Active retrieval facilitates across-episode binding by modulating the content of memory

Abstract

The contents of memory can be updated when information from the current episode is bound with content retrieved from previous episodes. Little is known regarding factors that determine the memory content that is subject to this across-episode binding. We tested whether across-episode binding preferentially occurs for memory content that is currently “active” and identified relevant neural correlates. After studying objects at specific locations on scene backgrounds, subjects performed one of two retrieval tasks for the objects on different scene backgrounds. In an active condition, subjects recalled object locations, whereas subjects merely dragged objects to predetermined locations in a passive condition. Immediately following each object-location retrieval event, a novel face appeared on a blank screen. We hypothesized that the original episode content would be active in memory during face encoding in the active condition, but not in the passive condition (despite seeing the same content in both conditions). A ramification of the active condition would thus be preferential binding of original episode content to novel faces, with no such across-episode binding in the passive condition. Indeed, memory for faces was better when tested on the original background scenes in the active relative to passive condition, indicating that original episode content was bound with the active condition faces, whereas this occurred to a lesser extent for the passive condition faces. Likewise, early-onset negative ERP effects reflected binding of the face to the original episode content in the active but not the passive condition. In contrast, binding in the passive condition occurred only when faces were physically displayed on the original scenes during recognition testing, and a very similar early-onset negative ERP effect signaled binding in this condition. ERP correlates of binding were thus similar for across-episode and within-episode binding (and were distinct from other encoding and retrieval ERP signals in both cases), indicating that active retrieval modulated when binding occurred, not the nature of the binding process per se. These results suggest that active retrieval promotes binding of new information with contents of memory, whereas without active retrieval, these unrelated pieces of information might be bound only when they are physically paired.

Flexible retrieval: When true inferences produce false memories.

“…We suggest that the effects that we have documented here reflect the joint operation of two related but distinct mechanisms: cross-episode binding (e.g., Bridge & Voss, 2014a, 2014b) and retrieval-based reactivation and recombination (e.g., Bridge & Voss, 2014a, 2014b; Hupbach, Gomez, Hardt, & Nadel, 2007; St. Jacques & Schacter, 2013).…”

“…The studies noted earlier by Bridge and Voss (2014a, 2014b) suggest that simply co-activating memories during retrieval can lead to source misattributions, wherein co-activation of existing memory traces produces cross-episode binding of peripheral features from each episode. Although these results are consistent with the results reported here, it is unlikely that simple co-activation of elements from different episodes is sufficient to account for our key results.…”

“…Binding processes that link disparate elements of an episode into a unified representation have been extensively studied in recent years, and have been linked closely to the operation of the hippocampus (e.g., Eichenbaum & Cohen, 2001; Hannula & Ranganath, 2008; Shimamura, 2010). As Bridge and Voss (2014b) point out, however, most such studies have focused on binding of elements within an episode. Bridge and Voss (2014b) studied cross-episode binding processes, and provided evidence that participants sometimes bind elements from distinct episodes (e.g., a face from one episode and a scene from another), resulting in memory error (for additional evidence linking binding processes to memory distortions, see Lew & Howe, in press).…”

“…As Bridge and Voss (2014b) point out, however, most such studies have focused on binding of elements within an episode. Bridge and Voss (2014b) studied cross-episode binding processes, and provided evidence that participants sometimes bind elements from distinct episodes (e.g., a face from one episode and a scene from another), resulting in memory error (for additional evidence linking binding processes to memory distortions, see Lew & Howe, in press). We suggest that such cross-episode binding in our paradigm occurs most often and most extensively for episodes that result in successful, as opposed to unsuccessful, associative inference.…”

Distinct Hippocampal versus Frontoparietal Network Contributions to Retrieval and Memory-guided Exploration

“…Memory retrieval is crucial for adaptive processes such as exploration (Okeefe & Nadel, 1979; Voss, Gonsalves, Federmeier, Tranel, & Cohen, 2011; Voss, Warren, et al, 2011), decision making (Gupta et al, 2009; Johnson & Redish, 2007; Redish, 2016; Wang, Cohen, & Voss, 2015), future planning (Buckner, 2010; Eichenbaum & Fortin, 2009; Schacter et al, 2012), creative thinking (Duff, Kurczek, Rubin, Cohen, & Tranel, 2013), and memory updating (Bridge & Paller, 2012; Bridge & Voss, 2014a, 2014b; Iordanova, Good, & Honey, 2011; Winters, Tucci, Jacklin, Reid, & Newsome, 2011). However, mechanisms supporting memory’s influence on adaptive functions such as learning remain unresolved.…”