Neural signatures of endogenous event boundaries in self-guided behaviors

COEX 

Studies on event segmentation and its neural mechanisms typically focus on exogenous event boundaries determined by changes in external stimuli. However, as active agents in the real world, humans also internally generate event boundaries by spontaneously switching between goals and mental states. In three fMRI studies, we employed naturalistic, self-guided tasks to characterize neural responses to endogenous event boundaries. In our first study, we found that during free narrated recall of a series of short movies, the default mode network (DMN) exhibited consistent activation patterns at boundaries between memories for different movies. These activation patterns were highly similar to those observed at exogenous boundaries between movies during movie-watching. In the second study, we used a 'think-aloud' task to illustrate that the DMN boundary pattern also emerged at transitions between different topics in a stream of spontaneous thoughts. Our third study extended these findings beyond verbal responses and observed the DMN boundary pattern during spontaneous switching between different task goals in a continuous web browsing task. Together, our results demonstrate that endogenous event boundaries elicit generalized neural responses in higher associative cortices, similar to those seen at exogenous boundaries.