The primary research question for this study was to determine if physiological correlates of encoding and retrieval could be observed across three levels of processing. It was hypothesized that physiological correlates of encoding and retrieval would be observed at electrode sites near Cz with the semantic processing condition yielding the most positive going event-related-potential, the phonological processing condition yielding an intermediate positive going event-related-potential, and the perceptual processing condition yielding the least positive going-event-related-potential. The experiment had a study phase and test phase. For the study phase, participants were encouraged to process the target word at one of three different levels, by indicating if the word was in capital or lower-case letters, if it rhymed with a given criterion word, or if the object referred to by the word was a member of a designated category. These were referred to as the perceptual, phonological, and semantic conditions, respectively. Thirty trials were presented in each condition. For the test phase, the 90 previously viewed words and 90 new words were presented in random order. Performance data and ERP data were recorded during the study phase and test phase. The results supported the hypothesis as ERP data indicated that the phonological processing condition yielded intermediate ERP positivity for the late positive component (LPC) when compared to the perceptual and semantic processing conditions. This trend was observed at approximately 550 ms at electrode sites CPz and Pz in both study and test phase data. Because there were no differences in amplitude among the three levels of processing for the Ni, P2, and N400, these findings suggest that the differences in physiological activity occurs predominately for late ERP components, and not early ERP components. The findings may also suggest different voltage topographies for the LPC. For the study phase data, the voltage maps appear to show more cortical activity to the frontal region for words that were later correctly remembered compared to words that only yielded successful categorization. For the test phase data, the voltage maps appear to suggest that prior encoding processes influenced subsequent recognition based upon the different voltage topographies for each processing condition. The data from the study phase and test phase appear to show differences in cortical activity based on levels of processing and how previous learning can influence subsequent recognition.
Master of Arts (MA)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Evoked potentials; Cognition -- testing; Thought and thinking; Problem solving.
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Merrifield, Warren Scott, "The Effect of Levels of Processing on Event-Related-Potentials" (2004). Loma Linda University Electronic Theses, Dissertations & Projects. 708.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives