Hippocampal CA3 cells are predominantly connected to themselves. Only 1/3rd comes from elsewhere.
"CA3 cell ensemble characteristics are consistent with completely distinguishing between two places and with making an additional distinction between related sensory configurations within each place. Although each of these two modes of processing corresponds roughly to pattern separation, they do not necessarily result in global attractor dynamics in CA3."
Locally continuous, but globally orthogonal representation.
CA1 and CA3 are primarily characterized by place-cell firing - principal cells are activated when the animal is in specific locations in the world. It forms a map of space.
Maps made by hippocampus can change depending on context - changing a black cylinder to a white one can completely change the hippocampus map (Muller and Kubie, 1987). Introducing a barrier - cells close to the barrier would remap, but distal cells would stay the same.
Visually identical enclosures: CA1 will fire similarly to similar sensory cues. CA3 will always respond differently if the location is different, even if other sensory cues are identical. CA3 has large path-integration component.
CA3 pattern completes. Spatial map can remain stable, even when some of the sensory cues are removed. So long as location remains unambiguous the CA3 map can remain stable. Recurrent activity and plasticity are necessary for this mapping. CA3 is more bound to the current sensory state, and CA1 more reliant on temporal sequence of sensory information. If sensory cues change dramatically, or the animal is moved to an entirely different location, CA3 will form a new, orthogonal map.
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