Document Type

Dissertation

Publication Title

ProQuest Dissertations

Abstract

The electrophysiological correlates of recognition memory retrieval were examined in order to identify the neural conditions that precede accurate memory retrieval, characterize the processes that contribute to high and low confidence memory responses, and determine which memory processes are impaired after brain injury. Human electroencephalogram (EEG) was recorded during recognition confidence and source memory judgments in three experiments. In Experiment 1, mid-frontal pre-stimulus theta oscillations were found to precede the stimulus presentation of items that were successfully recollected, but they were not found to be predictive of item familiarity. Moreover, during stimulus presentation, recollection was associated with an increase in theta over left parietal regions, and the magnitude of this effect was predicted by the earlier per-stimulus theta effects. The results suggest that pre-stimulus processes set the stage for and facilitate subsequent recollection. In experiment 2, high and low confidence source memory judgments were found to be supported by two electrophysiologically distinct processes. Whereas correct high confidence source memory was associated with a late positive component indicative of recollection, correct low confidence source memory was associated with a late onset negative going ERP that was distinct from both recollection and familiarity based responses. The results indicate that correct source memory responses can be observed even in the absence of recollection. In experiment 3, ERPs were recorded in amnesics in order to determine whether they exhibited selective deficits in recollection, as previous behavioral studies had suggested. Behavioral data showing relatively preserved item recognition along with severely impaired source recollection was consistent with prior studies of these patients, and ERPs revealed that the patients showed no evidence of recollection-related neurophysiology, but maintained normal ERP correlates of familiarity. These results indicate that these patients exhibit selective recollection deficits, are consistent with dual process models of memory, and suggest that source memory depends critically upon the medial temporal lobe structures, such as the hippocampus, which are typically disrupted in amnesia

DOI

AAI3499396

Publication Date

Fall 12-1-2011

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