Every time we move through a familiar environment, the hippocampus consults an internal map, a detailed spatial representation built up through repeated experience. But what happens when something unexpected occurs on a well-known route? Researchers at the University Hospital Bonn (UKB) and the University of Bonn demonstrated in a mouse model that the brain does not redraw its maps from scratch. Instead, it annotates them, preserving the underlying spatial layout while overlaying new information on top of the existing map. The paper is published in the Proceedings of the National Academy of Sciences.
The hippocampus, the brain’s working memory, is shaped like a seahorse and is located in the temporal lobe of both the left and right hemispheres. Hippocampal CA3 circuits, which link information and support the recognition of memories, keep their spatial maps stable while layering new annotations on top, much like a navigation app that preserves your route while flagging an incident ahead.
A Bonn-based research team arrived at these findings by recording the activity of CA3 axons in mice traversing a familiar linear running route. At a fixed point along the route, the scientists introduced a mildly aversive but harmless air puff stimulus, comparable to an unexpected obstacle on a road, and tracked how the hippocampal network updated its representation before, during and after the event.
