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Abstract:
These experiments show that words can elicit conceptual
information both consciously and unconsciously encoded during brief
picture presentations. In experiment one, each functional run
consisted of alternating test and study blocks, with a variable
interstimulus interval to allow for event-related analysis. During
study,10 pictures were presented for 50 msec each and followed by a
500 msec pattern mask. During test, 20 words (10 of which named the
previous 10 pictures) were presented. Subjects had to respond "OLD"
(if the word named one of the pictures) or "NEW" (did not name one
of the pictures). Subjects received 4-8 study/test blocks during
2-4 functional runs. Comparing imaging during pictures associated
with recognized words (hits) to imaging during pictures associated
with unrecognized words (misses) demonstrated increased activity in
the posterior-medial temporal lobe in the left hemisphere, as well
as in the hippocampus and prefrontal cortex, bilaterally. However,
direct comparison of hits and misses confounds differential
assessment of conscious and unconscious processing. Experiment 2
uses the same block/event-related interleaved design, with the
addition of "mask-alone", and "fixation-alone" trials during study.
This permits evaluation of functional activation related to hits
separately from functional activation related to misses, which in
turn, allows for differential assessment of conscious and
unconscious cross-form processing.
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