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Abstract:
We used fMRI to examine the effect of experience with
specific items from different categories on neural activity during
naming. Seven subjects were familiarized with 90 photographs of
animals and 90 photographs of tools outside of the scanner. Four
days later, whole brain gradient-echo, echo-planar images were
obtained on a 1.5 Tesla scanner while subjects silently named these
and 180 new photographs of animals and tools, presented in a
blocked design. Naming latencies documented a significant learning
effect for previously studied pictures. Replicating our previous
results, we found category-related activity in a number of regions.
Specifically, the medial region of the fusiform gyrus, middle
temporal gyrus, and left premotor and posterior parietal cortices
responded preferentially to tools, whereas the lateral fusiform and
superior temporal sulcus responded preferentially to animals.
Activity in these areas was modulated by experience. In most
regions, reduced activity was associated only with previously
studied pictures from the preferred category. However, in the
fusiform gyrus, experience also modulated the response to the
non-preferred object category, suggesting that the response to the
non-preferred category is also part of the category-specific object
representation in ventral temporal cortex. In addition, previously
studied pictures of animals and tools elicited increased activity
in several regions associated with explicit retrieval, including
the hippocampus, parahippocampal gyrus, precuneus, and bilateral
prefrontal cortex.
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