recruited
left superior temporal and prefrontal regions. Relative to
implements, motion verbs recruited right prefrontal areas. These
results suggest that words with semantic overlap but grammatical
distinctions involve different neural substrates. This calls into
question the hypothesized link between the apparent semantic
content (e.g., knowledge of motor activity) and regions recruited
(e.g., motor areas), and suggests a role for grammatical
information in lexical representation.
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