Science Daily has a report on investigation of animal sense of direction. (here) R. Langston found that baby rats have a space map before they can see or navigate outside the nest.
The research team implanted miniature sensors in rat pups before their eyes had opened (and thus before they were mobile). That enabled the researchers to record neural activity when the rat pups left the nest for the first time to explore a new environment.
The researchers were not only able to see that the rats had working navigational neurons right from the beginning, but they were also able to see the order in which the cells matured.
The first to mature were head direction cells. These neurons are exactly what they sound like — they tell the animal which direction it is heading, and are thought to enable an internal inertia-based navigation system, like a compass. “These cells were almost adult-like right from the beginning,” Langston says.
The next cells to mature were the place cells, which are found in the hippocampus. These cells represent a specific place in the environment, and in addition provide contextual information — perhaps even a memory — that might be associated with the place. Last to mature were grid cells, which provide the brain with a geometric coordinate system that enables the animal to figure out exactly where it is in space and how far it has travelled. Grid cells essentially anchor the other cell types to the outside world so that the animal can reliably reproduce the mental map that was made last time it was there.
It has been assumed by many, for a long time that our 3D space perception is hard-wired and not gained from experience of space. This and similar research seems to confirm that assumption.
I don’t know how this means 3D perception is hard-wired. Even if they mapped a 3D space - which they don’t - grid cells definitely don’t work like actual space. To see why this must be the case (experiments show this too), think just how many you would need to represent everywhere a rat could possibly travel. A rat that travels a sufficient distance would have to “go off its own grid” if the grid worked exactly like euclidean. Rats do solve this problem, but it means that its not quite like euclidean space - still leaving the question of how a coherent euclidean space comes to be.
JK: Thank you very much for your comment. Three points - first, the quote did not mention border cells. These are cells that fire when activity moves to grid cells near the edge of the grid. The idea (not proven but generally accepted, I think) is that there is a store of ‘maps’ in the hippocampus. They are various scales and so on. A single map is selected and “superimposed on the grid”. When movement comes to the edge of the map then another is placed on the grid. Second point - I am not sure that the grid gives 3 dimensions. I would guess that it gives 2 plus ‘landmarks’ that give some depth to the perception. I presume that object perception has more to do with 3D perception then the navigation grid. Third point - I think the hard-wired support comes from the navigation system being ready to actually do some navigating before the rat can have created a navigation system by learning. So maybe I over-stated the case in calling it 3D space rather then ability to navigate - thanks for the correction. On the other hand, my belief that something as essential as our concept of space would be hard-wired has not been shaken by anything I have read to date. If we learn 3D space, we must learn it very, very quickly because we need it in place before we can learn most other things.