contextual stability as a continuous moderator of event segmentation

Our senses receive a constant stream of information, with one moment leading continuously to the next. Afterwards, however, we remember our experiences as discrete events. These events are thought to be typically organized around stable contexts, with context often consisting of an unchanging goal or physical location. Studies of the individual differences in this segmentation process have contributed insights into basic cognition and mapped novel clinical markers. For instance, the ability to normatively detect the boundaries between these events is weakened across such wide-reaching disorders as Alzheimer’s disorder, schizophrenia, autism-spectrum disorder, and even during healthy aging. While the hippocampus is known to hold a critical role in event segmentation broadly, current functional models have yet to be extended to its role in event segmentation. A major limitation of the existing literature to parse these individual differences and neural functional models, however, is that it has treated event boundaries as binary occurrences. Theoretical accounts hold that more stable contexts should lead to stronger event boundaries, and that the ability to gradate these event boundaries ought to rely on mechanisms of cognitive control. Critically, these claims have yet be tested. This ommission leaves sources of variance that, in tandem with cognitive control functions, may provide meaningful clinical markers as well as provide theoretical insight.

To test this, I built a paradigm that modulates the stability of a context as a continuous function rather than a binary occurence. This allowed me to test how individuals’ event segmentation behaviors evolved over a continuous range of contextual stability, and particularly how these developed non-linearly and differently from each other. I found that the difference in participants’ memory for boundary and non-boundary item-color memory (a standard measure of event segmentation) increased non-linearly as contexts became more stable and that participants did this very differently, with some increasing very smoothly and others increasing suddenly at an inflection point. Future work will tie these behaviors to existing clinical markers and cognitive control measures known to covary with clinical outcomes. fMRI studies can then examine how univariate signals evolve across the body of the hippocampus as well as how multivariate signals in the lateral entorhinal cortex process temporal context at different levels of contextual stability.