Integrating and fragmenting memories under stress and alcohol

Abstract

Stress can powerfully influence the way we form memories, particularly the extent to which they are integrated or situated within an underlying spatiotemporal and broader knowledge architecture. These different representations in turn have significant consequences for the way we use these memories to guide later behavior. Puzzlingly, although stress has historically been argued to promote fragmentation, leading to disjoint memory representations, more recent work suggests that stress can also facilitate memory binding and integration. Understanding the circumstances under which stress fosters integration will be key to resolving this discrepancy and unpacking the mechanisms by which stress can shape later behavior. Here, we examine memory integration at multiple levels: linking together the content of an individual experience, threading associations between related but distinct events, and binding an experience into a pre-existing schema or sense of causal structure. We discuss neural and cognitive mechanisms underlying each form of integration as well as findings regarding how stress, aversive learning, and negative affect can modulate each. In this analysis, we uncover that stress can indeed promote each level of integration. We also show how memory integration may apply to understanding effects of alcohol, highlighting extant clinical and preclinical findings and opportunities for further investigation. Finally, we consider the implications of integration and fragmentation for later memory-guided behavior, and the importance of understanding which type of memory representation is potentiated in order to design appropriate interventions.

Keywords: Alcohol; Configural; Episode; Memory integration; Schema; Stress.

Fig. 1

Schematic of different levels of integration. A, Illustration of two events: one in which a person purchases coffee at a shop, and another in which the person witnesses an explosion while drinking a coffee and reading the morning paper. B, Examples of different ways that components of this experience can be integrated. These include more disjoint representations (item, elemental) as well as integration between features (relational, configural) and with the underlying spatiotemporal architecture (see Section 2). C, Linking of discrete events separated in time (Section 3). D, Integration of event with pre-existing knowledge or comprehension structure (Section 4).