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. 2006 Mar 29;26(13):3567–3583. doi: 10.1523/JNEUROSCI.5050-05.2006

Figure 3.

Figure 3.

Instabilities of the symmetric fixed point solution of Equations 12345–6. In A and B, the network settles at the unstable symmetric fixed point at t = −500 ms. It remains there until t = 0 when the cortical population in circuit 1 is perturbed by a brief external current. After a short while, an instability develops. Red, Cortex; black, thalamus; blue, GPi. Solid (resp. dashed) lines, The activities in circuit 1 (resp. circuit 2). A, Symmetry-breaking instability for G+ = 2.47, G− = 2.85. The network ends in an asymmetric state in which the cortical population is active in one circuit alone. B, Oscillatory instability for G+ = 0.18 and G− = 2.85. The network settles in a homogeneous oscillatory state. C, Solid line, The frequency of the unstable mode at instability onset as a function of the overall delay Δ derived from Equation 36. Circles, The frequency of the oscillations as a function of Δ at the instability onset for G− = 2.85.