In a study published in *Nature Neuroscience* (2007), Kamran Diba and György Buzsáki investigated the hippocampal place-cell sequences during ripples in rats. They found that during running on an elevated track, place-cell sequences were replayed in reverse order at the end of a run and in forward order before the run, coinciding with sharp waves. These sequences reflected the spatial relationships between place fields, suggesting a role in forming episodic memories. The study recorded hippocampal activity in three rats running back and forth on a linear track for water rewards. During running, neurons fired in a sequence corresponding to the track's locations. After running, the same neurons fired in reverse order during immobility, confirming previous findings. Additionally, neurons fired in forward order before the run. The researchers analyzed these sequences and found that 36% of events were significantly forward correlated, while 19% were reverse correlated. Most forward correlated events occurred before the run (preplay), and reverse correlated events occurred after the run (replay). Both types of events were associated with sharp-wave ripples. The study also showed that ripple-associated sequences preserved distance information between place fields. Cross-correlations between cell pairs during running and immobility events revealed that temporal offsets during preplay and replay correlated with track distances. Additionally, the temporal offsets during running correlated with theta oscillations during preplay but not during replay. The findings suggest that forward preplay may be more directly linked to the cellular representation of the run sequence than reverse replay. The study highlights the role of hippocampal activity in memory formation, with forward associations being favored during free recall. The results also suggest that preplay events may play a role in planning upcoming trajectories.In a study published in *Nature Neuroscience* (2007), Kamran Diba and György Buzsáki investigated the hippocampal place-cell sequences during ripples in rats. They found that during running on an elevated track, place-cell sequences were replayed in reverse order at the end of a run and in forward order before the run, coinciding with sharp waves. These sequences reflected the spatial relationships between place fields, suggesting a role in forming episodic memories. The study recorded hippocampal activity in three rats running back and forth on a linear track for water rewards. During running, neurons fired in a sequence corresponding to the track's locations. After running, the same neurons fired in reverse order during immobility, confirming previous findings. Additionally, neurons fired in forward order before the run. The researchers analyzed these sequences and found that 36% of events were significantly forward correlated, while 19% were reverse correlated. Most forward correlated events occurred before the run (preplay), and reverse correlated events occurred after the run (replay). Both types of events were associated with sharp-wave ripples. The study also showed that ripple-associated sequences preserved distance information between place fields. Cross-correlations between cell pairs during running and immobility events revealed that temporal offsets during preplay and replay correlated with track distances. Additionally, the temporal offsets during running correlated with theta oscillations during preplay but not during replay. The findings suggest that forward preplay may be more directly linked to the cellular representation of the run sequence than reverse replay. The study highlights the role of hippocampal activity in memory formation, with forward associations being favored during free recall. The results also suggest that preplay events may play a role in planning upcoming trajectories.