Encoding-Retrieval Relationships in Episodic Memory: A Functional Neuroimaging Perspective

Abstract

<p>The ability to re-experience the past is a defining feature of episodic memory. Yet we know that even the most detailed memories are distinct from the initial experiences to which they refer. This relationship between the initial encoding and subsequent retrieval of information is central to our understanding of memory and its capacity to connect us to the past. Past research has shown that neural signatures present during perception are reactivated during later memory, but the correspondence between this reactivation and various aspects of memory function remains unclear. This dissertation attempts to connect behavioral measures of memory to the reinstatement and modification of neural information that takes place when memories are retrieved. In the first two studies reported, functional magnetic resonance imaging (fMRI) is used to assess event-specific cortical patterns from encoding that are reinstated during retrieval (encoding-retrieval similarity, ERS). Increases in this fine-grained of reinstatement are found in occipitotemporal cortex (OTC) during detailed memory for scenes (Study 1), and in the medial temporal lobes (MTL) for the recovery of relational information (Study 2). In addition to reflecting encoding-related content, retrieval is also found to strengthen previously encoded information via hippocampally-mediated mechanisms in Study 3. Together, these studies demonstrate the detailed nature of information that is recovered across varying degrees of memory and show how retrieval can also alter stored representations, emphasizing the interactive nature of memory processes.</p>