grid cells

• observed to correspond to location tracking in rats, monkeys
  • namely, the function of dead reckoning
• hippocampus and entorhinal cortex
• think of the grid cells as a literal regular grid
  • the phase space of the grid cells is toroidal: you can shift the grid up and down and return to the same grid configuration
• data can be encoded by having multiple grid cell "modules", each with their own periods \(\lambda_i\)
• my questions:
  • We talk about the mapping between external states and grid cell states changing, even though the internal states do not. Where is that mapping stored? How does that mapping arise?
  • The hippocampus is involved in both navigation and episodic memory. Is the input to episodic memory the same as the velocity inputs?
  • There are probably unfavorable selections of \(\lambda_i\) that limit the capacity of the system. Is the hope that this will not happen on average for a random selection of \(\lambda_i\) 's? Or is there some type of pressure to choose co-prime periods?
• my question for vectorHASH:
  • What are the organization of the hashes? Are similar inputs given similar hashes?
  • Once an input is associated with a basin, do you have to stay there? Can you deepen the basin?