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Priming pictures and words : an investigation of the N400 and LPC


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Ayre, Marie Louise 1995 , 'Priming pictures and words : an investigation of the N400 and LPC', Coursework Master thesis, University of Tasmania.

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Two ERP components are discussed in relation to studies of
semantic and mnemonic processing, namely the N400 and LPC. The
N400 is a monophasic negativity typically observed between 250 - 500
ms post-stimulus. Semantic and repetition priming studies utilising
linguistic stimuli in the visual modality (i.e. words, nonwords), and
stimulus paradigms (i.e. sentence priming and lexical decision tasks)
have indicated that the N400 is readily evoked by semantic anomaly
and is sensitive to word frequency (low frequency words eliciting
greater amplitude N400s than high frequency words), word class
(larger N400s to content words), semantic relatedness (larger N400s to
unrelated words), subject expectancy (larger N400s to unexpected
words within a context), phonology (larger N400s to non-rhyming
words and nonwords), and repetition (attenuated N400s following
word repetition). Theoretical formulations suggest the N400 indexes
the degree of spreading activation throughout the semantic network
(Morton, 1969), contextual integration (Rugg, 1990), semantic
expectancy (Kutas & Hillyard, 1984), or a memory search process
(Bentin & McCarthy, 1994). Which of these formulations most
accurately explains the N400 is currently unresolved. Whether the
negativity observed following semantic anomaly in paradigms
employing nonlinguistic stimuli (e.g. pictures, faces, and music) is
reflecting the same process as the N400 elicited by linguistic anomaly,
is also the subject of considerable debate.
Enhanced LPC amplitudes in language tasks are typically recorded
to sentence final words. The broad, post N400 positivity, occurs
approximately 550-800 ms post-stimulus and is presumed to reflect
processes associated with closure (Friedman, Simson, Ritter, & Rapin,
1975; Kutas & Hillyard, 1982), certainty (Stuss, Picton, Cerri, Leech, &
Stethem, 1992), and integrative elaborative processing (Andrews,
Mitchell, & Ward, 1993). All task relevant stimuli appear to elicit the
LPC, its amplitude being inversely related to subjective probability.
The LPC is also associated with certain aspects of mnemonic
processing. Enhanced LPC amplitudes have been recorded to stimuli
which are subsequently recognised, to 'seen' stimuli as compared to
'unseen', and to the second presentations of stimuli. Subsequent to
these findings, it has been hypothesised that the LPC observed in
memory and repetition paradigms reflects some process associated
with both encoding and retrieval. Resulting from the perceived
similarity between the LPC component elicited in these various
paradigms, some investigators posit that similar episodic processes
subserve them (Besson & Kutas, 1993).

Item Type: Thesis - Coursework Master
Authors/Creators:Ayre, Marie Louise
Keywords: English language, Human information processing in children, Memory in children, Cognition in children, Language acquisition
Copyright Holders: The Author
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Copyright 1995 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references (leaves 34-40). Thesis (M.Cl.Psych.)--University of Tasmania, 1995

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