A study led by researchers at NYU Langone Health has identified what looks like a switchboard for memory in the mouse brain. Roughly one in four memory cells in the hippocampus appear to function as shared hubs, linking incoming signals to outgoing ones. The implication is that the brain recycles the same cells across many different memories without scrambling them or writing over what came before.
The finding speaks to a puzzle that has occupied neuroscientists for decades: how a brain can stay plastic enough to absorb new information while remaining stable enough to hold on to old knowledge. Too much flexibility and yesterday's memories get overwritten; too much stability and nothing new gets in.
To probe that balance, the team traced a chain of connected regions running from the hippocampus, which sits deep in the brain and organizes experiences into memories, out to the neocortex, the outer layer where long-term information is stored. Along that route they examined CA3, a hippocampal region that feeds in rapidly changing information; CA1, which serves as the central hub; and the retrosplenial cortex, a region important for navigation and reconstructing scenes.
The work was done in mice, so how closely it maps onto human memory remains an open question. Still, understanding the wiring that lets healthy brains add new memories without disturbing old ones gives researchers a clearer reference point for what may go wrong when that system starts to fail.