Parallel computation in memory-making The hippocampus plays a central role in the encoding, consolidation, and recall of memories. Consolidation and recall are thought to be executed by the replay of previously acquired memory traces by hippocampal cell assemblies. The hippocampus is thus considered to be the initiator of memory redistribution processes. However, O'Neill et al. now report that the superficial layers of the medial entorhinal cortex show replay events that are independent of hippocampal activity (see the Perspective by Moser and Gardner). Computations in memory systems may thus be organized in a less hierarchical, more parallel way than previously thought. Science , this issue p. 184 ; see also p. 131