+The Default Mode Network (DMN) has previously been shown to be involved in resting state cognition, internal attention, and more recently, the creation and updating of internal event models. This analysis uses naturalistic stimuli to examine whether event processing within the DMN differs when the stimulus presented is novel or known. While in an fMRI, subjects watched the same 14-minute video twice, and subsequent neural analysis focused on the regions within the DMN, comparing the event segmentation across subjects in the first viewing and the second viewing of the stimulus. Using a Hidden Markov Model, event boundaries were found to align with important narrative shifts and moments of surprise, confirming the role of the DMN in event segmentation. Particularly in the precuneus and posterior cingulate cortex (PCC), event segmentation in the first viewing was found to be less coherent and made with a greater emphasis on sensory input and very obvious narrative shifts, while event segmentation in the second viewing appeared to locate more nuanced conceptual narrative shifts. These results further confirm the role of the DMN (and in particular the PCC/precuneus) in event models and the integration of external stimuli with internal representations of the event at hand. This research speaks to the brain’s predictive capacities, and this study’s use of event segmentation also relates to the ability of the brain to continuously “chunk” ongoing experiences, which holds important implications for learning and memory.
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