The formation of numerous independent maps in the hippocampus has obvious advantages for memory formation, as it allows the network to store new representations in a manner that minimizes interference with previously stored memories. The orthogonal nature of hippocampal representations is expressed in its ability to ‘remap’ between experiences and environments31 (Fig. 3). Even minor changes in the configuration of landmarks or the motivational context can completely alter the firing pattern of the hippocampal place cell population. As a result, each environment can be represented by a unique combination of active place cells and place fields. The apparent orthogonalization is strongest in the CA3 subfield34,35, where firing locations of any two cells across environments are no more correlated than expected by chance34. By virtue of the vast and densely connected random graph of recurrent collaterals between neurons in this area36, the CA3 region has the ability to read and register the rich combinatorial output of the entorhinal cortex grid modules. The multiplicity of representations may be generated by independent changes of grid maps in the medial entorhinal cortex, but the
