The dynamics of memory: Context-dependent updating

Abstract

Understanding the dynamics of memory change is one of the current challenges facing cognitive neuroscience. Recent animal work on memory reconsolidation shows that memories can be altered long after acquisition. When reactivated, memories can be modified and require a restabilization (reconsolidation) process. We recently extended this finding to human episodic memory by showing that memory reactivation mediates the incorporation of new information into existing memory. Here we show that the spatial context plays a unique role for this type of memory updating: Being in the same spatial context during original and new learning is both necessary and sufficient for the incorporation of new information into existing episodic memories. Memories are automatically reactivated when subjects return to an original learning context, where updating by incorporating new contents can occur. However, when in a novel context, updating of existing memories does not occur, and a new episodic memory is created instead.

Effects of psychosocial stress on episodic memory updating

“…In contrast, reactivation accompanied by increased attention or arousal (Sara, 2000a, b) or additional exposure to the same materials (Lee, 2008) may strengthen a memory trace. Finally, new information may be incorporated into the reactivated memory trace, yielding updating rather than interference (Hupbach et al, 2008;Lee, 2009Lee, , 2010. Following reactivation, the memory trace undergoes re-consolidation to stabilize the memory representation again.…”

“…Therefore, it is reasonable to hypothesize that memory updating might be impaired under stress, a possibility we decided to explore. We used a well-established episodic memory updating paradigm recently described for humans (Hupbach, Gomez, Hardt, & Nadel, 2007;Hupbach, Hardt, Gomez, & Nadel, 2008;Hupbach, Gomez, & Nadel, 2009). This updating paradigm involves learning a list of objects on Day 1.…”

Modification of episodic memories by novel learning: a failed replication study

“…To achieve this, participants were tested by another experimenter and in a spatial context that was different from Day 1. This context switch was necessary, because memories are directly reactivated when participants return to the original learning context (Hupbach et al, 2008). Moreover, self-reports suggest that participants in all groups rarely reactivated pictures they originally learned before they came back to the lab, which renders it unlikely that unintended reactivation can account for the Re+NL group and NL group performing similarly.…”

“…By now, it is clear that reconsolidation is an intricate process, not merely dependent on reactivation followed by an intervention. It is a process that is suggested to be conditional on a number of boundary conditions, such as the context in which reactivation takes place (Hupbach et al, 2008), the original memory’s age and strength (Wichert et al, 2011), or whether something new is learned after reactivation (i.e. prediction error; Sevenster et al, 2012, 2013).…”

“…Participants in the reactivation groups (Re+NL, Re) were brought back to the same spatial context as learning on Day 1 (see Hupbach, Hardt, Gomez, & Nadel, 2008). During reactivation, participants in these groups had two minutes to think back on the pictures that were presented on Day 1.…”