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Abstract:
Abstract: Several studies revealed remarkably high levels of
illusory recognition of items that are semantically related to
studied items. However, the issues of what brain mechanisms are
recruited by true and illusory recognition and whether recollection
and familiarity contribute similarly to both forms is not yet
resolved. Using event-related fMRI we recorded the BOLD response
(TR. 2.25 s; TE: 40 ms) while 12 subjects made recognition
judgments to old words, new words and new words that were
categorically similar to old words (lures). Relative to baseline
trials all recognition judgments recruited the left inferior
frontal sulcus and the anterior insula, presumably reflecting
general task-coordination processes. Correct old responses and
correct rejections of lures but not false alarms to lures led to
strong activations in the retrosplenial cortex (BA29/30), posterior
cingulate (BA23) and precuneus. Given that recollection contributes
not only to the recognition of old words but also to the rejection
of similar words, this result suggests that these regions are
recruited by the recollection of episodic information. Notably,
basal forebrain structures (nucleus accumbens) and fronto-median
cortex (BA9/10) were more strongly activated for correct old
responses than for other judgments suggesting that either an
internal reward or an expectancy confirmation mechanism accompanied
correct old judgments. The results show that a network including
the hippocampal-anterior thalamus axis is involved in recollection
of episodic information and dissociates recollection-based from
illusory recognition.
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