Date of Award
Master of Arts
Recent functional neuroimaging research has highlighted the role of the posterior parietal cortex (PPC) during episodic memory retrieval (Vilberg & Rugg, 2007; Vincent et al., 2006; Wagner et al., 2005; Wheeler & Buckner, 2003; Yonelinas et al., 2005). It has been shown that the PPC is active during the retrieval of old information, when subjects incorrectly believe that new information has been encountered before (false alarms), and when retrieval is accompanied by recollection (Wagner et al., 2005). A preliminary positron emission tomography (PET) study suggests that the PPC is also active when retrieval occurs unintentionally or incidentally, prompted by the presence of an old stimulus item. Collectively these studies suggest that activity in the PPC may be driven by familiarity, irrespective of task demands and independent of its veracity. The main goal of this thesis was to explore, with functional magnetic resonance imaging (fMRI), the conditions under which activity in the PPC may be modulated by the familiarity of veridical and perceived memories. Subjects were presented with scene/word pairs that were repeated 1, 3, or 7 times on Day 1. On Day 2, while MRI scans were recorded, subjects studied either, new items, old pairs (same-form) one additional time (2nd,, 4th, or 8th presentation), or pairs in which the word associated with each picture was changed (different-form) one additional time (2nd,, 4th, or 8th presentation). Same form pairs activated bilateral inferior parietal lobule compared to novel pairs replicating the findings from the PET study on incidental retrieval. Same and different form pairs did not differ on amount of parietal activity. Additionally, same form pairs that were repeated 8 times displayed more PPC activity than same form pairs repeated two and four times while there was no difference across different form repetitions. Together these results indicate that items that are old and that those that are new but are perceived as old activate the inferior parietal lobule.
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