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Abstract:
We used event related potentials (ERPs) to investigate the
relationship between attention and processes involved in encoding
information into episodic memory. ERPs were recorded while subjects
studied visually presented words under focused attention or while
performing an auditory-motor continuous performance task (divided
attention). Episodic memory was measured using free recall and
Remember/Know recognition tests. We averaged ERPs at encoding as a
function of attention (focused vs. divided) and as a function of
later memory performance (recalled, not recalled; remembered, known
or missed). Our analyses identified an early positive waveform
(200-400 ms) modulated by attention and enhanced in all categories
of successfully retrieved items (recalled, "remembered", "known"),
followed by a posterior positivity (400-750 ms) that was strongly
influenced by the attentional manipulation but did not clearly
differentiate items on the basis of later memory. Frontal and
inferior posterior slow waves (750-2000 ms) were modulated by
attention and enhanced for later recalled or "remembered" items,
but did not differentiate between later "known" and "missed" items.
Our findings suggest that episodic encoding is a two-stage process
consisting of: (1) early processes related to conceptual stimulus
evaluation which, although they require some involvement of the
anterior attentional system, only result in an initial,
uncontextualized memory trace, and (2) subsequent processes which
depend on complete transfer to working memory and which further
elaborate this initial trace to form a contextualized episodic
memory.
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