Distinct functional roles across hippocampal subfields in anticipation to event boundaries during schema learning

Continuous experiences are constantly segmented into separate events in memory, which is accompanied by increased hippocampal activity at the boundaries between these events. Extracting knowledge across all these experiences about what type of events to expect in a certain environment leads to event schemas being represented in the brain. These event schemas help to predict future events. What are the differences across the various distinct hippocampal subfields in peaks of activity around event boundaries? And what is the influence of event schema learning on these hippocampal subfield peaks? Here, this was investigated using data from an fMRI experiment in which participants learned two (related) event schemas by exposure to many similar animated videos of wedding ceremonies in a novel fictional culture. Results revealed that the hippocampus (CA1, CA2/3, dentate gyrus and subiculum) showed peaks in activity before event boundaries. Interestingly, the CA1, CA2/3 and dentate gyrus pre-boundary peaks attenuated due to event schema learning. This provides evidence for these subfields signaling uncertainty about upcoming events in the seconds prior to event boundaries. These results give a more precise understanding about the temporal dynamics around event boundaries in the distinct hippocampal subfields, and how these hippocampal subfields responses interact with schema learning.