Repeated Viewing of a Narrative Movie Changes Event Timescales in The Brain

Many everyday experiences share a recurring structure: routines, familiar routes, rewatched films, and replayed songs. How do repeated encounters with such structure alter the brains representations of events? We hypothesized that, with repeated viewing of a film clip, event representations in the brain may adapt by becoming either finer (more detailed) or coarser (more generalized). To test this hypothesis, we analyzed data from 30 human participants (12 males, 18 females) who underwent functional magnetic resonance imaging (fMRI) while watching three 90-second clips from "The Grand Budapest Hotel" six times each. We used hidden Markov models and pattern similarity analysis applied to searchlights across the brain to quantify the strength of event structure at different timescales for each clip presentation. We then tested how event structure strength changed at both slow and fast timescales with repeated viewings. Most brain regions exhibited stability in the strength of event structure at both slow and fast timescales. Other regions, however, showed flexible event representations that became more or less granular across repeated clip presentations. Notably, several brain regions exhibited consistent changes in the strength of event structure at a slow timescale across different movie clips. Furthermore, in lateral occipital cortex and middle temporal gyrus, slow timescale structure was correlated with subsequent memory for the clips. These results highlight that event dynamics in the brain are not fixed, but can change flexibly with experience. Significance StatementMany day-to-day experiences recur over time, as we retrace the same route to work or listen to our favorite song on repeat. We asked how increasing familiarity with an experience changes the brains representations of it. Individuals repeatedly watched film clips while undergoing fMRI. We examined how the brains temporal representations of events in the clips changed with repeated viewing. As clips became familiar, some brain regions exhibited fine-tuned event representations that divided film clips into smaller events. Other brain regions showed coarser event representations that grouped previously distinct events. The strength of event structure at a coarse timescale was correlated with memory. These results show that the brain flexibly changes how it represents events as they become more familiar.