Boundaries Shape Cognitive Representations of Spaces and Events

Efficient navigation from one place to another is facilitated by the ability to use spatial boundaries to segment routes into their component parts. Similarly, memory for individual episodes relies on the ability to use shifts in spatiotemporal contexts to segment the ongoing stream of experience. The segmentation of experiences in spatial and episodic domains may therefore share neural underpinnings, manifesting in similar behavioral phenomena and cognitive biases. Here, we review evidence for such shared mechanisms, focusing on the key role of boundaries in spatial and episodic memory. We propose that a fundamental event boundary detection mechanism enables navigation in both the spatial and episodic domains, and serves to form cohesive representations that can be used to predict and guide future behavior. Both efficient navigation and episodic memory require the detection of crucial junctions separating individual segments of space or experience. In both the spatial and episodic domains, boundaries segregate elements of experience and serve as cues to bind information into cohesive units. The segmentation of experiences in spatial and nonspatial domains may share neural underpinnings, manifesting in similar behavioral phenomena and cognitive biases. The interplay between hippocampal and cortical dynamics offers insight into the mechanism by which space and events are segmented. A crucial question is how different brain regions support coarse versus fine-grained boundary detection. Evidence from patients with localized brain damage or disorders such as dementia provides some insight into this question, but future neuroimaging studies will enable the development of precise mechanistic models.