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Abstract:
Recognition is theorized to involve two processes: 1)
Recollection of thoughts or actions associatively linked to test
items, and 2) Familiarity assessment of items accompanied by
feelings of recent encounter. Behavioral and fMRI studies were
conducted to assess the neural substrates of these processes.
During encoding, subjects alternated between "pleasant/unpleasant"
or "abstract/concrete" decisions for individually presented words.
Subsequently, recognition was tested using pairs (2AFC) that fully
crossed encoding type with relative study lag (first or second
half). "Source" recognition required participants to select the
word encoded using the "pleasant<>unpleasant" decision
whereas relative "recency" required selection of the most recently
encountered word. Varying the response deadline and study lag
doubly dissociated source and recency performance.
Neuroanatomically, the judgments elicited strikingly lateralized
and non-homologous patterns of activation. Right hemisphere
regions, including anterior prefrontal cortex (~BA 10), were more
active during recency than source, suggesting involvement with
"monitoring" processes engaged when item familiarity is evaluated.
In contrast, left structures, including inferior prefrontal cortex
(~BA 45/47), were more active during source than recency
recognition. This pattern is consistent with recent findings
implicating left prefrontal cortex in the retrieval of episodic
detail. Collectively, these findings suggest that subjects
strategically engage different networks depending on the potential
utility of information during recognition attempt.
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