The neural basis of event segmentation: Stable features in the environment are reflected by neural states

Our senses receive a continuous stream of complex information. Parsing this information into meaningful events allows us to extract relevant information, remember it, and act upon it. Previous research has related these events to so-called neural states: temporally and regionally specific stable patterns of brain activity, which tend to coincide with events in the stimulus. Neural states show a temporal cortical hierarchy: short states are present in early sensory areas, while longer states can be found in higher-level areas. Here we investigated what these neural states represent. We hypothesized that states at different levels of the cortical hierarchy are shaped by aspects of the stimulus to which these brain areas are responsive. To test this hypothesis, we analyzed fMRI data of participants watching a movie, using a data-driven method to identify the neural states. We found support for the aforementioned hypothesis: specifically the parahippocampal place area and retrosplenial cortex, known to be sensitive to places, showed an alignment between neural state boundaries and moments in the movie with a change in location, independent of changes in visual features and other covariates. These findings suggest that neural states reflect stable features in the (internal model of) the external environment, and that the cortical temporal hierarchy partly reflects the temporal scales at which representations of the environment evolve.