Continuous tracking of long timescale memory replay across event boundaries

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Consulting our memory often involves replaying a long sequence of events. This morning we may have left the house, taken the train to work and then talked to our colleagues at the office. While we can all intuitively perform such a mental journey through our past, surprisingly little is known about how such continuous episodes are replayed from memory. Importantly, the neural mechanisms that determine which information comes back at what time are not well understood. Recent advances in analysis methods in neuroscience have now made it possible to track information based on neural activity that is measured via electrophysiology. This means that we now have a window into the brain to observe individual memories as they are replayed. These methods will be applied in this project using a rare opportunity to work with patients that are undergoing intracranial recordings in the course of epilepsy treatment. This will make it possible to track continuous episodes as they unfold in memory in recordings from electrodes that are implanted directly into the human brain. Importantly, recent evidence suggests that the structure of a continuous episode may impact how this information reappears in memory. Specifically, event boundaries – moments when one natural and meaningful unit ends, and another begins – may be crucial to guide our brain through extended episodes. This project will therefore test the specific hypothesis that the boundaries between events (e.g. when we just left the house, or when we arrive at work) are starting points that guide us through continuous episodes in memory. Like a CD player allows us to play tracks in real time but also to skip ahead and start a new track from the beginning, event boundaries may provide us with starting points to replay patterns from memory and we may be able to skip ahead to these starting points. Behavioral experiments will systematically investigate what determines how long it takes to search long episodes in memory for an answer. It is predicted that longer episodes will take longer to search, however, it is not clear how event boundaries will influence this memory search. The direct electrophysiological recordings from the human brain will further help to understand how different brain structures collaborate during memory replay and therein at event boundaries.