Conclusions
The typical STDPs observed in CA1 region are classified into two types [5]: symmetric and asymmetric plasticity rules. We show both of these rules are included in the theoretically derived set of optimal STDPs. The theoretically derived STDPs qualitatively coincide with the first two Fourier series approximations for those reported in CA1 neurons. Furthermore, we demonstrate that the system, which can retrieve normal and doubly spread-out patterns, can also retrieve reversed patterns with the same quality.