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Abstract:
The majority of ERP studies of recognition memory have
focused on 'retrieval success'. Those that have attempted to
investigate pre-retrieval processes such as 'orientation' and
'effort' have tended to confound these processes. We employed a 2x2
factorial design in an effort to dissociate the neural correlates
of retrieval effort and retrieval orientation. Subjects were
presented with study lists of either words or pictures of namable
objects. Study conditions were manipulated to produce an "easy" and
"hard" condition for each type of item by manipulating study list
length and study-test interval. Following each study list
recognition memory for the studied material was tested using words
as test items while ERPs were recorded for each item. The ERP
correlates of retrieval effort were identified by assessing the
effects of difficulty. To investigate retrieval orientation, the
ERPs elicited by new words were compared as a function of study
material (pictures or words). ERPs did not differ as a function of
difficulty. They did however differ according to orientation, such
that a positive going modulation was apparent from ~300ms onwards
when information about objects relative to words was to be
retrieved. This effect did not vary according to difficulty. The
findings suggest that ERPs are sensitive to differences in
retrieval orientation brought about by the requirements to probe
memory for different types of information.
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