The Role of VMPC in Metamemorial Judgments of Content Retrievability David M Schnyer1 2 Lindsay Nicholls1 and Mieke Verfaellie1 Abstract Making judgments about the retrievability of information is a critical part of the metamemory processes engaged during remembering A recent study of patients with frontal lesions suggests that ventral medial prefrontal cortex VMPC plays a critical role in such judgments Schnyer D M Verfaellie M Alexander M P Lafleche G Nicholls L Kaszniak A W A role for right medial prefrontal cortex in accurate feeling of knowing judgments Evidence from patients with lesions to frontal cortex Neuropsychologia 42 957 966 2004 The observed impairment was thought to reflect an inability to determine the accessibility of memory contents To further examine the neuroanatomical basis of content accessibility INTRODUCTION The attempt to retrieve information from memory is not always immediately successful Faced with failure a person must determine the extent to which information seems readily accessible and therefore whether there is sufficient reason to continue to try and retrieve it Koriat 2000 The cognitive mechanisms by which such metamemory judgments are made have been the focus of extensive study using the feeling of knowing FOK paradigm Koriat 1993 Metcalfe 1993 Reder Ritter 1992 Two theoretical views have dominated this area of research One view has argued that FOK judgments are made primarily on the basis of the relative familiarity of the recall cue Metcalfe 1993 Reder Ritter 1992 and reflect a rapid assessment prior to engaging in a retrieval attempt A second view has suggested that these judgments are made by engaging the retrieval process and making assessments of the perceived accessibility of memory contents Koriat 1993 Illustrating the role of familiarity Reder 1987 found that increasing the familiarity of retrieval cues through priming resulted in higher FOK ratings with no effect on actual retrieval Illustrating the role of content accessibility Koriat 1993 found a positive relationship between the 1 Memory Disorders Research Center Boston University School of Medicine and the Boston VA Healthcare Center 2 MGH MIT HMS Athinoula A Martinos Center D 2005 Massachusetts Institute of Technology assessment we used fMRI in an episodic feeling of knowing FOK paradigm Participants were asked to make trial by trial predictions about the retrievability of the final word that completed studied sentences and then to select the correct completion from among alternatives Results indicated that the VMPC is engaged during accurate FOK judgments and its activation is modulated by retrieval rating Structural equations modeling supported the notion that VMPC as part of a broader left hemisphere network involved in memory retrieval monitors the output of the retrieval process More generally VMPC may participate in metacognitive processes that allow for the comparison of available data against an internal model amount of fragment information retrieved by a participant and ratings of future retrievability This relationship was found irrespective of accuracy Although familiarity and accessibility views have often been pitted against each other Miner Reder 1994 there recently has been an attempt to integrate the two Koriat Levy Sadot 2001 Koriat and Levy Sadot 2001 have proposed that retrieval predictions entail a cascading two step process involving both assessments of cuefamiliarity and evaluation of the accessibility of memory contents By this view items are initially assessed for familiarity and then either discounted feeling of notknowing or slated for further search Assessment of content availability consists of implementing the search or retrieval process and monitoring the results Although that process may not always be successful it can produce fragments of information that are then evaluated in order to come to a judgment about an item s availability in memory Koriat 2000 Although considerable knowledge has been gained about the cognitive processes that contribute to metamemory judgments much less is known about the functional neuroanatomy of these decisions Research has suggested that frontal cortical structures are critically involved in predictions about memory retrieval in the FOK paradigm Souchay Isingrini Espagnet 2000 Janowsky Shimamura Squire 1989 Shimamura Squire 1986 but there has as yet been little attempt to elucidate the role of specific frontal regions or other regions in the assessment of either cue familiarity or Journal of Cognitive Neuroscience 17 5 pp 832 846 accessibility of memory contents the two processes that are thought to mediate these judgments In a recent FOK study in patients with damage to the frontal cortex Schnyer et al 2004 we found that patients whose lesion encompassed the right ventral medial prefrontal cortex VMPC were impaired in making predictions about their subsequent recognition performance Because familiarity based assessment was demonstrated to be intact in these patients we concluded that the primary contribution of this region to metamemory judgments was in the assessment of the accessibility of memory contents This conclusion is in line with a recent proposal by Moscovitch and Winocur 2002 that the VMPC and the anterior prefrontal cortex play an important role in the intuitive evaluation of actual stored memory contents The findings in patients with damage to the prefrontal cortex leave unanswered several important questions about both the neuroanatomical underpinnings of metamemory judgments and the functional role of the VMPC in these judgments First lesion studies cannot delineate whether the effect of a lesion is due to damage in local gray matter or to pathways that connect distributed nonaffected regions Price Warburton Moore Frackowiak Friston 2001 This connectivity issue is especially important in determining the role of the VMPC as this region contains many of the major pathways connecting the frontal cortex with the limbic and temporal regions Second although lesion studies are essential for pinpointing regions that are critically involved in task performance they fail to identify additional regions that may also contribute to performance and they provide little evidence as to how these regions interact Price Mummery Moore Frackowiak Friston 1999 The VMPC may be involved in evaluating the accessibility of memory contents but access to these contents most likely depends on effective retrieval attempts that
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