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Abstract:
Neuroimaging research has indicated that perceptually-based
implicit memory (priming) is mediated by posterior cortex whereas
conceptually-based implicit memory is mediated by left prefrontal
cortex. The involvement of posterior cortex in implicit memory has
been confirmed by ERP studies. However, ERP studies have not been
able to produce electrophysiological correlates of conceptual
implicit memory. The present study divided 'old' words at test into
whether words were primed or not as well as being recognised or
not. The behavioural measure of priming was conceptually-based.
Words were categorised as primed, not recognised (PNR) or not
primed, not recognised (NPNR). When NPNR words were compared with
correct rejections (CRs), a reliable effect of implicit memory
ensued in posterior regions from 200-400msec. This took the form of
ERPs to NPNR words being more positive than those to CRs. The
PNR/CR comparison led to no early modulations but instead revealed
that PNR words led to more positive-going ERPs than CRs in
posterior areas from 500-700msec. It is suggested that the NPNR/CR
reflects percetually-based implicit memory in the absence of
awareness. There was no correlation with the conceptual priming
measure. The results of the PNR/CR comparison suggest that an EEG
correlate of conceptual priming is not detectable at the scalp and
explicit memory contamination may have occurred.
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