Today, I pick up the following paper (because of my personal reflection).
Preplay of future place cell sequences by hippocampal cellular assemblies.
Dragoi G, Tonegawa S.
Temporal sequences of place cell firing are observed during awake quiescence and slow-wave sleep following exploring behaviors. This is called “replay”. This paper shows that such temporal sequences are also observed before exploring (figure 1). They call this “preplay”. Preplay is also observed in animals which haven’t explored linear tracks (figure 4). This phenomenon may reflect network dynamics.
This paper may indicate that many (but less than number of all combination of firing order) activity patterns exist as a candidate sequence for information coding. If a candidate pattern matches the sequence during exploration, it will be strengthen during replay. In this view, preplay is a preparation for future learning, and learning is selecting suitable pattern from prepared patterns. Preparing many candidates may require much energy, but it may enable animals to learn quickly, so such mechanism may have advantage in evolutions.