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Abstract:
The goal of this study was to investigate different neural
mechanisms underlying episodic encoding and retrieval of sentences
and pictures. One specific question related to whether recovery of
information from memory will involve the same material-specific
networks as those engaged during encoding. A second question
related to brain responses associated with level of retrieval
success. Positron emission tomography was used to monitor brain
activity during encoding and subsequent yes/no recognition in 12
subjects. Three recognition conditions were included for each type
of material, varying with respect to target density (0%, 50%,
100%). A partial-least-squares analysis revealed two significant
activity patterns.The first pattern related to processing of
pictures versus sentences independent of the type of cognitive
process (encoding or retrieval). Picture processing strongly
activated occipito-temporal regions, and sentence processing
activated left lateral temporal and frontal regions.The second
pattern distinguished type of cognitive process across materials.
Encoding was associated with increased activity in left
dorsolateral prefrontal cortex and bilateral inferior temporal
cortices. Retrieval activated right anterior prefrontal and left
parietal cortices. Univariate analyses showed that activation
changes relating to the manipulation of target density were weak.
These results provide support that encoding and recognition
engage overlapping material-specific brain regions, and indicate
that other kinds of approaches, such as covariance-based analyses,
may be necessary to understand the neural basis of retrieval
success.
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