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Abstract:
Abstract: Non-identical neural systems mediating knowledge
about living and nonliving objects have been suggested by a number
of neuropsychological and neuroimaging studies. In our lab we have
used ERPs, which have high temporal resolution, to show that these
category-specific systems may differ not only anatomically but also
in their time-courses of operation. That is, pictures of animals
elicited larger N300-like anterior negativity, while pictures of
tools - larger N400-like posterior negativity. The present study
further contrasted processing of animals and tools by recording
ERPs to words, rather than pictures, that either were or were not
semantically primed by a category name (e.g. animal - dog vs. tool
- dog). We hypothesized that the anterior N400 priming effect,
previously reported to concrete words and suggested to reflect
processing in an image-based semantic system, would reveal
activation of semantic representations of objects' imagistic
features. However, the posterior N400 effect, thought to be
generated in an amodal semantic system, would show processing
conceptual characteristics. Results showed that both animals and
tools elicited two negative-going components in the N400
time-window, one affected by semantic priming in the
frontal-central electrode sites, while another - in the posterior
sites. However, the time-course of these components was different
between object categories, suggesting that even though knowledge of
all objects may depend on the representations/processes in both
imagistic and amodal systems, people tend to use these systems
differently when process concepts of animals and tools.
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