Although we know that groups of cells working together in a specific brain region — the hippocampus — are vital for making, storing, and retrieving many types of memories, we still don’t have a clear idea of how these cells are organized. Researchers in Japan have recently identified an important piece of this puzzle; in rats, fear-based memories were made when cells in the hippocampus formed discrete clusters, suggesting that memory formation requires cells to be organized in a specific arrangement. The research also indicates that sleep is important for the stability of these cell clusters.
Most previous studies looking at the cellular organization of memories have used a technique called electrophysiology, which is based on brain activity that brain cells use to talk to one another. A major limitation of this technique is that it only allows the examination of a relatively small…
