The nature of item representations in memory.

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The overarching goal of our research is to understand the nature of memory and the neural systems that support the formation and retrieval of different classes of memory representations. The focus of this proposed research is on the nature of item memory representations. The objectives of this work are to use neuroimaging and eye movement monitoring to reveal the existence of distinct types of item representations in memory and to understand the underlying neural and behavioral mechanisms that support conscious recognition of items. We will examine the relationship between neural repetition suppression effects in distinct regions, eye movement repetition effects and conscious recognition under a variety of conditions to provide evidence for multiple types of item representations. We predict that there are complementary neural systems (hippocampus versus cortical regions) that support the formation of item representations. However, the nature of those representations, and the manner by which they support conscious recognition, would differ. We propose that representations mediated by the cortex, including the perirhinal cortex, would be inflexible and hyperspecific, such that any change made to a previously viewed item (e.g., viewpoint, feature change) would cause a change in perceptual processing and a decline in conscious recognition. By contrast, the hippocampus would mediate flexible item representations through the integration of associated information, which could be used to support conscious recognition even when the item has undergone a change. In addition to providing evidence that there are flexible, as well as specific, item representations mediated by distinct neural systems, this work will relate neural repetition suppression effects to behavior, and resolve debates in the literature regarding the neural systems that underlie eye movement repetition effects. Finally, we will reveal whether our memories for single items are inflexible and unchanging, or constantly in flux and influenced by the information that has come to be associated with them over time. The latter finding would suggest that 'perception' and 'memory' are not clearly delineated, but that these cognitive processes influence each other.