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Abstract:
Verb generation is widely used in functional neuroimaging
studies to investigate semantic retrieval. Yet little behavioral
research has been done with this task, and it is unknown how
cerebral asymmetries for verb generation compare to other
frequently studied lexical tasks. A role for the normal right
hemisphere has been implicated in studies of word meaning
comprehension, but it is unclear whether the right hemisphere can
contribute when words must be produced based on semantic retrieval
cues. The current study addressed these issues by presenting
concrete nouns to the left or right visual half-field (LVF, RVF).
Participants either pronounced the noun or generated an appropriate
verb. The stimuli were nouns that Thompson-Schill, et al. (1997)
determined had high or low selection demands; we hypothesized that
high selection items would pose particular difficulty for the right
hemisphere if it is unable to inhibit strongly activated
alternative responses. We obtained a highly reliable RVF advantage
for pronunciation, but not for verb generation, responses. In verb
generation, high selection items had slower responses than low
selection items regardless of visual field. The absence of a
RVF/left hemisphere advantage for verb generation is unexpected,
and we will present the results of follow-up experiments that
investigate whether the observed task differences can be attributed
to temporal factors. We then discuss whether semantic or
temporally-based task demands minimize cerebral asymmetries during
verb generation.
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