Thomas Grabowski
Department of Neurology
Wednesday, October 8
3-4:30pm
Streams of knowledge in
the naming brain
Using a picture-word
interference paradigm in an fMRI experiment, we
aimed to isolate neural systems involved in prelexical and
lexical-semantic processing during word production, and to
evaluate the
evidence for segregation by conceptual category of the systems
supporting these two levels of processing. English speakers overtly
named photographs of animals and manipulable
objects while in the
scanner, ignoring simultaneously presented auditory
distracters that
were semantically related or unrelated to the target
entities.
effects of category for animals versus manipulable objects were found in
occipital versus parietal regions and no effects of
semantic
interference were seen in these regions. Semantic interference effects
were found in the left posterolateral
temporal lobe for both categories,
whereas other inferotemporal
and left inferior frontal regions presented
category-related semantic interference effects. Target word frequency
effects and distracter word frequency effects (assumed to
arise at
phonological output stages of processing), occurred only in
posterior
superior temporal gyrus, and not
in IT or IFG. The results demonstrate
that neural systems representing these two categories
of entities are
significantly segregated at two levels: in occipito-parietal
networks,
presumably related to prelexical
conceptual processing, and in
inferotemporal
and inferior frontal networks, related to lexical
selection.