Hiroyuki Nakahara, Shun-ichi Amari
We present an information-geometric measure to systematically investigate neuronal firing patterns, taking account not only of the second-order but also of higher-order interactions. We begin with the case of two neurons for illustration and show how to test whether or not any pairwise correlation in one period is significantly different from that in the other period. In order to test such a hy(cid:173) pothesis of different firing rates, the correlation term needs to be singled out 'orthogonally' to the firing rates, where the null hypoth(cid:173) esis might not be of independent firing. This method is also shown to directly associate neural firing with behavior via their mutual information, which is decomposed into two types of information, conveyed by mean firing rate and coincident firing, respectively. Then, we show that these results, using the 'orthogonal' decompo(cid:173) sition, are naturally extended to the case of three neurons and n neurons in general.