Replay and Preplay in Human Planning

Animals and humans replay neural patterns encoding trajectories through their environment, both whilst they solve decision-making tasks and during rest. We have been using magnetoencephalography to detect replay in human subjects as they perform decision-making tasks. I will show our initial attempts, in a complex task; and our recent attempts, with a simpler task. In this, replay differed significantly between subjects who flexibly adjusted their choices to changes in temporal, spatial and reward structure and those who were slower to adapt to change. The former group predominantly replayed comparatively less good trajectories during task performance, and subsequently avoided these inefficient choices. The latter replayed comparatively preferred, but suboptimal, trajectories during rest periods between task epochs. We suggest that online and offline replay both contribute to planning, but each is associated with distinct model-based and model-free decision strategies