Figure 27. Phase lag maps for the mixed motifs as an excitatory reversal potential varies.

Here, we choose values , and , for the reversal potential, in the two excitatory connections originating from cell 3. (A) Increasing causes two saddle-node bifurcations, and breaks the rotational symmetries and hence annihilates the FPs at and . This widens the basins of the blue and green stable FPs at and , and shrinks that of the red stable FP at . (B) Making two connections more excitatory produces a closed heteroclinic connection between the remaining FPs, which becomes a stable invariant circle wrapped around the torus (inset C). Black-labeled trajectories indicate the direction field on the torus and the separatrices of saddles.