How does the brain learn about space? Twopapers in Science show that neural representations of place and direction appear in baby rats astonishingly early - within just a couple of days of beginning to explore outside the nest.
Two teams of researchers, Langston et al, and Wills et al, found that at just 16 days after birth, rats possess adult-like direction cells and place cells in the hippocampus and entorhinal cortex, areas known to be critical for spatial cognition. A couple of days later, grid cells appear.
Bear in mind that rats are born much earlier in their development than people are. Human babies are born with fully-functioning senses and are able to see. The eyes of baby rats however are sealed shut until about day 14. So this is very convincing evidence that the hippocampal system is "hard-wired" to store representations of space in the way that it does. Sensory input provides the actual data about particular places, but the hard work of designing a way of coding space has already been done by evolution.
That's great news for baby rats, because otherwise they would have to learn not just about their environment, but about the very concept of space. That would be asking a lot because baby rats are not the smartest of creatures. It seems very likely that the same is true of humans. It's tricky to stick electrodes into the brains of babies (the parents tend to object), but we know that in adults, damage to the hippocampus and related areas causes spatial processing and memory deficits just like those seen in rats. It's probably not just space, either - Noam Chomsky has built his career on the theory that we also possess a specialized language-learning mechanism.
These data would have come as no surprise to Kant, whose philosophy was based on the notion that our knowledge of the world is dependent upon the existence of innate mental "categories", such as space and time, which we do not learn by experience, but which rather allow us to make sense of experience. Incidentally, Kant looked a bit like a rat.
Yet a mystery remains, and it has nothing to do with the brain. What's the story behind this pair of all-but-identical articles? They're literally the two most similar scientific papers I have ever read - they found the same results, using the same methods, with only a few minor technical differences.
The fact that two independent groups have shown the same thing is great evidence for the reliability of these findings, but it's very rare for journals to publish simultaneously in this way, although arguably it should happen more often. So what's the story? Did these two groups not know they were working on the same thing, or was there a "Space Race" to publish first? Are they friendly collaborators or bitter rivals? We can only imagine...
Langston, R., Ainge, J., Couey, J., Canto, C., Bjerknes, T., Witter, M., Moser, E., & Moser, M. (2010). Development of the Spatial Representation System in the Rat Science, 328 (5985), 1576-1580 DOI: 10.1126/science.1188210
Wills, T., Cacucci, F., Burgess, N., & O'Keefe, J. (2010). Development of the Hippocampal Cognitive Map in Preweanling Rats Science, 328 (5985), 1573-1576 DOI: 10.1126/science.1188224
