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Abstract:
We previously reported category-related activations in the
posterior temporal lobe when subjects viewed and named pictures of
objects from different semantic categories such as animals and
tools. Do these activations reflect processes associated solely
with picture identification or do they reflect more abstract,
semantic processes? To address this issue, we collected gradient
echo echoplanar images from the posterior cortex (18, 5mm coronal
slices, TR = 3, TE = 40 ms) while subjects (n = 8) read names and
named pictures of animals and tools. Animal and tool stimuli were
presented in alternating blocks for reading (runs 1-6) and naming
(runs 7- 12). Subjects always performed the reading task first so
that word reading was not influenced by the pictorial examples. To
ensure that subjects read the words, each block was preceded by a
general question about animals and tool. Subjects responded with
button press. Common category-related patterns of activation were
noted in the posterior temporal cortex for reading and naming. In
particular, reading animal names and naming pictures of animals
activated the right lateral fusiform gyrus, possibly reflecting
stored information about object form. In contrast, reading tool
names and naming pictures of tools activated the left middle
temporal gyrus, possibly reflecting stored information about object
motion. Taken together, these data suggest a common, form
independent semantic system for storing information about different
object categories.
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