The scientists did experiments where they let a rats learn a maze. On a daily basis they change reward locations of food. They measured firing fields of grid cells before rewards, during learning of reward locations, and after learning to understand the firing rates. They found that the grid fields moved toward the reward locations and that these fire fields lasted for days in grid cells. They call this mnemonic coding, althoughI don’t understand why that is so.
“Goal learning can lead to the local and long-lasting distortion of the entorhinal spatial maps. This demonstrates the influence of non-geometrical cognitive factors on the grid structure itself.”
“Here, we found evidence for a grid code at the structural level that goes beyond simple metrics: Individual grid fields moved toward newly learned goal locations, leading to the deformation of the grid map, independently from variations of spatial sampling, trajectories, speed, or heading inherent to our behavioral paradigm.”
This paper shows that the grid code is not a 100% invariant grid code across all environments. The default grid structure is this uniform layout, but the grid structure can and does change. What does this change represent? And when will it change?
Somehow it seems multiple maps are stored in the MEC. What are the inputs to these maps? And how many maps are stored? Are these morphed grid structures the result of some kind of compound effect or calculated in some other way? There are more questions than answers that I have after reading the paper.