Hippocampal place cells encode global location but not connectivity in a complex space.
Duvelle É., Grieves RM., Liu A., Jedidi-Ayoub S., Holeniewska J., Harris A., Nyberg N., Donnarumma F., Lefort JM., Jeffery KJ., Summerfield C., Pezzulo G., Spiers HJ.
Flexible navigation relies on a cognitive map of space, thought to be implemented by hippocampal place cells: neurons that exhibit location-specific firing. In connected environments, optimal navigation requires keeping track of one's location and of the available connections between subspaces. We examined whether the dorsal CA1 place cells of rats encode environmental connectivity in four geometrically identical boxes arranged in a square. Rats moved between boxes by pushing saloon-type doors that could be locked in one or both directions. Although rats demonstrated knowledge of environmental connectivity, their place cells did not respond to connectivity changes, nor did they represent doorways differently from other locations. Place cells coded location in a global reference frame, with a different map for each box and minimal repetitive fields despite the repetitive geometry. These results suggest that CA1 place cells provide a spatial map that does not explicitly include connectivity.