Rats, nets, maps, and the emergence of place cells

We study through computer simulations the motion in space of small networks consisting of a few sensory, intermediate, and motor units linked by feedforward connections of initially random strengths. Evolutionary pressure, exerted through random differentiation and selective reproduction, can force such objects to adapt to perform elementary navigation tasks similar to those used in investigating hippocampal function in rats. The connection strengths resulting from the adaptation process are shown to provide intermediate units with response characteristics similar to those of place cells found in the rat hippocampus. These results illustrate the ease with which “place” units emerge in any minimal circuitry geared to solve simple navigation tasks, and highlight the importance of considering the complexity of the memory performance required, rather than the relatively trivial spatial “computations” involved, while using those tasks to explore hippocampal structure and function.

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