Oscillation patterns in tori of modified FHN neurons

We analyze the dynamics of a network of electrically coupled, modified FitzHugh-Nagumo (FHN) oscillators. The network building-block architecture is bidimensional squared array shaped as torus, with unidirectional nearest neighbor coupling in both directions. Linear approximation about the origin of a single torus reveals that the array is able to oscillate via a Hopf bifurcation, controlled by the interneuronal coupling constants. Group theoretic analysis of the dynamics of one torus leads to discrete rotating waves moving diagonally in the squared array under the influence of the direct product group Z(N) x Z(N) X Z(2) X S-1. Then, we studied the existence multifrequency patterns of oscillations, in networks formed by two coupled tori. We showed that when acting on the traveling waves, this group leaves them unchanged, while when it acts on the in-phase oscillations, they are shifted in time by phi. We therefore proved the possibility of a pattern of oscillations in which one torus produces traveling waves of constant phase shift, while the second torus shows synchronous in-phase oscillations, at N-times the frequency shown by the traveling waves. (C) 2010 Elsevier Inc. All rights reserved.