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Abstract:
The magnitude of left inferior prefrontal (LIPC) activation
during the encoding of words predicts subsequent memory for those
words, implicating LIPC in episodic encoding. Prior experience with
a word results in reduced LIPC activation during the later
processing of that same word, with this "priming" effect reflecting
implicit memory for the initial experience. To assess whether there
is a negative consequence of priming for new episodic learning, we
conducted an event-related fMRI study of the spacing effect. In
each fMRI scan, participants performed an incidental encoding task
for words encountered 24 hours prior to the scan (Long Lag), for
words encountered just prior to the scan (Short Lag), and for new
words (New) (BOLD fMRI, 3.0T GE scanner with ANMR EPI, 16 axial
slices, TR=2 sec). Priming and LIPC activation were negatively
correlated: Reaction times were faster in the Short Lag compared to
the Long Lag condition, whereas the magnitude of LIPC activation
was greater in the Long Lag compared to the Short Lag condition.
Importantly, subsequent memory performance on a recognition test
administered 48 hours after scanning revealed superior memory
retention in the Long Lag compared to the Short Lag condition.
Thus, greater priming was associated with reduced activation in
LIPC and reduced subsequent memory. Priming can impair new episodic
learning.
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