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Abstract:
Abstract: Previous fMRI studies have found changes in early
visual processing areas after nondeclarative (nonconscious)
category learning (Reber, Stark & Squire, PNAS, 1998a; Reber,
Stark & Squire, Learn&Mem, 1998b) that are distinct from
stimulus-correlated activity observed during recognition
(conscious) memory. To directly compare these two types of memory,
fMRI was used to examine stimulus-correlated activity during
categorization after conscious or nonconscious category learning.
Participants learned a category of dot patterns from a set of
exemplars under either (a) incidental learning conditions in which
they were instructed to attend to study patterns with no mention of
the categorical structure; or (b) by being told of the underlying
category and attempting to learn it. Scanning occurred during a
subsequent categorization test. Participants who learned the
category incidentally exhibited reduced activity in early visual
processing areas for the categorical patterns versus noncategorical
patterns, replicating previous results (Reber et al. 1998a,b). In
contrast, after the conscious category learning, increased
activation was observed in occipital cortex for the categorical
patterns, including a region that has been shown to exhibit
increased activity for targets during recognition (Reber et al.
1998b). These results suggest that a reduction in activation in
visual cortex is associated with nonconscious, nondeclarative
memory of the category while the use of conscious category
knowledge to judge membership instead evokes recognition-like
retrieval processes.
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