Spatial coding and attractor dynamics of grid cells in the entorhinal cortex

- Spatial responses of grid cells with identical spacing are precisely matched.
- Grid cell firing is modulated primarily by slowly varying synaptic inputs.
- Inhibitory neurons mediate recurrent connectivity between grid cells in layer II.
- These recent results support attractor models of grid cell dynamics.
- Grid cell activity may represent position with exceptionally large dynamic range.

Recent experiments support the theoretical hypothesis that recurrent connectivity plays a central role within the medial entorhinal cortex, by shaping activity of large neural populations, such that their joint activity lies within a continuous attractor. This conjecture involves dynamics within each population (module) of cells that share the same grid spacing. In addition, recent theoretical works raise a hypothesis that, taken together, grid cells from all modules maintain a sophisticated representation of position with uniquely large dynamical range, when compared with other known neural codes in the brain. To maintain such a code, activity in different modules must be coupled, within the entorhinal cortex or through the hippocampus.