Fig. 7From: On the Effects on Cortical Spontaneous Activity of the Symmetries of the Network of Pinwheels in Visual Area V1Sketch of the possible phase portraits on the perturbed torus. One case (left) is shown, assuming that a periodic orbit surrounds the focus at the center. Another case (right) is shown in the case of reflection symmetry. The presence or absence of periodic orbits is essentially related to the sign of the real part of the eigenvalues of the Jacobian at the central focusBack to article page