Although regions of the parietal cortex have been consistently implicated in episodic memory retrieval, the functional roles of these regions remain poorly understood. The present review presents a meta-analysis of findings from event-related fMRI studies reporting the loci of retrieval effects associated with familiarity- and recollection-related recognition judgments. The results of this analysis support previous suggestions that retrieval-related activity in lateral parietal cortex dissociates between superior regions, where activity likely reflects the task relevance of different classes of recognition test items, and more inferior regions where retrieval-related activity appears closely linked to successful recollection. It is proposed that inferior lateral parietal cortex forms part of a neural network supporting the 'episodic buffer' [Baddeley, A. D. (2000). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417-423].

The importance of the medial temporal lobe to episodic memory has been recognized for decades. Recent human fMRI findings have begun to delineate the functional roles of different MTL regions, most notably the hippocampus, in the retrieval of episodic memories. Importantly, these studies have also identified a network of cortical regions – each interconnected with the MTL – that are also consistently engaged during successful episodic retrieval. Along with the MTL these regions appear to constitute a content-independent network that acts in concert with cortical regions representing the contents of retrieval to support consciously accessible representations of prior experiences.

The present experiment used fMRI to investigate whether neural correlates of recognition memory behave in a manner consistent with the proposal that recognition decisions are based on a unidimensional memory strength variable. A modified Remember/Know recognition test was used in which participants could indicate two levels of recollection. Participants were required to indicate whether a test item was new, familiar (known), elicited recollection of general contextual details from the study episode (R1 response), or elicited a specific recollection of the item with which it was paired at study (R2 response). Little evidence could be found to support the view that Remember/Know/New judgments reflect variations along a single strength dimension. Instead, the findings replicated prior research in indicating that the neural correlates of recollection and familiarity can be doubly dissociated. Two recollection-sensitive regions - left lateral inferior parietal and left fusiform cortex - were found to be sensitive to amount of information recollected, as operationalized in the contrast between R2 and R1 responses. It is proposed that these regions may support the representation of recollected information.

The electrophysiological correlates of recollection were investigated with a modified Remember/Know task in which subjects signaled whether they fully or partially recollected visual object information in each study episode. A positive-going ERP deflection--the left parietal old/new effect--was sensitive to the amount of information recollected, demonstrating greater amplitude when elicited by test items associated with full relative to partial recollection. These findings support prior proposals that the left parietal ERP old/new effect is sensitive to the amount of information recollected from episodic memory. An early-onsetting (ca. 150 ms), left frontal old/new effect differentiated items accorded correct old versus correct new responses regardless of whether the items were endorsed as familiar or recollected. This finding extends the range of circumstances under which early, frontally distributed old/new effects occur, and adds weight to previous suggestions that these effects are a neural correlate of familiarity-driven recognition memory.

The present study addressed the question whether neural activity in left lateral parietal cortex is modulated by amount of information recollected. In two experiments (one using fMRI, the other ERPs) subjects first studied pairs of pictures presented for either one or six seconds. They then performed a standard 'Remember/Know' recognition memory test in which the old items comprised one of the pictures from each studied pair. In both experiments, a surprise post-test indicated that subjects recollected more details about the study presentation of the items presented for the longer duration. In the fMRI experiment, recollection-and familiarity-based recognition elicited activity in distinct cortical networks. Additionally, recollection-related activity in left inferior parietal cortex was of greater magnitude for test items presented for six seconds than for one second. In the ERP study the 'left-parietal old/new effect' -a putative correlate of successful recollection -was likewise modulated by amount of information retrieved. Together, these findings provide further support for dual-process models of recognition memory and add weight to the proposal that retrieval-related activity in left inferior parietal cortex reflects processes supporting the online representation of retrieved episodic information.Keywords episodic memory; recognition memory; remember-know; event-related potential; episodic buffer Numerous functional neuroimaging studies have implicated the left posterior parietal cortex in recognition memory (for reviews see Wagner et al., 2005;Skinner & Fernandez, 2007; Ciaramelli, Grady, & Moscovitch, in press; Vilberg & Rugg, in press). Activity in this region has been reported to dissociate according to whether recognition judgments are made on the basis of recollection, when contextual information from a study episode is recovered, as opposed to familiarity, when an item is recognized without contextual retrieval (e.g., Yonelinas et al., 2005;Wheeler & Buckner, 2004; see also Vilberg & Rugg, in press). Whereas recollection-sensitive left parietal activity tends to be located in and slightly posterior to the angular gyrus (Brodmann Area (BA) 39/19), familiarity-sensitive regions are located more superiorly in the vicinity of the intraparietal sulcus (IPS; BA 7). Current evidence suggests that the left parietal region associated with familiarity is actually responding to something akin to the salience of the eliciting test items rather than directly reflecting a memory signal (Vilberg & Rugg, in press), but the functional significance of recollection-related left inferior parietal activity remains unclear.Correspondence: Kaia L. Vilberg, Center for the Neurobiology of Learning and Memory, University of California Irvine, Irvine, CA 92697-3800. Email: E-mail: kvilberg@uci.edu. NIH Public Access NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptIn a recent study (Vilberg & Rugg, 2007) we attempted to adjudicate between two competing hypotheses regarding the role of the ...